Benzophenones from Hypericum elegans with antioxidant and acetylcholinesterase inhibitory potential

Background: Hypericum elegans is used in Bulgarian folk medicine for treatment of wounds, depression, gastrointestinal and bacterial diseases. Objective: Recently, new natural benzophenones: Elegaphenone and O-glycosides: Hypericophenonoside, Neoannulatophenonoside and Elegaphenonoside as well as already known 7-Epiclusianone were isolated from the titled species. The aim of the present study was to evaluate the antioxidant and acetyl cholinesterase inhibitory potential of the isolated compounds. Materials and Methods: 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) di-ammonium salt (ABTS) free radicals, ferric reducing antioxidant power (FRAP) assay as well as inhibition of lipid peroxidation in linoleic acid system were used for determination of antioxidant activity. Modified Ellman's colorimetric method was carried out to assess the acetyl cholinesterase inhibition potential. Hyperoside and Galantamine hydrobromide were used as positive controls. Results: Hypericophenonoside was found to possess the strongest DPPH radical scavenging activity (IC ₅₀ = 181.85 ± 6.82 μM), while Neoannulatophenonoside showed the highest ABTS (IC ₅₀ = 0.25 ± 0.005 μM) and lipid peroxidation inhibitor activity. FRAP activity was demonstrated only by prenylated aglycones - Elegaphenone [942.16 ± 4.03 μM Trolox Equivalent (TE)] and 7-Epiclusianone (642.95 ± 3.95 μM TE) and was stronger compared to the control Hyperoside (421.75 ± 9.29 μM TE). Elegaphenone and 7-Epiclusianone were found to possess moderate acetyl cholinesterase inhibitory potential with IC ₅₀ values of 192.19 ± 3.54 μM and 142.97 ± 4.62 μM, respectively. Conclusion: The results obtained revealed that H. elegans is a potential natural source of bioactive compounds and benzophenones could be useful in therapy of free radical pathologies and neurodegenerative disorders.