Phenolic profile and biological activity of Hypericum perforatum L.: Can roots be considered as a new source of natural compounds?

The aim of this study was to evaluate the phytochemical composition, antimicrobial activity and enzyme inhibitory properties of roots (RO), non-flower shoots (NFS) and flower shoots (FS) of Hypericum perforatum L. originating from the Republic of Macedonia. The identification and quantification of phenolic compounds in plant material were performed by using HPLC/DAD/ESI-MSn analysis. The antimicrobial activity on some selected species of bacteria and fungi was tested by microdilution assay. The in vitro enzyme inhibitory activity of plant extracts was measured against key enzymes involved in depression (monoamine oxidase A; MAO A), neurodegenerative disorders (acetylcholinesterase; AChE, butyrylcholinesterase; BChE and tyrosinase; TYR) and diabetes (α-amylase; α-AMYL and α-glucosidase; α-GLUC). The aerial plant samples showed biosynthetic potential for the production of phenolic acids, flavan-3-ols, flavonols, naphthodianthrones and acyl-phloroglucinols. The NFS and FS extracts exhibited strong antistaphylococcal and anticandidal activity that was related to the presence of hypericins and hyperforins. Chlorogenic acid, flavonol aglycones and glycosides, as well catechins and procyanidins from aerial parts were considered as potential AChE and TYR inhibitors. This study revealed, for the first time, the co-presence of phenolic acids, flavan-3-ols and xanthones in RO extracts. The antibacterial activity of RO extracts against Bacillus subtilis, Escherichia coli and Pseudomonas aeruginosa was related to the presence of garcinone C and γ-mangostin. The roots rich in xanthones displayed the strongest MAO A and BChE inhibition highlighting their antidepressant and neuroprotective effects. With respect to antidiabetic properties, RO extracts showed significant α-AMYL and α-GLUC inhibitory activities that were related to the contents of procyanidins and xanthones. Based on phytochemical composition and enzyme inhibitory properties, H. perforatum roots could be considered as an alternative source to obtain antidepressant, neuroprotective and antidiabetic active substances.