Gabriella Roda

On the selectivity of oxynitrilases towards α-oxygenated aldehydes1

Abstract Different α-alkoxy and α,β-di-alkoxy substituted aldehydes have been submitted to the catalytic action of the oxynitrilases from almond ( PaHNL ) or from Hevea brasiliensis ( HbHNL ), in order to explore the possibility of using these enzymes for the preparation of complex cyanohydrins. The selectivity of both enzymes towards these compounds was found to be largely dependent on the substitutents, being low with the aldehydes carrying the sterically more demanding phenyl substituent. Contrary to the chemical addition of HCN, which always occurs with a slight preference for the formation of the anti diastereoisomers, the enzymatic cyanuration—occurring with a facial preference, Si or Re according to the biocatalyst used—gave a mixture of cyanohydrins that, depending on the starting enantiomeric aldehyde, can be enriched in the syn diastereoisomers.

ALMOND OXYNITRILASE-CATALYZED TRANSFORMATION OF ALDEHYDES IS STRONGLY INFLUENCED BY NAPHTHYL AND ALKOXY SUBSTITUENTS

Abstract Different α- and β-substituted aldehydes have been submitted to the catalytic action of almond oxynitrilase (PaHNL), in order to explore the influence of a stereocenter already present in the substrate on the selectivity of this enzyme. [1] The results indicate that naphthyl and alkoxy substituents in the α- and also in the β-position to the aldehyde group significantly influence the stereochemical outcome of the PaHNL-catalyzed transformation.

Selectivity of the (S)-oxynitrilase from Hevea brasiliensis towards α- and β-substituted aldehydes

Abstract The performance of ( S )-oxynitrilase from Hevea brasiliensis (HbHNL) has been investigated with several α- and β-substituted alkyl or alkoxy aldehydes and the results have been compared to the data previously obtained with the ( R )-specific enzyme from almonds (PaHNL). With both enzymes there was no chiral discrimination between the enantiomers of the racemic substrates, therefore this reaction cannot be used as a preparative method to achieve both the kinetic resolution of the starting racemic aldehyde and the production of diastereomerically pure (or enriched) cyanohydrins. Additionally, in comparison with the ( R )-PaHNL the ( S )-selective enzyme from Hevea gave products with higher de, but was more negatively effected by oxygenated substituents.

Determination of the active principles of Catha Edulis: Quali–quantitative analysis of cathinone, cathine, and phenylpropanolamine

In the last years, all the vegetable material supposed to belong to the Catha Edulis species, seized at the Malpensa and Orio al Serio airports, were analyzed in our laboratory on behalf of the Tribunals of Busto Arsizio and Bergamo, respectively. After a preliminary botanic examination, the quali-quantitative determination of the active principles cathinone, cathine and phenylpropanolamine (PPA) was carried out by means of GC/MS and GC/FID techniques, which meet the requirements of the forensic analyses. We developed a fast, effective and reliable derivatization procedure which allowed to simultaneously detect cathine and PPA, whose discrimination is mandatory since PPA is not a psychoactive agent. Cathine was distributed in the various parts of the plant (leaves and stems) and its quantity ranged from 0.03% to 0.17% of the weight of the vegetable material; PPA was not detected in the twigs and its quantity in the leaves ranged from 0.07% to 0.16%. The quantitative determination of cathinone was carried out directly on the methanol solution after maceration of the vegetable material, its quantity ranging from 0.02% to 0.10%. No significant difference in the content of the two active principles was found between the fresh and the dried material.

Characterization of in vitro metabolites of JWH-018, JWH-073 and their 4-methyl derivatives, markers of the abuse of these synthetic cannabinoids.

In vitro incubation with human liver microsomes of JWH-018, JWH-073, JWH-122 and for the first time 1-butyl-3-(1-(4-methyl)naphthoyl)indole (the 4-methylnaphthoyl analogue of JWH-073) was investigated to identify the principal metabolites of alkylindole synthetic cannabinoids, thus helping the discovering of synthetic cannabinoids abusers. The results obtained showed that the most abundant metabolites were mono-hydroxylated derivatives either on the alkyl chain (ω or ω-1 position) or on the indole (presumably in position 5 or 6) and naphthalene moieties. Moreover the extraction conditions of these derivatives from biological fluids, mainly plasma and urine spiked with commercially available metabolite standards, and the incubation procedure were investigated to obtain a fast, reliable and suitable extraction protocol to detect either the parent drugs or their metabolites by means of GC/MS.

