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The chiral purity of some molecules such as nutraceuticals is fundamental to ensure their beneficial activities and it must be checked during quality control analysis. Carnosine is a natural histidine dipeptide used as ingredient for food supplements, but only his L-enantiomer is absorbed and active. Despite of this feature, a method for the separation of carnosine enantiomers without derivatization has only recently been published. Herein, we validated a method based on a Chirobiotic T column and an UV detector for the direct quantification of carnosine enantiomers, following ICH guideline. Moreover, we demonstrated that elution with water containing 0.1% formic acid and 20-40% ensures stereo-, chemo- and regio-selectivity for the separation and the identification of carnosine enantiomers and natural analogues. Moreover, the method allows a direct hyphenation with electrospray mass spectrometry to increase detection selectivity and sensitivity. As far as we know, this is the first method allowing the simultaneous identification and quantification of natural analogues of carnosine, which can be important for application such as the identification of enantiomeric impurities or adulteration that can occur during the storage or the preparation of foods or food supplements containing histidine dipeptides., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A novel ultra-high performance liquid chromatography (UHPLC) procedure, coupled with tandem mass spectrometry (MS/MS), was established for the analysis of anserine (ANS) and carnosine (CAR) in meat and bone meal (MBM) (bovine, ovine, porcine, and poultry origins). The pretreatment strategies were optimized for four types of MBM samples prior to UHPLC-MS/MS analysis. This method allowed determining CAR and ANS in short analysis time (18 min per sample). The limits of detection (LODs) and limits of quantification (LOQs) of two analytes in four types of MBM samples were in the ranges of 0.41⁻3.07 ng/g and 0.83⁻5.71 ng/g, respectively. The recovery rates spiked with low, intermediate, and high levels of two analytes in four types of MBM samples were 48.53⁻98.93%, 60.12⁻98.94%, and 67.90⁻98.92%, respectively. Acceptable inter-day reproducibility (RSD < 12.63%) supported the application of this proposed method for determining CAR and ANS in MBM samples. Overall, this rapid, effective, and robust method was successfully applied for quantitative detection of CAR and ANS in MBM samples. Furthermore, The CAR/ANS ratio was found to be in the decreasing order: porcine > bovine > ovine > poultry MBM. This proposed methodology was novelly applied to identify the biomarker (CAR/ANS ratio) for species-specific identification of MBM.

The aim of the study was to compare three types of meat snacks made from ostrich, beef, and chicken meat in relation to their nutrients content including fat, fatty acids, heme iron, and peptides, like anserine and carnosine, from which human health may potentially benefit. Dry meat samples were produced, from one type of muscle, obtained from ostrich ( m. ambiens ), beef ( m. semimembranosus ), and broiler chicken meat ( m. pectoralis major ). The composition of dried ostrich, beef, and chicken meat, with and without spices was compared. We show that meat snacks made from ostrich, beef, and chicken meat were characterized by high concentration of nutrients including proteins, minerals (heme iron especially in ostrich, than in beef), biologically active peptides (carnosine-in beef, anserine-in ostrich then in chicken meat). The, beneficial to human health, n -3 fatty acids levels differed significantly between species. Moreover, ostrich jerky contained four times less fat as compared to beef and half of that in chicken. In conclusion we can say that dried ostrich, beef, and chicken meat could be a good source of nutritional components.

