A new bibenzyl and a new methylflavan from the tubers of Bletilla striata

A new bibenzyl, (+)-(1S)-4ʹ,5ʺ-dihydroxy-1,3ʹ,5ʹ,3ʺ-tetramethoxybibenzyl (1), and a new methylflavan, (2S)-7,4′-dihydroxy-5-methoxy-8-methylflavan (2), together with 10 known compounds were isolated from the methanolic extract of the tubers of Bletilla striata. Their chemical structures were elucidated based on spectrometric data interpretation, especially 1D and 2D NMR, HRESIMS, and electronic circular dichroism (ECD) data. All isolates (1 - 12) were evaluated for their inhibitory properties on nitric oxide production induced in RAW 264.7 cells, and dihydrophenantrenes 4 and 6 exhibited the best inhibitory effects with IC50 values of 29.5, and 6.5 μM, respectively. Additionally, significant activity possessed phenantrene 5 and methylflavane 2 with IC50 values of 38.9, and 44.9 μM, respectively.