Chemical constituents of Erythrina speciosa

Three unreported pterocarpans, erystrictin D (1) and a pair of diastereoisomers, erystrictins E/F (2a/2b), along with fifteen known compounds (3-17) were isolated from Erythrina speciosa. Their structures were established by extensive spectroscopic analyses, including HRESIMS, 1D and 2D NMR, and electronic circular dichroism (ECD) spectra. All the compounds were isolated from this plant for the first time. Compounds 1-3, 5 and 6 were evaluated for their inhibitory activities against a panel of cancer cell lines by MTS method. Compound 1 showed inhibitory activities against HepG2 and SW480 cells, with IC50 values of 3.160 ± 0.069 and 6.575 ± 0.525 μM, respectively; compound 5 against HepG2 cells, with IC50 value of 22.05 ± 0.83 μM.