IDENTIFICATION OF CYLINDROSPERMOPSIN IN APHANIZOMENON-OVALISPORUM (CYANOPHYCEAE) ISOLATED FROM LAKE KINNERET, ISRAEL

Aphanizomenon ovalispolum (Forti) was identified and isolated from Lak e Kinneret upon its first appearance as a dominant bloom in late 1994. This cyanobacterial species, not previously known to be toxic, was ev aluated by a commonly used mouse bioassay and was demonstrated to indu ce toxic symptoms that were distinguishable from the typical symptoms of the neurotoxins previously reported in Aphanizomenon flos-aquae (L. ) Ralfs. Mice died 5-24 h after crude extracts were injected intraperi toneally, and the LD50 value was estimated as 465 mg dry wt biomass ma ss.kg(-1) mouse. A toxicity-guided fractionation of the active extract indicated that the potent substance is polar in nature. The structure of the active compound was determined by its mass spectrometry and NM R data. The compound was found to be the sulfate-guanidinium zwitterio n, cylindrospermopsin, previously isolated from the cyanobacterium Cyl indrospermopsis raciborskii (Woloszynska) and recently also reported i n Umezakia natans (Watanabe). This is the first time that Aphanizomeno n ovalisporum has been reported to contain a toxic compound.