Antibacterial and Antioxidant Activities of Dacryodes edulis Methanolic Leaf Extract

Dacryodes edulis is used for the treatment of several ailments such as malaria, oral and ear infection. This study was designed to determine the antibacterial and antioxidant potentials of Dacryodes edulis methanolic leaf extract as well as its rate of killing on some selected bacterial strains.

The antimicrobial activity of the crude extract obtained was determined against panel of bacteria using agar-well diffusion method. The minimum inhibitory concentrations (MIC), minimum bactericidal concentrations (MBC), phytochemical and antioxidant properties of the crude extract were also studied.

The extract showed appreciable antibacterial activity against Bacillus polymyxa (LIO), Bacillus stearothermophilus (NCIB 8222), Citrobacter freundii (LIO), Trueperella pyogenes (LIO), Enterococcus faecalis (NCIB 775), Escherichia coli (NCIB 86), Klebsiella pneumoniae (NCIB 418), Micrococcus luteus (NCIB 196), Pseudomonas aeruginosa (NCIB 950), Shigella sp. (LIO) and Staphylococcus aureus (NCIB 8588) at a final concentration of 35 mg/mL. The mean diameter of zones of inhibition exhibited by the extract ranged between 12.0±0.0 mm and 23.3±1.2 mm while conventional streptomycin and ampicillin diameter of zones of inhibition ranged from 13.0±0.0 mm – 31.0±1.0 mm and 18.3±0.6 mm - 29.3±1.5 mm respectively. The MIC exhibited by the extract against susceptible test organisms ranged between 0.27 mg/mL and 4.375 mg/mL while MBC ranged between 0.55 mg/mL and 17.5 mg/mL. The phytochemical analysis revealed the presence of tannins, flavonoids, saponins and alkaloids. The antioxidant property result revealed 50% inhibition of the extract at 0.01045 mg/mL while that of the standard (ascorbic acid) was 0.00288 mg/mL. The time kill assay showed that the percentage of the cells killed increased with increasing concentrations of the extract, as well as, contact time intervals.

In conclusion, D. edulis methanolic leaf extract consisted of various phytochemical compounds which accounted for the appreciable antioxidant activity as well as the antibacterial activity exhibited against some of the test organisms used for this study and this supports its usefulness in folklore remedies.