Inhibition of 2‐Amino‐3, 8‐dimethylimidazo[4,5‐f]quinoxaline‐mediated DNA‐adduct Formation by Chlorophyllin in Drosophila

The effect of chlorophyllin on 2‐ammo‐3,8‐dimethylimidazo[4,5‐f]quinoxaline (MeIQx)‐mediated DNA‐adduct formation in Drosophila was studied. Third‐instar larvae of Drosophila were fed MeIQx at 1 mg/6.5 g‐feed/bottle, with or without chlorophyllin (100–300 ing). After a 6 h feeding exposure to MeIQx, the larvae were divided into 2 groups. The first group was examined for covalent DNA adducts by (32)P‐postlabeIing assay. The second group was assayed for DNA damage by allowing the larvae to develop to adults and measuring the male/female ratio (males, DNA repair‐deficient; females, DNA repair‐proficient). The (32)P‐postlabeling results indicated a significant decrease in DNA adduct levels in larvae treated with MeIQx and 300 mg chlorophyllin (1.7±0.7 adducts/10(7) nucleotides) as compared with MeIQx‐treated larvae (6.5±2.1 adducts/10(7) nucleotides). The results on male/female sex ratios also indicated a chlorophyllin‐indnced decrease in DNA damage by exposure to MeIQx. The suppressive effect of chlorophyllin on the genotoxic actions of a polycyclic mutagen, MeIQx, may be a result of complex formation between chlorophyllin and the mutagen.