N-Methyl welwitindolinone C isothiocyanate (7), the major indole alkaloid in the blue-green algae (cyanobacteria) Hapalosiphon welwitschii W. & G. S. West UHIC-52-3 and Westiella intricata Borzi UH HT-29-1 (Stigonemataceae), is responsible for some of the multiple-drug-resistance (MDR) reversing activity in H. welwitschii and most of the insecticidal activity in W. intricata. The oxindole was isolated from the lipophilic extracts of the two cyanophytes and its structure and absolute stereochemistry determined by X-ray crystallography. Fourteen additional alkaloids were isolated from H. welwitschii as minor constituents, viz. a novel spiro oxindole, welwitindolinone A isonitrile (1), five tetracyclic oxindoles (1-6) related to 7, and eight biogenetically-related fischerindoles (8-11) and hapalindoles (12-15). In addition to 1, five other alkaloids were isonitriles and these six compounds collectively accounted for the fungicidal activity of H. welwitschii. The gross structures and relative stereochemistries of 1-6 and 8-15 were elucidated by spectral analysis. The biogenesis of these alkaloids is discussed.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry