Antioxidant activity of some benzimidazole derivatives to definite tumor cell lines

A group of bis(benzimidazol-2-yl) amines have been already evaluated for cytotoxicity in vitro to human colorectal cancer cell line HT-29, breast cancer cells MDA-MB-231 and normal spleen cells and two of them (B1 and B2) have been taken for the purposes of our present investigations. From the second group of compounds representing 1,3-disubstituted-2,3-dihydro-2-iminobenzimidazoles two substances (B3 and B4) have been chosen because of their most pronounced anti-proliferative effect to human colorectal cancer cell line HT-29, breast cancer cells MDA-MB-231 and normal spleen cells, using the in vitro proliferative MTS-test. It was important to estimate the cause for this suppressive activity of the compounds. We proposed that this could be due to their antioxidant capacity. The substances were examined for antioxidant activity against hydroxyl and peroxyl radicals, applying the HORAC and ORAC methods and showed considerable capacity. The scavenging capacity of B2 towards hydroxyl radicals is the highest, followed by B1. It was estimated that B2 has the greatest scavenger capacity of oxygen radicals, emitted by the examined cells followed in descending order by B1, B3 and B4. The observed differences can be considered as impact of their structure on the Me2-helating activity and effective H-atom donation. A correlation was observed between the structure of the particular substance and the expressed antioxidant potential. The latter correlated also with the effect on the tested tumor cell lines. This result means that tumor cells are accompanied by a measurable emission of ROS which might be regulated by a proper application of antioxidants.