Pro-oxidative and pro-apoptotic action of defatted seeds of Oenothera paradoxa on human skin melanoma cells.

Three extracts of defatted seeds of Oenothera paradoxa Hudziok, aqueous extract, 60% ethanolic extract, and 30% isopropanolic extract, differing by their total content of phenolic compounds and by their contents of individual polyphenols, were investigated in this study. The extracts exerted cytotoxic action on HTB-140 human skin melanoma cells. After 24 h of incubation, IC(50) values of 169.7 +/- 5.9 micog/mL, 72.4 +/- 3.8 microg/mL, and 155.3 +/- 6.3 microg/mL were obtained for HTB-140 cells with the aqueous extract, 60% ethanolic extract, and 30% isopropanolic extract at the tested concentrations (5-200 microg/mL), respectively, while IC(50) for normal fibroblast cells NHDFs was not attained. Moreover, for HTB-140 cells, LD(50) (concentration at which 50% of cells were dead) of 89.2 +/- 4.3 microg/mL and 181.4 +/- 6.5 microg/mL were obtained with 60% ethanolic extract and 30% isopropanolic extract, respectively. In melanoma cells, all three extracts caused a concentration-dependent increase of ROS production, GSH, and ATP lowering, and appearance of phosphatidylserine on the external surface of cellular membranes where it was bound to annexin V-FITC; furthermore, apoptosis without activation of caspase-3 took place. The most effective was 60% ethanolic extract, which had the greatest total content of phenolic compounds and the greatest content of pentagalloyloglucose (PGG).