Biological Evaluation of Secondary Metabolites from the Root of Machilus obovatifolia

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 SC 50 values of 11.7±0.5, 12.3±1.1, 11.0±0.1, 10.6±0.3, and 9.5±0.2 μ M in 20 min, respectively. In addition, kachirachirol B ( 17 ) showed cytotoxicity against the NCI‐H460 cell line with an IC 50 value of 3.1 μg/ml.