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Abstract
The essential oil of Origanum elongatum is known by numerous biological activities, which are linked to its chemical composition. The aim of this study was to evaluate the effect of hydro-distillation time on the chemical composition and the antibacterial activity of the essential oil extracted from the aerial parts of O. elongatum growing in the north of Morocco. The essential oil fractions were captured at nine regular time intervals after the beginning of hydro-distillation process. Maximum essential oil yield was achieved at a hydro-distillation time of 140 min. The dissolved volatile fraction was extracted from the hydrosol at the end of hydro-distillation process. The chemical composition was determined by GC-FID and GC/MS. The chemical profile of the essential oil showed the predominance of oxygenated compounds (65.14 %) followed by hydrocarbon compounds (28.02 %). Thymol accounted for 63.44 % of the total EO. Dissolved volatile fraction was dominated by oxygenated monoterpenes with 91.93 % of thymol. The results revealed that hydro- distillation time produces oil fractions with specific chemical profiles. The antibacterial activity was tested against four bacterial strains. The results showed that essential oil fractions captured from 80 to 160 min had greater antibacterial activity than fractions recovered at the beginning of the distillation and the whole oil. The inhibitory zones diameters were linearly correlated with the increase of thymol concentration in each fraction up to 160 min (r-Pearson ranges between 0.95 and 0.97 with p < 0.0001). The strongest activity was observed with essential oil fractions from 141 to160 min of hydro-distillation time with MIC values ranged from 0.0312 to 0.125 % (v/v) and MBC from 0.0312 to 0.25 % (v/v). These data may help to reduce the cost and the time of essential oil extraction and to select the oil fraction with desirable composition for it use in pharmaceutical, cosmetic or food industries.