Antioxidative Constituents from the Whole Plant of Actinostemma lobatum Maxim
2010
Kim, D.K., Woosuk University, Jeonju, Republic of Korea
As part of an ongoing search for natural plants with antioxidant compounds by measuring the radical-scavenging effect on DPPH (1,1-diphenyl- 2-picrylhydrazyl), a total extract of the whole plant of Actinostemma lobatum (Cucurbitaceae) was found to show potent antioxidant activity. Subsequent activity-guided fractionation of the methanolic extract led to the isolation of eight compounds: actinostemmoside C (1), kaempferol-3-O-α-L-rhamnopyranosyl (1→6)-β-D-glucopyranoside (2), quercetin-3-O-β-L-rhamnopyranosyl (1→6)-β-D-glucopyranoside (3), quercetin-3-O-β-D-glucopyranoside (4), kaempferol (5), quercetin (6), lobatoside C (7), and lobatoside B (8). Their structures were elucidated using spectroscopic studies. Compounds 2, 4, 5, and 6 were isolated for the first time from this plant. Compounds 2-4 and 6 showed significant antioxidative effects during the DPPH-free radical-scavenging test and the superoxide quenching activity test.
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