Abstract:
This study was undertaken to determine the chemical composition, antimicrobial and antioxidant
activities of the seed oil extracted from Caesalpinia decapetala collected from Haramaya
University, Eastern Ethiopia. The seed oil was obtained by Soxhlet extraction and it was found to
be clear and yellow in color with a pleasant smell. The oil was analyzed by GC/MS and 38
compounds were identified which corresponds to 99.95% of the total oil. The major
components of the oil were found to be 4-(2,7,7-trimethyl Bicyclo[3,2,0] Hept-2-en-1-yl) but-3-
en-2-one (22.98%) and 9,12-Octadienoicacid (22.25%), 17-(Acetloxy)-4,4-dimethyl-3-Oxandroste
(18.80%), 1,2-Benzenedicarbo-xylic acid (5.67%), Hexadecanoic acid (3.42%), Atractylone
(3.44%), di-α- tocopherol (3.10%) and Caryophyllene (2.59%). In this study the classes of
compounds identified from the oil of Caesalpinia decapetala includes oxygenated monoterpene,
terpenoides, fatty acids and hydrocarbons and derivatives of hydrocarbons. In vitro antimicrobial
activities of the seed oil was determined by paper disk diffusion method and showed wide zone
of inhibition against both bacteria and fungi at 20 μL dose level. Gram (+) bacteria
(Staphylococcus aureus and Streptococcus agalactiae) and Gram (-) bacteria (E. coli and Shigella
flexneri) were used as test bacterial species where as Apergillus niger and Fusarium oxysporum were selected as test fungi. The antioxidant activity of this plant was also evaluated and moderate
antioxidant property of Caesalpinia decapetala was revealed.The IC50 (the concentration required
to inhibit a radical formation by 50%) of extract was found to be 18.31 μg/mL whereas the IC50
value of standard ascorbic acid was found to be 26.21 μg/mL. The results of this study showed in
the antimicrobial activities, antioxidant activities and chemical composition of the seed oil of
Caesalpinia decapetala. The presence of monoterpene, oxygenated monoterpene, fatty acids,
steroids and flavonoids as the major constituents of the seed oil might be responsible for the
antimicrobial activities observed in this study.
