Publications


In Press

2014

Omosa, LK, Amugune B, Ndunda B, Milugo TK, Heydenreich M, Yenesew A, Midiwo JO.  2014.  Antimicrobial flavonoids and diterpenoids from Dodonaea angustifolia. South African Journal of Botany. Abstract

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.

2013

Machumi, F, Midiwo JO, Jacob MR, Khan SI, Tekwani BL, Walker LA, Muhammad I.  2013.  Phytochemical, Antiparasitic and Antimicrobial Investigations of Terminalia brownii. AbstractPhytochemical, Antiparasitic and Antimicrobial Investigations of Terminalia brownii

Terminalia brownii is an African medicinal plant used to treat parasitic and microbial infections [1]. Chromatographic separations on the stem bark extract aimed at identifying the active components led to isolation of a new oleanane-type triterpenoid, along with seven known oleanane-type triterpenoids and seven ellagic acid derivatives. The new compound was identified using spectroscopic methods as 3β,24-O-ethylidenyl-2α,19α-dihydroxyolean-12-en-28-oic acid (1). The compounds were evaluated for their antiplasmodial, antileishmanial and antimicrobial activities giving the most potent antiplasmodial activity with IC50 values of 2.76 µg/mL for 23-galloylarjunolic acid (2) against P. falciparum W2 strain and the most potent antimicrobial activity with IC50 values of 0.32 µg/mL for diellagic lactone (3) against C. glabrata.

2012

Machumi, F, Yenesew A, Midiwo JO, Heydenreich M, Kleinpeter E, Khan S, Tekwani BL, Walker LA, Muhammad I.  2012.  Antiparasitic and anticancer carvotacetone derivatives from Sphaeranthus bullatus. Website

2011

Waters, NC, Midiwo JO, Yenesewa A, Akala HM, Kiremire BT, Derese S, Evase FL.  2011.  Antiplasmodial and Radical Scavenging Activities of flavonoids from Kenyan Erythrina species. antiplasmodial_and_radical_...0001.pdfWebsite
Midiwo, JO, Yenesew A, Aluoch A 0, Avoo JA.  2011.  Alkaloids and lignans from zanthoxylum usambarense and zanthoxylum chalybeum. Website

2010

Midiwo, JO, Yenesew A, Juma BF, Omosa KL, Omosa IL, Mutisya D.  2010.  Phytochemical Evaluation of So me Kenyan Medicinal Plants. AbstractPhytochemical Evaluation of So me Kenyan Medicinal Plants

11 th NAPRECA Symposium Book of Proceedings, Antananarivo, Madagascar Pages 9-19 Midiwo et al. 9 Phytochemical Evaluation of So me Kenyan Medicinal Plants J. Ogweno Midiwo, A. Yenesew, B.F. Juma Kerubo L Omosa, Irene L Omosa, Daniel Mutisya. Department of Chemistry, University of Nairobi, P.o. Box 30197, Nairobi. Kenya. E-mail: jmidiwo@uonbi.ac.ke Abstract There are more than 1200 described medicinal pl ants in Kenya from a flora of approximately 10,000 members. Strong cross-medical informati on from the 42 ethnic groups points to the high potential of some of these species. The Myrsinaceae are well established ethno-anthel mintics and anti-bacterials. They are harbingers of long alkyl side chain benzoquinones which clearly have a protective function from their histochemical disposition. The main benzoqui none 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 le ngth or the presence / absence of 6-methyl group is in accord with morphological sub-fam ily de-limitation. The benzoquinones showed anti- feedant, anti-microbial, phytotoxic, acaricidal, in secticidal and nematicidal activity. Many other benzoquinones of medium and mi nor 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 deriva tive, nepodin was more selectively distributed. The leaf of Polygonum senegalense is upto 17% surface exudate; about thirteen non polar flavonoid derivatives (chalcones, di hydrochalcones, 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 a nd their glycosides. The only unique compound isolated from this plant was 2'-glucosy l-6'-hydroxy-4'-methoxychalcone whose aglycone, uvangolatin is part of the exuda te mixture. Other leaf exuda te plants studied included the stomach-ache medicine, Psiadia punctulata (Compositae) from which novel methylated flavonoids, kaurene and trachyloba n diterpenes have been found.

Dr. Derese, S, Omosa LK, Midiwo JO, Yenesew A, Peter MG, Heydenreich. M.  2010.  neo-Clerodane diterpenoids from the leaf exudate of Dodonaea angustifolia. Abstractneo-Clerodane diterpenoids from the leaf exudate of Dodonaea angustifolia

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

Martin, PG, Yenesew A, Heydenreich M, Guchu SM, lrungu B, Derese S, Midiwo JO.  2009.  Flavonoids and isoflavonoids of Erythrina burttii. isoflavanoes_...0001.pdfWebsite

2008

Clough, JM, Midiwo JO.  2008.  Aspects of African Biodiversity.

2007

2006

Andayi, AW, Yenesew A, Derese S, Midiwo JO, Gitu PM, Jondiko OJI, Akala H, Liyala P.  2006.  Antiplasmodial Flavonoids from Erythrina sacleuxii. Website

2005

ABIY, PROFYENESEW, O PROFMIDIWOJACOB.  2005.  Antimicrobial flavonoids from the stem bark of Erythrina burttii. Fitotherapia, 469-472. Abstract
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2004

2003

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