VARIATION IN CHEMICAL COMPOSITION AND ANTIMICROBIAL ACTIVITIES OF ESSENTIAL OIL OF LEAVES OF KNOB WOOD (ZANTHOXYLUM CHALYBEUM) COLLECTED FROM THREE DIFFERENT PLACES OF EASTERN ETHIOPIA

Abstract

The differences in chemical compositions and functional properties of Zanthoxylum chalybeum species (Knobwood) leaves essential oils have been found depending on growing locations. In this study the variation in chemical composition and antimicrobial activities of the hydrodistilled essential oils of the Knob Wood (Zanthoxylum chalybeum) fresh leaves collected from three different places in Eastern Ethiopia (Awale, Diredawa Administration; Awaday, Haramaya Woreda and Lange, Kersa woreda, East Hararghe Zone of Oromia Region), were investigated. The chemical composition of the respected essential oils as determined by the GCMS analysis varied with different places. 13, 12 and 17 compounds representing 99.98%, 100.00% and 100.00% of the total leaves essential oil from the plant growing in Eastern Ethiopia region (Awale, Awaday and Lange) were, respectively, identified. The essential oils of Awale, Awaday and Lange were mostly β-phellanderene (23.96%, 45.31%, 23.45% respectively), whereas highest amount of other components in the essential oils of Lange: terpine-4-ol (25.02%) and sabinene (11.73%); Awaday: α-phellanderene (12.85%) and Awale: the sole β-myrcene (29.33%) was identified. Invitro antimicrobial activity in 20 μL dose of each essential oil evaluated by disc diffusion method indicated strong antibacterial activities against the test bacteria (S.thyphi, Str.agalactia, S.aureus and E.coli ) and slight antifungal activities against the test fungi (A.niger, F.oxysporium). The GC-MS identified essential oils' major constituents, the monoterpenoids, such as phellandrenes (α and β), terpinen-4-ol and sabinene could be responsible for the significant antimicrobial activities in this study. The Zanthoxylum chalybeum essential oils' chemical composition and the antimicrobial activities significantly differ with growing locations. The findings confirm the plants medicinal properties in traditional uses. The results open the many possibilities for further research on biocidal and antimicrobial activities of the essential oil and its individual components of the species growing in different regions of Ethiopia.