Composition and antimicrobial activity of the essential oil of six Hypericum species from Serbia

Abstract

The volatile composition of six Hypericum species has been studied. The essential oils were obtained by steam distillation in 500 mL H₂O for 2 h in a modified Clevenger apparatus with a water-cooled oil receiver to reduce hydrodistillation over-heating artifacts, and their analyses were performed by GC and GC–MS. Identification of the substances was made by comparison of mass spectra and retention indices with literature records. A total of 100 different compounds were identified. The main constituents of the investigated populations of each taxon have been revealed as follows: Hypericum alpinum: (−)-β-pinene, γ-terpinene, (−)-(E)-caryophyllene; Hypericum barbatum: (−)-α-pinene, (−)-β-pinene, (−)-limonene, (−)-(E)-caryophyllene, (−)-caryophyllene oxide; Hypericum rumeliacum: (−)-α-pinene, (−)-β-pinene, (−)-limonene, Hypericum hirsutum: nonane, undecane, (−)-(E)-caryophyllene, (−)-caryophyllene oxide; Hypericum maculatum: spathulenol, globulol; Hypericum perforatum: (−)-α-pinene, (Z)-β-farnesene, germacrene D; Monoterpene hydrocarbons were shown to be the main group of the taxa belonging to the section Drosocarpium, while the taxa of section Hypericum were more rich in sesquiterpene hydrocarbons.

Introduction

Hypericum L., a member of the Hypericaceae (Guttiferae) family, is a genus with a number of species growing in Balkan Peninsula. This family consists of 46 genera and 1000 species, distributed across tropic and subtropic regions, as well as across Europe, Asia, Africa and North America. The genus Hypericum is represented by 350 species distributed throughout the world (Robson, 1977). Systematical research of the Hypericum species growing in Europe was carried out by several authors. In some more recent and comprehensive investigations of taxonomy of Hypericum (Robson, 1996, Robson, 2001, Robson, 2002), this genus is divided into 30 sections. In flora of Serbia, 19 species are present (Stjepanovic-Veselicic, 1972).

The present study aims at investigating the volatile compounds of six different taxa: Hypericum alpinum, Hypericum barbatum and Hypericum rumeliacum belonging to the sect. Drosocarpium; Hypericum maculatum, and Hypericum perforatum belonging to the sect. Hypericum and Hypericum hirsutum, belonging to sect. Taeniocarpium.

Among them H. perforatum is one of the best chemically investigated species, while few studies have been carried out on the essential oils of the other taxa.

Since antiquity up-to-date some of them, and mainly H. perforatum, are used as herbal medicines with antidepressant, antiviral, and antibacterial effects (Mabberley, 1997, Blumenthal, 1998). Therefore, it seemed interesting to investigate their antimicrobial potential.