Acute dermal toxicity and repeated dose 90-day oral toxicity studies of the bioinsecticide from Stemona curtisii Hook. F.

Abstract

A formulation of bioinsecticide from Stemona curtisii Hook. F. (Family Stemonaceae), marketed in Thailand as Biopes, is used in agriculture by the farmers in the northern area of Thailand. Subsequently, this insecticide used for insect control has become common and may lead to pesticide toxicity to both consumers and farmers. The aim of the present study is to evaluate the safety of Biopes (containing 20% w/w of Stemona crude extract) to mammals. Safety assessments included an acute oral toxicity test and a repeated dose 90-day oral toxicity test in Sprague-Dawley rats, and acute dermal irritation test in guinea pigs. In the acute oral toxicity test, Biopes showed lethal effect with the LD50 of 1,078.95 and 630.96 mg/kg-body weight in male and female rats, respectively. In the repeated dose 90-day oral toxicity test with the doses of 80 and 140 mg/kg-body weight (50 and 100 folds to the concentration used in agriculture), there were minimal but significant differences in body weight gains, some values of hematology, blood biochemical indices and organ weights between control and treated groups. The histopathology findings indicated small toxic effects of Biopes on gastrointestinal tract, lung and liver of the treated rats. In dermal irritation test, the direct exposure to non-diluted Biopes caused irritation on the skin, and death in two female guinea pigs on day10 and day14. Therefore, bioinsecticide Biopes should be used with caution because it might be harmful to the users when being directly exposed. The diluted solution of Biopes at the concentration used in agriculture slightly caused dermal irritation but it was improved within a short period.