Isolation and characterization of carbinolamide and phenolic glucuronide conjugates of (+-)-N-methyl-N-(1-methyl-3,3-diphenylpropyl) formamide and N-formylmethamphetamine by FAB/MS, LC/MS/MS, and NMR

Abstract

The metabolic disposition of (+-)-N-methyl-N-(1-methyl-3,3- diphenyl-propyl)formamide, especially with regard to the formation of water soluble glucuronides, is described. The glucuronide conjugates, (+-)-N-hydroxymethyl-N-(1-methyl-3,3-diphenylpropyl)formamide glucuronide, (+-)-N-methyl-N-[1-methyl-3-(4'-hydroxyphenyl)-3-phenylpropyl]formamide glucuronide, and (+-)-N-methyl-N-[1-methyl-3-(4'-hydroxy-3'-methoxyphenyl)-3- phenylpropyl]formamide glucuronide were isolated from the bile of rats dosed with the parent compound. These conjugates were characterized spectroscopically by 1H-NMR, FAB/MS, and LC/MS/MS. Because it is becoming more common to isolate the intact glucuronide conjugates of xenobiotics, we investigated some common mass spectral fragmentation patterns of these conjugates, especially by LC/MS/MS. The fragmentation patterns for each of the conjugates were obtained under MS/MS conditions and compared. Specifically, the fragmentation patterns of phenolic glucuronide and an aliphatic O-glucuronide, in particular a carbinolamide glucuronide, were investigated. The data obtained from these studies was used to predict the nature of glucuronide conjugates obtained from rats dosed with the formamide analog, N-formylmethamphetamine. This is the first spectroscopic characterization of an intact carbinolamide glucuronide conjugate isolated from the bile of rats.