Respirantin, a novel insecticidal cyclodepsipeptide from Streptomyces.

In the course of our screening search for insect growth regulators from microorganism, we have found a new insecticidal antibiotic termed respirantin (1) from the mycelial extract of a Streptomyces sp.No. 4403, which was isolated from a soil sample collected at Eiheiji-cho, Fukui, Japan.In this communication, we report the fermentation, isolation, structure elucidation and biological activities of1.Bioassay for insect growth regulators was carried out according to the method previously reported1 '2).A cultured broth was suspended with an artificial diet for Pseudalitia (Leuicania) separata3) in a flask, which was then autoclaved at 1 10°C for 15 minutes.Assay larvae of P. separata had been previously reared under aseptic conditions and three larvae in the third larval molting were transferred to an assay flask.These assay flasks were kept at 25°C and the effect of each sample was examined.The fermentation was carried out in 500-ml Erlenmeyer flasks containing: 100ml of medium with a following composition: Glucose 0.4%, yeast extract 0.4% and malt extract 1%.The pH of the mediumwas adjusted to 7.3 before sterilization.The seed culture was inoculated to the flask, and the fermentation was carried out at 26.5°C for 5 days on a rotary shaker.The acetone extract of the mycelial cake was concentrated under reduced pressure and the resulting aqueous solution was extracted with ethyl acetate.