Evaluation of the antibacterial properties of the extracts and fractions of Ipomoea triloba l. (Convolvulaceae) on selected enteric diarrheagenic bacteria

Abstract

Diarrhoea is a leading killer of young children accounting for approximately 8% of all deaths among children ˂ 5 years worldwide and causes neonatal mortality and hospitalization in geriatrics. Ipomoea triloba L. has been claimed to have antidiarrheal properties. This study evaluated antibacterial properties of the ethanol / aqueous extracts and fractions of I. triloba on diarrheagenic bacteria to validate its use in trado-medical treatment of diarrhoea. Aqueous and ethanol extracts of pulverized I. triloba were prepared by cold maceration and phytochemical screening was performed using standard procedures. Diarrheagenic bacteria were isolated from twenty (20) composite diarrhoeal stool samples by community bioprospecting using appropriate selective and differential media. In vitro antibacterial activity of extracts and fractions of I. triloba was determined by the modified agar-well diffusion technique, while minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) was determined by reference standard agar-dilution technique (ADT) after re-incubation of MIC samples at 37o C for 24 h. A total of 74 isolates, belonging to six genera, were identified with their numbers and percentages of occurrence as follows: Escherichia coli, 26 (35.1%), Staphylococcus aureus, 4 (5.4 %), Pseudomonas aeruginosa, 9 (12.2%), Shigella dysenteriae, 18 (24.3%), Salmonella typhi, 8 (10.8%) and Vibrio cholera, 9 (12.2%). Flavonoids, saponins, terpenes, carbohydrates and steroids were detected in both extracts. Ethanol extracts (≥30 mm) showed more potent broad-spectrum antibacterial activity than aqueous extract (≥18 mm). The MIC and MBC values ranged from 250 to 500 mg/mL and 500 to 1000 mg/mL respectively, thus establishing a time-dependent bactericidal mode of antibacterial activity. The best antibacterial activity was elicited by dichloromethane fraction. From the study, I. triloba possesses antibacterial potentials and may be exploited in the chemotherapy of bacterial diarrhoea.