Antioxidant and Anti-proliferative Activities of Flavonoids from Bidens pilosa L var radiata Sch Bip
Purpose: To investigate the chemical composition of Bidens pilosa L. var. radiata. Sch Bip. (BP), as well as its antioxidant and anti-proliferative activities.
Methods: The whole herb of BP was extracted with 95 % ethanol, which was then partitioned sequentially with petroleum ether, ethyl acetate and n-butyl alcohol to obtain petroleum ether, ethyl acetate (EE-BP), n-BuOH and water fractions. EE-BP was further isolated and purified by repeated column chromatography. The obtained compounds were identified by comparing 1H and 13C nuclear magnetic resonance (NMR) spectra with published data for the compounds. Flavonoids were evaluated for 1,1-diphenyl-2-picrylhydrazy (DPPH) and 2, 2 -azino-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) free radical scavenging activity by colorimetric methods, while their anti-proliferative effect against human colon cancer RKO cells was determined by 3-(4,5) dimethylthiahiazo (-z-y1)-3,5-diphenytetrazoliumromide (MTT) method.
Results: A total of 6 compounds were isolated from BP, including flavonoids or flavonoid glycosides, among which were isoquercitrin (1), vitexin (2), astragalin (3), 5,6,7,4'-tetramethoxylflavone (4), 5,3',4'- trihydroxy-3,7-dimethoxylflavone (5) and quercetin (6). The results indicate that compound 6 was the most effective in both DPPH and ABTS free radical-scavenging assays, with half maximal inhibitory concentration (IC50) of 10.7 μmol/L and 17.5 μmol/L, respectively. Both compounds 4 and 5 exhibited significant growth inhibitory effect on RKO cells with IC50 of 39.08 μmol/L and 17.68 μmol/L, respectively (p < 0.01).
Conclusion: BP contains a series of flavonoid compounds, possessing significant antioxidant activity and antiproliferative effect in RKO cells, thus suggesting that it is a potential health supplement and an easily available resource of natural antioxidants for use in colon cancer prevention.
Keywords: Bidens pilosa, Flavonoid, Antioxidant, Anti-proliferation, Colon cancer