Chemical and Biological Screening of the Leaves of Stachytarpheta cayennensis (l. VAHL)

Stachytarpheta cayennensis belongs to the family Verbenaceae; it is a species of flowering and is applied by many traditional healers to treat a host of diseases including diabetes, dysentery pain, wounds, eye infections, bacterial infections, chicken pox, measles, blood pressure, toothache and malaria. The leaf of Stachytarpheta cayennensis was studied to evaluate its chemical constituents and to confirm its traditional medicinal use. The phytochemical screening of the leaves of this plant revealed the presence of carbohydrates, steroids, terpenoids, tannins, saponins, alkaloids and flavanoids. The antimicrobial screening against some selected human pathogens; showed that the extract was sensitive to Escherichia coli, Staphilococcus aureus, Pseudomonas aeruginosa, Micrococcus luteus and Candida albicans. The Gas Chromatography/Mass Spectrometry (GC-MS) analysis of the steam distillate showed 32 peaks. This led to the identification of several compounds with valuable biological activities including enzo[d]isothiazol-3-one (C8H7O3) a disinfectant, a platelet aggregation inhibitor and a xenobiotic, dodecanoic acid (C12H24O2) which is an antibacterial agent and an algal metabolite, hexanol, (Z)-9-tricosene, phthalic acid, octade-9-enoic acid, heptacosan-1-ol. The Gas Chromatography/Mass Spectrometry (GC-MS) analysis revealed that the steam distillate is mainly composed of oxygenated hydrocarbons, predominantly esters and carboxylic acids, a few long chain hydrocarbons and alcohols. The crude methanol extract of the leaf was also subjected to antimalarial screening at daily doses of 200, 400 and 800mg extract/kg body weight of mice infected with plasmodium berghei in a four-day treatment. The percentages of suppression of the parasitaemia at the doses of 200, 400, and 800 mg extract/kg body weight were, respectively, 36.62%, 50.36%, and 61.06%. The findings on antiplasmodial activity of this plant justify the traditional use by local populations against malaria. The findings therefore, suggest that there is an indication that S.cayennensis leaves contain phytochemicals that may be linked to its beneficial effects on health. Thus, the isolation of the active compounds from this plant is suggested for possible antimalarial drugs.