Isolation of toxins from natural blue‐green algae and unicellular cultured Microcystis aeruginosa

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Abstract
The differences between toxins derived from natural populations and cultures of Microcystis aeruginosa and Microcystis viridis, and the toxins of harvested extracts from four strains of Microcystis were investigated using DEAE‐cellulose chromatography. Toxins extracted from algal populations consisting of 75% (total Microcystis cells/ml) M. aeruginosa from Lake Kasumigaura, Japan, contained an F‐II fraction determined by ion‐exchange chromatography; toxins extracted from algal populations consisting of 70% M. viridis from Lake Suwa, Japan, also contained this fraction. Using an improved gradient procedure with ion‐exchange chromatography to analyze crude extracts of unicellular cultures of M. aeruginosa strain PS‐434, five extracted fractions — F‐II, F‐IV, F‐V, F‐VI and F‐VII — were determined to contain toxic substances. These fractions were identified as toxic (intraperitoneal injection) in mouse toxicity studies. No toxic fractions were identified in cultures of M. aeruginosa strain NIES‐44. Mice LD50s for the crude extracts of cultures of strain PS‐434 and the extracts from Lakes Kasumigaura and Suwa were calculated as less than 89.5, 260 and 570 mg/kg, respectively. In natural populations of M. aeruginosa or M. viridis, four toxic fractions (F‐IV, F‐V, F‐VI and F‐VII) were not found.