Characterization Of New Metabolites Research Articles

Small molecules putative structure elucidation in endemic Colombian fruits: CFM-ID approach

ABSTRACT The main goal of any structural elucidation process is to achieve the highest level of confidence possible. This is usually attained using identical standards that can confirm the unequivocal structure of a metabolite. Nevertheless, the use of standards is not always possible given the great structural diversity among bioactive compounds. To overcome this problem, informatics tools can be used, such as the open source “CFM-ID” for structure elucidation, along with a meticulous mass fragmentation analysis as an initial step for putative identification. Herein, the “CFM-ID” tool was used on three Colombian fruits especially rich in phenolic compounds: Bactris gasipaes, Borojoa patinoi, and Myrciaria dubia. Thus, we obtained the characterization of new metabolites. To complete this picture, the bioactive content was measured using in-vitro assays (antioxidant, anti-inflammatory, and neuroprotective) with promising results, and was eventually related to the twenty-six new compounds reported here for the first time.

Sensitive quantification of BB-22 and its metabolite BB-22 3-carboxyindole, and characterization of new metabolites in authentic urine and/or serum specimens obtained from three individuals by LC\u2013QTRAP-MS/MS and high-resolution LC\u2013Orbitrap-MS/MS

PurposeA synthetic cannabinoid BB-22 and its metabolite BB-22 3-carboxyindole have not yet been quantified in human urine. The aim of this study is to establish a sensitive analytical method for the quantification of BB-22 and its 3-carboxyindole in human serum and urine specimens, and the characterization of the unreported metabolites of BB-22 in authentic urine specimens from three individuals.MethodsThese compounds were extracted from β-glucuronide-hydrolyzed and unhydrolyzed urine and/or serum via liquid–liquid extraction. The identification and quantification were performed using liquid chromatography (LC)–QTRAP-tandem mass spectrometry (MS/MS) and the characterization of the new metabolites was made by high-resolution LC–MS/MS.ResultsThe limits of detection of BB-22 and BB-22 3-carboxyindole were 3 and 30 pg/mL in urine, respectively. The devised method was applied to quantify these compounds in authentic serum and urine obtained from two drug abusers and in urine from one drug abuser. The serum levels of BB-22 were 149 and 6680 pg/mL, and those of BB-22 3-carboxyindole were 0.755 and 38.0 ng/mL in cases 1 and 2, respectively. The urine levels of BB-22 were 5.64, 5.52 and 6.92 pg/mL and those of BB-22 3-carboxyindole were 0.131, 21.4 and 5.15 ng/mL in cases 1, 2 and 3, respectively. New monohydroxyl metabolites retaining the structure of BB-22 were found in the urine specimens.ConclusionsThe synthetic cannabinoid BB-22 and its metabolite BB-22 3-carboxyindole were identified and quantified in authentic human serum and urine specimens for the first time, and new metabolites of BB-22 were tentatively identified in authentic urine specimens obtained from three drug users in this study.

A decade of understanding secondary metabolism in Pseudomonas spp. for sustainable agriculture and pharmaceutical applications

Pseudomonas spp. have been widely studied for their plant growth promoting and antimicrobial metabolites. The genus got attention due to the production of array of secondary metabolites involved in the suppression of phytopathogens and ability to stimulate plant growth by means of nitrogen-fixation, production of hydrolytic enzymes, regulatory hormones, and solubilization of inorganic minerals. In recent years, research was focused towards identification of biosynthesis pathways and genes involved in the production of secondary metabolites that led to the discovery of novel metabolites including many new phenazine derivatives, quorum-sensing signals, rhizoxin analogues, cyclic lipopeptides, and a new class of alkyl-substituted aromatic acids. Identification of these biosynthetic pathways provided insights for their successful application in agriculture and for environmental sustainability. In addition, many genomic and metabolomic databases such as; METLIN, KEGG, GNPS, CFM-ID, MassBank, and MetaboLights, allowed exploring intricate metabolic pathways and significant genes involved in the biosynthesis of compounds. Several softwares, genome-mining tools and new techniques, such as MALDI-IMS and MALDI-FTICR MS were developed to facilitate the characterization of new metabolites. Additionally, use of MALDI-imaging techniques facilitated real-time visualization of complex microbial communities and their relationship with pathogens. Secondary metabolites of Pseudomonas spp. were also demonstrated for their apoptotic, anti-mitotic, nematocidal, herbicidal, anthelmintic, insecticidal, and phytotoxic effects. Total biosynthesis of metabolic derivatives and genetic engineering enabled to develop strains with improved yield of targeted bio-products. Availability and access to published genomic sequences and comparative bioinformatics tools helped in identification of strain-specific traits and development of multifunctional inocula. This review highlights significant advances in identification of Pseudomonas secondary metabolites for their successful agricultural and pharmaceutical applications.

