Determination of Antimicrobial, Antioxidant and Phytochemical Properties of Cocos nucifera linn Endocarp Extract on Bacteria Associated with Human Infection

The study investigated that the antioxidant properties and mode of action of Cocos nucifera Linn endocarp extracts on pathogens associated with human infections with a view of producing natural product that serve as a potential template for new antibacterial against multiple resistant bacterial pathogens. Cocos nucifera endocarp was collected from Ile-Ife, Osun State, Nigeria, and oven dried at 40oC for four days and ground into fine powder. The powdered sample was cold extracted using methanol and sterile distilled water in ratio 3:2 (v/v). The mixture obtained was concentrated in vacuo using rotary evaporator to drive out the organic solvent, while the aqueous layer was subsequently lyophilized. The crude extract obtained was screened for the antimicrobial activity against panel of bacterial strains implicated in human infections. The crude extract was later partitioned using four different organic solvents in order of their polarity. The antibacterial potentials of the crude extract along with the fractions obtained were determined using agar-well diffusion method. The minimum inhibitory concentration and minimum bactericidal concentration of the extracts against the bacterial strains were also determined. The rate of killing, protein, nucleotide and potassium ion leakage were determined using Staphylococcus aureus and Escherichia coli as representative of Gram positive and Gram negative bacteria respectively. The most active fraction which was ethyl acetate fraction was further partially purified by thin layer and column chromatography. The antimicrobial activity of the resulting samples was tested against the previously used bacterial strains. The most active sample of partially purified ethyl acetate fraction was analyzed using Gas Chromatography-Mass Spectrometry. The results showed that the endocarp extract of C. nucifera and various fractions obtained from it exhibited varying degree of antibacterial activities. The phytochemical screening of the extract showed the presence of phenols, flavonoids, tannins, alkaloids, triterpenes and saponins. The minimum inhibitory concentration of the crude extract ranged between 0.27 and 8.75 mg/mL while the most active fraction ranged between 0.31 and 2.50 mg/mL. The rate of kill assay showed that the percentage of the cells killed increased with increasing concentration of the fraction and contact time intervals. Leakage of nucleotides, protein and potassium ions from test cells also followed the same trend observed for killing rate. Cocos nucifera endocarp extract exhibited 50% inhibition of free radicals at 0.011 mg/mL, whereas the ascorbic acid used as standard had IC50 of 0.020 mg/mL. The major active constituent of the purified sample was identified as Ethyl Vanillin. Cocos nucifera endocarp extracts which possessed antioxidant properties exhibited appreciable antibacterial activities against the test pathogens.

Author(s): Abegunde MT, Akinpelu DA1, Omololu-Aso J, Otusanya OO and Akinlolu JT

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