Evaluation of free radical-generating compounds for toxicity towards the cyanobacterium Planktothrix perornata, which causes musty off-flavour in pond-raised channel catfish (Ictalurus punctatus)

Abstract

The cyanobacterium Planktothrix perornata grows in channel catfish (Ictalurus punctatus) production ponds in the southeastern United States and produces the musty-odor compound 2-methylisoborneol (MIB). MIB can rapidly accumulate in the flesh of the catfish, thereby rendering the fish unpalatable and unmarketable. A group of compounds that produce reactive oxygen intermediates (ROI) were evaluated using a rapid bioassay for their selective toxicities towards P. perornata. The most selectively toxic compounds were tert-butyl hydroperoxide and the 8-aminoquinoline derivative (-)-(R)-8-[(4-amino-1-methylbutyl)amino]-6-methoxy-4-methyl-5-[3,4-dichlorophenoxy]quinoline succinate], with lowest-complete-inhibition concentrations (LCIC) of 0.01 µM and 1.0 µM, respectively. The 8-aminoquinoline derivative and tert-butyl hydroperoxide are not likely candidates to pursue for efficacy studies in catfish production ponds due to their respective high manufacturing cost and toxicity profile. However, this study demonstrates that ROI-producing compounds are a priority target group for evaluation of selective toxicity towards P. perornata as the first step in the discovery of novel cost-effective, environmentally safe algaecides.