Antibacterial Screening of Two Indigenous Nigerian Spices; Piper guineense and Xylopia aethiopica

Abstract

Leaf and fruit extracts of Piper guineense and Xylopia aethiopica were respectively evaluated for their antibacterial activities against two (2) organisms; Staphylococcus aureus and Pseudomonas aeruginosa. The antibacterial activity was measured by agar well diffusion method using 8 mm diameter cork borer. All the extracts except hot aqueous extract of P. guineense leaves showed antibacterial activity against the test bacterial isolates. Cold aqueous extract of X. aethiopica did not exhibit antibacterial activity against P. aeruginosa, also hot aqueous extract of X. aethiopica did not exhibit antibacterial activity against P. aeruginosa. The ethanolic extracts of P. guineense showed inhibitory activity against the two test bacterial isolates with zone diameter of inhibition that ranged between 12.5 mm to 28.0 mm, while X. aethiopicashowed activity with zone diameter of inhibition that ranged between 11.5 mm to 20.0 mm. The cold aqueous extracts of P. guineense showed antibacterial activity against both test bacterial isolates with zone diameter of inhibition that ranged between 12.0 mm to 25.0 mm, while X. aethiopica showed activity only against S. aureus with zone diameter of inhibition ranged between 9.5 mm to 19.0 mm. The hot aqueous extracts of P. guineense showed no antibacterial activity against the test organisms, while that of X. aethiopica showed activity only against S. aureus with zone of inhibition ranged between 9.0 mm to 25.0 mm. Amoxicillin and Ciprofloxacin antibiotics were used as positive controls, while the extracting solvents were used as negative controls. The phytochemical screening revealed the presence of saponins, flavonoids, and tannins and the absence of alkaloids in both spices studied. The MIC result revealed variability in the inhibitory concentration of each extract for both organisms tested. All active extracts ofPiper guineense where found to possess an MIC of 3.12 mg/ml, while the MIC range for all the active extracts of Xylopia aethiopica ranged between 3.12 mg/ml to 12.5 mg/ml. Based on this finding, these extracts show promise and form a primary platform for further phytochemical and pharmacological studies for use as alternative medicine.