Glucuronidation of bioflavonoids by human UGT1A10: structure–function relationships

Abstract

The extrahepatic human UDP glucuronosyltransferase 1A10 is found throughout the gastrointestinal tract and is thought to participate in the removal of orally ingested lipophilic chemicals. However, its substrate specificity towards these chemicals has not been fully characterized. The structurally diverse bioflavonoids are present in considerable amounts in fruits, vegetables and plant–derived beverages and have been shown to have many biological functions, including antioxidant properties. This study proposes features of the bioflavonoid structure necessary to confer it as a substrate of UGT1A10. The preferred substrates of UGT1A10 contain the hydroxyl group to be glucuronidated at C6 or C7, but not C5 of the A–ring or on C4′ of the B–ring. Up to two additional hydroxyl groups on the A–ring enhance activity, whereas the presence of other groups, notably sugar groups, decreases activity. The high glucuronidation efficiency towards many bioflavonoids observed suggests that the contribution of UGT1A10 in the metabolism of these dietary compounds in the gastrointestinal tract may be significant.

Key words::

• Bioflavonoids
• glucuronidation
• UDP glucuronosyltransferase–