Assessment of Phytochemical Constituent, Antibacterial and Cytotoxic Activities of A. laxiflora (Ewe pepe) Extracts

Aim: This study was done to determine the phytochemical constituents, antibacterial and cytotoxic activities of leaf extracts of A. laxiflora (“ewe pepe”).

Place and Duration of Study: Department of Science Laboratory Technology (Microbiology and Analytical Chemistry Laboratories), Rufus Giwa Polytechnic, Owo, Nigeria, between August 2016 and March 2017.

Methodology: The methods used include manual grinding of the air-dried leaves and solvent (aqueous and ethanol) percolation for 72 hrs. The resultant crude extracts were kept in sterile airtight bottles and stored in the refrigerator. Then, they were screened for phytochemical constituents. Furthermore, the plant extracts were screened for antibacterial activities against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, Klebsiella pneumonia and Salmonella typhi. In addition, the plant extracts were investigated for cytotoxic activity against Artemia salina nauplii.

Results: The results of the phytochemical analyses showed the presence of flavonoid, saponin, tannin, alkaloid and phenols in the aqueous and ethanol extracts of the plant. In the antibacterial activity screening, of the plant extracts showed a concentration dependent trend as higher activities was observed as the concentration gradient increased. S. aureus (19.33±0.58), K. pneumoniae (18.33±0.58) and E. faecalis (18.67±0.58) showed the highest susceptibility to the plant extracts while S. typhi showed the least susceptibility against the plant extracts. The lowest minimum inhibitory concentration (MIC) was found in K. pneumoniae (2.5 mg/ml) while S. aureus, E. coli and E. faecalis recorded an MIC of 5 mg/ml respectively. The ethanol extract of A. laxiflora was more active against the selected pathogens compared with aqueous extract. Moreover, in the cytotoxic assay, A. salina showed high mortality against the plant crude extracts. The LC₅₀ value of less than 100 ppm/ml was obtained from the aqueous (41.01 ppm) and ethanol (8.91 ppm) extracts.

Conclusion: The results of this study revealed that the A. laxiflora leaf extracts contain important phytochemicals such as alkaloids, flavonoids, phenols, saponins and tannins which may be responsible for the antibacterial and cytotoxic effects exhibited by A. laxiflorat and new antimicrobial and anticancer agents may be developed from the plant.