Biological activities of Helleborus vesicarius: Cytotoxicity, induction of apoptosis and antioxidant potential

Helleborus vesicarius, an endemic species, grows in South Anatolia, the Amanos Mountains, Kahramanmaraş, and the Gaziantep region. Biological activity studies on H. vesicarius are restricted. Therefore, the study aims to investigate the antioxidant potential, DNA-protecting capacity, cytotoxic activity and apoptotic effect of H. vesicarius. In this study, the phenolic and flavanoid contents of H. vesicarius methanol extract were determined as 18.95 ± 0.65 mg/g (expressed as gallic acid equivalent) and 18.97 ± 0.17 mg/g (expressed as catechin equivalent), respectively. The extract displayed an inhibitory capacity against FeCl3/ascorbic acid-induced phosphatidylcholine liposome oxidation (EC50 = 5.16 ± 0.12 mg/mL), eliminated stable 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) cation (ABTS+), 2,2-Diphenyl-1- picrylhydrazyl (DPPH) and superoxid anion (O2 -) radicals (EC50 = 4.23 ± 0.05 mg/mL; 3.87 ± 0.24 mg/mL; 1.20 ± 0.06, respectively), and act as reducing agent as expressed by the Ferric reducing antioxidant power (FRAP) value (2.87 ± 0.04 mM/L Fe2+) at 10 mg/mL. Furthermore, DNA-protecting activity was identified by DNA nicking assay. The extract dosedependently protected pBR322 plasmid DNA against hydroxyl (OH) radical formed by the Fenton reagent. Also, cytotoxic activity was established on lung (A549), prostate (PC3), endometrial (ECC-1) cancer cells and primary dermal fibroblast (PCS) cells by using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)- 2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay. The cytotoxic effect of the extract was more powerful on A549 (IC50: 45.80 μg/mL) and PC3 (IC50: 54.97 μg/mL) cell lines compared to that of the ECC-1 (IC50: 367.62 μg/mL). The selectivity indexes for A549, PC3 and ECC-1 cell lines were 14.46, 12.09 and 1.81, respectively. Additionally, caspase-3 activity was also evaluated via the colorimetric method, the results revealed that the extract triggered apoptosis via active caspase-3 formation in the PC-3 cells. It was concluded that the extract may be used as a source of natural anticancer agents. Further investigations are needed to clarify the cytotoxic mechanism of the extract.