Bioactive metabolites of Senna didymobotrya used as biopesticide against Acanthoscelides obtectus in Bungoma, Kenya.

Post-harvest pests are known to cause severe losses of beans in particular the bean weevil, Acanthoscelides obtectus, necessitating immediate and long term control measures. Convectional pesticides have been used for decades to protect stored grain from pests, but their harmful environmental impact and pest resistance resulting from the need for increased pesticide use have triggered researchers to search for eco-friendly, biodegradable and potent biopesticides. The use of natural products derived from metabolic activity of plants may constitute a new avenue of pest control. This paper describes phytochemical and biological investigations of leaves, root, and stem bark crude extracts and isolated compounds of selected Kenyan plants used to control the bean weevil. Bioassays tests of the compounds were done against brine shrimp to test their insecticidal activity against the bean weevil. Antibacterial and antifungal activity of the crude extracts of S. didymobotrya was also done. The extracts of S. didymobotrya showed high toxicity as well as adulticidal activity against bean weevil.

In vitro Anti-plasmodial Activity of Rubia cordifolia, Harrizonia abyssinica, Leucas calostachys Olive and Sanchus schweinfurthii Medicinal Plants.

Plasmodium falciparum is becoming increasingly resistant to conventional antimalaria drugs. Rapid increase of parasite resistant strains, resistance of the vector to insecticides and the difficulty in creating efficient vaccines has lead to an urgent need for new anti-malarial drugs. To determine anti-plasmodial activity of Rubia cordifolia, Harrizonia abyssinica, Sachus schweinfurthii and Leucas calostachys Olive plants. Aqueous and methanolic crude extracts were prepared from R. cordifolia, H. abyssinica, S. schweinfurthii and L. calostachys plants. The extracts were then prepared into appropriate concentrations for anti-plasmodial activities. In vitro anti-plamsodial activities of herbal drugs were analysed according to the methods of Tona et al., 1999. Methanolic extracts were more efficacious than aqueous extracts. S. schweinfurthii and L. calostachys had IC50 (Inhibition Concentration) of between 1.10μg/ml and 3.45μg/ml and had highest parasite inhibition ranging between 3.5% and 5.2%. R. cardifolia and H. abyssinica had IC50 of between 1.5μg/ml and 3.0μg/ml and it had moderate parasitaemia ranging between 5.20% and 7.22%. Vernonia lasiopa and Erythrina abysinnica had insufficient yields. S. schweinfurthii and L. calostachys had the highest parasite inhibition while R. cardifolia and H. abyssinica had moderate inhibition.