Unexpected Variation of the Codeine/Morphine Ratio Following Fatal Heroin Overdose

Postmortem samples from 14 cases of suspected heroin overdose were subjected to a preliminary systematic toxicological analysis in order to highlight the presence of unknown exogenous compounds (e.g., drugs of abuse, alcohol) that may have played a role in the mechanism of death. This analysis unveiled histories of poly-drug use in seven of the cases under investigation. Moreover, the concentrations of morphine and codeine in the brain were also investigated, and the results were compared with the data obtained from the blood specimens. The concentration of morphine in blood ranged from 33 to 688 ng/mL, while the concentration of codeine ranged from 0 to 193 ng/mL. However, in the brain, the concentration of morphine was found to be between 85 and 396 ng/g, while the levels of codeine ranged from 11 to 160 ng/g. The codeine/morphine ratio in the blood ranged from 0.043 to 0.619; however, in the brain, the same ratio was found to be between 0.129 and 0.552. In most cases, a significantly higher codeine/morphine ratio was found in the brain, suggesting the accumulation of codeine in brain tissue due its high lipophilicity as compared with morphine.

Effect of chemical composition of SBA-15 on the adsorption and catalytic activity of α-chymotrypsin

The adsorption of α-chymotrypsin (α-CT) on Al-containing mesoporous materials based on SBA-15 topology was investigated. The insertion of various amounts of aluminium was achieved using the two-step (pH-adjusting) method and the physico-chemical properties of these materials were characterized by small angle X-ray diffraction, nitrogen adsorption/desorption isotherm curves and 27Al MAS NMR spectroscopy, ammonia adsorption microcalorimetry and chemical analyses. The amount of adsorbed enzyme was found to be dependent on the Si/Al ratio of solid surfaces, pH of adsorption and, in the case of Al-containing material, on the ionic strength. Various mechanisms of adsorption are discussed. The activity of immobilized α-CT was examined using the transesterification of N-acetyl-L-phenylalanine ethyl ester with 1-propanol as test-reaction. The catalytic efficiency is strongly dependent on the nature of the support. In order to reduce the leaching of enzyme from the support surface and improve its reusability, cross-linking of the adsorbed enzyme was carried out by glutardialdehyde. In general, these mesoporous silica materials are attractive candidates for enzyme immobilization and biomedical applications due to their high surface area, tunable surface properties and pore size, large pore volume and biocompatibility.

Synthesis and biological evaluation of new amino acids structurally related to the antitumor agent acivicin

A set of racemic conformationally constrained analogues of the antitumor antibiotic acivicin (+)-1 has been prepared through a strategy based on 1,3-dipolar cycloaddition of bromonitrile oxide to suitable dipolarophiles. The bromo analogue (2) of acivicin was also synthesized and tested as a reference compound, together with its stereoisomer 3. The antitumor properties of novel amino acids 4-7 were evaluated in vitro against human tumor cell lines. Their efficacy to inhibit glutamate synthase (GltS) from Azospirillum brasilense was also assayed. None of the studied compounds, but 2, showed significant activity.

Identification of 1-butyl-3-(1-(4-methyl)naphtoyl)indole detected for the first time in “herbal high” products on the Italian market

The results of the analysis of some herbal products and powders adulterated with alkylindoles recovered on the Italian market between 2010 and 2011 are reported. Besides the well-known alkyindoles JWH-018 and JWH-073, other derivatives such as JWH-250 and AM-694 have been detected and for the first time in Italy 1-butyl-3-(1-(4-methyl)naphthoyl)indole (compound 1), the 4-methylnaphthoyl analogue of JWH-073. This compound as well as the other alkylindoles has been synthesized and characterized by (1)H NMR, (13)C NMR, DSC, GC/MS, and elemental analysis. The quantitative analyses of the samples have been carried out by means of the GC/FID method developed in our laboratory for the analysis of herbal high products containing naphthoylindoles; the quantity of the cannabimimetic substances ranged from 6 mg/g to 47 mg/g.

An improved synthesis of enantiomerically pure CIP-AS, a potent and selective AMPA-kainate receptor agonist

Abstract CIP-AS (−)-2, a chiral amino acid structurally related to glutamic acid, behaves as a potent agonist at the ionotropic AMPA-kainate receptors and was previously prepared in low overall yield through the 1,3-dipolar cycloaddition of ethoxycarbonylformonitrile oxide to N-BOC-3,4-didehydro-(S)-proline methyl ester (−)-6. Herein, we report an alternative strategy based on the cycloaddition of the same dipolarophile to N-(4-methoxybenzyl)-α-ethoxycarbonylnitrone 12. The mixture of stereoisomeric 3-ethoxycarbonyl-N-(4-methoxybenzyl)isoxazolidinyl prolines 13 was then converted into the corresponding 3-ethoxycarbonyl-Δ2-isoxazolinyl prolines by DDQ mediated oxidation. The new strategy yielded the precursor of CIP-AS in satisfactory overall yield and represents an improvement upon the existing procedure in terms of yield and efficiency.