Flavonoids from the fruits of Phyllanthus acidus (L.) Skeels with anti-α-glucosidase activity

Eleven flavonoids including one new flavonol glycoside, quercetin-3-O-(2-α-L-rhamnopyranosyl)-β-D-glucuronopyranosyl methyl ester (1), were isolated for the first time from the fruits of Phyllanthus acidus (L.) Skeels (Phyllanthaceae). Their structures were determined by extensive spectroscopic data. The known flavonoids, quercetin-3-O-β-D-glucuronide methyl ester (3), quercetin-3-O-(2''-α-L-rhamnopyranosyl-6''-O-α-L-rhamno pyranosyl)-β-D-glucopyranoside (5), myricetin (9), and 6-methoxy-naringenin (11) were isolated for the first time from the genus Phyllanthus. Flavonoids 4, 6 and 9 (IC50 = 6.01, 6.32, and 7.84 μM, respectively) showed stronger α-glucosidase inhibitory activities than the positive control, acarbose (IC50 = 306.45 μM). The fruits of P. acidus might be further developed as an anti-diabetic food supplement.