The scavenging capacity of
reactive oxygen species, such as
hydroxyl radicals, is reported not to decrease in boiled garlic (an odorless garlic preparation). We therefore examined the modifying effect of boiled garlic
powder (BGP) on 1,2-dimethylhydrazine-induced
mucin-depleted foci (
MDF) and
aberrant crypt foci (ACF), preneoplastic lesions, in the rat colorectum. Male F344 rats (5 weeks old) were fed a basal diet, or experimental diets containing 5% or 1% BGP for 5 weeks. One week later, all rats were injected s.c. with
DMH (40 mg/kg, once weekly for 2 weeks).
At 10 weeks of age, all the rats were sacrificed, and the colorectum was evaluated for
MDF and ACF. In rats given
DMH and the 5% or 1% BGP diets (Groups 2 and 3), the numbers of
MDF decreased significantly in a dose-dependent manner, compared with the
DMH and basal diet value (Group 1) (p<0.01). The numbers of ACF in Group 2, but not Group 3, showed a non-significant tendency to decrease. Next, the effects of BGP on the formation of
DMH-induced
O6-methylguanine (O6-MeG)
DNA adducts in rats were studied. Male F344 rats (5 weeks old) were fed the basal diet, or 10% BGP diet for 5 weeks. All rats were injected i.p. once with 40 mg/kg
DMH at the end of week 5. The animals were sacrificed 6 hours after
DMH injection to analyze the O6-MeG
DNA adducts in the colorectal mucosa. Dietary administration of BGP significantly inhibited the O6-MeG
DNA adduct levels in the colorectal mucosa, compared with the controls (p<0.01). These results suggested that BGP may exert chemopreventive effects against colon
carcinogenesis at least in the initiation stage.