Cytotoxicity of fractions of <i>Pistia stratiotes</i> l. On larvae of Culex mosquito and <i>A. salina</i>

Crude chloroform and aqueous extracts of the duckweed, Pistia stratiotes L., were bioassayed at various concentrations for larvicidal activities against larvae of Culex mosquito and Artemia salina (brine shrimp). The crude (LC50 = 159.50μg/ml) and chloroform extracts (LC50 = 0.0909μg/ml) exerted mortality at 40μg/ml of 16.67 % and 90.0 % respectively on Culex mosquito larvae, while the aqueous extract (LC50 = >1000μg/ml) at 200μg/ml, resulted in 3.33 % mortality. The crude (LC50 = 2524.22μg/ml) was moderately toxic on A. salina larvae at 1000μg/ml which killed 30.00 % of the test organisms. Whereas the chloroform extract showed lower activity on bine shrimp larvae (3.3 % mortality, LC r 50 > 1000μg/ml). The aqueous extract demonstrated no activity on brine shrimp at all concentrations tested. The study showed that the chloroform extract of P. stratiotes selectively exerts cytotoxic effect on Culex mosquito larvae resulting in high mortality with LC50 = 0.0909μg/ml than on the brineshrimp larvae at LC 50 >1000μg/ml. It is therefore recommended that these extracts of P. stratiotes L. should be tested for adulticidal and/or mosquitocidal activity as well as toxicity in higher animals up to man. This may yield a more base line data valuable for use in the development of a microbially active chloroform fraction of the plant for possible use in modern medicine. Keywords : Toxicity, Pistia stratioes Chloroform fractions, Aqueous fractions, Artemia salina, Culex mosquito. Animal Research International Vol. 1 (2) 2004 pp. 95-99