Chemical characterization, neuroprotective, antimicrobial and enzyme inhibitory activities of Hypericum volatile oils

Abstract

St. John’s wort (Hypericum perforatum) is a well-known medicinal plant often used to treat mild to moderate mental depression. In southwest China, four species of Hypericum including H. perforatum, H. hookerianum, H. bellum and H. pseudohenryi have been used as traditional medicines for skin care, such as healing wounds, burns, and snake bites by local people. Hypericum volatile oils of these four species were obtained by supercritical CO2 extraction and analyzed by GC–MS. From H. perforatum, 56 compounds were identified, the amounts of marker components are different between two collection sites. From H. hookerianum, 71 compounds were identified, mainly comprised of alkanes. From H. bellum, 43 compounds were identified, and its essential oil contains mainly oxygenated sesquiterpenoids. From H. pseudohenryi, 57 compounds were identified, and the essential oil has relatively high levels of alkanes. Because Hypericum species are used traditionally to treat depression, wounds, and other skin problems, their volatile oils were evaluated in vitro for neurite outgrowth-promoting, neuroprotective, antimicrobial, and enzyme inhibitory activities. H. bellum and H. perforatum from Wushan demonstrated significant neurite-promoting and neuroprotective activity. The Gram-positive Staphylococcus aureus ssp. aureus was inhibited by most of the tested oils. Sesquiterpenoids and alkanols are the most abundant constituents of H. hookerianum and H. bellum oils which showed strong antibacterial activity and help to explain the observed antimicrobial activity of the oil. H. perforatum collected in Wushan showed tyrosinase inhibition activity. Based on the current results, three Asian Hypericum species and two Chinese H. perforatum populations may be promising ingredients for cosmetics, foods, and pharmaceuticals.