A 2ND ALGICIDAL NATURAL PRODUCT FROM THE CYANOBACTERIUM, SCYTONEMA-HOFMANNI

We had previously reported the isolation and characterization of an he rbicidal metabolite, cyanobacterin, from the freshwater cyanobacterium (cyanophyte), Scytonema hofmanni UTEX 2349. This compound was identif ied as a chlorine-containing, diaryl-substituted, gamma-lactone. The n atural product inhibits electron transport in photosystem II and is to xic to a number of algae and higher plants. Crude cell extracts of Scy tonema contain other chlorinated metabolites with biological activity. We have isolated and characterized a more hydrophilic analog of cyano bacterin in which an hydroxyl group replaces the methylene dioxy group on the chlorine-containing aromatic ring. Although it is an effective inhibitor of photosynthetic electron transport in isolated thylakoid membranes, the analog has little effect on the growth of intact algal cells. It readily dehydrates in air at 25 degrees C. The hydroxy analo g is present in very small quantities in Scytonema cells and is probab ly a metabolic precursor of cyanobacterin.