Comparison of Antimutagenic Activity of Phenolic Compounds in Newly Harvested and Stored Common Beans Phaseolus vulgaris against Aflatoxin B ₁

Phenolic compounds were extracted from recently harvested or stored black Jamapa beans ( Phaseolus vulgaris ) that were subjected or not to thermal treatment. The beans studied were cropped in the same area and were from the same lot. The highest amount of condensed tannins (CT) was found in the seed coat of recently harvested beans [222.41 ± 16mg of (+)‐catechin equivalents per gram of seed coat]. After 2 yof storage, the amount of CT dropped significantly [35.8 ± 3.4 mg of (+) ‐catechin equivalents per gram of seed coat]. Thermal treatment significantly reduced the amount of CT in whole beans by approximately 70%. The raw seeds contained 13.76 ±1.2 mg of (+)‐cat‐echin equivalents per gram of seeds and a portion of CT appeared in the broth [9.4 ± 0.1 mg of (+) ‐catechin equivalents per gram of lyophilized broth]. The antimutagenic activity of these extracted phenolic compounds was tested against aflatoxin B 1 (AFB 1 ) in the Kado microsuspension assay. Newly harvested beans showed higher antimutagenic activity against AFB 1 mutagenicity than stored beans. The results suggest that to take the maximum advantage of components with biological activity present in beans, they must be used fresh.