Publications

Found 88 results

Sort by: Author Title Type [ Year  (Desc)]
2016
Yenesew A. "Two pterocarpans from Millettia dura and Millettia micans." Advances in Drug Discovery and Development. 2016;1(1):1-8.paper_81_marco_et_al-2016.pdf
2015
2014
Yenesew A, Atilaw Y, Heydenreich, Ndakala A, Hoseah M, Akala, M Kamau E. "3-Oxo-14α,15α-epoxyschizozygine: A new schizozygane indoline alkaloid from Schizozygia coffaeoides." Phytochemistry Letters . 2014;10:28-31. Abstractpaper_73_atilaw_et_al_phyto_2014.pdf

The stem bark extract of Schizozygia coffaeoides (Apocynaceae) showed moderate antiplasmodial activity (IC50 = 8–12 μg/mL) against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum. Chromatographic separation of the extract led to the isolation of a new schizozygane indoline alkaloid, named 3-oxo-14α,15α-epoxyschizozygine. In addition, two dimeric anthraquinones, cassiamin A and cassiamin B, were identified for the first time in the family Apocynaceae. The structures of the isolated compounds were deduced on the basis of spectroscopic evidence. The schizozygane indole alkaloids showed good to moderate antiplasmodial activities (IC50 = 13–52 μМ).

Yenesew A, Derese, S., Barasa, L., Akala HM, Yusuf, A.O., Kamau E, Heydenreich. "4'-Prenyloxyderrone from the stem bark of Millettia oblata ssp. teitensis and the antiplasmodial activities of isoflavones from some Millettia species." Phytochemistry Letters ,. 2014;8:69-72. Abstractpaper_68_derese_et_al_phyto_2014.pdf

The CH2Cl2/MeOH (1:1) extract of the stem bark of Millettia oblata ssp. teitensis showed antiplasmodial activity (IC50 = 10–12 μg/mL) against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum. Chromatographic separation of the extract led to the isolation of a new isoflavone, 4′-prenyloxyderrone (1), together with known isoflavones (8-O-methylretusin, durmillone, maximaisoflavone B, maximaisoflavone H and maximaisoflavone J), a rotenoid (tephrosin) and a triterpene (lupeol). Similar investigation of Millettia leucantha resulted in the identification of the isoflavones afrormosin and wistin, and the flavone chrysin. The identification of these compounds was based on their spectroscopic data. Five of the isoflavones isolated from these plants as well as 11 previously reported compounds from Millettia dura were tested and showed good to moderate antiplasmodial activities (IC50 = 13–53 μM), with the new compound, 4′-prenyloxyderrone, being the most active (IC50 = 13–15 μM).

Yenesew A, Muiva-Mutisya L, Macharia B, Heydenreich M, Andreas Koch, Hoseah M. Akala SDLOK. "6α-Hydroxy-α-toxicarol and (+)-Tephrodin with antiplasmodial activities from Tephrosia species." Phytochemistry Letters . 2014. Abstractpaper_75_muiva_et_al_phyto_2014.pdf

The CH2Cl2/MeOH (1:1) extract of the roots of Tephrosia villosa showed good antiplasmodial activity against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with IC50 values of 3.1 ± 0.4 and 1.3 ± 0.3 μg/mL, respectively. Chromatographic separation of the extract yielded a new rotenoid, 6α-hydroxy-α-toxicarol, along with five known rotenoids, (rotenone, deguelin, sumatrol, 12a-hydroxy-α-toxicarol and villosinol). Similar treatment of the extract of the stem of Tephrosia purpurea (IC50 = 4.1 ± 0.4 and 1.9 ± 0.2 μg/mL against D6 and W2 strains of P. falciparum, respectively) yielded a new flavone having a unique substituent at C-7/C-8 [trivial name (+)-tephrodin], along with the known flavonoids tachrosin, obovatin methyl ether and derrone. The relative configuration and the most stable conformation in (+)-tephrodin was determined by NMR and theoretical energy calculations. The rotenoids and flavones tested showed good to moderate antiplasmodial activities (IC50 = 9 − 23 μМ). Whereas the cytotoxicity of rotenoids is known, the flavones (+)-tephrodin and tachrosin did not show significant cytotoxicity (IC50 > 100 μМ) against mammalian African monkey kidney (vero) and human larynx carcinoma (HEp2) cell lines.

Yenesew A, N A, Heydenreich M, Midiwo JO, Ndakala A, Majer Z, Neumann B, Stammler H-G, Sewald N. "8-Hydroxy-6-methylxanthone-1-carboxylic acid and 6',8-O-dimethylknipholone from the roots of Bulbine frutescens." Phytochemistry Letters . 2014;9:67-73. Abstractpaper_70_abdissa_et_al_phyto_2014.pdf

Phytochemical investigation of the dichloromethane/methanol (1:1) extract of the roots of Bulbine frutescens led to the isolation of a new xanthone, 8-hydroxy-6-methylxanthone-1-carboxylic acid (1) and a new phenylanthraquinone, 6′,8-O-dimethylknipholone (2) along with six known compounds. The structures were elucidated on the basis of NMR and MS spectral data analyses. The structure of compound 1 was confirmed through X-ray crystallography which was then used as a reference to propose the revision of the structures of six seco-anthraquinones into xanthones. The isolated compounds were evaluated for cytotoxicity against human cervix carcinoma KB-3-1 cells with the phenylanthraquinone knipholone being the most active (IC50 = 0.43 μM). Two semi-synthetic knipholone derivatives, knipholone Mannich base and knipholone-1,3-oxazine, were prepared and tested for cytotoxic activity; both showed moderate activities (IC50 value of 1.89 and 2.50 μM, respectively).

Yenesew A, L. K., Omosa, Beatrice, Amugune, Ndunda B, Milugo TKTK, Heydenreich M, Midiwo JO. "Antimicrobial flavonoids and diterpenoids from Dodonaea angustifolia." South African Journal of Botany. . 2014;91, :58-62. Abstractpaper_67_omosa_et_al_south_africa_jou..2014.pdf

The surface exudates of the leaves of Dodonaea angustifolia from Ngong forest population (6 km from Nairobi city center, Kenya) demonstrated antimicrobial activity against Gram-negative (Escherichia coli), Gram-positive (Staphylococcus aureus and Bacillus pumilus) bacteria and the fungus Sacchromyces cerevisiae. Chromatographic separation of the exudates yielded eight methylated flavonoids; 5-hydroxy-3, 4′,7-trimethoxyflavone (1), 3,5-dihydroxy-4′,7-dimethoxyflavone (2), santin (3), kumatakenin (4), rhamnocitrin (5), isokaempferide (6), 3,4′,5,7, tetrahydroxy-6-methoxyflavone (7), pinocembrin (8); two clerodanes, dodonic acid (9) and 2β-hydroxyhardwickiic acid (10) and one labdane; (ent-3β,8α)-15,16-epoxy-13(16),14-labdadiene-3,8-diol (11) diterpenoids. The flavonoid aglycones; 6, 7 and the clerodane diterpenoids; 9 and 10 and labdane diterpenoid, 11 were isolated for the first time from this plant species. The structures of the isolated compounds were identified using ultraviolet (UV), mass spectroscopy (MS), one dimension (1D) and two dimension (2D) nuclear magnetic resonance (NMR) spectroscopy and by comparison of the spectral data with literature. The quercetin derivative, 3,4′,5-trihydroxy-3′,7-dimethoxyflavone (12) showed broad spectrum antibacterial activities against E. coli and B. pumilus with minimum inhibition concentration (MIC) values less than 31.25 μg/well and against S. aureus with MIC below 62.5 μg/well. This compound showed poor antifungal activity against S. cerevisiae (MIC < 500 μg/well). Good antifungal activities were observed for 5,4′-dihydroxy-7-methoxyflavanone (13) and hautriwaic acid lactone (14) against S. cerevisiae with MIC values less than 7.8 μg/well. The most active antifungal compound was 5,7-dihydro-3,4′,6-trimethoxyflavone (3, santin) with an MIC value less than 3.9 μg/well against S. cerevisiae. The rest of the compounds exhibited weak to moderate activities. For comprehensive structure activity relationship studies (SAR), hautriwaic acid lactone (14), hautriwaic acid (15), penduletin (16) isolated from the surface exudates of D. angustifolia from Voi (200 km from Mombasa city center, Kenya) and 12 and 13 from Senecio roseiflorus isolated earlier were included in the bioassays.

Yenesew A, Irungu BN, Erdélyi M., Orwa, J.A. GFLKMAPG. "Constituents of the roots and leaves of Ekebergia capensis and their potential antiplasmodial and cytotoxic activities." Molecules . 2014;19:14235-14246. Abstractirungu_et_al_molecules-2014-19-14235-v2.pdf

A new triterpenoid, 3-oxo-12β-hydroxy-oleanan-28,13β-olide (1), and six known
triterpenoids 2–7 were isolated from the root bark of Ekebergia capensis, an African
medicinal plant. A limonoid 8 and two glycoflavonoids 9–10 were found in its leaves. The
metabolites were identified by NMR and MS analyses, and their cytotoxicity was evaluated
against the mammalian African monkey kidney (vero), mouse breast cancer (4T1), human
larynx carcinoma (HEp2) and human breast cancer (MDA-MB-231) cell lines. Out of the
isolates, oleanonic acid (2) showed the highest cytotoxicity, i.e., IC50’s of 1.4 and 13.3 μM
against the HEp2 and 4T1 cells, respectively. Motivated by the higher cytotoxicity of the
crude bark extract as compared to the isolates, the interactions of oleanonic acid (2) with five triterpenoids 3–7 were evaluated on vero cells. In an antiplasmodial assay, seven
of the metabolites were observed to possess moderate activity against the D6 and W2
strains of P. falciparum (IC50 27.1–97.1 μM), however with a low selectivity index
(IC50(vero)/IC50(P. falciparum-D6) < 10). The observed moderate antiplasmodial activity
may be due to general cytotoxicity of the isolated triterpenoids.

