Stability of cylindrospermopsin, the toxin from the cyanobacterium, Cylindrospermopsis raciborskii: Effect of pH, temperature, and sunlight on decomposition

Cylindrospermopsin is a powerful hepatotoxin produced by the cyanobacterium Cylindrospermopsis raciborskii. It is considered a potential threat to liv estock, wildlife, and humans, and is the suspected cause of an outbreak of hepatoenteritis on Palm Island, Queensland, Australia, and various stock po isoning incidents around Australia. In this study, the stability of cylindr ospermopsin was investigated using different parameters, including visible and UV light, sunlight, temperature and pH. Cylindrospermopsin decomposes r apidly (half-life of 1.5 h) when exposed to sunlight in an algal extract so lution; however, no decomposition was recorded in pure cylindrospermopsin a nd Milli-Q water solutions. Cylindrospermopsin decomposes slowly in tempera tures ranging from 4 to 50 degrees C at pH 7. After 10 weeks at 50 degrees C, cylindrospermopsin had degraded to 57% of the original concentration. Th is degradation was accompanied by an increase in another compound which is believed to be structurally related to cylindrospermopsin. Boiling does not cause a significant degradation of cylindrospermopsin within 15 min. Initi al investigations indicate that cylindrospermopsin is degraded slowly under artificial light ranging from 42, 29, and 9 mu E m(-1) S-1 and in darkness . Degradation of cylindrospermopsin was not affected by changes in pH. Expe riments were performed in sterile conditions. (C) 1999 by John Wiley gr Son s, Inc.