Identification of thiocyanates by Gas Chromatography - Mass Spectrometry in explosive residues used as a possible marker to indicate black powder usage.

Black Powder (BP) is one of the most common improvised explosives, due to broad access in precursors and simple home-made preparation. Deflagration of black powder results in residues the chemical analysis of which presents limitations and has been performed with several techniques until today; nevertheless, Gas Chromatography-Mass Spectrometry (GC-MS) has never been used. In this study, a simple experimental protocol has been developed towards black powder residues identification, using GC-MS. The sample preparation does not require specialized equipment. Derivatization of thiocyanates coming from BP deflagration and identification of the relative derivative (PBF-SCN) was achieved by monitoring ions m/z 239, 181 and 161. This characteristic derivative was used as a marker to indicate BP usage. The protocol was optimized by investigating individually all experimental parameters and it was evaluated for false positives and negatives. Repeatability and limit of detection were calculated to be %RSD 7.67 and < 1 mg, respectively. No interference coming from other ingredients that might co-exist in BP residues was observed. This protocol may be applied directly and without previous preparation to evidence coming from cases of explosions, thus practically contributing in BP residues identification.

A rapid method for the identification of nitrocellulose in high explosives and smokeless powders using GC-EI-MS.

Nitrocellulose (NC) is one of the most common ingredients in explosive mixtures, however because of its non-volatility, its detection using Gas Chromatography-Electron Ionization-Mass Spectrometry (GC-EI-MS) has not been achieved until today. A rapid method for the identification of NC in bulk explosives using GC-EI-MS was developed. The sample preparation is simple and takes place in a test tube, employing standard equipment of a forensics laboratory. The protocol was optimized and applied to seven, both high and low, commercial explosives, which contained the substance of interest. Moreover, three explosives in the absence of NC were tested to cross check for false positives. Fourteen different standard explosive substances that are usually found in explosive mixtures were then employed in order to monitor the effect of the method on these compounds and check for interferences. Results showed that NC was detected, by its trimethylsilyl (TMS) derivatives, in all the explosive mixtures analyzed and no false positives were observed. The proposed method showed selectivity for NC, as it had no interference coming from other ingredients of explosive mixtures. The protocol introduced offers considerable improvement in identifying the individual components of an explosive mixture and contributes in successful classification of explosives.

Glucose-derived spiro-isoxazolines are anti-hyperglycemic agents against type 2 diabetes through glycogen phosphorylase inhibition.

Glycogen phosphorylase (GP) is a target for the treatment of hyperglycaemia in the context of type 2 diabetes. This enzyme is responsible for the depolymerization of glycogen into glucose thereby affecting the levels of glucose in the blood stream. Twelve new d-glucopyranosylidene-spiro-isoxazolines have been prepared from O-peracylated exo-D-glucals by regio- and stereoselective 1,3-dipolar cycloaddition of nitrile oxides generated in situ by treatment of the corresponding oximes with bleach. This mild and direct procedure appeared to be applicable to a broad range of substrates. The corresponding O-unprotected spiro-isoxazolines were evaluated as glycogen phosphorylase (GP) inhibitors and exhibited IC50 values ranging from 1 to 800 µM. Selected inhibitors were further evaluated in vitro using rat and human hepatocytes and exhibited significant inhibitory properties in the primary cell culture. Interestingly, when tested with human hepatocytes, the tetra-O-acetylated spiro-isoxazoline bearing a 2-naphthyl residue showed a much lower IC50 value (2.5 µM), compared to that of the O-unprotected analog (19.95 µM). The most promising compounds were investigated in Zucker fa/fa rat model in acute and sub-chronic assays and decreased hepatic glucose production, which is known to be elevated in type 2 diabetes. This indicates that glucose-based spiro-isoxazolines can be considered as anti-hyperglycemic agents in the context of type 2 diabetes.

Discovery of the glycogen phosphorylase-modulating activity of a resveratrol glucoside by using a virtual screening protocol optimized for solvation effects.