Keywords: Ekebergia capensis; tritepenoid; antiplasmodial; cytotoxicity; Vero; 4T1;
HEp2; MDA-MB-231; 3-oxo-12β-hydroxy-oleanan-28,13β-olide

Yenesew A, Gumula I, Erdélyi M, Patrick. A, J Isaiah Omolo Ndiege PS, Omolo, N, Sunnerhagen P. "Cytotoxic and Antioxidant Flemingins G-P from the Leaves of Flemingia grahamiana." Journal of Natural Products . 2014. Abstractpaper_76_ivan_et_al_jnp_2014_77_2060_2067.pdf

The known flemingins A-C (1-3) and nine new chalcones, named flemingins G-O (4-12), along with deoxyhomoflemingin (13) and emodin (14) were isolated from a leaf extract of Flemingia grahamiana. The isolated chalcones were found to have a geranyl substituent modified into a chromene ring possessing a residual chain, as shown by spectroscopic methods. The leaf extract showed an IC50 value of 5.9 μg/mL in a DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay. The chalcones flemingins A, B, C, G, and H were active in the DPPH radical scavenging assay (ED50 4.4-8.9 μM), while flemingins A and C showed cytotoxicity against MCF-7 human breast cancer cells (IC50 8.9 and 7.6 μM, respectively).

Yenesew A, Sunnerhagen, P., Erdelyi M, Abdissa N, Induli, M., Fitzpatrick P, Alao JP, Landberg G. "Cytotoxic Quinones from the Roots of Aloe dawei." Molecules. 2014;19,:3264-3273. Abstractpaper_69_abdissa_et_al_molecules_2014.pdf

Seven naphthoquinones and nine anthraquinones were isolated from the roots of Aloe dawei by chromatographic separation. The purified metabolites were identified by NMR and MS analyses. Out of the sixteen quinones, 6-hydroxy-3,5-dimethoxy-2-methyl-1,4-naphthoquinone is a new compound. Two of the isolates, 5,8-dihydroxy-3-methoxy-2-methylnaphthalene-1,4-dione and 1-hydroxy-8-methoxy-3-methylanthraquinone showed high cytotoxic activity (IC₅₀ 1.15 and 4.85 µM) on MCF-7 breast cancer cells, whereas the others showed moderate to low cytotoxic activity against MDA-MB-231 (ER Negative) and MCF-7 (ER Positive) cancer cells.

Yenesew A, Bosire CM, Deyou T, Kabaru JM, Kimata DM. "Larvicidal activities of extracts and rotenoids from Millettia usaramensis subspecies usaramensis on Aedes aegypti (Linnaeus, 1762) (Diptera: Culicidae)." Journal of Asia-Pacific Entomology . 2014; 17(3):531-535. Abstractpaper_71_bosire_et_al__asia-2014.pdf

The dichloromethane/methanol (1:1) extract of the stem bark of Millettia usaramensis subspecies usaramensis was tested for its larvicidal activity against the 4th instar Aedes aegypti larvae and demonstrated activity with LC50 value of 50.8 ± 0.06 μg/mL at 48 h. Compounds isolated from the extract were also tested for their larvicidal activities, and the rotenoid usararotenoid-A (LC50 4.3 ± 0.8 μg/mL at 48 h) was identified as the most active principle. This compound appears to be the first rotenoid having a trans-B/C ring junction and methylenedioxy group at C-2/C-3 with high larvicidal activity. Related rotenoids with the same configuration at the B/C-ring junction did not show significant activity at 100 μg/mL.

Yenesew A, Judith O, Saffudin D, Catherine L. "Phytochemical screening of Dierama cupuliflorum Klatt. (Iridaceae)." Journal of Pharmacy Research. 2014; 8:589-592. Abstractpaper_72_judith_et_al_jou_of_pharma._res._2014.pdf

Background: Plants continue to play a vital role in their therapeutic value. This is because of the vast secondary metabolites that many of them produce. These natural products have been utilised as single or in combination with other compounds for utilization as source of drugs for many ailments in form of antibacterials, antifungals, antivirals, antihelminthes, and antimalarials among others. Plants evaluated phytochemically in most cases have previous reports on biological activity, ethnomedicinal or traditional medicine usage. However, many other plants with no such previous reports may be as important with variety of natural products with potential significance in pharmaceuticals for drug development. Dierama cupuliflorum is one such plant. The aim of the present study was to investigate the presence of phytochemicals in this plant. Method : The organic solvent extracts from Methanol: Dichloromethane (1:1) along with dry powder/ground portions from corms and aerial parts were screened for the presence of selected phytochemicals using standard chemical procedures. Results: Phytochemical screening revealed the presence of terpenoids, alkaloids, saponins, tannins, flavanoids, glycosides and anthraquinones. More phytochemicals were detected in corms than in the aerial parts. Conclusion: Although there is no available report on the use of this plant for medicinal purposes, the phytochemical data presented here has demonstrated that this plant has the potential to be used significantly for therapeutic purposes in many health challenges. This study has therefore laid down a good foundation for future studies on this plant whose bioactivity studies are currently underway.

2013
Yenesew A., Peggoty Mutai, Matthias Heydenreich GTGMKC. "3-Hydroxyisoflavanones from the stem bark of Dalbergia melanoxylon: Isolation, antimycobacterial evaluation and molecular docking studies." Phytochemistry Letters . 2013;6 :671-675. Abstractpaper_65_mutai_et_al_phyto_2013.pdf

Two new 3-hydroxyisoflavanones, (S)-3,4′,5-trihydroxy-2′,7-dimethoxy-3′-prenylisoflavanone (trivial name kenusanone F 7-methyl ether) and (S)-3,5-dihydroxy-2′,7-dimethoxy-2″,2″-dimethylpyrano[5″,6″:3′,4′]isoflavanone (trivial name sophoronol-7-methyl ether) along with two known compounds (dalbergin and formononetin) were isolated from the stem bark of Dalbergia melanoxylon. The structures were elucidated using spectroscopic techniques. Kenusanone F 7-methyl ether showed activity against Mycobacterium tuberculosis, whereas both of the new compounds were inactive against the malaria parasite Plasmodium falciparum at 10 μg/ml. Docking studies showed that the new compounds kenusanone F 7-methyl ether and sophoronol-7-methyl ether have high affinity for the M. tuberculosis drug target INHA.

Yenesew A, Endale M, M., Erdelyi, Ekberg A, HM A, Ndakala A, A., Sunnerhagen. "Anthraquinonesof the roots of Pentas micrantha." Molecules . 2013;18,:311-321. Abstractpaper_61_endale_et_al_molecules-2013-18-00311.pdf

Pentas micrantha is used in the East African indigenous medicine to treat malaria. In the first investigation of this plant, the crude methanol root extract showed moderate antiplasmodial activity against the W2- (3.37 μg/mL) and D6-strains (4.00 μg/mL) of Plasmodium falciparum and low cytotoxicity (>450 μg/mL, MCF-7 cell line). Chromatographic separation of the extract yielded nine anthraquinones, of which 5,6-dihydroxylucidin-11-Omethyl ether is new. Isolation of a munjistin derivative from the genus Pentas is reported
here for the first time. The isolated constituents were identified by NMR and mass spectrometric techniques and showed low antiplasmodial activities.

Keywords: anthraquinone; malaria; Pentas micrantha; Rubiaceae; 5,6-dihydroxylucidin-11-O-methyl ether 1.

Yenesew A., Martha Induli, Meron Gebru NAHAIWRBMHSM. "Antiplasmodial Quinones from the Rhizomes of Kniphofia foliosa." Natural Products Comunications . 2013;8:1261-1264. Abstractpaper_64_induli_et_al-npc-2013.pdf

Extracts of the rhizomes of Kniphofia foliosa exhibited antiplasmodial activities against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with IC50 values of 3-5 microg/mL. A phenyloxanthrone, named 10-acetonylknipholone cyclooxanthrone (1) and an anthraquinone-anthrone dimer, chryslandicin 10-methyl ether (2), were isolated from the rhizomes, along with known quinones, including the rare phenylanthraquinone dimers, joziknipholones A and B. The structures of these compounds were determined based on spectroscopic data. This is the second report on the occurrence of the dimeric phenylanthraquinones in nature. In an in vitro antiplasmodial assay of the isolated compounds, activity was observed for phenylanthraquinones, anthraquinone-anthrone dimers and dimeric phenylanthraquinones, with joziknipholone A being the most active. The new compound, 10-acetonylknipholone cyclooxanthrone, also showed anti-plasmodial activity. In an in vivo assay, knipholone anthrone displayed marginal antimalarial activity.

