Chlorothalonil is a broad-spectrum organochlorine fungicide that forms adducts with glutathione and cysteine residues on enzymes leading to GST depletion and enzyme deactivation, respectively.1 In vitro, it inhibits the growth of C. albicans and C. orbiculare fungi, S. aureus and B. cereus Gram-positive bacteria, and E. coli and P. aeruginosa Gram-negative bacteria (MICs = 0.7, 5, 1.3, 0.7, 0.5, and 1.7 µg/ml, respectively).2,3 In vivo, chlorothalonil (100 µg/ml) completely inhibits the growth of P. infestans, the tomato late blight pathogen, on tomato plants.4 It is toxic to aquatic organisms, including species of fish, crustaceans, molluscs, and algae with tenth percentile of toxicity values of 25.23, 40.59, 0.69, and 3.94 µg/L, respectively, as well as to other aquatic invertebrates.5 Chlorothalonil is carcinogenic in animal models and induces neoplasms in the forestomach and kidneys of rats when administered at a dose of 3.8 mg/kg per day, but it is not genotoxic.6 Formulations containing chlorothalonil have been used as fungicides in agriculture.
1.Tillman, R.W., Siegel, M.R., and Long, J.W.Mechanism of action and fate of the fungicide chlorothalonil (2,4,5,6-tetrachloroisophthalonitrile) in biological systems. I. Reactions with cells and subcellular components of Saccharomyces pastorianusPestic. Biochem. Physiol.3(2)160-167(1973) 2.Shi, L.-P., Jiang, K.-M., Jiang, J.-J., et al.Synthesis and antimicrobial activity of polyhalobenzonitrile quinazolin-4(3H)-one derivativesBioorg. Med. Chem. Lett.23(21)5958-5963(2013) 3.Lee, J.Y., Moon, S.S., and Hwang, B.K.Isolation and antifungal activity of kakuol, a propiophenone derivative from Asarum sieboldii rhizomePest. Manag. Sci.61(8)821-825(2005) 4.Lee, Y.M., Moon, J.S., Yun, B.-S., et al.Antifungal activity of CHE-23C, a dimeric sesquiterpene from Chloranthus henryiJ. Agric. Food. Chem.57(13)5750-5755(2009) 5.DeLorenzo, M.E., and Fulton, M.H.Comparative risk assessment of permethrin, chlorothalonil, and diuron to coastal aquatic speciesMar. Pollut. Bull.64(7)1291-1299(2012) 6.Wilkinson, C.F., and Killeen, J.C.A mechanistic interpretation of the oncogenicity of chlorothalonil in rodents and an assessment of human relevanceRegul. Toxicol. Pharmacol.24(1 Pt 1)69-84(1996)