Effects of soya bean flakes and liquorice root extract on enzyme induction and toxicity in B6C3F1 mice.

Both soya bean flakes (SBF) and liquorice root extract (LRE) have previously been reported to have anticarcinogenic properties, which have been thought to be related to an increased activity of specific enzymes responsible for the detoxification of chemical carcinogens. 30- and 90-day studies were conducted in male B6C3F1 mice to determine which, if any, of several detoxification enzymes are induced by SBF or LRE. Mice fed 8 and 25% LRE showed a variety of adverse clinical signs, poor weight gain and 30% mortality. Significant increases in liver:body weight ratios were observed in both the SBF and LRE groups. No significant treatment-related gross autopsy findings were observed in any of the SBF groups. A number of abnormalities were observed in the LRE groups, including lesions of the kidney, liver, spleen and thymus. Liver samples from the 90-day study were analysed for 7-ethoxycoumarin O-deethylase (7-ECOD), benzo[a]pyrene hydroxylase (BPH), superoxide dismutase (SOD), glutathione S-transferase (GST) and UDP-glucuronyl transferase (UDPGT) at 90 days, and at an interim 30-day autopsy. No treatment-related increases were observed for BPH or SOD. Both SBF and LRE induced modest increases in UDPGT activity. SBF induced modest increases in GST activity, but LRE decreased this activity. 7-ECOD activity was significantly increased by LRE and decreased by SBF. Samples from a 30-day study in which both LRE and SBF were administered at various dose levels were examined for UDPGT activity; all dose groups showed decreases in UDPGT activity relative to controls. The results suggest that both SBF and LRE may alter the activities of specific enzymes involved in the detoxification of chemical carcinogens; however, the combination of these two foodstuffs may not produce an additive effect in B6C3F1 mice.