3-Amino-2-naphthoic acid

Beta-cyclodextrin decorated nanostructured SERS substrates facilitate selective detection of endocrine disruptor chemicals.[Pubmed:23261701]

Biosens Bioelectron. 2013 Apr 15;42:632-9.

We demonstrate the selective detection of endocrine disruptor chemicals (EDCs) from river water using surface enhanced Raman scattering (SERS). By means of nanosphere lithography, the SERS substrate was prepared via the initial deposition of a monolayer of silica nanospheres (with diameter of approximately 330 nm) on a silicon substrate as the template. Subsequently, a 180 nm thick layer of silver followed by a 20 nm layer of gold was deposited. This surface was modified with mono-6-deoxy-6-((2-mercaptoethyl)amino)-beta-cyclodextrin (beta-CD) in order to produce a selective capture surface suitable for EDC capture and their detection by means of SERS. We show that EDC model compounds, including 3-Amino-2-naphthoic acid (NAPH), potassium hydrogen phthalate (PHTH) and the EDC beta-estradiol (ESTR), were captured by the beta-CD decorated surface. This surface facilitated SERS detection with limits of detection of 3.0 muM (NAPH), 10 muM (PHTH) and 300 nM (ESTR), all 10-100 times lower than that without the surface modification with beta-CD. Individual and simultaneous detection of NAPH and PHTH from their mixture was achieved as evidenced using the bianalyte Raman technique.

Simultaneous quantification of levetiracetam and gabapentin in plasma by ultra-pressure liquid chromatography coupled with tandem mass spectrometry detection.[Pubmed:21297550]

Ther Drug Monit. 2011 Apr;33(2):209-13.

INTRODUCTION: Gabapentin (Neurontin) and levetiracetam (Keppra) are anticonvulsants with novel structures and suggested therapeutic ranges of 2-10 mg/L and 6-20 mg/L, respectively. Gabapentin is also used extensively to manage neuropathic pain, and for this indication, wherein higher doses are prescribed, plasma concentrations of 15-30 mg/L are typical. OBJECTIVE: Here, we describe a simple rapid assay to support therapeutic drug monitoring of gabapentin and levetiracetam in plasma by ultra-pressure liquid chromatography couples to tandem mass spectrometry (UPLC-MS/MS) detection. METHODS: After the addition of internal standard and protein precipitation of patient plasma with methanol:acetonitrile in a 50:50 ratio, 1 muL of supernatant sample is injected onto an Acquity UPLC HSS T3, 1.8 mum, 2.1 x 50 mm (Waters) column. Elution occurs using a linear gradient of acetonitrile and water, each having 0.1% formic acid added. The column is eluted into a Waters Acquity UPLC TQD, operating in a positive mode to detect gabapentin at transition 172.18 > 154.11, levetiracetam at 171.11 > 126, and internal standard (3-Amino-2-naphthoic acid) at 188.06 > 170. Secondary transitions for each analyte are also monitored for gabapentin at 172.18 > 137.06, levetiracetam at 171.11 > 154, and internal standard at 188.06 > 115. Runtime is 1.5 minutes per injection with baseline resolved chromatographic separation. RESULTS: The analytical measurement ranges were 1-150 mg/L for gabapentin and for levetiracetam. Intra-assay imprecision by the coefficient of variance (CV) was less than 8% and interassay CV was less than 5% for both analytes, at 4 different concentrations. Results obtained from patient samples were compared with results generated by established high-performance liquid chromatography-UV methods with the following regression statistics: y = 1.12x - 0.77, r = 0.996, Sy, x = 0.89, and n = 29 for gabapentin and y = 0.991x + 0.70, r = 0.997, Sy, x = 2.24, and n = 30 for levetiracetam. No analytical interferences were identified. CONCLUSION: : In summary, a simple reliable UPLC-MS/MS method was developed and validated for routine clinical monitoring of gabapentin and levetiracetam.

Direct formation of ring-fused 1,3-thiazine-2,4-dithiones from aromatic o-amino carboxylic acids: observation of a carbon disulfide mediated thionation.[Pubmed:20666472]

Org Lett. 2010 Aug 20;12(16):3662-5.

A facile synthesis of 2H-3,1-benzothiazine-2,4(1H)-dithiones (trithioisatoic anhydrides) or 2H-naphtho[2,3-d][1,3]thiazine-2,4(1H)-dithione solely from anthranilic acids or 3-Amino-2-naphthoic acid and carbon disulfide, performed at room temperature in 1,4-dioxane in the presence of Et(3)N, is reported. Corresponding 2-alkylsulfanyl derivatives were obtained in one-pot reactions under the same conditions after addition of alkyl halides. The mechanism of the thiazine cyclization was investigated using (13)C-labeled carbon disulfide to reveal that carbon disulfide was incorporated into the heterocycle and additionally acted as a thionation reagent.

A metabonomic investigation of the biochemical effects of mercuric chloride in the rat using 1H NMR and HPLC-TOF/MS: time dependent changes in the urinary profile of endogenous metabolites as a result of nephrotoxicity.[Pubmed:15152332]

Analyst. 2004 Jun;129(6):535-41.

The effects of the administration of a single dose of the model nephrotoxin mercuric chloride (2.0 mg kg(-1), subcutaneous) to male Wistar-derived rats on the urinary metabolite profiles of a range of endogenous metabolites has been investigated using (1)H NMR and HPLC-MS. Urine samples were collected daily for 9 days from both dosed and control animals. Analysis of these samples revealed marked changes in the pattern of endogenous metabolites as a result of HgCl(2) toxicity. Peak disturbances in the urinary metabolite profiles were observed (using both NMR and HPLC-MS) at 3 days post dose. Thereafter the urinary metabolite profile gradually returned to a more normal composition. Markers of toxicity identified by (1)H NMR spectroscopy were raised concentrations of lactate, alanine, acetate, succinate, trimethylamine (TMA), and glucose. Reductions in the urinary excretion of citrate and alpha-ketoglutarate were also seen. Markers identified by HPLC-MS, in positive ion mode, were kynurenic acid, xanthurenic acid, pantothenic acid and 7-methylguanine which decreased after dosing. In addition an ion at m/z 188, probably 3-Amino-2-naphthoic acid, was observed to increase after dosing. As well as these identified compounds other ions at m/z 297 and 267 decreased after dosing. In negative ion mode a range of sulfated compounds were observed, including phenol sulfate and benzene diol sulfate, which decreased after dosing. As well as the sulfated components an unidentified glucuronide at m/z 326 was also observed to decrease after dosing. The results of this study demonstrate the complementary nature of the NMR and MS-based techniques for metabonomic analysis.