Pharmacognostic standardization and insecticidal activity of the leaves of Hyptis suaveolens (L.) Poit (Lamiaceae)

Abstract

Lamiaceae have traditionally been used in developing countries for their insecticidal and repellant properties against several insect species. Hyptis suaveolens has been reported to repel mosquitoes and other insects effectively when burnt overnight in rooms. This study was aimed at establishing the Pharmacognostic profile and insecticidal/repellant activity of the leaves of H. suaveolens (L.) Poit against maize/bean weevils. Evaluation of the fresh, powdered and anatomical sections of the leaves was carried out to determine the macromorphological, micromorphological, chemomicroscopic, numerical and phytochemical profile. Evaluation of the insecticidal activity involved the determination of antifeedant properties, repellant and insecticidal actions of the extract and its fractions against adult Sitophilus zeamais (maize weevil) and Acanthscelides obtectus (bean weevil). Macro and microscopic studies gave results that could serve as a basis for proper identification, collection and investigation of the leaves of H. suaveolens. Phytochemical screening revealed the presence of alkaloids, tannins, saponins and cardiac glycosides. The crude extract and fractions produced antifeedant, repellant and insecticidal activities to varying degrees against Adult Sitophilus zeamais (maize weevil) and Acanthscelides obtectus (bean weevil). H. suaveolens has the potential to act as a lead in the commercial production of insecticides of plant origin. This will go a long way in ameliorating the deleterious effects associated with synthetic chemicals.

Keywords: H. suaveolens; Pharmacognostic profile; Insecticidal activity; Phytochemical constituents; Weevils