Desmutagenic activity of natural humic acids: inhibition of mitomycin C and maleic hydrazide mutagenicity.

Humic acids are natural components of organic matter widespread in the environment. In spite of the incomplete knowledge about their composition, increasing interest in humic acid activity is justified by their ubiquity. Four different humic acids have been tested in Chinese hamster ovary cells in vitro, both alone and in combination with two well-known mutagens (mitomycin C and maleic hydrazide). Data about sister-chromatid exchanges, mitotic and proliferation indices were collected. Our results, on the whole, indicate: (i) a slight mutagenicity and toxicity of tested humic acids, probably due to chlorination during sample preparation; (ii) a desmutagenic rather than antimutagenic activity of the tested humic acids.