In vitro and in vivo transformation of Centaurium erythraea Rafn extracts and resulting bioactivities

Abstract

The main secondary metabolites of Centaurium erythraea Rafn are biologically active secoiridoid glycosides (SGs) swertiamarin, gentiopicrin and sweroside. Removing the non-reducing terminal glucosyl residues from glycosylated compounds (deglycosylation) leads to the formation of highly active, but unstable aglycones. The present study was designed to evaluate the differences in biological activities between non-hydrolyzed and hydrolyzed methanol extracts (ME and HME, respectively) and major SGs of C. erythraea. Metabolite profiling of extracts following their β-glucosidase mediated enzymatic hydrolysis revealed significant changes in β-d glucoside/aglycone ratio of secoiridoid compounds and phenolics. Developed and validated UHPLC/DAD/ + HESI−qqqMS method for the identification and quantification of SGs and their aglycones in both ME and HME revealed gentiopicral and erythrocentaurin as the major aglycones. The same metabolites also appeared after the hydrolysis of swertiamarin, the dominant SG of C. erythraea. The present study was further aimed at ascertaining the differences in biological activities between ME and HME. High antimicrobial activities of both ME and HME, which surpassed the effects of the reference antibiotics and antimycotics, could be attributed to SGs in either of the glycosylation forms. Plant extracts and pure SGs were especially effective against most of the tested Penicillium species. Nonetheless, Penicillium funiculosum developed a mechanism to exceed sublethal concentrations of SGs and to overcome the fungitoxic effects of SGs, which involved their biotransformation and complete degradation. Interestingly, antioxidant activities of swertiamarin and sweroside recorded in ABTS assay increased after the compounds have been hydrolyzed, which highlighted their possible antioxidant role during ingestion. Thus, present work contributes to the clarification of the role and fate of C. erythraea SGs after digestion within in vivo systems, and further promotes the applications of this remarkable plant in pharmaceutical and food industry