Microbial toxicity mechanism of copper-8-quinolinolate

Sapstain, an abnormal discoloration in wood caused by microbial growth, can significantly lower the price of a lumber and thus fresh sawn softwood lumber of a susceptible species is often treated with a biocide such as pentachlorophenol (PCP) to prevent the development of sapstain during shipping and prolonged storage. Very recently, chlorophenol-based antisapstain agents have been banned in Canada, because of environmental toxicity. The purpose of this study was to elucidate the microbial toxicity mechanism of the copper salts of 8-quinolinolate (Cu-8-HQ), one of the replacement chemicals for PCP in sapstain control. The results revealed that the biocidal activity of Cu-8-HQ originates from a stable metal (copper) chelate and that the molecular integrity of the chelate is most critical in the expression of its toxicity potential. The chelating power of 8-hydroxyquinoline for trace metals was not found to be directly responsible for the biocidal activity of Cu-8-HQ as suggested in the literature. The anion groups were found to have no significant impact on the biocidal activity of Cu-8-HQ, which has been observed with other organometallic compounds. © 1994 by John Wiley & Sons, Inc..