Chemical composition and antimicrobial activity of Hypericum hircinum L. Subsp. majus essential oil

Abstract

throats, colds, and as an antitussive [3]. In this study we report the chemical composition of the essential oils hydrodistilled from different parts during the phenological cycle and analyzed by GC and GC-MS, and the antimicrobial activity of the oils against a panel of human opportunistic pathogenic bacteria and fungi by using the agar diffusion and dilution method [4, 5]. Ninety-two volatile components were identified in the oils of H. hircinum subsp. majus (61 in leaves, 53 in flowers, and 64 in fruits), representing 81.41–94.36% of the total essential oils (Table 1). The oils from leaves and flowers were dominated by sesquiterpene hydrocarbons, while the fruits oils were rich in monoterpenes. The major compounds were cis--guaiene (23.25–41.23%) and -selinene (8.48–25.20%) in leaves, -selinene (18.29%) and limonene (15.23%) in flowers, and limonene (14.01–38.72%) and -pinene (9.88–16.31%) in fruits. The development stages of the plant during the annual phenological cycle influence the composition of the fruits oils much more than the leaves oils. The results of antimicrobial activity (Tables 2 and 3) indicated that the essential oils were active against the gram-positive bacteria S. aureus, S. mutans, and B. subtilis, the gram-negative E. coli, and the yeast C. albicans; the latter was the most sensitive microorganism tested, with the lowest MIC value (155 g/mL). The ANOVA test (P 0.05) showed significantly different activities for different harvesting times. In particular, the most active oils were those obtained during the fruiting stage, confirming the harvesting time of the plant in the traditional uses [3]. The maximum inhibition zones and MIC values of the bacteria and yeast species sensitive to the essential oils were in the range of 9.6–20.5 mm and 155–625 g/mL. In particular, S. mutans, an oral pathogen responsible for caries, showed good sensitivity to the oils (MIC values in the range of 625–1250). Recently, it has been shown that oral bacteria are associated with many systemic diseases, such as pneumonia and cardiovascular diseases [6]. The results support the traditional use of this plant in Southern Italy, and suggest its use in the treatment of sore throats and colds.