Formation of intermediate conjugates in the reductive transformation of gonyautoxins to saxitoxins by thiol compounds

The activity of bacterial extracts to transform gonyautoxins to saxitoxins was found to be due to glutathione. This activity was also found in another thiol compound, 2-mercaptoethanol. These thiol compounds did not reduce 1- N-OH of gonyautoxin 1 and 4. Interestingly, the stable intermediate conjuga tes of paralytic shellfish toxins and thiol compounds were formed in the co urse of the reaction, which demonstrates that this is a two-step reaction c onsisting of formation of intermediate and degradation of the intermediate to saxitoxins.