Carnosine is present in high concentrations in specific human tissues such as the skeletal muscle, and among its biological functions, the remarkable scavenging activity toward reactive carbonyl species is noteworthy. Although the two enantiomers show almost identical scavenging reactivity toward reactive carbonyl species, only d-carnosine is poorly adsorbed at the gastrointestinal level and is stable in human plasma. Direct methods for the enantioselective analysis of carnosine are still missing even though they could find more effective applications in the analysis of complex matrices. In the present study, the use of two different chiral stationary phases is presented. A chiral ligand-exchange chromatography stationary phase based on N,S-dioctyl-d-penicillamine resulted in the direct enantioseparation of carnosine. Indeed, running the analysis at 25°C and 1.0 mL/min with a 1.5 mM copper(II) sulfate concentration allowed us to obtain separation and resolution factors of 3.37 and 12.34, respectively. However, the use of a copper(II)-containing eluent renders it hardly compatible with mass spectrometry detectors. With the teicoplanin-based stationary phase, a mass spectrometry compatible method was successfully developed. Indeed, a water/methanol 60:40 v/v pH 3.1 eluent flowed at 1.0 mL/min and with a 25°C column temperature produced separation and resolution factors of 2.60 and 4.16, respectively., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In the present study, a new analytical methodology was developed enabling the enantiomeric determination of N-derivatized di- and tri-peptides in dietary supplements using chiral micro-LC on a monolithic column consisting of poly(O-9-[2-(methacryloyloxy)-ethylcarbamoyl]-10,11-dihydroquinidine-co-2-hydroxyethyl methacrylate-co-ethylene dimethacrylate) (poly(MQD-co-HEMA-co-EDMA)). After optimization of the mobile phase conditions, a baseline resolution of the stereoisomers of 24 out of 53 N-derivatized di- and tri-peptides was obtained. 3,5-Dinitrobenzoyl- and 3,5-dichlorobenzoyl-peptide stereoisomers were separated with exceptionally high selectivity and resolution. The monolithic column was then applied to the quantitative analysis of l-carnosine and its enantiomeric impurity in three different commercial dietary supplements. Method validation demonstrated satisfactory results in terms of linearity, precision, selectivity, accuracy and limits of detection and quantification. The determined amounts of l-carnosine in commercial formulations were in agreement with the labeled content for all analyzed samples, and the enantiomeric impurity was found to be below the limit of detection (LOD), showing the potential of the poly(MQD-co-HEMA-co-EDMA) monolithic column as a reliable tool for the quality control of l-carnosine in dietary supplements by micro-LC., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Cyclophosphamide is one of the most widely used chemotherapeutic agents in treating cancers. Chemotherapy drug-induced oxidative stress produces side effects. The severity of myelosuppression increases with a high dose of cyclophosphamide. Chicken soup or chicken essence, a traditional Chinese aliment, is a popular health supplement for patients with cancers or other diseases in Asia. As a major functional component of chicken meat extract, carnosine (beta-alanyl-L-histidine), a dipeptide of the amino acids beta-alanine and histidine, has been shown to have strong antioxidant activities. In the present study, we investigated the effects of carnosine on hematopoietic suppression in mice treated with cyclophosphamide. As expected, we found that cyclophosphamide administration (with a single dose of 150 mg/kg) induced a rapid (within 24 hours) and severe hematopoietic suppression in mice. We further showed that carnosine administration (100 mg/kg/day or 200 mg/kg/day for continuous seven days) could substantially improve suppressed hematopoietic functions and accelerate the recovery of leukocyte counts, bone marrow spontaneous proliferation, colony stimulating activity (CSA) in serum, and production of endogenous cytokines such as interleukin-3 (IL-3) and stem cell factor (SCF). These results indicate that carnosine has the potential to promote the recovery from hematopoietic suppression induced by cyclophosphamide. Our data suggest that carnosine holds a potential in clinical application to minimize the side effects induced by chemotherapeutic agents such as cyclophosphamide and thus will substantially improve the overall anti-tumor effects of the standard chemotherapies.

An improved method, based on ultra-performance liquid chromatography (UPLC) coupled to tandem mass spectrometry (MS/MS), has been developed to determine the bioactive dipeptides carnosine (CAR) and anserine (ANS) in chicken broth. These analytes are hydrophilic (polar) and in order to improve their retention, the chromatographic mode used was hydrophilic interaction chromatography (HILIC) (1.7 μm particle size). In order to remove the salt before the chromatographic analysis of the chicken broth (0.8%, w/w), an exhaustive sample pre-treatment strategy was necessary since the salt is not volatilized and could block the ionization source and lead to signal suppression. The chicken broth was firstly centrifuged to remove the fat and chicken proteins, and then was pretreated by off-line solid-phase extraction (SPE), using traditional cartridges, or off-line μElution plate (μSPE), using microplates, and the results were compared. Due to the high polar character of the dipeptides studied and the sample matrix, these compounds were not retained in the sorbent hydrophilic-lipophilic balanced (HLB) and were eluted in the load step, whereas the salt was retained in the sorbent. This fact was observed by the addition of silver nitrate in the chicken broth extract, where before the SPE or μSPE a white precipitate (silver chloride) was formed and after the SPE or μSPE this precipitate was not observed. By using these sample pre-treatment strategies, the extraction recoveries were higher than 80%, and the matrix effect was lower than 12%. Once the improved method was developed, the quality parameters of the method were studied. The LODs and LOQs of the CAR and ANS were lower than 6 and 1.8 μg/l, respectively. Then, the method was applied to analyse a commercial chicken broth. This improved method allowed determining CAR and ANS between 6 and 10mg dipeptide/l chicken broth in 10 min (sample pre-treatment and chromatographic analysis). Therefore, the proposed improved method is concluded to be rapid, sensitive and selective for the determination of polar compounds by MS in samples that contain salt., (Copyright © 2012 Elsevier B.V. All rights reserved.)

A micropreparative-scale multicompartmental electrolyzer called ConFrac has been developed and tested for isoelectric trapping separations. ConFrac can be operated in pass-by-pass mode or recirculating mode, using either asymmetrical feeding (feed enters only the anodic or the cathodic flow-through compartment) or symmetrical feeding (feed enters both the anodic and the cathodic flow-through compartment). Symmetrical feeding results in higher processing rates and is the preferred operation mode. Residence time in the flow-through compartments is set as a compromise between processing rate and temperature rise in the effluent. Ampholytic components have been isolated from 5 to 50 mL volumes of micromolar feed solutions and hundredfold concentrated into 100-μL collection compartments. Samples containing ampholytic analytes in highly conducting salt solutions were readily desalted and fractionated in ConFrac in one operation. pH transients formerly observed in other isoelectric trapping devices were observed in ConFrac as well. The pH transients were caused by the unequal ion transmission rates of the anodic- and cathodic-side buffering membranes., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A multicompartmental electrolyzer called ConFrac has been developed and tested for micropreparative-scale isoelectric trapping separations. ConFrac contains n separate, minimalistic isoelectric trapping core units, each with a separate anode compartment, anodic flow-through compartment, collection compartment, cathodic flow-through compartment and a shared cathode compartment. The collection compartments are all isolated from each other and have volumes of 100 μL each. The liquid held in the collection compartments is stagnant. The respective anodic and cathodic flow-through compartments are hydraulically serially connected to each other by flexible, minimum-length, narrow internal diameter tubes. The respective feed solutions whose volumes are larger and variable are recirculated through the serially connected flow-through compartments. Poly(vinyl alcohol)-based buffering membranes are placed between the anode compartments, anodic flow-through compartments, collection compartments, cathodic flow-through compartments and cathode compartment. The membranes establish two orthogonal pH gradients in ConFrac. The primary pH gradient is parallel with the direction of the recirculating flows and orthogonal to that of the electric field. The secondary pH gradient is parallel with the direction of the electric field and orthogonal to that of the recirculating flows. Since the recirculating liquids are kept in thermostated reservoirs and the residence times in the flow-through compartments are shorter than 2 s, ConFrac can tolerate power loads as high as 2 W without overheating the solutions. The operation and performance of ConFrac has been quantitatively characterized: four 25 μM ampholytic components were isolated from 5 mL of feed solution in 20 min and their concentration increased approximately 50-fold., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Adsorption of histidine-containing dipeptides such as carnosine (Car) was investigated using copper(II) immobilized cation exchange resins. Adsorption of Car was enhanced using Cu(II) immobilized resins, on the basis of metal affinity interactions. In particular, iminodiacetic acid chelating resin with immobilized Cu(II) (Cu-IDA) can adsorb Car from saline water. Car was adsorbed on Cu-IDA even in the presence of 1000 mM of NaCl. Adsorption of various amino acids on Cu-IDA was compared under same conditions. Histidine and the histidine-containing dipeptides were selectively adsorbed on Cu-IDA over other amino acids, both in the absence and in the presence of NaCl. Therefore, immobilized metal affinity adsorption is an efficient method for recovering histidine-containing dipeptides from saline water.

The Biflow, a new isoelectric trapping instrument was designed to obtain a narrow DeltapI fraction from a complex feed in one step. The Biflow contains two identical separation units, each unit houses: an anode and cathode compartment, an anodic and cathodic membrane, an anodic and cathodic separation compartment, and a separation membrane. The separation units are connected to independent power supplies. The anodic membranes in Units 1 and 2 typically buffer at the same pH value and so do the cathodic membranes. The separation membranes in Units 1 and 2 buffer at different pH values, these determine the pI range (DeltapI) of the product. The cathodic separation compartments in Units 1 and 2 contain the feed and harvest streams. The two anodic separation compartments, connected through an electrically insulating air gap, form the transfer loop through which the transfer stream is recirculated between Units 1 and 2. Ampholytic components in the feed, with pI values lower than the pH of the buffering membrane in Unit 1, pass into the transfer stream and are shuttled into Unit 2. In Unit 2, components in the transfer stream which have pI values higher than the pH of the buffering membrane in Unit 2, pass into the harvest stream. This double transfer of the target component, oppositely directed, guarantees the complete exclusion of products outside the desired DeltapI range from the harvest stream. The utility of the Biflow unit was demonstrated by isolating carnosine from a mixture of UV-absorbing ampholytes and ovalbumin isoforms as well as 4.4

A new HPLC procedure based on hydrophilic interaction chromatography (HILIC) has been developed for the simultaneous determination of carnosine, anserine, balenine, creatine, and creatinine in meat. This is the first time that HILIC has been directly applied to the study of meat components, having the advantage of not requiring complex cleanup and/or sample derivatization procedures. The chromatographic separation has been developed using a silica column (4.6 x 150 mm, 3 microm), and the proposed methodology is simple, reliable, and fast (<13 min per sample). The method has been validated in terms of linearity, repeatability, reproducibility, and recovery and represents an interesting alternative to methods currently in use for determining the mentioned compounds and other polar substances. The detection limits are 5.64, 8.23, 3.66, 3.99, and 0.06 microg/mL for carnosine, anserine, balenine, creatine, and creatinine, respectively.

A capillary electrophoresis (CE) method with laser-induced fluorescence (LIF) detection was developed for the separation and detection of carnosine-related peptides (carnosine, anserine, and homocarnosine). A sensitive and fluorogenic regent, 3-(4-carboxybenzoyl) quinoline-2-carboxaldehyde (CBQCA) was selected as a precapillary labeling reagent for imidazole dipeptides to form isoindole derivatives. The optimized molar ratio between CBQCA and peptide was found to be 75:1, and 50 mmol/L borate buffer (pH 9.2) was used for the derivatization in order to achieve good efficiency. Three imidazole dipeptides were baseline-separated within 20 min by using 112 mmol/L sodium borate (pH 10.4-10.8) as running buffer. Concentration detection limits (signal-to-noise ratios) for carnosine, anserine, and homocarnosine were 4.73, 4.37, and 3.94 nmol/L, respectively. This method has been applied to the analysis of human cerebrospinal fluid (CSF) and meat dry powder of pig and sheep. Recoveries were in the range of 82.9-104.8% for homocarnosine in CSF. For carnosine and anserine, the recoveries are 98.3% and 80.2% in meat dry powder of pig and 111.2% and 112.8% in meat dry powder of sheep, respectively.

