New antioxidant phenylethanol glycosides fromTorenia concolor

Two new phenylethanol glycosides, phenylethyl-O-alpha-l-rhamnopyranosyl-(1 --> 2)-beta-D-glucopyranoside (torenoside A, 1) and 2'-O-3,4-dihydroxy-beta-phenylethoxy-O-alpha-L-rhamnopyranosyl-(1'' --> 3')-(4'-O-caffeoyl)-beta-D-glucopyranoside (torenoside B, 2), along with the 17 known compounds (3-19) were isolated from Torenia concolor. Those structures were established on the basis of spectroscopic analysis including NMR spectroscopic techniques (13C, 1H, 1H-1H COSY, HMQC, HMBC, TOCSY, and NOESY). Moreover, phenylethanol glycosides 3-6 exhibited significant antioxidant activities in DPPH radical scavenging assay.