In vitro studies of the antimicrobial properties and qualitative phytochemical analysis of selected Chadian medicinal plants

Abstract

The aim of this study was to evaluate the antimicrobial potential and perform the phytochemical screening of ethanolic (70%) leaf extracts of Bauhinia rufescens and Ocimum basilicum and root extracts of Salvadora persica, three plants used for the treatment of numerous diseases in Chad. The extraction of the plants was made in a ratio of 70% volume of ethanol against 30% volume of distilled water. The yields obtained in the extraction of the leaves of Bauhinia rufescens, Ocimum basilicum, and Salvadora persica roots were respectively 20, 17, and 8.8%. With the disc diffusion method, the results of the antimicrobial assessment revealed that Bauhinia rufescens leaf extracts were active against Escherichia coli, Escherichia coli ATCC 25922, Salmonella typhi, Salmonella typhi ATCC 35723, and Shigella dysenteriae with inhibition zones ranging between 20.500.2 and 100.14. Ocimum basilicum leaf extracts and Salvarora persica root extracts showed activities against Escherichia coli, Escherichia coli ATCC 25922, and Salmonella typhi with inhibition diameters ranging from 18.650.32 to 10.550.1mm at 100 mg/mL. With the broth microdilution method, all the extracts of the three plants showed effectiveness against all the bacteria and fungi tested in this study with Minimum Inhibitory Concentrations ranging from 100 to 6.25 mg/mL and Minimum Bactericidal Concentrations also ranging from 100 to 6.25 mg/mL. A time-kill assay was also carried out in order to follow the activities of Bauhinia rufescens, the most active plant as function of time. After 45 min, the extracts completely inhibeted the growth of Salmonella typhi and after an h, bactericidal effects were observed against Escherichia coli and Shigella dysenteriae. The phytochemical screening on the hydro-ethanol extracts of three plants identified polyphenols, alkaloids, saponins, flavonoids and terpenes/steroids in all three plants. These chemical compounds may be endowed with antimicrobial properties.