Yenesew A, Abdissa, N., Ndakala A, Induli, M., Akala, H.M., Heydenrich, M., Midiwo, J.O. "Knipholone Cyclooxanthrone and an Anthraquinone Dimer with Antiplasmodial Activities from the Roots of Kniphofia foliosa." Phytochemistry Letters . 2013;6:241-245. Abstractpaper_62_abdissa_phytol-2013.pdf

A new phenylanthrone, named knipholone cyclooxanthrone and a dimeric anthraquinone, 10-methoxy-
10,70-(chrysophanol anthrone)-chrysophanol were isolated from the roots of Kniphofia foliosa together
with the rare naphthalene glycoside, dianellin. The structures were determined by NMR and mass
spectroscopic techniques. The compounds showed antiplasmodial activities against the chloroquineresistant (W2) and chloroquine-sensitive (D6) strains of Plasmodium falciparum with 10-methoxy-10,70-(chrysophanol anthrone)-chrysophanol being the most active with IC50 values of 1.17 0.12 and 4.07 1.54 mg/ml, respectively.

Yensew A. "Limitations to Use of Infrared Spectroscopy for Rapid Determination of Carbon-Nitrogen and Wood Density for Tropical Species. Advances in Analytical Chemistry." Advances in Analytical Chemistry . 2013;3(3). Abstractpaper_63_kennedy10.5923.j.aac_.20130303.01.pdf

Infrared (IR) spectroscopy was used as a rapid and non-destructive method to determine, carbon (C), nitrogen (N) and tree wood density.A total of 82 sample cores were scanned in the reflectance mode from 4000 to 400 cm-1 for mid-infrared (MIR) spectra and from 8000 to 4000cm-1 and 11000-4000cm-1 for near infrared (NIR) spectra. The reference values for C and N were measured using combustion method while wood density was calculated using auger method. Calibration equations were developed using partial least-squares and first derivative spectra. Root mean square error (RMSEP) was used to calculate prediction error. Prediction of Cusing MIR spectra gave R2 = 0.59, RMSEP = 0.02; NIR spectra R2 = 0.50, RMSEP = 0.02, whileN prediction usingMIR spectra had R2 = 0.54, RMSEP = 0.22; NIR spectra R2 = 0.48, RMSEP =0.24. Wood density prediction was fair for MIR (R2= 0.79, RMSEP = 0.14); NIR (R2= 0.69, RMSEP = 0.17).Improved predictions using NIR were for extendedspectral range;though accuracies were inferior to MIR. Both MIR and NIR models showed good potentials to be used as rapid and cost effective method of predicting C-N andwood density.

Keywords Infrared Spectroscopy, Partial Least Squares Regression,Carbon, Nitrogen,Wood Density

2012
Yenesew A. "Antimicrobial and Anticancer Carvotacetone Derivativesof Sphaeranthus." Natural Product Communications . 2012;7:1123-1126. Abstractpaper_58_machumi_npc_publication-sphaeranthus_bullatus-2012.pdf

The CH2Cl2-MeOH (1:1) extract of the aerial parts of Sphaeranthus bullatus, an annual herb native to tropical East Africa, showed activity against chloroquine sensitive D6 (IC50 9.7 μg/mL) and chloroquine resistant W2 (IC50 15.0 μg/mL) strains of Plasmodium falciparum. Seventeen secondary metabolites were isolated from the extract through conventional chromatographic techniques and identified using various spectroscopic methods. The compounds were evaluated for their in vitro antiplasmodial, antileishmanial and anticancer activities revealing activity of four carvotacetone derivatives, namely 3-acetoxy-7-hydroxy-5-tigloyloxycarvotacetone (1), 3,7-dihydroxy-5-tigloyloxycarvotacetone (2), 3-acetoxy-5,7-dihydroxycarvotacetone (3) and 3,5,7-trihydroxycarvotacetone
(4); with antiplasmodial IC50 values of 1.40, 0.79, 0.60 and 3.40 μg/mL, respectively, against chloroquine sensitive D6 strains of P. falciparum;
antiplasmodial activity of IC50 2.00, 0.90, 0.68 and 2.80 μg/mL, respectively, against chloroquine resistant W2 strains of P. falciparum; antileishmanial IC50
values of 0.70, 3.00, 0.70 and 17.00 μg/mL, respectively, against the parasite L. donovanii promastigotes, and anticancer activity against human SK-MEL, KB,
BT-549 and SK-OV-3 tumor cells, with IC50 values between <1.1 - 5.3 μg/mL for 1-3. In addition, cytotoxic effects of the active compounds were evaluated against monkey kidney fibroblasts (VERO) and pig kidney epithelial cells (LLC-PK11). The structures of carvotacetone derivatives were determined by 1D and 2D NMR spectroscopy; the absolute stereochemical configuration of 3-acetoxy-7-hydroxy-5-tigloyloxycarvotacetone (1) was determined as 3R, 4R, 5S by circular dichroism, specific rotation, 1H NMR and 2D NMR ROESY and NOESY experiments.

Keywords: Sphaeranthus bullatus, Asteraceae, Antiplasmodial, Antileishmanial, Anticancer, Carvotacetones.

Yenesew A. "Antinocieptive Activities of the Root Extracts of Rhus natalensis Kraus and Senna singueana." Phytopharmacology . 2012;2:1-6. Abstractpaper_59_karuki_et_al-2012.pdf

Rhus natalensis and Senna singuaenae are traditional African plants commonly used as medicinal plant in East Africa for the management of pain. The plants are used for management of rheumatism among others. This study investigated the antinociceptive activities of R. natalensis and S. singuaenae in Swiss albino mice using the tail-flick and hot plate tests. Extract solvent (vehicle), morphine and aspirin were employed as controls. Root extract of R. natalensis (100 and 200 mg /kg) and 100 mg /kg of S. singuaenae showed no significant antinociceptive activity in the hot plate while the 200mg /kg of S. singuaenae showed significant antinociceptive activity (p<0.05). In the tail flick tests, root extract of R. natalensis (100 and 200 mg / kg) showed highly significant antinociceptive activity (p<0.01) while 200mg / kg of S. singuaenae showed significant antinociceptive activity (p<0.05) compared to the controls. The 100 mg /kg of S. singuaenae showed no significant antinociceptive activity in the tail flick. This study lends support to the anecdotal evidence for use of R. natalensis and S. singuaenae in the management of painful conditions.

Keywords: Rhus natalensis; Senna singuaenae; analgesic; Rhus natalensis; Senna singuaenae; rheumatism

Yenesew A. "Antinocieptive activity of Toddalia asiatica (L) Lam. in models of central and peripheral pain." Phytopharmacology . 2012;3(1):122-129. Abstractpaper_60_kariuki_et_al_phytopharmacology_2012.pdf

Toddalia asiatica within the context of traditional African medicine is a commonly used medicinal plant in East Africa for the management of pain and inflammatory conditions. It is used by the Masai in both Kenya and Tanzania for management of rheumatism among others. The present study was undertaken to investigate the antinociceptive activities of T. asiatica in Swiss albino mice in acetic acid-induced writhing, tail-flick and hot plate pain tests. The extract solvent (vehicle), morphine and aspirin were employed as negative and positive controls respectively. The acetic acid -induced writhing test was used as the screening test and as the root bark extract was found to be more potent than the leaf extract, the former was investigated using the hot plate and the tail flick tests. The root bark extract (200 mg / kg) showed highly significant (p < 0.001) antinociceptive activity in the hot plate and the tail flick tests. The 100mg/kg dose showed significant (p < 0.05) activity in the tail flick test but not significant in the hot plate test. The present study, therefore lends support to the anecdotal evidence for use of T. asiatica in the management of painful conditions.

Yenesew A. "The Antiplasmodial and Radical Scavenging Activities of Flavonoids of Erythrina burttii." Acta Tropica . 2012;123:123-127. Abstract

The acetone extract of the root bark of Erythrina burttii showed in vitro antiplasmodial activity against
the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with
IC50 values of 0.97 ± 0.2 and 1.73 ± 0.5 g/ml respectively. The extract also had radical scavenging activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical with an EC50 value of 12.0 g/ml. The isoflav-3-enes burttinol-A and burttinol-C, and the 2-arylbenzofuran derivative burttinol-D were identified as the most active antiplasmodial (IC50 < 10 M) and free radical scavenging (EC50 ca. 10 M) principles. The acetone extract of E. burttii at 800 mg/kg/day, in a 4-day Plasmodium berghei ANKA suppressive test, showed in vivo antimalarial activity with 52% hemosuppression. In the same in vivo test, marginal activities were also
observed for the extracts of the root and stem bark of Erythrina abyssinica and the root bark of Erythrina
sacleuxii.

