New catechol derivatives and pharmaceutically acceptable salts and esters thereof useful as pharmaceutical antioxidants are disclosed. Cellular damage by oxygen derived radicals is a significant factor in heart disease, rheumatoid arthritis, cancer, inflammatory disease, transplant rejection reactions and ischemia.

The compound (-)-[[4-(1,4,5,6 tetrahydro-4-methyl-6-oxo-3 pyridazinyl) phenyl]-hydrazono] propane dinitrile and its salts are prepared and used for treating congestive heart failure.