Antimycobacterial butanolides from the root of Lindera akoensis

Three racemic butanolides, majorenolide (1), majorynolide (2), and majoranolide (3), with 18 known compounds, including ten butanolides, i.e., litsenolide A(2) (4), litsenolide B(2) (5), litsenolide C(1) (6), litsenolide C(2) (7), hamabiwalactone A (8), hamabiwalactone B (9), litseakolide A (10), litseakolide B (11), isoobtusilactone (12), and obtusilactone (13); one lignan, i.e., (+/-)-syringaresinol (14), two flavans, i.e., (+)-catechin (15), and (-)-epicatechin (16), one coumarin, i.e., scopoletin (17), and four steroids, i.e., a mixture of beta-sitosterol (18) and stigmasterol (19), and a mixture of beta-sitosteryl-3-O-beta-D-glucoside (20) and stigmasteryl-3-O-beta-D-glucoside (21) were isolated from the root of Lindera akoensis. The structures of the isolates were elucidated by in-depth spectroscopic analysis. Compounds 1-3 were previously assigned a delta-lactone structure, which was then revised to a gamma-lactone structure, based on 1D-NMR data. The cigar-HMBC technique was used to confirm the accuracy of the gamma-lactone structure, and the zero [alpha] (20)_D value of compounds 1-3 suggested that they were considerably racemized. Nine butanolides 1-3, 4-8, and 10 showed antimycobacterial activities against M. tuberculosis H(37)Rv, with MIC values of 15-50 microg/ml.