Yenesew A., Endale, M. AAREDNMWSJPHM. "Antiplasmodial Quinones from Pentas longiflora and Pentas lanceolata." Planta medica . 2012;78:31-35. Abstractpaper_53_endale_et_al_planta_medica_2012-78-31-35.pdf

The dichloromethane/methanol (1 : 1) extracts of the roots of PENTAS LONGIFLORA and PENTAS LANCEOLATA showed low micromolar (IC (50) = 0.9-3 µg/mL) IN VITRO antiplasmodial activity against chloroquine-resistant (W2) and chloroquine-sensitive (D6) strains of PLASMODIUM FALCIPARUM. Chromatographic separation of the extract of PENTAS LONGIFLORA led to the isolation of the pyranonaphthoquinones pentalongin ( 1) and psychorubrin ( 2) with IC (50) values below 1 µg/mL and the naphthalene derivative mollugin ( 3), which showed marginal activity. Similar treatment of PENTAS LANCEOLATA led to the isolation of eight anthraquinones ( 4-11, IC (50) = 5-31 µg/mL) of which one is new (5,6-dihydroxydamnacanthol, 11), while three - nordamnacanthal ( 7), lucidin- ω-methyl ether ( 9), and damnacanthol ( 10) - are reported here for the first time from the genus PENTAS. The compounds were identified by NMR and mass spectroscopic techniques.

Yenesew A. "Busseihydroquinones A-D from the Roots of Pentas bussei." Journal of Natural Products. 2012;75 :1299-1304. Abstractpaper_57_endale_et_al_j_nat_prod_2012.pdf

Four new naphthohydroquinones, named busseihydroquinones A−D (1−4), along with a known homoprenylated dihydronaphthoquinone (5), were isolated from the CH2Cl2/MeOH (1:1) extract of the roots of Pentas bussei. Although the genus Pentas is frequently used by traditional healers for the treatment of malaria, only marginal activities against the chloroquine-sensitive (D6) and the chloroquineresistant (W2) strains of Plasmodium falciparum were observed for the crude root extract and the isolated constituents of this plant.

Yenesew A. "Four Isoflavanones from the stem bark of Platycelphium voënse." Phytochemistry Letters . 2012;5:150-154. Abstractpaper_54_ivan_et_al_phytol-2012.pdf

From the stem bark of Platycelphium voe¨nse (Leguminosae) four new isoflavanones were isolated and
characterized as (S)-5,7-dihydroxy-20,40-dimethoxy-30-(300-methylbut-200-enyl)-isoflavanone (trivial
name platyisoflavanone A), ()-5,7,20-trihydroxy-40-methoxy-30-(300-methylbut-200-enyl)-isoflavanone
(platyisoflavanone B), 5,7-dihydroxy-40-methoxy-200-(2000-hydroxyisopropyl)-dihydrofurano-[400,500:30,20]-
isoflavanone (platyisoflavanone C) and 5,7,20,300-tetrahydroxy-200,200-dimethyldihydropyrano-[500,600:30,40]-isoflavanone (platyisoflavanone D). In addition, the known isoflavanones, sophoraisoflavanone A and glyasperin F; the isoflavone, formononetin; two flavones, kumatakenin and isokaempferide; as well as two triterpenes, betulin and b-amyrin were identified. The structures were elucidated on the basis of spectroscopic evidence. Platyisoflavanone A showed antibacterial activity against Mycobacterium tuberculosis in the microplate alamar blue assay (MABA) with MIC = 23.7 mM, but also showed cytotoxicity (IC50 = 21.1 mM) in the vero cell test.

Yenesew A. "Naphthoquinones from the roots of Aloe secundiflora (Asphodelaceae)." Phytochemistry Letters . 2012;5:506-509. Abstractpaper_56_induli_et_al_phytol_-2012.pdf

Two new naphthoquinones, 5-hydroxy-3,6-dimethoxy-2-methylnaphthalene-1,4-dione and 5,8-dihydroxy-
3-methoxy-2-methylnaphthalene-1,4-dione, were isolated from the roots of Aloe secundiflora together with the known compounds chrysophanol, helminthosporin, isoxanthorin, ancistroquinone C, aloesaponarins I and II, aloesaponols I and II, laccaic acid D methyl ester and asphodelin. The structures were elucidated based on spectroscopic evidence. This appears to be the first report on the occurrence of naphthoquinones in the genus Aloe. Aloesaponarin I and 5-hydroxy-3,6-dimethoxy-2-methylnaphthalene-1,4-dione showed anti-bacterial activity against Mycobacterium tuberculosis with MIC values of 21–23 mg/mL in the Microplate Alamar Blue Assay (MABA) and Low Oxygen Recovery Assay (LORA); 5-hydroxy-3,6-dimethoxy-2-methylnaphthalene-1,4-dione also showed cytotoxicity against the Vero cell line (IC50 = 10.2 mg/mL)

2011
Yenesew A. "Phytochemical and Antimicrobial Investigation of Girardinia diversifolia (Link) Friis (Urticaceae)." East and Central African Journal of Pharmaceutical Sciences. 2011;14:89-94.njogu_et_al-2011-ecajps.pdf
Yenesew A., Juma, W.P. AEMHOGPWIHMFL. "Terpurinflavone: An Antiplasmodial Flavone from The Stem of Tephrosia purpurea." Phytochemistry Letters .. 2011;4:176-178. Abstractpaper_51_juma_et_al_phytol-2011.pdf

The stem extract of Tephrosia purpurea showed antiplasmodial activity against the D6 (chloroquine-sensitive) and W2 (chloroquine-resistant) strains of Plasmodium falciparum with IC50 values of 10.47 ± 2.22 μg/ml and 12.06 ± 2.54 μg/ml, respectively. A new prenylated flavone, named terpurinflavone, along with the known compounds lanceolatin A, (−)-semiglabrin and lanceolatin B have been isolated from this extract. The new compound, terpurinflavone, showed the highest antiplasmodial activity with IC50 values of 3.12 ± 0.28 μM (D6) and 6.26 ± 2.66 μM (W2). The structures were determined on the basis of spectroscopic evidence.

2010
Yenesew A., Machumi, F. SDMWJTKWVSJ. "Antimicrobial and Antiparasitic Abietane Diterpenoids from the roots of Clerodendrum eriophyllum." Natural Product Communications . 2010;5 :853-858. Abstractpaper_49_machumi_et_al-npc-2010.pdf

Chromatographic separation of the roots of a Kenyan medicinal plant, Clerodendrum eriophyllum, led to the isolation of ten abietane diterpenoids (1-10), one of which (1) was isolated for the first time from a natural source. Using spectroscopic data, the structure of 1 was determined to be 12-hydroxy-8,12-abietadiene-3,11,14-trione. Circular dichroism (CD) spectra showed that the stereochemistry of compounds 1, 3, and 6-8 belongs to the normal series of abietane diterpenes, which confirmed the absolute stereochemistry of the isolated compounds. Compounds 1-10 were evaluated for their in vitro antiplasmodial, antileishmanial, antifungal and antibacterial activities. Compounds 3 and 7 exhibited potent antifungal activity (IC50/MIC 0.58/1.25 and 0.96/2.5 microg/mL, respectively) against C. neoformans, whereas 3, 6 and 7 showed strong antibacterial activity against Staphylococcus aureus and methicillin-resistant S. aureus with IC50/MIC values between 1.33-1.75/2.5-5 and 0.96-1.56/2.5 microg/mL, respectively. In addition, compounds 3 and 9 exhibited potent antileishmanial activity (IC50 0.08 and 0.20 microg/mL, respectively) against L. donovani, while 3 and 7 displayed weak antimalarial activity against Plasmodium falciparum, but 9 was inactive

Yenesew A., Omosa, L. K. DMHPSJOM. "Neo-clerodane diterpenes from Dodonaea angustifolia." Phytochemistry Letters . 2010;3: 217-220. Abstractpaper_50_omosa_et_al_phytol-2010.pdf

Phytochemical investigation of the leaf surface exudate of Dodonaea angustifolia L.f. yielded two new neo-clerodane diterpenes, neo-clerodan-3,13-dien-16,15:18,19-diolide (mkapwanin) and 15-methoxy-neo-clerodan-3,13-dien-16,15:18,19-diolide (15-methoxymkapwanin). In addition, ten known compounds were identified. The structures were determined on the basis of spectroscopic evidence. This additional chemical information could contribute towards solving the taxonomical controversy that exists between Dodonaea angustifolia and Dodonaea viscosa Jacq., which are morphologically similar.

2009
Yenesew A. "8-Methoxyneorautenol and Radical Scavenging flavonoids from Erythrina abyssinica." Bull. Chem. Soc. Ethiopia . 2009;23:205-210. Abstractpaper_47_yenesew_et_l_bull_chem_soc_ethiop-2009-23-205.pdf

A new pterocarpan (named 8-methoxyneorautenol) was isolated from the acetone extract of the
root bark of Erythrina abyssinica. In addition, the known isoflavonoid derivatives eryvarin L, erycristagallin and
shinpterocarpin were identified for the first time from the roots of this plant. The structures were determined on the basis of spectroscopic evidence. The new compound showed selective antimicrobial activity against
Trichophyton mentagrophytes. The acetone extract of the root bark of E. abyssinica showed radical scavenging activity towards 2,2-diphenyl-1-picrylhydrazyl radical (DPPH). The pterocarpenes, 3-hydroxy-9-methoxy-10-(3,3-dimethylallyl)pterocarpene and erycristagallin, were the most active constituents of the roots of this plant and showing dose-dependent activities similar to that of the standard quercetin.

