In Vitro and in Vivo Metabolite Profiling of Valnemulin Using Ultraperformance Liquid Chromatography–Quadrupole/Time-of-Flight Hybrid Mass Spectrometry

Abstract

Valnemulin, a semisynthetic pleuromutilin derivative related to tiamulin, is broadly used to treat bacterial diseases of animals. Despite its widespread use, metabolism in animals has not yet been fully investigated. To better understand valnemulin biotransformation, in this study, metabolites of valnemulinin in in vitro and in vivo rats, chickens, swines, goats, and cows were identified and elucidated using ultraperformance liquid chromatography–quadrupole/time-of-flight hybrid mass spectrometry (UPLC-Q/TOF-MS). As a result, there were totally 7 metabolites of valnemulin identified in vitro and 75, 61, and 74 metabolites detected in in vivo rats, chickens, and swines, respectively, and the majority of metabolites were reported for the first time. The main metabolic pathways of valnemulin were found to be hydroxylation in the mutilin part (the ring system) and the side chain, oxidization on the sulfur of the side chain to form S-oxides, hydrolysis of the amido bond, and acetylization in the amido of the side chain. In addition, hydroxylation in the mutilin part was proposed to be the primary metabolic route. Furthermore, the results revealed that 2β-hydroxyvalnemulin (V1) and 8α-hydroxyvalnemulin (V2) were the major metabolites for rats and swines and S-oxides (V6) in chickens.

In vitro and in vivo metabolism of ochratoxin A: a comparative study using ultra-performance liquid chromatography-quadrupole/time-of-flight hybrid mass spectrometry

“…All the manipulation was in compliance with Chinese laws and guidelines (GKFCZ2001545) and accorded to the China Agricultural University regulations concerning protection of animals used for scientific purposes (2010-SYXK-0037). Hepatic microsomes were prepared according to the procedure reported by Yang et al [26,27]. The protein content of the microsomes was estimated according to Lowry et al using crystalline bovine serum albumin as the control standard [32].…”

“…In recent years, liver microsomes have been extensively utilized in drug metabolism studies because of their lower cost, good reproducibility, and simple preparation [26][27][28]34]. In order to rapidly characterize the metabolism of OTA, rat liver microsomes were incubated with OTA and NADPH.…”

“…Compared to the in vitro system, the in vivo results are more scientifically credible because in vivo studies account for lots of factors [26,27]. In addition and to our knowledge, no information on OTA metabolism in chickens was available.…”

“…Currently, liquid chromatography combined with mass spectrometry (LC-MS) is playing an important role in the area of metabolite identification. In particular, ultraperformance liquid chromatography-quadrupole/time-offlight tandem mass spectrometry (UPLC-Q/TOF-MS) became an increasingly popular technique to identify unknown compounds, due to its high speed, superior selectivity, large sensitivity, and mass accuracy [26][27][28][29][30][31]. To completely characterize the OTA metabolites, the metabolism of OTA in liver microsomes of rats, chickens, swine, goats, cows, and humans was compared using UPLC-Q/TOF-MS.…”

Unraveling the in vitro and in vivo metabolism of diacetoxyscirpenol in various animal species and human using ultrahigh-performance liquid chromatography-quadrupole/time-of-flight hybrid mass spectrometry

“…Hepatic microsomes were prepared from the homogenized livers of untreated animals (rats, chickens, swine, goats, and cows) by differential centrifugation, according to the procedure reported by Yang et al [26][27][28][29]. Microsomes and cytosol were frozen in liquid nitrogen, then stored at −80°C until use.…”