Direct Analysis of Glucuronides with Liquid Chromatography-Mass Spectrometric Techniques and Methods

Abstract

Glucuronidation is one of the main phase II metabolic reactions in humans and animals. A variety of analytical techniques and methods have been used for the detection and quantification of glucuronides of both endogenous and xenobiotic compounds from different biological samples of humans and animals. Drug metabolism has been extensively studied with both in vitro and in vivo experiments under various conditions. The purpose of this review is to explore in detail the benefits and drawbacks of different liquid chromatography-mass spectrometric (LC/MS) methods and techniques in detection and identification of all forms of glucuronide conjugates from in vitro, biological, and environmental samples. The entire analytical procedure is covered, from sample treatment, separation, and ionization to qualitative and quantitative analyses. The aim of this review is not to cover every published paper where glucuronides are identified and/or quantified, but rather to focus on special cases where a new analytical approach or technical development has led to a better, more specific, or more comprehensive detection, identification, or quantitation of glucuronide conjugates.

Current applications of high-resolution mass spectrometry in drug metabolism studies

“…It can also be more laborious consisting of solid-phase extraction (SPE) prior to injection into the LC system as demonstrated be Philipp et al for detection of phase II metabolites of alkaloids of the herbal drug of abuse Kratom [3-5, 38, 39]. A comprehensive overview of direct analysis of glucuronides with LC-MS techniques and methods was recently published by Ketola and Hakala [45].…”

Analytical Methods for Quantification of Drug Metabolites in Biological Samples

“…That fact has represented a hindrance for direct metabolite determination because chromatographic separation between these polar analytes and interfering matrix components could not be achieved in many cases. However, this problem has been o v e r c o m e b y a d v e n t o f p o w e r f u l l i q u i d chromatography-tandem mass spectrometry instruments which allow direct quantification of these metabolites [42]. LC-MS/MS nowadays play predominant role in bioassays for pharmacokinetic and metabolism studies due to its inherent specificity, sensitivity and speed.…”

“…These metabolites are determined by cleavage of conjugates to yield the parent drug, which is subsequently detected. This indirect approach has several limitations, including the risk of incomplete hydrolysis, moderate repeatability and time consuming sample preparation [42]. Another drawback is non-selectivity of this procedure toward study of particular metabolite of interest when distinct drug metabolite conjugates are present in sample, like in case of morphine which is transformed to two isomeric metabolites.…”

“…Moreover, the absence of proteins in these matrices allows direct injection without sample pretreatment. Nevertheless, it is advisable to dilute and filter or centrifuge the samples to reduce matrix effect and to remove eventually present particles [42]. Many examples for metabolite determination using PP, mainly in serum and urine, can be found in recently published review articles [66][67][68].…”

“…The softest ionization technique, ESI, is the method of choice for polar and ionic compounds. The advantage of soft ionization is in providing reliable information about molecular weight of the phase II metabolites in comparison to other ionization techniques [42]. For parent drug and phase I metabolites with a lower polarity, APCI and APPI may provide better ionization efficiency and sensitivity [34].…”