KEY WORDS: Erythrina abyssinica, Root bark, Leguminosae, Pterocarpan, 8-Methoxyneorautenol,
Pterocarpenes, 3-Hydroxy-9-methoxy-10-(3,3-dimethylallyl)pterocarpene, Erycristagallin, Antimicrobial, Radical scavengers, DPPH

Yenesew A. "Antiplasmodial and larvicidal activities of flavonoids of Derris trifoliata." Bull. Chem. Soc. Ethiopia . 2009;23:409-414. Abstractpaper_48_yenesew_et_al_bull_chem_soc_ethiop-2009-23-409.pdf

From the dichloromethane-methanol (1:1) extract of the seed pods of Derris trifoliata, a new flavanone derivative (S)-lupinifolin 4´-methyl ether was isolated. In addition, the known flavonoids lupinifolin
and rotenone were identified. The structures were determined on the basis of spectroscopic evidence. Lupinfolin showed moderate in vitro antiplasmodial activity against the D6 (chloroquine-sensitive) and W2 (chloroquineresistant) strains of Plasmodium falciparum. The different parts of this plant showed larvicidal activities against Aedes aegypti and rotenoids were identified as the active principles.

KEY WORDS: Derris trifoliata, Leguminosae, Flavanone, (S)-Lupinifolin 4´-methyl ether, Lupinifolin,
Antiplasmodial, Rotenoid, Larvicide, Aedes aegypti

Yenesew A. "Antiplasmodial b-hydroxydihydrochalcone from seedpods of Tephrosia elata." Phytochemistry Letters . 2009;2:99-102. Abstractpaper_46_muiva_et_al_phytol-2009.pdf

From the seedpods of Tephrosia elata, a new b-hydroxydihydrochalcone named (S)-elatadihydrochalcone
was isolated. In addition, the known flavonoids obovatachalcone, obovatin, obovatin methyl ether
and deguelin were identified. The structures were determined on the basis of spectroscopic evidence.
The crude extract and the flavonoids obtained from the seedpods of this plant showed antiplasmodial
activities. The literature NMR data on b-hydroxydihydrochalcones is reviewed and the identity of some
of the compounds assigned b-hydroxydihydrochalcone skeleton is questioned.

2008
Yenesew A. "Joziknipholones A and B: The First Dimeric Phenylanthraquinones, from the Roots of Bulbine frutescens." Chem. Eur. J. . 2008; 14:1420-1429. Abstractpaper_45_Bringmann_et_al_joziknipholones.pdf

From the roots of the African plant Bulbine frutescens (Asphodelaceae), two unprecedented novel dimeric
phenylanthraquinones, named joziknipholones A and B, possessing axial and centrochirality, were isolated,
together with six known compounds. Structural elucidation of the new metabolites was achieved by spectroscopic and chiroptical methods, by reductive cleavage of the central bond between the monomeric phenylanthraquinone and -anthrone portions with sodium dithionite, and by quantum chemical CD
calculations. Based on the recently revised absolute axial configuration of the parent phenylanthraquinones, knipholone and knipholone anthrone, the new dimers were attributed to possess the P-configuration (i.e., with the acetyl portions below the anthraquinone plane) at both axes in the case of joziknipholone A, whereas in joziknipholone B, the knipholone part was found to be M-configured. Joziknipholones A and B are active against the chloroquine resistant strain K1 of the malaria pathogen, Plasmodium falciparum, and show moderate activity against murine leukemic lymphoma L5178y cells.

2007
Yenesew A. "C-Methylated and C-prenylated isoflavonoids from root extracts of Desmodium uncinatum." Phytochemistry 68, 646-651.. 2007;68(5):646-651. Abstractpaper_44_guchu_et_al_phyto_2007_68_646.pdf

A pterocarpan, 1,9-dihydroxy-3-methoxy-2-methylpterocarpan (named uncinacarpan) and two isoflavanones, 5,7-dihydroxy-2',3',4'-trimethoxy-6-(3-methylbut-2-enyl)isoflavanone (named uncinanone D) and ,4'-dihydroxy-7,2'-dimethoxy-6-methylisoflavanone (named uncinanone E), were isolated from the CH(2)Cl(2) root extract of Desmodium uncinatum (Jacq.) DC and characterised by spectroscopic methods. In addition, a rare pterocarpan edudiol and two known abietane diterpenes, 7-oxo-15-hydroxydehydroabietic acid and 7-hydroxycallitrisic acid were identified. The fraction of the root extract that was analysed induced germination of Striga hermonthica seeds, but none of the isolated compounds showed this activity.

Yenesew A. "The first 9-hydroxyhomoisoflavanone, and antiplasmodial chalcones, from the aerial exudates of Polygonum senegalense." Arkivoc 21-27. . 2007;ix:21-27. Abstractpaper_43_midiwo_et_al_arkivok_2007_21-27.pdf

Phytochemical re-examination of the aerial exudates of Polygonum senegalense forma senegalense has resulted in the isolation and charachterization of a novel homoisoflavonoid, 5,7-dihydroxy-3-(hydroxy-phenyl-methyl)-6-methoxy-chroman-4-one (trivial name: polygohomoisoflavanone). The structure was determined on the basis of spectroscopic evidence. The new compound along with other components of the aerial exudate showed good antiplasmodial activities towards chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum.

2006
Yenesew A. "Anti-plasmodial activities of flavonoids from Erythrina sacleuxii." Planta Medica . 2006;72:187-189. Abstractpaper_39_andayi_et_al_planta_med.-_2006_antiplasmodial_flavonoids_from_erythrina_sacleuxii.pdf

The acetone extracts of the root bark and stem bark of Erythrina sacleuxii showed antiplasmodial activities against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum. Chromatographic separation of the acetone extract of the root bark afforded a new isoflavone, 7-hydroxy-4'-methoxy-3'-prenylisoflavone (trivial name 5-deoxy-3'-prenylbiochanin A) along with known isoflavonoids as the antiplasmodial principles. Flavonoids and isoflavonoids isolated from the stem bark of E. sacleuxii were also tested and showed antiplasmodial activities. The structures were determined on the basis of spectroscopic evidence.

Yenesew A. "Three ent-trachylobane diterpenes in the leaf exudates of Psiadia punctulata." Phytochemistry. 2006;67,:1322-1325. Abstractpaper_41_juma_et_al_phyto_2006_67_1322.pdf

Three ent-trachylobane diterpenes have been isolated from the leaf exudates of Psiadia punctulata and characterised as 6a,17,19-enttrachylobantriol; 2a,18,19-ent-trachylobantriol; and 2b,6a,18,19-ent-trachylobantetraol. The structures were determined on the basis of spectroscopic evidence.

Yenesew A. "Two unusual rotenoid derivatives, 7a-O-methyl-12a-hydroxydeguelol and spiro-13-homo-13-oxaelliptone, from the seeds of Derris trifoliata." Phytochemistry. 2006;67:988-991. Abstractpaper_40_yenesew_et_al_derris-phyto-2006.pdf

The crude methanol extract of the seeds of Derris trifoliata showed potent and dose dependent larvicidal activity against the 2nd instar larvae of Aedes aegypti. From this extract two unusual rotenoid derivatives, a rotenoloid (named 7a-O-methyl-12a-hydroxydeguelol) and a spirohomooxarotenoid (named spiro-13-homo-13-oxaelliptone), were isolated and characterised. In addition a rare natural chromanone (6,7-dimethoxy-4-chromanone) and the known rotenoids rotenone, tephrosin and dehydrodeguelin were identified.
The structures were assigned on the basis of spectroscopic evidence. The larvicidal activity of the crude extract is mainly due to rotenone.

Yenesew A. "Vangueria, infausta, root bark: in vivo and in vitro antiplasmodial activity." British Journal of Biomedical Science . 2006; 63,:129-133. Abstractpaper_42_abosi_et_al-2006.pdf

Vangueria infausta burch subsp. infausta (Rubiaceae) produces fruits eaten by humans and animals. The leaf, fruit, stem bark and root bark are used as a remedy for many ailments and the roots are used to treat malaria. In this study, concentrations of fractions of the V. infausta root bark extract that produce 50% inhibition (IC50) are determined using the ability of the extract to inhibit the uptake of [G3H]-hypoxanthine by P. falciparum cultured in vitro. The root bark extract showed antimalarial activity against Plasmodium berghei in mice. It gave a parasite suppression of 73.5% in early infection and a repository effect of 88.7%. One fraction obtained from a chloroform extract gave an IC50 value of 3.8±1.5 μg/mL and 4.5±2.3 μg/mL against D6 and W2 strains of P. falciparum, respectively, and another from the butanol extract gave an IC50 value of 3.9±0.3 μg/mL against the D6 strain. Chloroquine had an IC50 value of 0.016 μg/mL and 0.029 μg/mL against D6 and W2 strains, respectively. The plant showed the presence of flavonoids, coumarins,
tannins, terpenoids, anthraquinones and saponins.

