Cytotoxic and pro-apoptotic effects of Hypericum species. Metabolites profiling and dereplication procedures for the identification of bioactive ingredients

Abstract

Hypericum perforatum or St John's wort of Hypericaceae family is one of the oldest used and most comprehensively investigated medicinal herbs, while preparations thereof are widely commercialized in EU and USA for the treatment of depression [1]. The genus Hypericum is considerably large including 490 species which are characterised by interesting phytochemical and biological profiles as well. Although most of the constituents of H. perforatum have been identified, the phytochemical studies as well as the biological properties of other related species are limited so far. In continuation of our studies for the discovery of new anti-neoplastic agents, 50 extracts of medicinal plants from Mediterranean biodiversity were investigated. The HL-60 human promyelocytic leukemia cell line was used to study the pro-apoptotic activity of the plant derived extracts. The cytotoxic and/or the pro-apoptotic capacity of each extract was estimated by trypan-blue exclusion method, the MTT assay and flow-cytometric analysis. Interestingly, from all extracts screened three methanol extracts exhibited the most significant cytotoxic activity and specifically those of H. triquetrifolium, H. perforatum, and H. rumeliacum. Based on these results, additional Hypericum species were collected and different extracts were produced (n = 22). All the derived extracts were subjected to profiling and dereplication procedures using HPLC-DAD and LC-(ESI)-HRMS/MS platforms. Interesting comparative results related to both known constituents such as naphodianthrones, phloroglucinol derivatives and flavonoids [2] as well as new metabolites were derived. Furthermore new findings concerning species and extract-specific negative and positive correlations were revealed.