Antioxidant phenolic compounds from Alchornea floribunda leaves
Alchornea floribunda leaves have been previously shown to posses potent anti-inflammatory compounds1 – 3. Further chemical investigation of a flavonoid sub-fraction of the methanol leaf extract of Alchornea floribunda led to the isolation of three flavans (-) catechin (+) catechin (-) epicatechin and a flavanone (2R, 3R) dihydroquercitin. The structures of these compounds were elucidated by 1 D and 2 D NMR spectroscopy and Liquid Chromatography- Electrospray Ionization Mass Spectrometry (LC-ESIMS). All the isolated compounds were assessed for their anti-oxidant potential in vitro using DPPH free radical scavenging and Ferric reducing ability4. In the DPPH model, (-) epicatechin, (+) epicatechin and (2R, 3R) dihydroquercitin showed high free radical scavenging activity with IC50 values of 19, 40 and 46 µg/mL respectively with the activity of (-) epicathechin comparable to that of the standard, chlorogenic acid (IC50 = 22 µg/mL). (-) catechin showed only mild activity with IC50 value of 88 µg/mL. In the Ferric reducing test, (-) catechin, (-) epicatechin and (+) epicatechin exhibited IC50 values of 46, 68 and 88 22 µg/mL respectively with the activity of (-) epicathechin higher than that of the standar, ascobic acid (IC50 = 66 µg/mL). (2R, 3R) dihydroquercitin showed poor Ferric reducing activity (IC50 > 100 µg/mL). The observed antioxidant activities of the isolated flavans may explain the efficacy of the extract of Alchornea floribunda leaves in the ethnomedicinal management of diseases associated with oxidative stress.
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