2005
Yenesew A. "7a-O-Methyldeguelol, a modified rotenoid with an open ring-C, from the roots of Derris trifoliata.." Phytochemistry . 2005;66:653-657. Abstractpaper_36_yenesew_et_al_phyto_2005_66_653.pdf

From the acetone extract of the roots of Derris trifoliata an isoflavonoid derivative, named 7a-O-methyldeguelol, a modified rotenoid with an open ring-C, representing a new sub-class of isoflavonoids (the sub-class is here named as rotenoloid), was isolated and characterised. In addition, the known rotenoids, rotenone, deguelin and a-toxicarol, were identified. The structures were determined on the basis of spectroscopic evidence. Rotenone and deguelin were identified as the larvicidal principles of the acetone extract of the roots of Derris trifoliata.

Yenesew A. "Antimicrobial flavonoids from the stem bark of Erythrina burttii." Fitotherapia . 2005;76:469-472. Abstractpaper_38_yenesew_et_al_fito_2005_76_469.pdf

The chloroform extract of the stem bark of Erythrina burttii showed antifungal and antibacterial activities using the disk diffusion method. Flavonoids were identified as the active principles. Activities were observed against fungi and Gram(+) bacteria, but the Gram() bacteria Escherichia coli was resistant.

Yenesew A. "Phtytochemical evaluation of Kenyan medicinal plants. .". In: The 11th NAPRECA Symposium. Antananarivo, Madagascar; 2005.midiwo_et_al-11th_napreca_proceedings.pdf
Yenesew A. "Three dimeric anthracene derivatives from Bulbine abyssinica." Tetrahedron . 2005;61:2667-2674. Abstractpaper_37_wanjohi_et_al_tetra_2005_61_2667.pdf

From the fruits of Bulbine abyssinica three new dimeric anthracene derivatives, (P)-8,9,10,80-tetrahydroxy-3,30-dimethyl[10,70-bianthracene]-1,4,90,100-tetraone (trivial name abyquinone A), (10R)-1,4,8,10,80-pentahydroxy-3,30-dimethyl-[10,70-bianthracene]-9,90,100(10H)-trione (trivial name abyquinone B), and (10R)-30,40-dihydro-1,4,8,30,80,90-hexahydroxy-3,30-dimethyl-[10,70-bianthracene]-9,10(10H,20H)-dione (trivial name abyquinone C) were isolated. Despite their structural differences, these three compounds are connected to each other by the apparently biomimetic conversion of abyquinone
C (a preanthraquinonylanthrone with two stereogenic centers) into
B (an anthraquinonylanthrone with one stereogenic center) and finally into A (an axially chiral bianthraquinone) under mild conditions, involving a highly efficient center-to-axis chirality transfer. In addition, the known anthraquinones islandicin and chrysophanol were identified. The structures were determined on the basis of spectroscopical evidences, chemical transformations, and quantum chemical CD calculations.

2004
Yenesew A. "Anti-plasmodial Flavonoids from the roots of Erythrina abyssinica." Phytochemistry. 2004; 65:3029-3032. Abstractpaper_35_yenesew_et_al_phyto_2004-erythrina_abyssinica.pdf

The ethyl acetate extract of the stem bark of Erythrina abyssinica showed anti-plasmodial activity against the chloroquine-sensitive (D6) and chloroquine-resistant (W2) strains of Plasmodium falciparum with IC50 values of 7.9 ± 1.1 and 5.3 ± 0.7 lg/ml, respectively. From this extract, a new chalcone, 20,3,4,40-tetrahydroxy-5-prenylchalcone (trivial name 5-prenylbutein) and a new flavanone, 40,7-dihydroxy-30-methoxy-50-prenylflavanone (trivial name, 5-deoxyabyssinin II) along with known flavonoids have been isolated as the anti-plasmodial principles. The structures were determined on the basis of spectroscopic evidence.

2003
Yenesew A. "Antiplasmodial activities and X-ray crystal structures of rotenoids from the stem bark of Millettia usaramensis subspecies usaramensis." Phytochemistry. 2003;64:773-779. Abstractpaper_34_yenesew_et_al_phyto_2003_64_773.pdf

The dichloromethane extract of the stem bark of Millettia usaramensis subspecies usaramensis showed anti-plasmodial activity against the chloroquine sensitive (D6) and chloroquine resistant (W2) strains of Plasmodium falciparum. Chromatographic separation of the extract led to the identification of a new rotenoid, (6aR,12aS)-2,3-methylenedioxy-9-methoxy-8-(3,3-dimethylallyl)-12ahydroxyrotenoid (trivial name, usararotenoid C) along with known flavonoids (usararotenoid A, 12a-epimillettosin, 6a,12a-dehydromillettone, barbigerone and 40-O-geranylisoliquiritigenin) as the anti-plasmodial principles. The structures were determined by spectroscopic analyses. CD and X-ray analyses established absolute configurations.

Yenesew A. "Flavonoids and isoflavonoids with anti-plasmodial activities from the roots of Erythrina abyssinica." Planta medica. 2003;69 :658-661. Abstractpaper_33__yenesew_et_al_planta_med_2003.pdf

From the root bark of Erythrina abyssinica a new pterocarpene [3-hydroxy-9-methoxy-10-(3,3-dimethylallyl)pterocarpene] and a new isoflav-3-ene [7,4′-dihydroxy-2′,5′-dimethoxyisoflav-3-ene] were isolated. In addition, the known compounds erycristagallin, licoagrochalcone A, octacosyl ferulate and triacontyl 4-hydroxycinnamate were identified. The structures were determined on the basis of spectroscopic evidence. The crude extract and the flavonoids and isoflavonoids obtained from the roots of this plant showed antiplasmodial activities.

Yenesew A. "A new isoflavone from stem bark of Millettia dura." Bulletin of the Chemical Society of Ethiopia.. 2003;17:113-115. Abstractpaper_31_derese_et_al_bull_chem_soc._ethiopia_2003.pdf

A new isoflavone (7,3’-dimethoxy-4’,5’-methylenedioxyisoflavone) and three known isoflavones [isoerythrinin A 4’-(3-methylbut-2-enyl) ether, isojamaicin and nordurlettone] were isolated from the stem bark of Millettia dura (Leguminosae). The structures were determined by spectroscopic methods.

Yenesew A., and B. Irungu, S. Derese MHPJOMMG. "Two prenylated flavonoids from the stem bark of Erythrina burttii." Phytochemistry . 2003;63:445-448. Abstractpaper_32_yenesew_et_al_phyto_2003_63_445.pdf

From the stem bark of Erythrina burttii, a new isoflavone, 5,2′,4′-trihydroxy-7-methoxy-6-(3-methylbut-2-enyl)isoflavone (trivial name, 7-O-methylluteone) and a new flavanone, 5,7-dihydroxy-4′-methoxy-3′-(3-methylbutadienyl)-5′-(3-methylbut-2-enyl)flavanone (trivial name, burttinonedehydrate) along with three known isoflavonoids (8-prenylluteone, 3-O-methylcalopocarpin and genistein) were isolated. The structures were determined on the basis of spectroscopic evidence.

2002
Yenesew A. "Antimicrobial activities of a new schizozygane indoline alkaloid from Schizozygia coffaeoides and the revised structure of isoschizogaline." Journal of Natural Products. 2002;65:566-569. Abstractpaper_28_kariba_et_al_j.nat_._prod._2002.pdf

Extracts from Schizozygia coffaeoides showed antimicrobial activity against fungal and bacterial species. Alkaloids isolated using bioassay-guided fractionation were isoschizogaline, schizogynine, and a new indoline alkaloid, 7,8-dehydro-19beta-hydroxyschizozygine, shown to be the most active antifungal compound. The structure of isoschizagaline, the only active antibacterial, is revised on the basis of NMR analysis.

Yenesew A. "Bioactive compounds from some Kenyan ethnomedicinal plants: Myrsinaceae, Polygonaceae and Psiadia punctulata." Phytochemical Reviews . 2002;1:311-323. Abstractpaper_29_midiwo_et_al_phytochemical_rev_2002.pdf

here are several described medicinal plants in Kenya from a flora of approximately 10,000 members. Strong cross-medical information from the 42 ethnic groups points to the high potential of some of these species. The Myrsinaceae are well established ethno-anthelmintics and anti-bacterials. They are harbingers of long alkyl side chain benzoquinones which clearly have a protective function from their histochemical disposition. The main benzoquinone in the sub-family Myrsinodae is embelin while for the Maesodae it is maesaquinone together with its 5-acetyl derivative; the distribution of these benzoquinones by their alkyl side chain length or the presence/absence of a 6-methyl group is in accord with morphological sub-family de-limitation. The benzoquinones showed anti-feedant, anti-microbial, phytotoxic, acaricidal, insecticidal and nematicidal activity. Many other benzoquinones of medium and minor concentration were also isolated and characterised. Some plants belonging to the Polygonaceae which are widely used as ethno-anthelmintics have been studied. The common anthelmintic anthraquinones were obtained from all five Rumex species while the naphthalenic acetogenin derivative, nepodin was more selectively distributed. The leaf of Polygonum senegalense is up to 17% surface exudate; about thirteen non polar flavonoid derivatives (chalcones, dihydrochalcones, flavanones and a flavone) have been isolated from it. From the internal aerial tissues of this plant, the major flavonoids were common flavonoids, quercetin, kaempferol, luteolin and their glycosides. The only unique compound isolated from this plant was 2′-glucosyl-6′-hydroxy-4′-methoxydihydrochalcone whose aglycone, uvangolatin is part of the exudate mixture. Other leaf exudate plants studied include the stomach-ache medicine, Psiadia punctulata (Compositae) from which novel methylated flavonoids, kaurene and trachyloban diterpenes have been found.

