Commercial virgin coconut oil : assessment of antimicrobial potential

Virgin coconut oil is defined as the oil obtained from fresh coconut meat, without undergoing any chemical processes. Virgin coconut oil is mainly sold on the basis of its antimicrobial activity which is contributed to by its lauric acid. This study aimed to investigate the antimicrobial activity of commercial virgin coconut oil. Agar well diffusion test and disc diffusion test were first done to test on both methanol extracted oil and pure oil samples against four types of bacteria. Both methods showed no antimicrobial activity. Broth dilution method was then done to determine the minimum inhibitory concentration of the oil samples against eight types of bacteria. Again, no antimicrobial activity was observed. In turn, gram negative bacteria (Coccus, Bacillus, Streptobacillus and Coccobacillus) were isolated from all the oil samples. The triglyceride in the oil samples have to be broken down to monoglyceride or free fatty acids by enzyme lipases in order to exert antimicrobial activity. Bacteria have the ability to produce non-specific enzymes to release free fatty acids and sn1,3 lipase to produce sn-2 monoglyceride. In fact, the free lauric acids released by lipase only possess weak antimicrobial activity and the sn-2 monoglycerides formed may not exert any antimicrobial activity. Bacteria were isolated from the oil samples because raw and unprocessed coconut meat can support growth of bacteria and no sterilization is done to prevent microbial contamination.