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.