Yenesew A., and J.O. Midiwo, M. Heydenreich GPSMMG. "Three isoflav-3-enes and a 2-arylbenzofuran from the root bark of Erythrina burttii." Phytochemistry. 2002;59 :337-341. Abstractpaper_27_yenesew_et_al_phyto_2002_59_337.pdf

From the root bark of Erythrina burttii three isoflav-3-enes, 7,4′-dihydroxy-2′-methoxy-6-(1″,1″-dimethylallyl)isoflav-3-ene (trivial name, burttinol-A), 4′-hydroxy-2′-methoxy-2″,2″-dimethylpyrano[5″,6″:8,7]isoflav-3-ene (trivial name, burttinol-B), 7,4′-dihydroxy-2′-methoxy-8-(3″,3″-dimethylallyl)isoflav-3-ene (trivial name, burttinol-C), and 2-arylbenzofuran, 6,4′-dihydroxy-2′-methoxy-5-(1″,1″-dimethylallyl)-2-arylbenzofuran (trivial name, burttinol-D) were isolated. In addition, the known compounds, abyssinone V-4′-methyl ether, bidwillol A, calopocarpin, erybraedin A, erythrabyssin II, isobavachalcone, phaseollidin and phaseollin were identified. The structures were determined on the basis of spectroscopic evidence.

2001
Yenesew A., and B.F. Juma MWJOPG. "Flavones and phenylpropenoids in the surface exudate of Psiadia punctulata." Phytochemistry. 2001;57 :571-574. Abstractpaper_26_juma_et_al_phyto_2001_57_571.pdf

Three flavones, 5,7-dihydroxy-2′,3′,4′,5′-tetramethoxyflavone, 5,4′-dihydroxy-7,2′,3′,5′-tetramethoxyflavone, and 5,7,4′-trihydroxy-2′,3′,5′ -trimethoxyflavone were isolated from the leaf exudate of Psiadia punctulata, together with the previously reported 5-hydroxy-7,2′,3′,4′,5′-pentamethoxyflavone and 5,7,3′-trihydroxy-2′,4′,5′-trimethoxyflavone. The two phenylpropenoids, Z-docosyl-p-coumarate and E-docosyl-p-coumarate were also isolated. The structures were determined on the basis of spectroscopic evidence.

2000
Yenesew A., and J.O. Midiwo, M. Heydenreich SPDMG. "Two isoflavanones from stem bark of Erythrina sacleuxii." Phytochemistry. 2000; 55: 457-459. Abstractpaper_25_yenesew_et_al_phyto_2000_55_457.pdf

From the stem bark of Erythrina sacleuxii two new isoflavanones, (R)-5,7-dihydroxy-2′,4′,5′-trimethoxyisoflavanone (trivial name, (R)-2,3-dihydro-7-demethylrobustigenin) and (R)-5-hydroxy-2′,4′,5′-trimethoxy-2″,2″-dimethylpyrano[5″,6″:6,7]isoflavanone (trivial name, (R)-saclenone) were isolated. In addition the known compounds shinpterocarpin, 2,3-dehydrokievitone, abyssinone V, abyssinone V-4′-methyl ether, erythrinasinate and 4′-O-methylsigmoidin B were isolated. The structures were determined on the basis of spectroscopic evidence.

1998
Yenesew A., and J.O. Midiwo HPMMG. "Four isoflavones from stem bark of Erythrina sacleuxii." Phytochemistry . 1998;49 :247-249. Abstractpaper_24_yenesew_et_al_phyto_1998_49_247.pdf

From the stem bark of Erythrina sacleuxii four new isoflavones were isolated and characterized as 5,7-dihydroxy-2′,4′,5′-trimethoxyisoflavone (trivial name, 7-demethylrobustigenin), 5,7-dihydroxy-4′-methoxy3′-(3-methylbut-2-enyl)isoflavone [3′-(3-methylbut-2-enyl)biochanin A], 5,7,3′-trihydroxy-4′-methoxy-5′-(3-methylbut-2-enyl)isoflavone [5′-(3-methylbut-2-enyl)pratensein] and 5,7,3′-trihydroxy-4′-methoxy-5′-formylisoflavone (5′-formylpratensein). The structures were determined on the basis of spectroscopic evidence.

Yenesew A., and Waterman MJOPG. "Rotenoids, isoflavones and chalcones from the stem bark of Millettia usaramensis subspecies usaramensis.." Phytochemistry. 1998; 47: 295-300. Abstractpaper_22_yenesew_et_al_phyto_1997_47_295.pdf

From the stem bark of Millettia usaramensis subsp. usaramensis four new 12a-hydroxyrotenoids with the unusual trans B/C ring junction ((+)-12a-epimillettosin, (+)-usararotenoid-A, (+)-12-dihydrousararotenoid-A, and (+)-usararotenoid-B), a new α-hydroxydihydrochalcone (α,4,2′-trihydroxy-4′-O-geranyldihydrochalcone), a new isoflavone, (norisojamicin), and a new cinnamyl alcohol derivative (4-O-geranylcinnamyl acetate) have been isolated and characterized. In addition, the known compounds 4′-O-geranylisoliquiritigenin, isoliquiritigenin, barbigerone, jamaicin and maximaisoflavone-G were identified. The structures were determined on the basis of spectroscopic evidence and chemical transformations.

Yenesew A., and J.O. Midiwo HPMMG. "Two prenylated flavanones from stem bark of Erythrina burttii." Phytochemistry. 1998; 48 :1439-1443. Abstractpaper_23_yenesew_et_al_phyto_1998_48_1439.pdf

From the stem bark of Erythrina burttii, two new flavanones were isolated and characterised as 5,7-dihydroxy-4′-methoxy-3′,5′-di-(3-methylbut-2-enyl)flavanone (trivial name, abyssinone V-4′-methyl ether) and 5,7-dihydroxy-4′-methoxy-3′-(3-hydroxy-3-methylbut-1-enyl)-5′-(3-methylbut-2-enyl)flavanone (trivial name, burttinone). In addition, seven known compounds were identified. Structures were determined on the basis of spectroscopic evidence.

1997
1996
Yenesew A., and Waterman MJOPG. "Four isoflavones from seed pods of Millettia dura." Phytochemistry. 1996;41: 951-955. Abstractpaper_20_yenesew_et_al_phyto_1996_41_951.pdf

Seed pods of Millettia dura yielded four novel isoflavones, which have been characterized as 3-(3,4-dimethoxyphenyl)-6-methoxy-8,8-dimethyl-4H,8H-benzo[1,2-b: 3,4-b′]dipyran-4-one (trivial name, durallone), 6-demethyldurallone, 3-(3,4-dimethoxyphenyl)-8-(3-methylbut-2-enyl)-6-methoxy-7-hydroxybenzopyran-4-one (trivial name, predurallone) and 3-(4-3-methylbut-2-enyloxy)-8,8-dimethyl-4H,8H-benzo[1,2-b: 3,4-b′]dipyran-4-one (trivial name, isoerythrinin-A 4′-(3-methylbut-2-enyl) ether. Structures of these compounds were determined on the basis of their spectroscopic data.

1995
Yenesew A., van B-E. WADE. "Chemotaxonomic significance of anthraquinones in the roots of Asphodeloideae (Aspholdelaceae)." Biochemical Systematics and Ecology. 1995; 23: 277-281. Abstractpaper_18_van_wyk_et_al_biochemical_sys_eco_1995_23_277.pdf

The distribution of seven anthraquinones in the roots of some 46 species belonging to the genera Asphodelus, Asphodeline, Bulbine, Bulbinella and Kniphofia was studied by TLC and HPLC, 1,8-Dihydroxyanthraquinones based on a chrysophanol unit are the main constituents of the subterranean metabolism in the subfamily Asphodeloideae. The genera Bulbine, Bulbinella and Kniphofia elaborate knipholone-type compounds. These compounds appear to be characteristic constituents for the three genera Bulbine, Bulbinella and Kniphofia and support the idea that Kniphofia is not related to the Alooideae.

Yenesew., B-E., van Wyk DE. "Chemotaxonomic significance of root anthraquinones and pre-anthraquinones in the genus Lomatophyllum (Asphodelacae)." Biochemical Systematics and Ecology. 1995;23 :805-808. Abstractpaper_19_van_wyk_et_al_biochemical_sys_eco_1995_23_805.pdf

The roots of seven species of Lomatophyllum were analysed by TLC and HPLC for the presence of nine different anthraquinones and pre-anthraquinones which are all known to be characteristic constituents of the subterranean metabolism of Aloe. Chrysophanol and asphodelin were detected in all the samples analysed. In addition, the 1-methyl-8-hydroxyanthraquinones aloesaponarin I, aloesaponarin II and laccaic acid d-methyl ester, together with the corersponding pre-anthraquinones were detected in all seven species. The results support the inclusion of Lomatophyllum in Aloe.

