HPLC-DAD-ESI-Q-TOF-MS/MS profiling of Verbascum ovalifolium Donn ex Sims and evaluation of its antioxidant and cytogenotoxic activities.

Abstract

Plant species of Verbascum genus have been intensively investigated in the last decades but most studies focused on evaluation of their biological activities; there are only few studies dealing with their chemical characterisation. Detailed investigation of the qualitative and quantitative chemical composition, antioxidant and cytogenotoxic activities of a previously non-studied Verbascum species (V. ovalifolium Donn ex Sims). Qualitative analysis of secondary metabolites was performed by HPLC-DAD-ESI-Q-TOF-MS/MS, whereas quantitative data were obtained through HPLC-DAD. Antioxidant activity was evaluated using in vitro assays; cytotoxic and genotoxic effects were assessed by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium (MTT) and comet assays, respectively. More than 50 secondary bioactive metabolites belonging to various classes (iridoids, phenylethanoids, flavonoids, phenolic acids) were detected in the methanolic extract of V. ovalifolium and its fractions. The fragmentation pathways of acylated catalpol-type iridoid diglycosides are thoughtfully described herein. The extracts showed good free radical scavenging and ferric ion reducing properties correlated with phenolic, flavonoid, chlorogenic acid and verbascoside contents. Moreover, 24h treatment of SK-MEL-2 cells with V. ovalifolium extracts produced significant changes in terms of tumour cell viability. The crude extract and the ethyl acetate fraction showed no important signs of cytogenotoxicity in non-tumour cells. The performed phytochemical and biological analyses contribute to the preclinical knowledge about V. ovalifolium and they could help exploiting it in novel herbal medicinal products.