Whole‐cell biotransformation of oleanolic acid by free and immobilized cells of Nocardia iowensis: Characterization of new metabolites

In this study, Nocardia iowensis was used to transform oleanolic acid (OA) into oleanane derivatives. The first derivative, which was found after 24 h of cultivation, was the known and already described OA methyl ester. After 1 week, two other derivatives (oleanonic acid methyl ester and an unknown metabolite) were identified as new products of a biotransformation by N. iowensis. These oleanane metabolites were characterized by HPLC, HPLC‐ESI‐MS, and HPLC‐1H NMR spectroscopy. The biotransformation was performed by suspended and immobilized cells (ICs) of N. iowensis. Cells immobilized in alginate beads were used in order to prepare a continuous process. The substrate uptake of free and ICs was similar, whereas the peak area of OA methyl ester of the ICs was only about 10% of the native cells. However, the final product (oleanonic acid methyl ester) concentrations were similar in both approaches, whereas the unknown metabolite 3 was only detected transiently in the medium of ICs. Based on these results, a new biosynthetic pathway for the biotechnological production of oleanonic acid methyl ester is proposed.

Study of in vitro metabolism of m-nisoldipine in human liver microsomes and recombinant cytochrome P450 enzymes by liquid chromatography–mass spectrometry

This is a report about the investigation of the metabolic fate of m-nisoldipine in human liver microsomes and the recombinant cytochrome P450 enzymes by using LC–MS/MS. A sensitive and reliable LC–MS/MS method was developed to obtain a rapid and complete characterization of new metabolites and the metabolism pathways. The analytes were separated on a reversed phase C18 column with acetonitrile and 0.1% aqueous formic acid as the mobile phase. Tandem mass spectrometry with positive electrospray ionization was used to enable the structural characterization of the metabolites. A total of 10 metabolites were characterized with proposed structures in the incubation of human liver microsomes by comparing their retention times and spectral patterns with those of the parent drug. Dehydrogenation of the dihydropyridine core and reactions of side chains such as hydroxylation and hydrolysis of ester bonds were the major metabolic pathways. The specific cytochrome P450 (CYP) enzymes responsible for m-nisoldipine metabolites were identified using chemical inhibition and cDNA expressed CYP enzymes. The results indicated that CYP2C19 and CYP3A4 might play major roles in the metabolism of m-nisoldipine in human liver microsomes.

Characterization of new metabolites from in vivo biotransformation of norisoboldine by liquid chromatography/mass spectrometry and NMR spectroscopy

Norisoboldine (1,9-dihydroxy-2,10-dimethoxynoraporphine) is one of the major bioactive isoquinoline alkaloids in Linderae radix, a commonly used Chinese herbal medicine. The aim of this study is to isolate and characterize metabolites of norisoboldine after gavage feeding in rats. High-performance liquid chromatography coupled with electrospray ionization and ion-trap mass spectrometry (HPLC-ESI/MS(n)) was used to identify metabolites of norisoboldine in rat urine and bile samples. A total of five metabolites of norisoboldine were characterized by comparing retention time and UV absorption in HPLC, and by molecular mass and fragmentation pattern of the analytes by mass spectrometry with those of norisoboldine. Two new glucuronide conjugates of norisoboldine, noriosboldine-1-O-beta-D-glucuronide and norisoboldine-9-O-alpha-D-glucuronide, were isolated from rat urine samples and their structures were confirmed by NMR spectroscopy ((1)H, (13)C, HMBC and HSQC) for the first time. The results suggested that glucuronidation and sulfation were involved in metabolic pathways of norisoboldine in rat.

Liquid chromatography/mass spectrometry-based structural analysis of new platycoside metabolites transformed by human intestinal bacteria

Platycosides, the main active constituents of Platycodi Radix, have been thoroughly studied for the characterization of their potent biological activities. However, metabolism of platycosides has not yet been characterized. A HPLC electrospray ionization-tandem mass spectrometry (LC/ESI-MS n ) approach was applied to new complex platycoside metabolites transformed by human intestinal bacteria to identify their structures and determine metabolic pathway. The molecular weights of metabolites were identified by LC/ESI-MS analysis in both positive and negative modes. Structures for the platycoside metabolites were proposed by the molecular weights and the expected enzymatic activity of intestinal microbes on platycoside. In the second step, successive LC–MS n analysis was used to demonstrate the proposed structures. Under ESI tandem mass conditions, the sequential fragmentation patterns of [M+Na] + ions exclusively showed signals, consistent with the cleavage of glycoside bonds, rearrangement and some cross-ring cleavage, thus allowing the rapid identification of platycoside metabolites. The metabolites identified in the time-dependent metabolism experiments enable us to propose several microbial pathways for platycosides. Even though the metabolites of some platycosides may have unknown structures and low levels, the analytical tools presented in this study made it possible to obtain a rapid and complete characterization of new metabolites and their metabolism pathway in human intestinal bacteria.

Characterization of new metabolites from in vivo biotransformation of 2‐amino‐ 3‐methylimidazo[4,5‐f]quinoline in mouse by mass spectrometry

In studying the metabolic pathways underlying the mechanism of carcinogenesis of the heterocyclic amine of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ), we recently found a new metabolite which gave an [M + H](+) ion of m/z 217 when subjected to electrospray ionization (ESI) in positive-ion mode. Following i.p. injection of this metabolite of m/z 217 (designated as m/z 217) to beta-naphthoflavone-treated mice, 57% of the total radioactivity was recovered in a 24-h mouse urine sample. HPLC separation followed by MS analysis indicates that the urine sample contained m/z 217 (36 +/- 3% of total recovered radioactivity) and two other peaks that gave rise to the [M + H](+) ions of m/z 393 (31 +/- 4%, designated as m/z 393) and m/z 233 (14 +/- 1%, designated as m/z 233). Beta-glucuronidase treatment of m/z 393 resulted in a radioactive peak corresponding to m/z 217. ESI in combination with various mass spectrometry techniques, including multiple-stage mass spectrometry, exact mass measurements and H/D exchange followed by tandem mass spectrometry, was used for structural characterization. The urinary metabolites of m/z 217, 393 and 233 were identified as 1,2-dihydro-2-amino-5-hydroxy-3-methylimidazo[4,5-f]quinoline, 1,2-dihydro-2-amino-5-O-glucuronide-3-methylimidazo[4,5-f]quinoline and 1,2-dihydro-2-amino-5,7-dihydroxy-3-methylimidazo[4,5-f]quinoline, respectively. Our results demonstrated that m/z 217 is biotransformed in vivo to m/z 393 by O-glucuronidation and to m/z 233 by oxidation. The observation of these more polar metabolites relative to IQ suggests that they may arise from a previously undescribed detoxification pathway.

Characterization of two novel propachlor degradation pathways in two species of soil bacteria.

Propachlor (2-chloro-N-isopropylacetanilide) is an acetamide herbicide used in preemergence. In this study, we isolated and characterized a soil bacterium, Acinetobacter strain BEM2, that was able to utilize this herbicide as the sole and limiting carbon source. Identification of the intermediates of propachlor degradation by this strain and characterization of new metabolites in the degradation of propachlor by a previously reported strain of Pseudomonas (PEM1) support two different propachlor degradation pathways. Washed-cell suspensions of strain PEM1 with propachlor accumulated N-isopropylacetanilide, acetanilide, acetamide, and catechol. Pseudomonas strain PEM1 grew on propachlor with a generation time of 3.4 h and a Ks of 0.17 +/- 0.04 mM. Acinetobacter strain BEM2 grew on propachlor with a generation time of 3.1 h and a Ks of 0.3 +/- 0.07 mM. Incubations with strain BEM2 resulted in accumulation of N-isopropylacetanilide, N-isopropylaniline, isopropylamine, and catechol. Both degradative pathways were inducible, and the principal product of the carbon atoms in the propachlor ring was carbon dioxide. These results and biodegradation experiments with the identified metabolites indicate that metabolism of propachlor by Pseudomonas sp. strain PEM1 proceeds through a different pathway from metabolism by Acinetobacter sp. strain BEM2.

Studies on the metabolism of a monoterpene ketone, R-(+)-pulegone--a hepatotoxin in rat: isolation and characterization of new metabolites.

1. The metabolic disposition of R-(+)-pulegone (I) was examined in rats following four daily oral doses (250 mg/kg). 2. Six metabolites, namely pulegol (II), 2-hydroxy-2-(1-hydroxy-1-methylethyl)-5-methylcyclohexanone (III), 3,6-dimethyl-7a-hydroxy-5,6,7,7a-tetrahydro-2(4H)-benzofuranone (IV), menthofuran (V), 5-methyl-2-(1-methyl-1-carboxyethylidene)cyclohexanone (VI), and 5-methyl-5-hydroxy-2-(1-hydroxy-1-carboxyethyl)cyclohexanone (VII) have previously been isolated from rat urine, and identified (Moorthy et al. (1989a). Eight new metabolites have now been isolated from rat urine, namely, 5-hydroxy-pulegone (VIII), piperitone (IX), piperitenone (X), 7-hydroxy-piperitone (XI), 8-hydroxy piperitone (XII), p-cresol (XIII), geranic acid (XIV) and neronic acid (XV). These were identified by n.m.r., i.r. and mass spectrometry. 3. Based on these results, metabolic pathways for the biotransformation of R-(+)-pulegone in rat have been proposed.

Microsomal metabolism of cyclopenta[cd]pyrene. Characterization of new metabolites and their mechanism of formation.

Oxidation of cyclopenta[cd]pyrene (CPP) by mouse and human liver microsomes was used to produce several previously undescribed metabolites, which were separated and isolated by reversed-phase HPLC. Three of these, 3,4-dihydroCPP-c-3,4-diol, 4-hydroxy-3,4-dihydroCPP, and 4-oxo-3,4-dihydroCPP, were fully characterized by GC-MS and UV spectroscopic analysis as well as by total synthesis. Two additional pairs of metabolites were identified as isomeric tetrahydrotetrols and dihydrotriols by GC-MS analysis of their trimethylsilyl derivatives. Their UV spectra were recorded and found to agree with the structure assignments. The tetrahydrotetrols were further characterized by the fact that either 3,4- or 9,10-trans-dihydrodiol could serve as their precursor, indicating that they are the two diastomeric 3,4,9,10-tetrahydroCPP-t-3,4-t-9,10-tetrols. The dihydrotriols were shown to possess t-3,4-dihydrodiol functionality. As found previously using rat liver microsomes, the most abundant metabolite was 3,4-dihydroCPP-t-3,4-diol. It was produced with one enantiomer in severalfold excess over the other, and the major enantiomer was shown to have 3R,4R configuration by exciton chirality circular dichroism. Microsomal oxidation of [4-2H]CPP, which was synthesized for this study, was used to determine the mechanisms of formation of 4-oxo- and 4-hydroxy-3,4-dihydroCPP. The ketone was produced without detectable retention of deuterium label, eliminating the NIH shift as a possible mechanism. The alcohol was shown to arise by NADPH-dependent reduction of both the ketone and another intermediate presumed to be the 3,4-epoxide.(ABSTRACT TRUNCATED AT 250 WORDS)