Qualitative phytochemical exploration guided in vitro antibacterial activity studies on crude stem bark extract of stereospermum kunthainum (Bignoniaceae)

Background: Stereospermum kunthianum plant is known by local name Botoro, in Ethiopia and widely used by traditional medical practitioners for the treatment of venereal diseases, dysentery and to treat toothache in different regions of the country. Objective: The study was designed to evaluate in vitro antibacterial activity of the crude stem bark extracts of S.kunthianum based on the result obtained from phytochemical exploration test. Methods: The plant part was collected from Wayu Tuka district, and air dried. The powdered plant material was subjected to gradient extraction with solvent system using maceration technique and the constituent matter was concentrated, separated and collected for further investigation. Preliminary phytochemical screening test was made using the dried extract. Results: Qualitative phytochemical exploration results showed that, the presence of alkaloid, flavonoids, terpenoids, saponins, Phenolics and tannins. The crude extract of the respected solvent containing relatively many phytochemicals was subjected to in vitro antibacterial evaluation using disc diffusion method against clinically isolated bacterial strains. In this study a promising results were recorded at higher concentration (500 ppm) of methanol extract against gram positive bacteria S. progens and S. aurous with zone of inhibition of 23± 1.46 and 21 ± 0.71, respectively and against gram negative strain, E.coli with zone of inhibition of 20 ± 1.63 showing close comparable antibacterial result with the antibiotics used as standard. Conclusion: in vitro antibacterial result of this study depicts that, antibacterial effect of methanol stem bark extracts of S.kunthianum was positively associated due to the presence tannins and phenolic phytochemicals.