Phenanthrenes from Dendrobium nobile and their inhibition of the LPS-induced production of nitric oxide in macrophage RAW 264.7 cells

A new phenanthrene, 3,4,8-trimethoxyphenanthrene-2,5-diol (1), along with nine known phenanthrenes and three known bibenzyls was isolated from Dendrobium nobile. All of the isolates were evaluated for their potential to inhibit the LPS-induced NO production in murine macrophage RAW 264.7 cells. Bioactivity-guided isolation of the methanol extract of the stems of Dendrobium nobile yielded a new phenanthrene together with nine known phenanthrenes and three known bibenzyls. Their structures were elucidated by analysis of the spectroscopic data including 2D-NMR. All of the isolates were evaluated for their potential to inhibit the LPS-induced production of nitric oxide in murine macrophage RAW 264.7 cells. Compounds 1–4, 7–13 inhibited nitric oxide production with the IC50 values ranging from 9.6μM to 35.7μM.