Aromatic compounds from the liverwort Conocephalum japonicum.

Two undescribed dimeric ArC2 derivatives, cis- and trans-1,2-bis(3,4-dimethoxyphenyl)cyclobutane (1 and 2), one new monoterpenes esters, 2alpha,5beta-dihydroxybornane-2-cis-cinnamate (3), along with eight known compounds, 2alpha,5beta-dihydroxybornane-2-trans-cinnamate (4), perrottetin E (5), isoriccardin C (6), marchantin A (7), marchantin E (8), marchantin C (9), and isomarchantin C (10) were isolated from the liverwort Conocephalum japonicum. All the structures were established by extensive spectroscopic analysis. The isolated compounds 3-10 were evaluated for their cytotoxicity against the human KB cell line with IC50 values ranging from 16.5 to 50.2 microM.