Destruxin A, a toxic cyclodepsipeptide, was purified from culture filtrates of the entomopathogenic fungus Metarhizium anisopliae (Metsch.) Sorok. by Reverse-Phase HPLC, and assayed for its effects on a larval Manduca sexta (L.) (Lepidoptera: Sphingidae) heart preparation. Destruxin A was found to cause reversible and dose-dependent acceleration of the heart beat. The heart bioassay was highly sensitive to pulse applications of destruxin A at concentrations as low as 35 pmol. Because of its high level of sensitivity, the M. sexta heart bioassay could be used to detect and quantify destruxins in tissue extracts from mycosed insects or to confirm bioactivity of HPLC fractions. The site of action of Destruxin A was not determined. However, this toxin did not act as a 5HT receptor agonist.
Insecta; Manduca sexta; heart; toxin; peptide; destruxin
