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 (IC
50) 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 IC
50 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.
