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

The essential oils of six Hypericum sp. growing in Serbia were analyzed by GC and GC-MS [1]. The main constituents were revealed as follows: H. alpinum: Waldst. et Kit. non Vill. (-)-β-pinene, γ-terpinene, (-)-(E)-caryophyllene; H barbatum: Jacq. (-)-α-pinene, (-)-β-pinene, (-)-limonene, (-)-(E)-caryophyllene, (-)-caryophyllene oxide; H. rumeliacum: Boiss. (-)-α-pinene, (-)-β-pinene, (-)-limonene, H. hirsutum L.: nonane, undecane, (-)-(E)-caryophyllene, (-)-caryophyllene oxide; H. maculatum L.: spathulenol, globulol; H. perforatum L.: (-)-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. The essential oils were screened for their antimicrobial activity [Table 1], using the microdilution method [2]. H. barbatum essential oil was proven the most active against all tested bacteria.

Table 1. Minimum Inhibitory Concentrations (MICs) of essential oils (µg/mL).

* Control: Streptomycin for bacteria; Bifonazole for Candida albicans
MIC	alpi	barb	rume	mac	perf	hirs	Control*
Bacillus cereus	12.5	6.25	12.5	12.5	12.5	12.5	50
Micrococcus luteus	12.5	6.25	12.5	12.5	12.5	25	50
Sarcina lutea	12.5	6.25	6.25	12.5	12.5	12.5	50
Staphylococcus aureus	12.5	6.25	6.25	12.5	12.5	25	50
Agrobacterium tumefaciens	25	25	25	25	25	50	100
Escherichia coli	50	25	25	25	25	50	100
Proteus mirabilis	-	50	50	50	50	-	200
Pseudomonas aeruginosa	-	50	25	25	50	-	-
Pseudomonas tolaasii	50	25	25	25	25	50	200
Salmonella enteritidis	50	25	25	25	25	50	200
Candida albicans	-	25	25	50	50	-	200

References: 1. Adams, R. (2001), Identification of Essential oil components by Gas Chromatography/Quadrupole Mass Spectroscopy, Allured Publishing Corporation, Carol Stream, Illinois, USA. 2. Daouk, K.D. et al. (1995), J. Food Prot. 58: 1147–1149.