In this study, three new compounds, roxburic acid A (1) and two flavone glycosides isorhamnetin-3-O-α-L-rhamnosyl-(1→6)-β-D-glucopyranose-(1→3)-β-D-glucopyranoside (2), and kaempferol-7-O-β-D-glucopyranosyl-(1→3)-β-D-glucopyranoside (3) were isolated from an ethanol extract of the fresh Anoectochilus roxburghii (Wall.) Lindl., together with 10 known compounds (4-13). The structures of these compounds were comprehensively characterized by HR-ESI-MS, 1H NMR, 13C NMR, and 2 D-NMR. The DPPH free radical scavenging activity of the isolated compounds was evaluated, and the results showed that kaempferol-7-O-β-D-glucopyranosyl- (1→3) -β-D-glucopyranoside (3) and rutin (11) has the potential antioxidant activity with IC50 values of 139 μg/mL and 22.5 μg/mL respectively.
Keywords: Anoectochilus roxburghii (Wall.) Lindl.; Orchidaceae; antioxidant activity; flavone glycosides.