The impact of seasonal variation on the volatile oil profile of leaves of Severinia buxifolia (Poir.) and its antimicrobial activity

The effect of the time of collection on the quality and quantity of the oil obtained from Severinia buxifolia leaves as well as its antimicrobial activity was studied. The chemical composition of the hydro-distilled oils of the leaves of S. buxifolia (Poir.)Tenore, collected at the four seasons was determined by GC/MS analysis. Moreover, antimicrobial activity was studied, for the oil sample regarding the yield and quality, against selected bacteria and yeast. The highest oil yield was obtained from the leaves collected during winter (0.5%) followed by autumn (0.308%), however, those collected in spring and summer scored almost the same yield; (0.26%) and (0.283%) respectively. Limonene was the most abundant hydrocarbon in winter (35.5%), and amounted to 29.3% in summer, whereas, spring and autumn samples constituted 21.15% and 19.17% of limonene respectively. α-Santalene, accounted to 20.87% in autumn sample followed by the winter sample (18.93%), then 13.56% in the spring sample and recorded its lowest concentration in the summer sample (8.1%). Furthermore, γ-elemene was detected in a lesser extent amounting to 7.75% in the spring sample, 7.33% in autumn sample, 6.28% in the winter sample and 5.54% in the summer sample. Based on the above results, as regards to limonene content, S. buxifolia leaf oil collected in winter was chosen for further antimicrobial study. The agar disc diffusion method was adopted for screening the antibacterial activity of the selected oil sample. Results show moderate effect against Escherichia coli, and Listeria monocytogenes. Nevertheless, it showed weak activity against Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus subtilus, MRSA, and Candida albicans. The MIC of the volatile oil against L. monocytogenes was 4 and 1 µl/ ml against S. aureus, P. aeruginosa, B. subtilus, MRSA and C. albicans. Key words: Severinia buxifolia (Poir.) Tenore, Rutaceae, GC/MS analysis, limonene, in vitro antimicrobial activity.