Antimicrobial and antispasmodic activity of leaf extract and fractions of Stachytarpheta cayennensis

Abstract

Objective To investigate the antimicrobial activity of the methanol leaf extract (ME), n-hexane fraction (HF), ethylacetate fraction (EF) and methanol fraction (MF), of Stachytarpheta cayennensis C. Rich (verbenaceae) as well as to ascertain the antispasmodic effects of the ME and the various fractions (HF, EF and MF) on acetylcholine (Ach) and histamine (H) induced contractions on isolated guinea pig ileum. Methods The in vitro agar well diffusion method was used for the antimicrobial studies while the isolated tissue method was employed for the antispasmodic test. Organisms used were all clinical isolates of Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella paratyphi, Candida albicans and Aspergillus niger. Results The extract and fractions exhibited dose dependent inhibition against all the bacteria tested and also exhibited insignificant antifungal activity against Candida albicans and Aspergillus niger. The minimum inhibitory concentration (MIC) of the extract and fractions (mg/mL) on Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella paratyphi respectively were ME 5.62, 14.12, 22.38, 2.11; EF 1.25, 6.30, 9.40, 9.40 and MF 3.98, 8.81, 39.80, 21.13. The n-hexane fraction exhibited MIC of 1.07 mg/mL against only Bacillus subtilis. The extract and fractions exhibited significant (P< 0.05) dose dependent attenuation of contractions induced by acetylcholine and histamine on isolated guinea pig ileum. Concentrations of the extract and fractions (μg/mL) which evoked 50% inhibition of maximal response exhibited by Ach were ME 0.64, HF 0.16, EF 0.08 and MF 0.15, while that of histamine included ME 5.12, HF 0.16, EF 0.04 and MF 0.64. Preliminary phytochemical studies on the extract and fractions indicated the presence of carbohydrates, alkaloids, saponins, flavonoids, steroids and terpenoids. Conclusions The extract and fractions of Stachytarpheta cayennensis possessed both antibacterial and antispasmodic effects confirming the claimed use in folkloric medicine for wound healing and gastrointestinal ulceration.