The identification of natural products that can modulate blood glucose levels is of great interest as it can possibly facilitate the utilization of mild interventions such as herbal medicine or functional foods in the treatment of chronic diseases like diabetes. One of the established drug targets for antihyperglycemic therapy is glycogen phosphorylase. To evaluate the glycogen phosphorylase inhibitory properties of an in-house compound collection consisting to a large extent of natural products, a stepwise virtual and experimental screening protocol was devised and implemented. The fact that the active site of glycogen phosphorylase is highly hydrated emphasized that a methodological aspect needed to be efficiently addressed prior to an in silico evaluation of the compound collection. The effect of water molecules on docking calculations was regarded as a key parameter in terms of virtual screening protocol optimization. Statistical analysis of 125 structures of glycogen phosphorylase and solvent mapping focusing on the active site hydration motif in combination with a retrospective screening revealed the importance of a set of 29 crystallographic water molecules for achieving high enrichment as to the discrimination between active compounds and inactive decoys. The scaling of Van der Waals radii of system atoms had an additional effect on screening performance. Having optimized the in silico protocol, a prospective evaluation of the in-house compound collection derived a set of 18 top-ranked natural products that were subsequently evaluated in vitro for their activity as glycogen phosphorylase inhibitors. Two phenolic glucosides with glycogen phosphorylase-modulating activity were identified, whereas the most potent compound affording mid-micromolar inhibition was a glucosidic derivative of resveratrol, a stilbene well-known for its wide range of biological activities. Results show the possible phytotherapeutic and nutraceutical potential of products common in the Mediterranean countries, such as red wine and Vitis products in general or green raw salads and herbal preparations, where such compounds are abundant.

Efficient atropodiastereoselective access to 5,5'-bis-1,2,3-triazoles: studies on 1-glucosylated 5-halogeno 1,2,3-triazoles and their 5-substituted derivatives as glycogen phosphorylase inhibitors.

Whereas copper-catalyzed azide-alkyne cycloaddition (CuAAC) between acetylated ß-D-glucosyl azide and alkyl or phenyl acetylenes led to the corresponding 4-substituted 1-glucosyl-1,2,3-triazoles in good yields, use of similar conditions but with 2 equiv CuI or CuBr led to the 5-halogeno analogues (>71 %). In contrast, with 2 equiv CuCl and either propargyl acetate or phenyl acetylene, the major products (>56 %) displayed two 5,5'-linked triazole rings resulting from homocoupling of the 1-glucosyl-4-substituted 1,2,3-triazoles. The 4-phenyl substituted compounds (acetylated, O-unprotected) and the acetylated 4-acetoxymethyl derivative existed in solution as a single form (d.r.>95:5), as shown by NMR spectroscopic analysis. The two 4-phenyl substituted structures were unambiguously identified for the first time by X-ray diffraction analysis, as atropisomers with aR stereochemistry. This represents one of the first efficient and highly atropodiastereoselective approaches to glucose-based bis-triazoles as single atropisomers. The products were purified by standard silica gel chromatography. Through Sonogashira or Suzuki cross-couplings, the 1-glucosyl-5-halogeno-1,2,3-triazoles were efficiently converted into a library of 1,2,3-triazoles of the 1-glucosyl-5-substituted (alkynyl, aryl) type. Attempts to achieve Heck coupling to methyl acrylate failed, but a stable palladium-associated triazole was isolated and analyzed by (1)H NMR and MS. O-Unprotected derivatives were tested as inhibitors of glycogen phosphorylase. The modest inhibition activities measured showed that 4,5-disubstituted 1-glucosyl-1,2,3-triazoles bind weakly to the enzyme. This suggests that such ligands do not fit the catalytic site or any other binding site of the enzyme.

Synthesis of 1,2,3-triazoles from xylosyl and 5-thioxylosyl azides: evaluation of the xylose scaffold for the design of potential glycogen phosphorylase inhibitors.

Various acetylenic derivatives and acetylated ß-D-xylopyranosyl azide or the 5-thio-ß-d-xylopyranosyl analogue were coupled by Cu(I)-catalyzed azide alkyne 1,3-dipolar cycloaddition (CuAAC) to afford a series of 1-xylosyl-4-substituted 1,2,3-triazoles. Controlled oxidation of the endocyclic sulfur atom of the 5-thioxylose moiety led to the corresponding sulfoxides and sulfones. Deacetylation afforded 19 hydroxylated xylose and 5-thioxylose derivatives, found to be only sparingly water-soluble. Compared to glucose-based analogues, they appeared to be much weaker inhibitors of glycogen phosphorylase, as the absence of a hydroxymethyl group weakens their binding at the enzyme active site. However, such new xylose derivatives might be useful glycomimetics.

C-Glucosylated malonitrile as a key intermediate towards carbohydrate-based glycogen phosphorylase inhibitors.

Glycogen utilization involves glycogen phosphorylase, an enzyme which appears to be a potential target for the regulation of glycaemia, as the liver isoform is a major player for hepatic glucose output. A single C-glucosylated malonitrile allowed for the synthesis of three glucose-based derivatives namely bis-oxadiazoles, bis-amides and a C-glucosylated tetrahydropyrimidin-2-one. When evaluated as glycogen phosphorylase inhibitors, two of the synthesized compounds displayed inhibition in the sub-millimolar range. In silico studies revealed that only one out of the bis-amides obtained and the C-glucosylated tetrahydropyrimidin-2-one may bind at the catalytic site.