Preparative enzymatic synthesis of glucuronides of zearalenone and five of its metabolites

摘要

The resorcylic acid lactones zearalenone (1), alpha-zearalenol (2), beta-zearalenol (3), alpha-zearalanol (zeranol) (4), beta-zearalanol (taleranol) (5), and zearalanone (6) were converted to their glucuronides on a preparative scale in good yields. Reactions were conducted with bovine uridine 5'-diphosphoglucuronyl transferase (UDPGT) as catalyst and uridine 5'-diphosphoglucuronic acid (UDPGA) as cofactor. The glucuronides were isolated by column chromatography and characterized by NMR spectroscopy and mass spectrometry. Although the principal products were 4-O-glucuronides (i.e., linkage through a phenolic hydroxyl), significant quantities of the 6'-O-glucuronides (i.e., linkage through the aliphatic hydroxyl) of alcohols 2, 4, and 5 were also isolated. In the case of 3, the 2-O-glucuronide was isolated as the minor product. Overall isolated yields of glucuronides, performed on a 20-50 mg scale, were typically ca. 80%. based on, the resorcylic acid lactone starting material. LC-UV-MS2 analysis of purified specimens revealed MS2 fragmentations useful for defining the point of attachment of the glucuronide moiety to the zearalenone nucleus.