Isolation and characterisation of alkyl phenols from Ozoroa sphaerocarpa with antimicrobial activity

Alkyl phenols are members of a group of compounds known as phenolic lipids, which have been isolated and identified in plants, fungi and bacteria. They have been reported to possess a number of biological activities such as antibacterial, antitumor, antifeedant and inhibition of triacylglycerol synthesis [1]. In the present study, the isolation, characterization and antibacterial activity of some alkyl phenols from Ozoroa sphaerocarpa (Anacardiaceae) are presented. The plant material was collected from the wild in Swaziland, Southern Africa. Soxhlet extraction was carried out using solvents of increasing polarity; hexane, chloroform and methanol. A water extract was obtained by ultrasound-assisted cold extraction. Antibacterial activity of the crude extracts, fractions and isolated compounds was investigated using the broth microdilution method to determine minimum inhibitory concentrations (MICs) against a range of antimicrobial strains [2]. Structure elucidation of the isolated alkyl phenols was achieved by 1D and 2D NMR. GC-MS was used to determine the position of the double bond in the dimethyl disulphide-trimethylsilyl derivatives of the alkyl phenols [3]. Mono-unsaturated alkyl phenols with hydrocarbon chains of different length were isolated from the fruit hexane extract. The double bond configuration was determined as cis- from 2D NMR and IR spectra. These alkyl phenols had antibacterial activity with MIC values between 16 and 32 mg/L against Staphylococcus aureus; and 64 and 512 mg/L against Escherichia coli, Candida tropicalis, C. albicans, Mycobacterium smegmatis and M. aurum.

Acknowledgements: Commonwealth Scholarship Commission, University of Swaziland.

Keywords: Alkyl phenols, dimethyl disulphide-trimethylsilyl derivatives, MIC, Antibacterial.

References:

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