Amphetamine-like discrimination stimulus effects of ephedrine and its stereoisomers in pigeons.

This study assessed the discriminative stimulus effects of (±)-ephedrine and its stereoisomers in pigeons discriminating 1.0 mg/kg of amphetamine from saline. Amphetamine, (±)-, (-)-, and (+)-ephedrine, and cocaine occasioned greater than 80% drug-key responding with the following rank order of potency: amphetamine > cocaine > (-)-ephedrine ≥ (±)-ephedrine ≥ (+)-ephedrine. Neither the α-adrenergic antagonist, phentolamine, nor the β-adrenergic antagonist, propranolol, antagonized the effects of amphetamine or (±)-ephedrine. In contrast, the dopamine receptor antagonist, haloperidol, antagonized the discriminative stimulus effects of amphetamine and (±)-ephedrine as well as those of (-)- and (+)-ephedrine. These results indicate that, like cocaine, (±)-ephedrine and its stereoisomers share discriminative stimulus effects with amphetamine. Moreover, these effects appear to be the result of increased activity in dopaminergic systems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Responses of braconid parasitoidsMicroplitis croceipes (Cresson) andM. demolitor Wilkinson to stereoisomers of kairomone 13-methylhentriacontane

The responses ofMicroplitis croceipes (Cresson) andMicroplitis demolitor Wilkinson to theR andS stereoisomers of the kairomone 13-meth-ylhentriacontane were evaluated. Singly and in combination at 5, 50-, and 500-ng dosage levels each were tested. There was a linear dosage response by both species to the three dosages. Furthermore, there was no difference between responses to the two stereoisomers or their combination by either species at any dosage level. The effects of the two stereoisomers were fully interchangeable and additive. This is the first report of parasitoid responses to stereoisomers of a kairomone.     

6-Iso-chlortetracycline or keto form of chlortetracycline? Need for clarification for relevant monitoring of chlortetracycline residues in food

Chlortetracycline (CTC) is a broad-spectrum antibiotic used in veterinary medicine for pulmonary or digestive infections and having a regulatory maximum residue limit (MRL) necessitating an official analytical control method. The purpose of this study was to clarify the identification of different forms of CTC observed in standard solution, in spiked muscle samples and in naturally incurred muscle samples of pigs analysed by LC-MS/MS and to demonstrate the in vivo formation of 6-iso-chlortetracycline and 4-epi-6-iso-CTC as a metabolite of CTC and 4-epi-CTC in muscle. The six following forms were identified, all being isobaric with a protonated molecule at m/z 479 (precursor ion): the keto-enol forms of CTC and the keto-enol forms of 4-epi-chlortetracycline (4-epi-CTC), 6-iso-chlortetracycline (6-iso-CTC) and 4-epi-6-iso-chlortetracycline (4-epi-6-iso-CTC). The 6-iso-CTC and 4-epi-6-iso-CTC were observed only in incurred pig samples so were identified for the first time as metabolites of CTC and 4-epi-CTC. Identification of the different forms was obtained by comparing incurred muscle samples with standard solutions and with spiked samples. Then the differences between the features of the chromatograms obtained by LC-TQ-MS and the fragmentation study of the different forms of CTC obtained by LC-Q-TOF-MS helped us to support this identification. The extraction steps and the LC-MS/MS conditions developed to analyse muscle tissue samples are described. This clarification concerning the rigorous identification of chromatographic peaks allowed us to evaluate the relevance of our monitoring method with regard to the regulations in place in the European Union and could be of help to laboratories involved in official control of antibiotic residues in food of animal origin. Additional results are also presented highlighting the transformation of the CTC when prepared in a mixture with other antibiotics.     

Gas chromatographic evaluation of amino acid epimerisation in the course of gelatin manufacturing and processing

 Using capillary gas chromatography on chiral stationary phases total hydrolysates of gelatins were investigated for their amounts of D-amino acids (D-AAs). