Tandem mass spectrometric studies of the fragmentation of penicillins and their metabolites

A Comprehensive Study to Identify Major Metabolites of an Amoxicillin–Sulbactam Hybrid Molecule in Rats and Its Metabolic Pathway Using UPLC-Q-TOF-MS/MS

Amoxicillin and sulbactam are widely used compound drugs in animal food. The amoxicillin–sulbactam hybrid molecule can achieve better curative effects through the combination of the two drugs. However, its pharmacokinetic behavior needs to be explored. In this study, a randomized crossover experiment was performed to investigate the metabolism of the novel amoxicillin–sulbactam hybrid molecule in rats after gastric administration. Ultrahigh performance liquid chromatography–quadrupole time-of-flight tandem mass spectrometry (UPLC-Q-TOF-MS/MS) was used to isolate and to identify the metabolites in rats. Amoxicillin, amoxicilloic acid, amoxicillin diketopiperazine, and sulbactam were eventually detected in the plasma, liver, urine, and kidneys; no hybrid molecules and their metabolites were detected in feces. The in vivo metabolism results showed that the hybrid molecule was absorbed into the body in the intestine, producing amoxicillin and sulbactam, then amoxicillin was partially metabolized to amoxicilloic acid and amoxicillin diketopiperazine, which are eventually excreted in the urine by the kidneys. In this study, four major metabolites of the amoxicillin–sulbactam hybrid molecule were identified and their metabolic pathways were speculated, which provided scientific data for understanding the metabolism of the hybrid molecule and for its clinical rational use.

Metabolic Profiling and In Vitro Assessment of the Biological Activities of the Ethyl Acetate Extract of Penicillium chrysogenum “Endozoic of Cliona sp. Marine Sponge” from the Red Sea (Egypt)

Marine sponge-derived endozoic fungi have been gaining increasing importance as promising sources of numerous and unique bioactive compounds. This study investigates the phytochemical profile and biological activities of the ethyl acetate extract of Penicillium chrysogenum derived from Cliona sp. sponge. Thirty-six compounds were tentatively identified from P. chrysogenum ethyl acetate extract along with the kojic acid (KA) isolation. The UPLC-ESI-MS/MS positive ionization mode was used to analyze and identify the extract constituents while 1D and 2D NMR spectroscopy were used for kojic acid (KA) structure confirmation. The antimicrobial, antioxidant, and cytotoxic activities were assessed in vitro. Both the extract and kojic acid showed potent antibacterial activity against Staphylococcus aureus and Pseudomonas aeruginosa with MIC 250 ± 0.82 µg/mL. Interestingly, the extract showed strong antifungal activity against Candida albicans and Cryptococcus neoformans with MIC 93.75 ± 0.55 and 19.53 ± 0.48 µg/mL, respectively. Furthermore, KA showed the same potency against Fusarium oxysporum and Cryptococcus neoformans with MIC 39.06 ± 0.85 and 39.06 ± 0.98 µg/mL, respectively. Ultimately, KA showed strong antioxidant activity with IC₅₀ 33.7 ± 0.8 µg/mL. Moreover, the extract and KA showed strong cytotoxic activity against colon carcinoma (with IC₅₀ 22.6 ± 0.8 and 23.4 ± 1.4 µg/mL, respectively) and human larynx carcinoma (with equal IC₅₀ 30.8 ± 1.3 and ± 2.1 µg/mL, respectively), respectively. The current study represents the first insights into the phytochemical profile and biological properties of P. chrysoenum ethyl acetate extract, which could be a promising source of valuable secondary metabolites with potent biological potentials.

Collision-Induced Dissociation Mass Spectrometry: A Powerful Tool for Natural Product Structure Elucidation

Mass spectrometry is a powerful tool in natural product structure elucidation, but our ability to directly correlate fragmentation spectra to these structures lags far behind similar efforts in peptide sequencing and proteomics. Often, manual data interpretation is required and our knowledge of the expected fragmentation patterns for many scaffolds is limited, further complicating analysis. Here, we summarize advances in natural product structure elucidation based upon the application of collision induced dissociation fragmentation mechanisms.

Identification of the related substances in ampicillin capsule by rapid resolution liquid chromatography coupled with electrospray ionization tandem mass spectrometry

Rapid Resolution Liquid Chromatography coupled with Electrospray Ionization Tandem Mass Spectrometry (RRLC-ESI-MS(n)) was used to separate and identify related substances in ampicillin capsule. The fragmentation behaviors of related substances were used to identify their chemical structures. Finally, a total of 13 related substances in ampicillin capsule were identified, including four identified components for the first time and three groups of isomers on the basis of the exact mass, fragmentation behaviors, retention time, and chemical structures in the literature. This study avoided time-consuming and complex chemosynthesis of related substances of ampicillin and the results could be useful for the quality control of ampicillin capsule to guarantee its safety in clinic. In the meantime, it provided a good example for the rapid identification of chemical structures of related substances of drugs.

Antibiotic removal from wastewaters: the ozonation of amoxicillin

The presence of amoxicillin, a widely used antibiotic, has been documented in Sewage Treatment Plant (STP) effluents. As for other pharmaceuticals, ozonation is proposed as a process for its abatement from these effluents. The results of ozonation experiments on amoxicillin-containing aqueous solutions indicate that ozone attack is mainly directed towards the phenolic ring of the studied molecule leading to the formation of hydroxyderivative intermediates. No direct evidences of attack on sulfur atom with sulfoxide formation are found. A kinetic investigation is carried out allowing the assessment of the kinetics of direct ozone attack and that of OH radicals to amoxicillin.

Residues of beta-lactam antibiotics in bovine milk: confirmatory analysis by liquid chromatography tandem mass spectrometry after microbial assay screening

A procedure for the simultaneous determination of the residues of seven beta-lactam antibiotics (penicillin G, ampicillin, oxacillin, amoxicillin, dicloxacillin, cephalexin, cephapirin) in bovine raw milk using tandem liquid chromatography mass spectrometry (LC-MS/MS) is described. The antibiotics were extracted by an acetic acid solution after centrifugation and filtration. The beta-lactams were separated using reversed-phase liquid chromatography. A triple quadrupole mass spectrometer was used in positive-ion mode as a detector via a Turbo Ionspray interface for electrospray ionization (ESI). The limits of detection and quantitation of the method were below the legal tolerances, except for ampicillin. The method was used to confirm 53 samples found positive by a microbial method (Delvotest SP) at the Istituto Zooprofilattico Sperimentale per la Lombardia e l'Emilia Romagna of Brescia during 2001. Penicillin G was found in 26 samples at concentrations ranging from less than 4 to 6240+/-550 microg x l(-1). Amoxicillin was found in three samples at concentrations ranging from 8.5+/-0.1 to 53.7+/-2.3 microg x l(-1). Cephapirin was found in two samples at 5.7+/-0.1 and 6.4+/-0.3 microg x l(-1).

Simultaneous determination of five beta-lactam antibiotics in bovine milk using liquid chromatography coupled with electrospray ionization tandem mass spectrometry

A multiresidue method for the detection of five important beta-lactam antibiotics (amoxicillin, ampicillin, cloxacillin, oxacillin, penicillin G) in fresh milk is presented that allows quantitation of the analytes well below established legislative limits. The method avoids the use of acid during the extraction procedure and entails a cleanup step over a C18 cartridge. The analytes are separated and detected by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) using a stable isotope-labeled internal standard. Mass spectral acquisition is done in the positive ion mode by applying selected reaction monitoring of two or more fragmentation transitions per analyte to provide a high degree of sensitivity and specificity. The typical recoveries for all five beta-lactams in fresh milk ranged from 76 to 94% at a fortification level of 4 microg/kg. This study also addresses common problems encountered in the stability of penicillins during sample preparation as well as the employment of postcolumn infusion of a standard compound to verify potential matrix-induced signal suppression in ESI-MS.

Comparative bioavailability of two cefadroxil formulations in healthy human volunteers after a single-dose administration

OBJECTIVE

To compare the bioavailability of two cefadroxil capsule (500 mg) formulations (Cefadroxila from Eurofarma Laboratórios Ltd, Brazil, as test formulation and Cefamox from Bristol-Myers Squibb, Brazil S.A. as reference formulation) in 24 volunteers of both sexes.

MATERIAL AND METHODS

The study was conducted open with randomized two-period crossover design and a 1-week washout period. Plasma samples were obtained over a 12-h interval. Cefadroxil concentrations were analysed by combined reversed-phase liquid chromatography and tandem mass spectrometry (LC-MS-MS) with positive ion electrospray ionization using a selected ion monitoring method. From the cefadroxil plasma concentration versus time curves the following pharmacokinetic parameters were obtained: AUC(last), AUC(0-infinity) and C(max).

RESULTS

Geometric mean of Cefadroxila/Cefamox 500 mg individual percent ratio was 103.97% for AUC(last), 104.08% for AUC(0-infinity) and 95.23% for C(max). The 90% confidence intervals (CI) were 98.14-110.16%, 98.37-110.12%, and 85.59-105.96%, respectively.

CONCLUSION

Since the 90% CI for C(max), AUC(last) and AUC(0-infinity) were within the 80-125% interval proposed by the Food and Drug Administration, it was concluded that the Cefadroxila 500 mg capsule was bioequivalent to the Cefamox 500 mg capsule, according to both the rate and extent of absorption.

Analysis of antibiotics by liquid chromatography-mass spectrometry

The current status of the application of LC-MS in the analysis of antibiotic and antibacterial compounds is reviewed. The main application area of LC-MS in this field is the confirmation of identity in animal food products for human consumption at maximum residue levels, set by the regulatory authorities. LC-MS is found to play an important role in the determination and confirmation of sulphonamides, beta-lactam antibiotics, (fluoro) quinolone antibiotics, as well as various other groups including aminoglycosides, chloramphenicol, ionophore antibiotics, 5-nitrofuran derived compounds and macrolide antibiotics. Currently available data on these compound classes are reviewed, with special emphasis on important aspects especially relevant to LC-MS and on the mass spectral information obtained.

Use of liquid chromatography-mass spectrometry in the analysis of residues of antibiotics in meat and milk

The advent of affordable LC-MS systems has led to a massive increase in a number of publications describing quantitative methods for the analysis and confirmation of veterinary drug residues. The lack of volatility and thermal instability of many antibiotics makes LC-MS the method of choice for their analysis. In the review, analytical methods for the determination of residues of each of the major classes of antibiotics are presented.

Chromatographic methods of analysis for penicillins in food-animal tissues and their significance in regulatory programs for residue reduction and avoidance

Chromatographic methods for penicillin analysis in animal tissues play a significant role in the regulation of the use of these drugs in livestock production. Regulatory agencies rely on data generated from these methods to establish withdrawal times and to determine whether presumptive positive tissue samples from slaughtered animals intended for human consumption contain violative levels of penicillins to necessitate regulatory action. The need to develop sensitive, accurate, and reliable methods to support regulatory programs is examined together with emerging techniques that could be taken advantage of to improve the sensitivity and usefulness of current chromatographic methods for tomorrow's regulatory agency.

Structural analysis of non-volatile compounds by liquid chromatography/mass spectrometry and liquid chromatography/tandem mass spectrometry: thermal isomerization of benzylpenicillin in a Plasmaspray interface

Isomerization and degradation of benzylpenicillin ((2S,5R,6R)-3,3-dimethyl-7-oxo-6-(2-phenylacetamido)-4-thia-1- azabicyclo[3.2.0]heptane-2-carboxylic acid) were studied using a combination of Plasmaspray (PSP) liquid chromatography/tandem mass spectrometry (LC/MS/MS) and liquid secondary ion tandem mass spectrometry (LSI MS/MS). Benzylpenicillin was isomerized to benzylpenicillenic acid (3-mercapto-N-[[5-oxo-2-(phenylmethyl)-4(5H)- oxazolylidene]methyl]valine) in the PSP interface/ion source. The isomerization was inferred from the probe temperature dependence of PSP LC tandem mass spectra and discrepancies in the daughter ions between PSP LC and LSI tandem mass spectra. High temperature at the PSP interface was responsible for the isomerization, since the difference between PSP LC and LSI tandem mass spectra became smaller as the probe temperature was lowered. It was also found that benzylpenicillin was decomposed to benzylpenilloic acid (5,5-dimethyl-2-[(phenylacetamido)methyl]thiazolidine-4-carboxylic acid), N-(phenylacetyl)glycine, N-(phenylacetyl)glycinal and 3-mercaptovaline in the PSP interface/ion source. The degradation products formed in the interface/ion source were identical to those formed in acidic solution. The results show that degradation of penicillins can be investigated by PSP LC/MS and PSP LC/MS/MS.

Development of analytical methods for some penicillins in bovine milk by ion-paired chromatography and confirmation by thermospray mass spectrometry

Analytical methods for the determination of cloxacillin, ampicillin/hetacillin, and amoxicillin in bovine milk were developed. The methods involved ultrafiltration of milk diluted with methanol, acetonitrile, and water on a 10,000-dalton cut-off filter. Separation of penicillins from other milk components was accomplished by ion-paired chromatography using a microbore column. The penicillins were detected using ultraviolet photodiode array (UV-PDA) detection and confirmed by thermospray liquid chromatography-mass spectrometry (LC-MS). The thermospray spectra of these compounds exhibited [M + H]+ and [M + Na]+ ions along with several fragment ions. The limits of detection for these antibiotics were estimated to be 50 to 100 ppb for LC with UV-PDA detection and 100-200 ppb for thermospray LC-MS detection.

Identification of metabolites of ampicillin using liquid chromatography/thermospray mass spectrometry and fast atom bombardment tandem mass spectrometry

Mass spectrometry is combined with liquid chromatography (LC/MS) and mass spectrometry (MS/MS) to identify ampicillin and two known metabolites--ampicillin penicilloic acid and ampicillin piperazine-2,5-dione--in human urine samples. Identifications were based on the fact that the metabolites or degradation products contain a substructure of ampicillin. In addition, two previously unidentified components in human urine samples were detected, corresponding to newly discovered metabolites or degradation products of ampicillin. Different chromatographic retention times in the LC mass spectra indicated two different compounds. However, the tandem mass spectra of these two components were similar, suggesting that they are stereoisomers. The use of LC/MS and MS/MS confirmed that the unknown components are the (3S,5R) and (3S,5S) epimers of ampicillin penilloic acid. Further study showed that only one of the components was eliminated from the body; the other arises from interconversion to the epimer in a urine sample. It is speculated that the component produced in vivo is the (3S,5R) epimer of ampicillin penilloic acid.