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

Abstract

• A new bibenzyl ( 1 ) and a new methylflavan ( 2 ) were isolated from Bletilla striata . • The absolute configuration of 1 and 2 were confirmed by ECD data. • Phenanthrenes 4 - 6 exhibited inhibitory effects on LPS-induced NO production. A new bibenzyl, (+)-(1 S )-4ʹ,5ʺ-dihydroxy-1,3ʹ,5ʹ,3ʺ-tetramethoxybibenzyl ( 1 ), and a new methylflavan, (2 S )-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 IC 50 values of 29.5, and 6.5 μM, respectively. Additionally, significant activity possessed phenantrene 5 and methylflavane 2 with IC 50 values of 38.9, and 44.9 μM, respectively.