Antimicrobial activity of Terminalia leiocarpa Baill. and Terminalia avicennioides Guill. & Perr. root bark extracts in resistant clinical isolates

Context: The utilisation of plants as a reservoir for potential chemotherapeutic and antimicrobial agents is a common practice in ethnomedicine. However, folkloric use of Terminalia leiocarpa and Terminalia avicennioides in treatment of microbial infection has prompted various pharmacological investigations, especially antimicrobial studies. Aims: To evaluate the antimicrobial activity of the bioactive compounds of T. leiocarpa and T. avicennioides roots bark extracts on clinical isolates. Methods: Phytochemical screening of the extracts was done following standard procedures. Antimicrobial activities of 500 mg/mL of each extract were performed through the agar well diffusion method on clinical isolates of E.coli, Klebsiella pneumonia, Staphylococcus aureus and Pseudomonas aeruginosa. The methanol extract of T. leiocarpa was fractionated into four fractions and tested at concentrations 31.25, 62.5, 125, 250 and 500 mg/mL. The Agar well diffusion method and 96 titre well were employed to ascertain the percentage inhibition of the fractions and determine the minimum inhibitory (MIC) and bactericidal concentrations (MBC). Compounds were identified utilising gas chromatography-mass spectrometry (GC-MS). Microsoft Excel and SPSS 20.0 version were used to analyze experimental data. Results: Phytochemical analysis revealed the presence of alkaloids, flavonoids, tannins, terpenoids, saponins, and cardiac glycosides. The dichloromethane fraction of T. leiocarpa revealed the highest activity with MIC of 31.25-125 mg/mL and of MBC 15.63-125 mg/mL while methanol gave MIC of 62.5-250 mg/mL and MBC of 31.25-125 mg/mL respectively. The GC-MS revealed 15 peaks in the dichloromethane fraction. Conclusions: The findings suggest the antimicrobial activity of the identified compounds, which could be a potential resistance-free template for future antimicrobial drug discovery.