Antioxidant Activities of Flavonoid Aglycones from Kenyan Gardenia ternifolia Schum and Thonn

Citation:
Awas E, Omosa LK, Midiwo JO, Ndakala A, Mwaniki J. "Antioxidant Activities of Flavonoid Aglycones from Kenyan Gardenia ternifolia Schum and Thonn." IOSR Journal of Pharmacy and Biological Sciences (IOSR-JPBS). 2016;11(3):136-141.

Abstract:

Phytochemical investigation of surface exudates of the leaves of Gardenia ternifolia resulted to
characterization of four flavonoids; 3,5,3′-trihydroxy-7,4′-dimethoxyflavone (1), 5,7-trihydroxy-4′-
methoxyflavone (2), 5,7-dihydroxy-3,4′-dimethoxyflavone (3), 5,4′-dihydroxy-7-methoxyflavanone (4) and two
tritepenoids; β-sitosterol (6) and stigmasterol (7). Compound 1 exhibited the highest antioxidant activity with
IC50 = 40.3± 1.55 μΜ. The rest of the flavonoids showed minimal activities with IC50 values of 75.5±1.75,
89±0.22, 94±0.11 μΜ for 2-4, respectively. The antioxidant activities of 1 was substantially lower than the
standard, quercetin (IC50 = 20.1±1.34 M). Methoxylation of quercetin at 7 and 4′-position in 1 substantially
reduced antioxidant potential. Lack of oxygenation at 3′ position, as observed for kaempferol derivatives was
responsible for further reduction in the radical scavenging potential as observed for 2 and 3. Furthermore,
methylation of 3-OH position in kaempferol derivatives further reduced the antioxidant activities as exhibited by
3 with an oxygenation pattern similar to 2 except for the methylation at 3-position. The results of this study are
consistent with previous findings that revealed that flavonols, exhibited better anti-oxidant activities as
compared to 3-methoxyflavones. Acetylation of 3 at the 5 and 7 positions resulting to 3,4′dimethoxy-5,7-
diacetylflavone (5), substantially reduced the activity of this compound. The triterpenoids exhibited were
inactive as expected.
Keywords: Antioxidant activities, Gardenia ternifolia, surface exudates

UoN Websites Search