| Abstract: | Bioassay-guided fractionation of the root of Machilus obovatifolia led to the isolation of four new lignans, epihenricine B (1), threo-(7'R,8'R) and threo-(7'S,8'S)-methylmachilusol D (2 and 3), and isofragransol A (4), along with 23 known compounds. The compounds were obtained as isomeric mixtures (i.e., 2/3 and 4/20, resp.). The structures were elucidated by spectral analyses. Among the isolates, 1, licarin A (12), guaiacin (14), (+/-)-syringaresinol (21), and (-)-epicatechin (23) showed ABTS (=2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) cation radical-scavenging activity, with SC50 values of 11.7+/-0.5, 12.3+/-1.1, 11.0+/-0.1, 10.6+/-0.3, and 9.5+/-0.2 muM in 20 min, respectively. In addition, kachirachirol B (17) showed cytotoxicity against the NCI-H460 cell line with an IC50 value of 3.1 mug/ml. |
