| Abstract: | Our recent studies have demonstrated that the aqueous extract prepared from Alexandrium tamarense, a harmful red tide phytoplankton, showed cytotoxicity on Vero cells. In this study, the toxic substance was purified from the culture supernatant of A. tamarense. Based on the gel‐filtration profile, the molecular mass of a purified toxin was estimated to be about 1,000 kDa. On sodium dodecylsulfate‐polyacrylamide gel electrophoresis (SDS‐PAGE) analysis, a main band with molecular mass of 1,000 kDa was detected with periodic acid‐Schiff (PAS) staining, but no protein bands were detected by Coomassie brilliant blue (CBB) protein staining. Sugar composition analysis of the toxin suggested that the toxin contains galactose, fucose, mannose, N‐acetylglucosamine, xylose, and other minor saccharides, whereas no significant levels of amino acids were detected by amino acid analysis. These results suggest that the toxin is a polysaccharide‐based compound. The toxin showed cytotoxic effects on various cell lines in a concentration‐dependent manner. Among the cell lines tested, U937 cells were the most susceptible to the toxin. In U937 cells treated with the toxin, a typical apoptotic nuclear morphological change and DNA fragmentation were observed. This is the first report demonstrating that a polysaccharide‐based toxin isolated from red tide phytoplankton can induce apoptotic cell death. © 2008 Wiley Periodicals, Inc. J Biochem Mol Toxicol 22:405–415, 2008; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/jbt.20253 |
