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 A₂ ( 4 ), litsenolide B₂ ( 5 ), litsenolide C₁ ( 6 ), litsenolide C₂ ( 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 β‐sitosterol ( 18 ) and stigmasterol ( 19 ), and a mixture of β‐sitosteryl‐3‐O‐β‐D ‐glucoside ( 20 ) and stigmasteryl‐3‐O‐β‐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 δ‐lactone structure, which was then revised to a γ‐lactone structure, based on 1D‐NMR data. The cigar‐HMBC technique was used to confirm the accuracy of the γ‐lactone structure, and the zero α] 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 H₃₇Rv, with MIC values of 15–50 μg/ml.