Seasonal variation of yield, chemical composition and antimicrobial activity of Teucrium polium L. essential oil growing in the south of Algeria

Abstract

Essential oils (EOs) have been recognized as potential secondary products of aromatic plants that are environmentally friendly while performing a variety of biological properties. In this research, the essential oil of aerial parts Teucrium polium L. (Lamiaceae), collected in winter and autumn in the south of Algeria was characterized in order to better understand differences in yield, chemical composition and antimicrobial activity. Seasonal changes have been recorded in the yield and composition of T. polium L. essential oil with a percentage of 0.20% (v/w) in autumn and a highest yield 0.42% (v/w) in winter. The autumn samples contained β-pinene (23.97%) and γ-muurolene (17.7%) as the major compounds while the winter samples contained mainly camphor (22.09%) and eucalyptol (13.70%). Six different bacteria strains consisting of three Gram positive, three Gram negative bacteria and nine toxigenic fungal strains were used for antimicrobial activity. A concentration of 10 μl/ml (v/v) of both seasons essential oils inhibited the growth of Bacillus subtilis, Staphylococcus aureus and Pseudomonas aeruginosa. For the other bacterial strains, the winter essential oil was more active than the autumn one with a minimal inhibitory concentration of 5 μl/ml and 10 μl/ml respectively. The essential oils from autumn and winter seasons inhibited the growth of Listeria monocytogenes at a minimal inhibitory concentration of 20 μl/ml. These essential oils exhibited fungicidal activity at the minimal fungicidal concentrations of 20 μl/ml for some strains, while the other strains showed no fungicidal effect (>20 μl/ml). Aspergillus flavus and Fusarium graminearum were inhibited from a concentration of 10 μl/ml (v/v), whereas A. flavus and Penicillium glabrum were sensitive at a minimal fungicidal concentration of 20 μl/ml. Overall, essential oils obtained in winter show more effective antifungal activity than autumn essential oil against the majority of fungal strains.