Effects of a benzimidazole compound on monooxygenase activities

A retinoid-type benzimidazole compound (benzimidazole-tetranaphthalene, BITN) was synthesized and its effects on hepatic cytochrome P450 (CYP) dependent ethoxyresorufin O-deethylase (EROD) and pentoxyresorufin O-depentylase (PROD) enzyme activities were determined in rats in vitro. In vitro addition of BITN in 10(-3) M concentration to the reaction medium caused inhibitions in EROD (94%) and PROD (82%) activities. With the same concentration (10(-3) M) all-trans-retinoic acid (RA) was able to inhibit EROD activity 65% and PROD activity 59% whereas buthylated hydroxytoluen (BHT) inhibited EROD and PROD activities 73% and 62%, respectively. The specific inhibitors of EROD activity (caffeine) and PROD activity (SKF 525A) at 10(-3) M concentration inhibited the corresponding enzymes 33% and 77%, respectively. Thus, these results reveal that the BITN has a stronger inhibitory effect than RA, BHT, caffeine and SKF 525 A on the enzyme activities. Since these enzymes (EROD, CYP 1A1/2 and PROD, CYP2B1) activate polycyclic hydrocarbons, aromatic amines and aliphatic halogenated hydrocarbons to their ultimate mutagenic or carcinogenic forms, and are effective in producing reactive oxygen species such as superoxide, hydroxyl radical and hydrogen peroxide, the new compound, BITN, appears to have a greater anticarcinogenic and antioxidant potential than RA and BHT.