Isolation and structure elucidation of the compounds from Teucrium hyrcanicum L. and the investigation of cytotoxicity, antioxidant activity, and protective effect on hydrogen peroxide-induced oxidative stress

Background Teucrium hyrcanicum L. (family Lamiaceae) is widely distributed in the North and Northwest of Iran. It has been used in the form of tea, tonic, and tincture for the treatment of various diseases such as cough, rheumatism, and fever.Methods In this study, the total phenolic and flavonoid contents, antioxidant and cytotoxic activities of methanol extract and different fractions of T. hyrcanicum were measured. Furthermore, the potential ability of T. hyrcanicum to protect against H2O2-induced oxidative stress was tested on the NIH3T3 cell line. Then, the isolation and structure elucidation of the compounds were performed on the most potent fractions. Finally, the quantification of isolated compounds in methanol extract (ME) was done by the HPLC method. Isolated phytochemicals were assessed for the cytotoxic and antioxidant activities.Results The results indicated that the methanol fraction (MF) had the highest amount of phenolic and flavonoid contents (69.36 mg GAE/g extract and 68.95 mg QE/g extract). The highest radical scavenging activities were observed from MF and ME (IC50 44.32 and 61.12 mu g.ml(-1), respectively). The best cytotoxicity was obtained by ethyl acetate fraction (EF) against A431 and MCF7 cell lines (IC50 values of 235.4and 326.6 mu g.ml(-1), respectively). The pretreatment with MF exerts the highest reduction in malondialdehyde (MDA) formation (IC50 2.51 mu M, p < 0.001) compared to the H2O2 group (5.77 mu M). Also, MF significantly inhibited H2O2-induced Glutathione (GSH) oxidation (p < 0.001). Furthermore, two phenolic compounds, acteoside and quercetin, were isolated and identified in MF and EF, respectively. The IC50 values of acteoside and quercetin in the DPPH assay were 7.19 and 5.56 mu g.ml(-1), respectively. Both quercetin and acteoside significantly reduced the MDA formation and inhibited GSH oxidation, which was comparable with BHA (as a standard antioxidant) (p < 0.05). Acteoside demonstrated significant cytotoxicity against all tested cell lines (IC50 = 32 to 145 mu g.ml(-1)). The HPLC quantification of isolated compounds revealed that the quantity of acteoside and quercetin in ME were 93.31 and 16.87 mu g.mg(-1), respectively.Conclusion The isolated compounds (quercetin and acteoside) had significant antioxidant activities and revealed a protective effect on H2O2-induced oxidative stress which was comparable with BHA.