Stilbenes with anti-inflammatory and cytotoxic activity from the rhizomes of Bletilla ochracea Schltr.

Four new dihydrophenanthrenofuran, bleochranols A-D (1-4), along with 21 known compounds including phenanthrenes (5-14) and bibenzyls (15-25) were isolated and elucidated from the rhizomes of Bletilla ochracea. Combination of 1D/2D NMR techniques and the Electronic Circular Dichroism (ECD) spectroscopy based on the empirical helicity rules, chemical structure of those isolates were determined. All the compounds were evaluated for cytotoxicity against HL-60, SMMC-7721, A-549, MCF-7 and SW480 human cancer cell lines by MTS assay and anti-inflammatory activity by nitric oxide (NO) production in LPS-stimulated RAW 264.7 macrophages. Among the 25 tested compounds, bleochranol A (1) showed remarkable cytotoxic activity against HL-60, A-549, and MCF-7 with IC50 values of 0.24 ± 0.03, 3.51 ± 0.09 and 3.30 ± 0.99 μM respectively. The anti-inflammatory assay showed that compound 12 exhibited most potential activity against NO production in RAW 264.7 macrophages with IC50 2.86 ± 0.17 μM. The results indicated that the main chemical constituents of B. ochracea were phenanthrene and bibenzyl and similar to that of B. striata.