Enantiomeric Separation and Detection of 2-Arylpropionic Acids Derivatized with [(N,N-Dimethylamino)sulfonyl]benzofurazan Reagents on a Modified Cellulose Stationary Phase by High-Performance Liquid Chromatography

Dual application of synthesized SnO2nanoparticles in ion chromatography for sensitive fluorescence determination of ketoprofen in human serum, urine, and canal water samples

Systematic layout of dual application of SnO₂NPs in ion chromatography for selective determination of non-fluorescent KP in complex samples.

Capillary electrophoresis with laser induced-fluorescence detection of profens derivatized with the water-soluble fluorogenic reagent 4-N-(4-N′-aminoethyl)piperazino-7-nitro-2,1,3-benzoxadiazole

Profens, including pranoprofen, fenoprofen, flurbiprofen, ketoprofen and ibuprofen (Ib), were derivatized by a water-soluble benzofurazan fluorescent reagent, 4-N-(4-N'-aminoethyl)piperazino-7-nitro-2,1,3-benzoxadiazole and then were run on capillary electrophoresis in a NH4Ac-HAc buffer of pH 3.1 containing 2.4 mM beta-cyclodextrin. At room temperature, the derivatization reaction was catalyzed by triphenyl phosphine and diphenyl disulfide in acetonitrile medium, and the derivatives fluoresce around 530 nm when excited at 488 nm. With the CE running on a 50 cm x 50 microm I.D. length fused-silica capillary of by using Ar+ laser induced-fluorescence detection, the detection limits attained were in the range of 0.16 to 0.3 fmol.

Identification of L-3-hydroxybutyrate as an original ketone body in rat serum by column-switching high-performance liquid chromatography and fluorescence derivatization

L-3-Hydroxybutyrate (L-3HB), the enantiomer of D-3-hydroxybutyrate (D-3HB), has traditionally been regarded the "unnatural" ketone body in mammals, although there is suspicion that it is a more-favorable energy fuel for mammalian tissues than D-3HB. In this study, we demonstrated that L-3HB is an original substance in rat serum by applying fluorescence derivatization and a column-switching high-performance liquid chromatography system as the analysis technique. Racemic 3HB in rat serum derivatized using 4-nitro-7-piperazino-2,1,3-benzoxadiazole was first separated by an ODS column and was further confirmed by verifying the disappearance of the racemic 3HB peak after pretreating rat serum with D-3-hydroxybutyryl dehydrogenase. A switching valve was used to simultaneously introduce isolated racemic 3HB to the enantiomeric separation by two CHIRALCEL OD-RH columns connected in tandem. An L isomer was found to accompany the D isomer, which were quantified to be 3.98 microM (3.61%) and 106.20 microM (96.39%), respectively. Using the present analytical method, the dubious interpretation of the existence of L-3HB was clarified.

Analytical Chemical Studies on High-Performance Recognition and Detection of Bio-molecules in Life

In order to understand the mechanism for maintaining life of animals based on the search of dynamics of biomolecules, I have developed several sensitive and selective methods for their quantification. Using the methods of derivatization with the developed benzofurazan fluorogenic reagents (4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), ammonium 7-fluoro-2,1,3-benzoxadiazole 4-sulfonate (SBD-F) and etc.) followed by high-performance liquid chromatography (HPLC)--fluorescence detection, a certain kind of biological and clinical importance was demonstrated of chiral bio-molecules (D-amino acids, D-lactic acid and so on), peptides and proteins. The proposed method (derivatization with SBD-F, isolation of the fluorescent proteins by two-dimensional HPLC, enzymatic digestion and identification of the altered proteins by HPLC-mass spectrometry (MS)/MS with database-searching algorithm) for proteomics studies revealed the changed proteins in the islets of Langerhans of the dexamethazone-induced diabetic rats. An importance of catecholamine metabolism on the blood pressure regulation was also suggested by the method of HPLC-chemiluminescence detection of catecholamines and their 3-O-methylmetabolites. A new field of Analytical Chemistry, i.e., Bio-Analytical Chemistry, was also proposed.

Resolution of enantiomers of ketoprofen by HPLC: a review

Today, a heightened awareness of the applicability of enantiomers in medicine and clinical practice has been gene-rated due to the continuous evolvement of the field of chirality. In this context, this article provides a review of separation of ketoprofen, an important drug, in a popular class of non-steroidal anti-inflammatory drugs (i.e. profens). This review highlights various methodologies, logistical considerations for separation and provides an exhaustive list of applications mainly focusing on the pharmacokinetic aspects. Clearly, the application of enantioselective methods for drug racemates paves the way to understand the in vivo behavior of individual enantiomer and hence an opportunity for an alternate and/or better option for treating the disease.

