Dengratiols E-G, three bioactive pairs of enantiomeric bibenzyl dimers from Dendrobium gratiosissimum

Abstract

Three pairs of enantiomeric bibenzyl dimers, (±)-dengratiols E-G [(±)-1–3], were obtained through various chromatographic techniques including chiral HPLC, from the ethanol extract of Dendrobium gratiosissimum. Their structures were elucidated to be R-(+)-1 and S-(−)-1, R-(+)-2 and S-(−)-2, and αR, α'R-(−)-3 and αS, α'S-(+)-3 on the basis of the extensive spectroscopic data and ECD analyses, respectively. The isolated enantiomerically pure along with their racemic forms showed moderate cytotoxicity against human HCT116, U87-MG, HepG2, BGC823, and PC9 cancer cell lines (IC50 9.25–48.01 μM). Enantiomers (+)-1 and (−)-1, and their racemate (±)-1 showed antiviral effects against HIV-1 with IC50 values of 12.26, 6.01, and 4.47 μM, respectively. Enantiomers (+)-2, and (−)-2 and their racemic form showed significant protein tyrosine phosphatase 1B (PTP1B) inhibitory activity with IC50 values of 5.07, 3.11, and 4.37 μM, respectively.