Commercial preparations of synthetic carnosine are commonly used by researchers to investigate carnosine's biological functions and potential applications. Our studies on the interaction of synthetic carnosine and aldehydic lipid oxidation products have led to the detection and structural identification of hydrazine, a strong reducing agent. The concentrations of hydrazine in various sources of commercial carnosine were in the range of 0.01-0.20% (w/w). The levels of contaminating hydrazine in commercial carnosine were capable of interfering with the analyses of headspace aldehydes, malonaldehyde, and thiobarbituric acid-reactive substances. Since hydrazine can potentially interfere with lipid oxidation reactions and measurement of lipid oxidation products, it will be necessary to use purified carnosine to reevaluate carnosine's biological and chemical properties., (Copyright 1998 Academic Press.)

Synthesis of carnosine (beta-alanyl-L-histidine) and related dipeptides could be demonstrated in primary muscle cell cultures derived from embryonic chick pectoral muscle. After incubation with radiolabeled beta-alanine or gamma-aminobutyric acid, the radiolabeled dipeptides were isolated from the cell extracts and also in small amounts from the culture medium. The kinetics of dipeptide formation indicated that anserine (beta-alanyl-1-methylhistidine) is not formed directly by these cells but as a secondary product via the methylation of carnosine. Coinciding with the morphological differentiation of the mononucleated myoblast to form multi-nucleated myotubes, a rapid increase in beta-alanine uptake and also in dipeptide synthesis could be observed. These results demonstrate that carnosine and related peptides are not merely deposited in skeletal muscles but that they are actively synthesized by muscle cells in culture.

The difference in the efficiency of carnosine as an antioxidant was found to be explained both by the source of carnosine and the specificity of models used to achieve visualization. Commercial carnosine samples were contaminated with compound (s) absorbing at 255-332 nm. At the same time they possessed better antioxidant activity in the models with Fe2-induced peroxidation process. In the case of chemical models for generation of active forms of oxygen (several modifications of the Fenton reaction) or during burst of superoxide generation by leucocytes, the antioxidant effect of carnosine did not depend of the source of the compound under study.

The phenolic diterpene carnosic acid appears to be the main substance for general oxidation leading to artifacts with gamma- or delta-lactone structure in extracts of Rosmarinus officinalis and Salvia officinalis. Until now it was only possible to prepare carnosic acid by hydrogenolysis of carnosol. A semipreparative HPLC method has been developed isolating carnosic acid among other phenolic diterpenes. The separated substances were identified by 13C-nuclear magnetic resonance (NMR), 1H-NMR, mass and IR spectroscopy. Conversion of carnosic acid and carnosol to other phenolic diterpenes was investigated by HPLC.

The transport properties of several peptides across blood-brain barrier (BBB) have been investigated theoretically in terms of simple diffusion and facilitated diffusion processes. Comparison of the calculated results from the simple diffusion and the experimental data reveals the presence of the facilitated diffusion of these substances which we have conceived of as a carrier-mediated process. The values of the partition coefficients f for these peptides were in the range 7 X 10(-4) less than or equal to f less than or equal to 200 X 10(-4). The calculated f values gave permeabilities, Ps, in lipids between 10(-7) less than or equal to Ps less than or equal to 14 X 10(-7) cm/s. These values were then used to estimate the extraction for peptides from simple diffusion alone which vary from 0.3 to 3.5% compared with the experimental extraction (0.4-12%) indicating the inadequacy of the simple diffusion alone to explain the experimental data. As for the carrier-mediated facilitated diffusion process we have used the activated-complex theory. The extraction in this case depends on the maximal rate of transport (Tmax)f and the reciprocal of the affinity constant Kt for the transport of peptides through BBB. We have deduced that (Tmax)f approximately 0.46 X 10(-3) pmol/g X s and Kt approximately 0.35 nM for Met-enkephalin (Met-ENK), Leu-enkephalin (Leu-ENK), glutathione, carnosine, alpha-MSH and MIF and (Tmax)f approximately 10 X 10(-3) pmol/g X s and Kt approximately 7 nM for AVP, beta LT, beta E and alpha E to explain the observed results. We have also obtained the quantitative variation of extraction with concentration of peptides in the brain-capillary and have established that the extraction decreases with increasing concentration of peptides, tending to a small constant value at high concentrations. It has been inferred that carrier-mediated facilitated diffusion is important for the transport of peptides across BBB.