Insecticidal activity of 12-epi-hapalindole J isonitrile.

12-epi-Hapalindole J isonitrile (1) and three previously described hapalindoles, 12-epi-hapalindole C isonitrile (2), hapalindole L (3) and 12-epi-hapalindole E isonitrile (4) were isolated and identified as insecticidal alkaloids of the biofilm-forming freshwater cyanobacterium Fischerella ATCC 43239 (Stigonematales). The structures of the purified compounds were elucidated by ESI-FTICR-MS, GC-EI-MS and various 2D NMR experiments. At 26 microM hapalindole 1 killed 100% of the larvae of the dipteran Chironomus riparius within 48h. Insecticidal activities were also found at similar concentration for the hapalindoles 2-4. The bioactivity of hapalindoles demonstrates that cyanobacterial biofilms can be considered as promising sources of insecticidal metabolites which might be useful for the biocontrol of dipterans.