Physicochemical Properties and Biological Activities of Koseret (Lippia adoensis Hochst. Var. Koseret) Seed and Leaf Oil Extracts.

Background: Lippia adoensis Hoechst var. adoensis (wild variety) and variety koseret (cultivated variety) have been used as traditional medicine, condiments, and endemic to Ethiopia.

Objective: This study aimed to assess the physicochemical properties and biological activities of oil extracts from seed and leaves of koseret (L. adoensis var. koseret).

Methodology: Soxhlet apparatus was used for oil extraction using hexane as a solvent. The oil quality assessment was based on oil yield, acid value, percent free fatty acid, and peroxide value, while the biological activities were investigated based on antioxidant and antimicrobial activities. The antimicrobial experiment was arranged as 2 x1x4 in a completely randomized factorial design with three replications.

Results: The result indicated that significantly higher oil yield (2.25%), acid value (2.66%) and free fatty acid (1.34%) were recorded for seed oil using the solvent extraction method. Leaf oil was recorded to have significantly higher values of DPPH (2,2- diphenyl-1- picrylhydrazyl), ascorbic acid and total carotenoid contents, but a lower value of hydrogen peroxide scavenging activity indicated that leaf oil presented higher antioxidant activity than seed oil in koseret. The koseret leaf oil demonstrated stronger antibacterial activity with a maximum zone of inhibition (14.50±0.21 mm), minimum inhibitory concentration (MIC, 0.25 μg/ml) and corresponding minimum bactericidal concentration (MBC, 0.25 μg/ml) against S. aureus. Furthermore, leaf oil has also presented stronger antifungal activity with a maximum zone of inhibition (14.83 mm), MIC (0.25 μg/ml), and minimum fungicidal concentration (MFC, 0.50 μg/ml) against Aspergillus versicolor.

Conclusion: It can be concluded from the results of this study that leaf oil extract has demonstrated better biological activities, including both antioxidant and antimicrobial potentials, than seed oil in koseret.