Pharmaceutical and biomedical applications of enantioseparations using liquid chromatographic techniques

The chiral separation methods using liquid chromatographic techniques can be divided into two categories: one is a direct method, which is based on a diastereomer formation on stationary phase or in mobile phase. The other is an indirect method, which is based on a diasteromer formation by reaction with a homochiral reagent. The enantiomer separation on a chiral stationary phases followed by derivatization with an achiral reagent is also dealt with this review article as the indirect method. The pharmaceutical and biomedical applications of enantioseparations using the direct and indirect methods have been considered in this review.

Fluorogenic and fluorescent labeling reagents with a benzofurazan skeleton

Fluorogenic and fluorescent labeling reagents having a benzofurazan (2,1,3-benzoxadiazole) skeleton such as 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), 4-N,N-dimethylaminosulfonyl-7-fluoro-2,1,3-benzoxadiazole (DBD-F), 4-aminosulfonyl-7-fluoro-2,1,3-benzoxadiazole (ABD-F), ammonium 7-fluoro-2,1,3-benzoxadiazole-4-sulfonate (SBD-F), 4-hydrazino-7-nitro-2,1,3-benzoxadiazole (NBD-H), 4-N,N-dimethylaminosulfonyl-7-hydrazino-2,1,3-benzoxadiazole (DBD-H), 4-nitro-7-N-piperazino-2,1,3-benzoxadiazole (NBD-PZ), 4-N,N-dimethylaminosulfonyl-7-N-piperazino-2,1,3-benzoxadiazole (DBD-PZ), 4-(N-chloroformylmethyl-N-methyl)amino-7-N,N-dimethylaminosulfonyl-2,1,3-benzoxadiazole (DBD-COCl) and 7-N,N-dimethylaminosulfonyl-4-(2,1,3-benzoxadiazolyl) isothiocyanate (DBD-NCS) are reviewed in terms of synthetic method, reactivity, fluorescence characteristics, sensitivity and application to analytes.

Reversed-phase liquid chromatographic separation of enantiomers on polysaccharide type chiral stationary phases

The direct chiral separation by chiral stationary phases (CSPs) is one of the most important techniques to analyze enantiomeric purity as well as to get enantiomerically pure material quickly. Among various types of CSPs, polysaccharide type CSPs are well known by their versatility and durability. They are not only effective under normal-phase conditions, but also under reversed-phase conditions. In order to get a good separation under the reversed-phase conditions, it is the key to choose an appropriate mobile phase. For example, a simple mixture of water/acetonitrile or water/methanol are sufficient for a neutral analyte, while it is necessary to use an acidic solution instead of water for an acidic analyte and a solution of a chaotropic salt (or a basic solution) for a basic analyte, respectively. The paper also presents lists of more than 350 separation examples that include 22 validated methods for drug analyses from serum, plasma, or urine samples on polysaccharide type CSPs under reversed-phase conditions.

Reviewing mobile phases used on Chiralcel OD through an application of data mining tools to CHIRBASE database

During the past decade, thousands of compounds have been resolved on Chiralcel OD (a cellulose-based chiral stationary phase) under diverse eluting conditions. Many researches have documented the effects of mobile phase on enantioselectivity for a given family of samples but today no comprehensive study aimed at identifying the associations between the structural features present on solute and appropriate mobile phase conditions has yet been proposed. In this review of mobile phases used on Chiralcel OD, we try to go far beyond a simple enumeration of eluting conditions and an effort is made to explore the utility of data mining tools for assessing the knowledge contained in CHIRBASE database. We have extracted from CHIRBASE the chemical features of 2363 chiral compounds separated on Chiralcel OD and their corresponding mobile phases. This data set was submitted to data mining programs for molecular pattern recognition and mobile phase predictions for new cases. Some substructural characteristics of solutes were related to the efficient use of some specific mobile phases. For example, the application of CH3CN/salt buffer at pH 6-7 was found convenient for reversed-phase separation of compounds bearing a tertiary amine functional group. Furthermore, a cluster analysis allowed the arrangement of the mobile phases according to similarity found in molecular patterns of solutes. A decision tree, which may lead to a more rational choice of the mobile phase under reversed-phase conditions, is also proposed.

Occurrence and determination of a natriuretic hormone, 2,7,8-trimethyl-2-(beta-carboxyethyl)-6-hydroxy chroman, in rat plasma, urine, and bile

The occurrence of a new natriuretic hormone, 2,7,8-trimethyl-2-(beta-carboxyethyl)-6-hydroxy chroman (LLU-alpha, gamma-CEHC) in rat plasma was demonstrated and its concentration was determined using a coupled-column HPLC with a fluorometric derivatization with 4-N,N-dimethylaminosulfonyl-7-piperazino-2,1,3-benzoxadiazol e (DBD-PZ) followed by O-acetylation. The concentration of LLU-alpha was 328 +/- 113 nM in rat plasma (N = 5). LLU-alpha was found in not only urine, but also bile, suggesting an enterohepatic circulation in body. We also assigned the configuration at C-2 of LLU-alpha in these biological fluids as (S)-form by an HPLC with a chiral column. The LLU-alpha concentration decreased significantly by fasting for 3 days (P < 0.01). These results support the possibility that LLU-alpha is produced from gamma-tocopherol in diet via oxidative metabolism without racemization.

