Phytochemical Screening and Antibacterial Activity of Prunus avium Extracts against Selected Human Pathogens

Abstract

Aim: This research was carried out to determine the phytochemical properties and antimicrobial activities of leaf and stem bark ethanol extracts of Prunus avium L. against selected human pathogens. Methodology: The methods used included mechanical pulverization of the air-dried plant materials and solvent percolation extraction for 72 hrs. The resulting crude extracts were stored in sterile airtight McCartney bottles and stored in the refrigerator until use. After, they were screened for the presence of phytochemicals. Furthermore, the plant leaf and stem bark extracts were assayed for antibacterial activities against Staphylococcus aureus, Streptococcus pneumoniae, Escherichia coli, Enterococcus faecalis, Klebsiella pneumoniae, and Salmonella typhi. The minimum inhibitory concentrations as well as time of kill of the extracts against the test pathogens was also determined. Results: The results showed that flavonoid, saponins, alkaloids, tannins and phenols were present in the stem bark extracts while saponin was absent in the leaf extract. Furthermore, in the antimicrobial activity test, the plant extracts revealed varied activities along concentration gradient as higher concentration was observed to correspond to wider zones of inhibition. E. faecalis showed the highest susceptibility to both extracts at all the concentrations tested showing 11.00±0.00 and 16.33±0.01 mm zone of inhibition for leaf and stem bark extracts respectively at 200 mg/mL while S. typhi showed the least susceptibility to the extracts recording no inhibition against leaf extract at all the concentration used albeit showing 7.00±0.00 mm inhibition zone against stem bark extract of the plant. The lowest MIC was found in stem bark extract against K. pneumoniae (3.125 mg/mL), while the highest was recorded in leaf extract against S. pneumoniae (75 mg/mL). The stem bark extracts showed the least time required to completely kill the pathogens, taking 15 minutes to completely inhibit K. pneumoniae followed by E. coli and E. faecalis which took 25 minutes each to be killed. However, the times recorded for the leaf extract to kill these organisms were higher than that recorded for stem bark extracts with S. pneumoniae recording the highest (100 min) exposure time to be killed. The stem bark extract of the plant was more potent against the pathogens than the leaf extract. Conclusion: The results of this study revealed that Prunus avium extracts contain biologically active constituents like saponins, alkaloids, tannins, flavonoids and phenols which may be responsible for the observed antibacterial activities of the plant against human pathogens.