Chemical constituents from the stems of Dendrobium gratiosissimum and their biological activities

Abstract

Eight C6–C3-based bibenzyl derivatives (dengraphenols A–G, K), three mono-bibenzyls (dengraphenols I, L–M), one bis-bibenzyl (dengraphenol H), one oxyneolignane (dengraphenol J), one phenanthrene (dengraphenol N), and one picrotoxane-type sesquiterpene (dengrasusane A) were isolated from the stems of Dendrobium gratiosissimum. The resolution of dengraphenols A–J by chiral HPLC afforded ten pairs of enantiomers [(±)-dengraphenols A–J]. Their structures with absolute configurations were elucidated on the basis of comprehensive spectroscopic analyses, computational calculation methods and single-crystal X-ray diffraction, among which twenty-four [(±)-dengraphenols A–E, (+)-dengraphenol F, (±)-dengraphenols G–J, dengraphenols K–N, dengrasusane A] were undescribed. Ten compounds [(±)-dengraphenol B, (±)-dengraphenols D–E, (±)-dengraphenol H, (−)-dengraphenol I and dengraphenol N)] showed potent cytotoxicity against eight human cancer cell lines (A431, A2780, H460, HCT8, BGC823, SW1990, Daoy, and HGC27) with IC50 values of 3.77–9.75 μM. At a concentration of 10 μM, (−)-dengraphenol C, (±)-dengraphenol F, and (±)-dengraphenol K exhibited remarkable hepatoprotective activity against APAP-induced toxicity with a cell survival rate of 65.8%, 70.6% and 73.5%, respectively; dengraphenol N displayed significant anti-inflammatory effects; and dengraphenol K showed strong inhibitory activity against α-glucosidase with IC50 values of 5.71 μM. These results would provide potential compounds for drug discovery.