Development of an amino acid sequence and D/L-configuration determination method of peptide with a new fluorescence Edman reagent, 7-methylthio-4-(2,1,3-benzoxadiazolyl) isothiocyanate

On the basis of the relationship between the fluorescence characteristics of the benzofurazan compounds and the Hammett constants (sigma p), a new fluorescence Edman reagent, 7-methylthio-4-(2,1,3-benzoxadiazolyl) isothiocyanate (MTBD-NCS) was designed and synthesized. MTBD-thiohydantoin (TH)-amino acid derivatives produced by the Edman sequencing method gave fluorescence, whereas other degradation byproducts such as MTBD-thiocarbamoyl (TC)- or carbamoyl (CA)-amino acids did not fluoresce. MTBD-NCS was applicable as an Edman sequencing reagent to the simultaneous determination of both the sequence and D/L-configuration of amino acids in peptides. Boron trifluoride (BF3) and HC1/methanol were adopted as the cyclization/cleavage and conversion reagents to suppress the amino acid residue racemization. The MTBD-TH-amino acids were separated on a reversed-phase column for amino acid sequencing, and their enantiomers were resolved on two types of polysaccharide-based chiral stationary phases for D/L-configuration determination. The method was successfully applied to the sequence and D/L-configuration determination of D-amino acid-containing peptide [D-Ala2]-deltorphin II.

Fluorimetric determination of D- and L-lactate derivatized with 4-(N, N-dimethylaminosulfonyl)-7-piperazino-2,1,3-benzoxadiazole (DBD-PZ) by high-performance liquid chromatography

A highly sensitive method, based on fluorescence derivatization with 4-N,N-dimethylaminosulfonyl-7-piperazino-2,1,3-benzoxadiazol e (DBD-PZ), was developed for the determination of D- and L-lactic acid. High-performance liquid chromatographic separation of the lactic acid derivative was achieved using an octadecylsilica column followed by enantiomeric separation on a phenylcarbamoylated beta-cyclodextrin chiral column. The separation factor for D, L-lactic acid derivatives was 1.30 using MeOH/H(2)O (80/20) as a mobile phase, and the detection limits were approximately 360 and 300 fmol on column for D- and L-lactic acid derivative, respectively. The proposed method was applied to determine D- and L-lactate in a wine and a lactic drink. Both D- and L-lactate could be determined simultaneously, with the precisions ranging from 3.50 to 5.78% for intra-day and 4.28-9.92% for inter-day determinations. The relative recovery was in the range of 91.6-100%.

Preparation of an IMI dye (imidazole functional group) containing a 4-(N,N-dimethylaminosulfonyl)-2,1,3-benzoxadiazole fluorophore for labeling of phosphomonoesters

We are studying dye-imidazole conjugates ("IMI dyes") as reagents for labeling phosphomonoesters such as nucleotides. Previously we have employed a BODIPY dye in our IMI reagents, and analyzed the labeled products by capillary electrophoresis with laser-induced fluorescence detection (CE-LIF) involving an argon ion laser. (The BODIPY fluorophore is a 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene). Here we broaden the technology by preparing a DBD-IMI dye [DBD = 4-(N,N-dimethylaminosulfonyl)-2,1,3-benzoxadiazole], and using a helium-cadmium laser. While DBD-IMI (IMI3) is about 50x more stable photolytically than a BODIPY-IMI dye (IMI2, a conjugate of a BODIPY dye with histamine, was tested), the detection limit for IMI2 (5.10(-11) M; S/N = 5, CE-LIF with an argon ion laser) is tenfold better than that for IMI3 (5.10(-10) M, S/N = 5, helium-cadmium laser). IMI3 conjugates of the four major DNA nucleotides were prepared and detected by CE-LIF.

N-(4-nitro-2,1,3-benzoxadiazoyl-7-yl)-N-methyl-2-aminoacetohydrazide (NBD-CO-Hz) as a precolumn fluorescent derivatization reagent for carboxylic acids in high-performance liquid chromatography

A new fluorescent reagent for carboxylic acids, N-(4-nitro-2,1,3-benzoxadiazoyl-7-yl)-N-methyl-2-aminoacetohydr azide (NBD-CO-Hz) was synthesized and its applicability as a precolumn derivatization reagent in high-performance liquid chromatography was examined. NBD-CO-Hz reacted with 2-arylpropionic acids (2-APAs), a group of non-steroidal antiinflammatory drugs (NSAIDs) in the presence of a condensing agent, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and pyridine at room temperature for 2 h to give fluorescent adducts. The reaction solution was subjected to a reversed phase or a chiral stationary phase HPLC and the derivatives were detected fluorometrically at a wavelength of 530 nm with an excitation of 475 nm. The detection limits were in the fmol range on column.