In vitro cytotoxicity of 1,4-naphthoquinone derivatives to replicating cells

The acute cytotoxicities of a series of alkyl-1,4-naphthoquinones (NQ) and of 2-hydroxy-3-alkyl-1,4-NQs, as well as some amino derivatives, were evaluated with the neutral red cytotoxicity assay, using BALB/c mouse 3T3 fibroblasts. As compared to the unsubstituted 1,4-NQ: (i) Substitution at the 2 position reduced toxicity, with the extent of reduction following the sequence, hydroxyl >> dimethylamino >> C1-C5 alkyl group. (ii) Substitution with C2-C5 alkyl groups at position 3 enhanced toxicity. As noted with the n-alkyl-1,4-NQs, increasing the chain length of the 2-hydroxy-3-alkyl-1,4-NQs did not appreciably change potency of the test agent. (iii) Substitution with amino groups at position 3 had little effect on cytotoxicity. Some differences in cytotoxicity of specific test agent were noted between the 3T3 fibroblasts and isolated rat hepatocytes, as reported in the literature.