Nine feruloyltyramine derivatives and one pyrrole with hepatoprotective activity isolated from fresh Portulaca oleracea L.

Nine feruloyltyramine derivatives (1, 2, 4-10) and one pyrrole (3) were isolated from 70% EtOH extract of fresh Portulaca oleracea L.. Among them, compounds 1, 2 and 4 were cyclized feruloyltyramine derivatives, the other feruloyltyramine derivatives (5-10) were non-cyclized. Compounds 1 and 2 were racemic mixtures, and were separated into enantiomers 1-a (R), 1-b (S), 2-a (R) and 2-b (S), respectively. Three compounds (1-3) were new, and their structures were elucidated by UV, IR, HRESIMS, 1D and 2D NMR, and ECD spectra, as well as optical rotations. All the compounds (1-10) were tested for their hepatoprotective activity in vitro. At a concentration of 10 μM, three cyclized feruloyltyramine derivatives (1-a, 2-a and 4) possessed significant hepatoprotective activity against the damage induced by N-acetyl-para-aminophenol (APAP) in human HepG2 liver cancer cells, with cell survival rates of 63.61, 65.44 and 65.52%. It was suggested that the cyclized feruloyltyramine derivatives with R configuration had better hepatoprotective activity than that of S configuration and non-cyclized feruloyltyramine derivatives.