Yenesew A., and B-E., van Wyk DE. "Chemotaxonomic survey of anthraquinones and pre-anthraquinones in roots of Aloe species." Biochemical Systematics and Ecology . 1995;23:267-275. Abstractpaper_17_van_wyk_et_al_biochemical_sys_eco_1995_23_267.pdf

Root samples from 172 species of Aloe were surveyed by TLC and HPLC for the presence of anthraquinones and pre-anthraquinones. With the exception of the three species of the series Serrulatae, 1,8-Dihydroxyanthraquinones (chrysophanol and asphodelin) were detected in all the species sampled. Compounds derived through the 1-methyl-8-hydroxyanthraquinone pathway, i.e. aloesaponarin I, aloesaponarin II and laccaic acid d-methyl ester, together with their corresponding pre-anthraquinones were detected in 129 species. The results also show that isoeleutherol is a useful chemotaxonomic character for the series Saponarieae.

1994
Yenesew A., Dagne E. "Anthraquinones and the chemotaxonomy of the Asphodelaceae." Pure & Appl. Chem. . 1994;66: 2395-2398. Abstractpaper_16_dagne_et_al_pure__appl_chem-1994.pdf

Phytochemical investigations on three genera of the Asphodelaceae, Aloe, KniphoJla and Bulbine showed that 1-methyl-8-hydroxyanthraquinones and anthrone-C-glycosides are characteristic constituents of the genus Aloe, while knipholone-type compounds distinguish fiiphoja and Bulbine.

Yenesew A., and E. Dagne, S. Asmellash DMSS. "Anthraquinones, pre-anthraquinones and Isoeleutherol in the roots of Aloe species." Phytochemistry . 1994;35:401-406. Abstractpaper_14_dagne_et_al_phyto_1994_35_401.pdf

Comparative TLC analysis of the root extracts of 32 Aloe species showed that chrysophanol, asphodelin, chrysophanol-8-methyl ether, aloechrysone, helminthosporin, aloesaponol III, aloesaponarin I, aloesaponol I, aloesaponarin II, aloesaponol II and laccaic acid D-methyl ester are widely distributed in these plants. Isoeleutherol, which is reported here for the first time as a natural product, occurs only in the Saponariae series of Aloe. The chemotaxonomic implication of the distribution of these compounds for the genus Aloe is discussed.

Yenesew A., and E. Dagne MSMW. "An anthrone, anthraquinone and two oxanthrones from Kniphofia foliosa." Phytochemistry . 1994;37:525-528. Abstractpaper_15_yenesew_et_al_phyto_1994_37_525.pdf

The compounds isoknipholone, isoknipholone anthrone, foliosone and isofoliosone were isolated from the stem of Kniphofia foliosa and their structures determined by spectral analyses. In addition, the known compounds, aloesaponol Ill, aloesaponol III-8-methyl ether and 4,6-dihydroxy-2-methoxyacetophenone were isolated and identified.

1993
Yenesew A., and Duddeck OJAH. "(R)-Prechrysophanol from Aloe graminicola." Phytochemistry . 1993;34 :1442-1444. Abstractpaper_13_yenesew_et_al_phyto_1993.pdf

From the subterranean stem of Aloe graminicola, a new pre-anthraquinone named prechrysophanol was isolated. Chrysophanol, helminthosporin, (R)-aloesaponol I, (R)-aloesaponol II, aloesaponarin I, aloesaponarin II and laccaic acid D methyl ester were also identified.

Yenesew A., Dagne E. "Knipholone anthrone from Kniphofia foliosa." Phytochemistry . 1993;34 :1440-1441. Abstractpaper_14_dagne_et_al_phyto_1994_35_401.pdf

A new anthrone named knipholone anthrone was isolated from the stem of Kniphofia foliosa. Its structure was determined by spectral analysis as well as conversion to knipholone.

1990
Yenesew A., and E. Dagne, F. Capasso MPNA. "Preliminary Studies on Antipyretic and Analgesic Properties of Taverniera abyssinica." Ethiopian Medical Journal . 1990;28 :155-161. Abstractpaper_11_yenesew_et_al_ethiop._med._1990_taverniera_abyssinca.pdf

In an attempt to ascertain the pharmacological basis of the use of the marketed traditional drug Taverniera abyssinica A. Rich. (Amharic name Dingetegna), crude extracts as well as purified substances of this plant were tested for their antipyretic and analgesic properties. Antipyretic activity was determined on rats made hyperthermic by yeast injection and analgesic activity was determined by the hot plate, as well as the acetic acid induced writhing, methods. The study showed that the plant possesses significant antipyretic and analgesic activities.

Yenesew A., Atta-Ur-Raman, M. Alam NDHE. "Three Steroidal Alkaloids from Buxus hildebrandtii." Phytochemistry . 1990;29 :1293-1296. Abstractpaper_9_atta-ur-raman_phyto_1990.pdf

From the leaves of Buxus hildebrandtii three new steroidal alkaloids have been isolated and their structures determined by spectroscopic analysis. The following derived names have been suggested for these new alkaloids: O(30)-benzoyl-16-deoxybuxidienine-C, 30-hydroxybuxamine-A and 30-norbuxamine-A. In addition the known alkaloids cyclomicrobuxamine, buxamine-A, cyclobuxoviridine, moenjodaramine, buxamine-C and cyclorolfeine were also isolated.

1989
Yenesew A., E. Dagne WPG. "Flavonoids and isoflavonoids from Tephrosia fulvinervis and Tephrosia pentaphylla." Phytochemistry. 1989;28 :3207-3210. Abstractpaper_8_dagne_et_al_phyto_1989.pdf

From the roots, leaves and pods of Tephrosia pentaphylla three new 6-oxygenated rotenoids (dihydrostemonal, 9-demethyldihydrostemonal and 6-acetoxydihydrostemonal) were isolated and characterized. In addition six known rotenoids (villosin, sumatrol, rotenone, cis-12a-hydroxyrotenone, 6-hydroxyrotenone and α-toxicarol) and the flavanone obovatin were obtained. A similar analysis of the roots of T. fulvinervis yielded only known rotenoids (α-toxicarol, deguelin, munduserone, cis-12a-hydroxymunduserone) and the common pterocarpan (-)-maackiain.

Yenesew A., and Waterman DEPG. "Flavonoids from the seed pods of Tephrosia pumila." Phytochemistry . 1989;28:1291-1292. Abstractpaper_7_yenesew_et_al_phyto_1989.pdf

Inaddition to the known pumilaisoflavones A and B two further isoflavonoids have been isolated from the seed pods of Tephrosia pumila collected in Ethiopia. These have been characterized, on the basis of spectral analysis, as pumilaisoflavone C (5,7,4′-trihydroxy-3′,5′-dimethoxy-6,2′-di(3,3-dimethylallyl)isoflavone) and pumilaisoflavone D (5,4′-dihydroxy-3′,5′-dimethoxy-2″,2″-dimethylpyrano[5″,6″: 6,7]isoflavone).

1988
Yenesew A., Dagne E. "Alkaloids of Teclea nobilis." Phytochemistry . 1988;27: 651-653. Abstractpaper_3_yenesew_et_al_phyto_1988.pdf

A new furoquinoline alkaloid to which we have assigned the trivial name nobiline, and seven other quinonline alkaloids were isolated and identified from the leaves and fruits of Teclea nobilis, an African medicinal plant.

Yenesew A., and N. Mascolo, A. Pinto DE. "Antipyretic and analgesic studies of the ethanolic extract of Teclea nobilis Delile." Phytotherapy Research. 1988; 2:154-156. Abstractpaper_6_mascolo_et_al_phytotherapy_1988.pdf

The crude ethanol extract of the leaves of an African medicinal plant Teclea nobilis has been studied for its antipyretic, analgesic and anti-inflammatory activities. The extract exhibited marked antipyretic and analgesic activities while it was found to be weakly active against carrageenin oedema.

Yenesew A., and E. Dagne WAIGPG. "The Chemical Systematics of the Rutaceae, Subfamily Toddalioideae in Africa." Biochemical Systematics and Ecology . 1988;16:179-188. Abstractpaper_4_dagne_et_al__biochemical_sys_eco..1988.pdf

A recent investigation of five Ethiopian species of the Rutaceae subfamily Toddalioideae, Teclea nobilis, T. simplicifolia, T. borenensis, Vepris dainellii and V. glomerata has led to the identification of alkaloids of the 2-quinolone, dihydrofuroquinoline, linear pyranoquinoline, furoquinoline and acridone types. The distribution of alkaloids and limonoids among African genera of the Toddalioideae is discussed in relation to their potential importance for an understanding of the systematics of this group of species.

Yenesew A., and Dagne WAE. "A comparative study of Anthraquinones in rhizomes of some Kniphofia species." Biochemical Systematics and Ecology. 1988; 16 :157-159. Abstractpaper_5_yenesew_et_al_biochemical_sys_eco_1988_16_157.pdf

The anthraquinone content of eight kniphofia species was compared using reversed phase HPLC method coupled with a photodiode array detector.

1987
Yenesew A., and Dagne DHE. "Isoflavonoids from Taverniera abyssinica." Bulletin of the Chemical Society of Ethiopia. 1987;1: 36-41.paper_2_yenesew_et_al_bull._1987_isoflavonoids_from_taverniera_abyssinica.pdf
1985

UoN Websites Search