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Chemical composition, antimicrobial and antioxidant activities of the essential oil of Guizotia scabra and Microglossa pyrifolia from Rwanda
Guizotia scabra (Vis.) Chiov. and Microglossa pyrifolia (Lam.) Kuntze, Asteraceae, are collected and used for infection diseases in Rwanda . Their essential oils obtained by hydrodistillation of leaves collected from Butare (Huye), Southern province of Rwanda, were simultaneously analysed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) [2,3,4,5]. As a result, a total of fifty components were characterized in Microglossa pyrifolia, representing 98% of the total oil with germacrene-D as the major component. 39 components were characterized in Guizotia scabra, representing 85.2% of the total oil with germacrene-D (26%) and limonene (10%) as the principal constituents.
The essential oils were evaluated for their antimicrobial activity using a microdilution assay resulting in the inhibition of a number of common human pathogenic bacteria (Staphylococcus aureus, Escherichia coli, Shigella flexneri, Pseudomonas aeruginosa and Salmonella typhi. The minimum inhibitory concentrations (MIC) of both M. pyrifolia and G. scabra varied between 0.25 and 0.5mg/ml which is within a moderate antimicrobial activity range. Furthermore, the antioxidant capacity of the essential oils was examined using an in vitro radical scavenging activity test. The essential oils scavenged 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), resulting in IC50>30% Equivalent quercetine.
References:  Rwangabo, P.C. (1993) La médicine traditionnelle au Rwanda. Paris, Karthala et ACCT.
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