Indirect fluorescence detection of amino sugars with the use of copper complexes of tryptophan and its analogues following high-performance liquid chromatographic separation

Synthesis, characterization, theoretical studies and biological (antioxidant, anticancer, toxicity and neuroprotective) determinations of a copper(II) complex with 5-hydroxytryptophan

5-Hydroxy-L-tryptophan (5-HTP) is a serotonin pathway metabolite of L-tryptophan in the brain. In the knowledge that the biological properties of some compounds can be modified upon metal complexation, a new solid metal complex, [Cu(5-hydroxytryptophan)₂].H₂O (Cu5HTP), has been synthesized and characterized to analyze the modification of some biological properties. The conformational investigations (optimized in gas phase at B3LYP/6-311G** theory level) suggest the coexistence of two conformers of Cu5HTP with cis- and trans- arrangements of the amino acids in the equatorial plane. The trans- Cu5HTP1 complex is the most stable conformer. The complexation led to an enhancement of the antioxidant properties of the ligand. The metal complex also improved the anticancer behavior of the ligand (tested in cancer cell lines derived from human lung (A549), cervix (HeLa) and colon (HCT-116)). It did not show toxicity against either the non-malignant human lung fibroblast (MRC-5) cell line or Artemia salina and did not behave as mutagenic agent (Ames test). Cellular reactive oxygen species production may be one of the possible mechanisms of action. Besides, the metal complex exerted neuroprotective action on cortical neurons from embryonic 18 days rats exposed to glutamate.

Capillary electrophoretic determination of glucosamine in osteoarthritis tablets via microwave-accelerated dansylation

A robust capillary electrophoretic method has been established to separate aminosaccharides including glucosamine, galactosamine, N-methyl-glucamine, N-acetyl-glucosamine and amino glucuronic acid. All the aminosaccharides were dansylated fast under microwave irradiation at 385 W for 6 min (about 50-fold faster than common methods) and detected via on-line UV adsorption at 214 nm. Baseline separation of the dansylatied products was achieved in 20 min using a running buffer of 320 mM borate at pH 9.50. Quantitation of glucosamine in osteoarthritis tablets was then conducted. A linear working range was found in between 2.00 microg/mL and 1.80 mg/mL with linear regression coefficient of 0.9964. The limit of detection reached 1.00 microg/mL glucosamine (signal-to-noise, S/N=3). Recoveries were determined by spiking a known amount of glucosamine in tablet-extracted solutions, giving a range of 88.0-99.7%. The run-to-run relative standard deviation was 0.24% (n=5) for migration time and 2.72% for peak area.

Monitoring enzyme-catalyzed production of glucosamine-6P by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: a new enzymatic assay for glucosamine-6P synthase

A matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) method for quantification of D-glucosamine-6P (GlcN-6P) that allows the kinetic study of glucosamine-6P synthase (Glms) is presented. The present report describes the optimization of the different steps of a new enzymatic assay for Glms based on in situ N-acetylation of GlcN-6P and MALDI-TOFMS analysis using N-(13C2)acetylglucosamine-6P as internal standard. Since no isotopically substituted GlcN-6P was available, the N-(13C2)acetyl derivative, easily obtained from (13C4)-acetic anhydride, was used as internal standard. Validation of the assay was achieved by measuring the fructose-6P Michaelis constant, in full agreement with reported values, and by studying the inhibition properties of arabinose-5P oxime.