Inhibitory effects of ellagic acid on the direct-acting mutagenicity of aflatoxin B1 in the Salmonella microsuspension assay

Ellagic acid (EA) is a phenolic compound that exhibits both antimutagenic and anticarcinogenic activity in a wide range of assays-in vitro and in vivo. It occurs naturally in some foods such as strawberries, raspberries, and grapes. In the previous work, we used the Salmonella microsuspension assay to examine the antimutagenicity of EA against the potent mutagen aflatoxin B-1 (AFB(1)) using tester strains TA98 and TA100. Briefly, the microsuspension assay was approximately 10 times more sensitive than the standard Salmonella/microsome (Ames) test in detecting AFB(1) mutagenicity, and EA significantly inhibited mutagenicity of all AFB(1) doses in both tester strains with the addition of S9. The greatest inhibitory effect of EA on AFB(1) mutagenicity occurred when EA and AFB(1) were incubated together (with metabolic enzymes). Lower inhibition was apparent when the cells were first incubated with EA followed by a second incubation with AFB(1), or when the cells were first incubated with AFB(1) followed by a second incubation with EA alone, all with metabolic enzymes. The result of these sequential incubation studies indicates that one mechanism of inhibition could involve the formation of an AFB(1)-EA chemical complex. In the present study, we further examine the effect of EA on AFB(1) mutagenicity, but without the addition of exogenous metabolic enzymes. We report the mutagenicity of AFB(1) in the microsuspension assay using TA98 and TA100 without the addition of S9. Neither the concentrations of AFB(1) (0.6, 1.2, and 2.4 mu g/tube) nor the concentrations of EA (0.3, 1.5, 3, 10, and 20 mu g/tube) were toxic to the bacteria. The results indicate that AFB(1) is a direct-acting mutagen, and that EA inhibits AFB(1) direct-acting mutagenicity. (C) 1998 Elsevier Science B.V.