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Abstract
The aim of this study is to assess the seasonal variation in the chemical composition and antimicrobial activity of essential oils extracted from leaves and stems of Erythroxylummonogynum.The essential oil from leaves and stems of Erythroxylummonogynum during summer, rainy, winter and spring seasons were obtained by hydrodistillation and the chemical composition was determined by GC and GC-MS. The main components identified in leaf essential oil in summer and rainy seasons were Limonene, sabinene, β-pinene, isofenchol, dihydrocarveol, isobornyl acetate, germacrene D and farnesol. While winter and spring seasons essentially contained geijerene, pregeijerene, germacrene D, isobornyl acetate, nerolidol and farnesol. The major compounds identified in stem essential oil in summer and rainy seasons were limonene, trans-β-ocimene, methyl eugenol, isobornyl acetate, decanal and germacrene D whereas winter and spring samples contained limonene, methyl eugenol, geijerene, pregeijerene, spathulenol and farnesol. The essential oil extracted from leaves and stems during spring season was evaluated for antimicrobial activity against two gram-positive and two gram-negative bacteria and four pathogenic fungi using agar disc diffusion technique. Further the minimum inhibitory concentration (MIC) was also determined.Among all the bacteria tested, B. subtilis was most susceptible at 100µg/ml with zone of inhibition of 23.3mm and 19.8 respectively for leaf and stem oils. While, among all the fungal species tested, A. niger inhibited more effectively at 100µg/mlwith a zone of inhibition of 18.2mm and 13.9mm respectively for leaf and stem oils. The results obtained were remarkable suggesting that the different seasons profoundly influences the chemical composition of plants and essential oil of this plant possess excellent antimicrobial properties where the studies can be extended for further field trials to explore this plant as an alternative bio-friendly source for various pharmaceutical industries.