Inhibitory activities on nitric oxide production of stilbenoids from Pholidota yunnanensis.

Three new stilbenoids, 1-(4′-hydroxybenzyl)-imbricatin (1), (E)-4′-hydroxy-2′,3,3′,5-tetramethoxystilbene (2), and (E)-3,4′-dihydroxy-2,6-bis(4-hydroxybenzyl)-2′,3′,5-trimethoxystilbene (3), together with 15 known stilbene derivatives, were isolated from Pholidota yunnanensis. Their structures were elucidated by spectroscopic methods and by comparison of their NMR data with those of related compounds. Furthermore, the inhibitory activities on nitric oxide (NO) production of the isolated compounds were examined in murine macrophages (RAW 264.7) activated by lipopolysaccharide. The cytotoxicity of 18 compounds was determined by the 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay. Among the tested compounds, eight stilbenoids, including three dihydrophenanthrenes, three stilbenes, and one bibenzyl derivative showed inhibitory effects on NO production without cytotoxicity with IC₅₀ values ranging from 4.07 to 7.77 μM, as compared to MG-132, which was used as a positive control (IC₅₀ of 0.10 μM). One dihydrophenanthrene, phoyunnanin C (5), showed cytotoxic effects at the test concentrations. [ABSTRACT FROM AUTHOR]