Abstract
Two new phenylethanol glycosides, phenylethyl-O-α-l-rhamnopyranosyl-(1 → 2)-β-d-glucopyranoside (torenoside A, 1) and 2′-O-3,4-dihydroxy-β-phenylethoxy-O-α-l-rhamnopyranosyl-(1″ → 3′)-(4′-O-caffeoyl)-β-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.
Acknowledgements
The authors are thankful to Drs Yao-Haur Kuo and Hui-Chi Huang for the bioassay test in the National Research Institute of Chinese Medicine, Taipei, Taiwan.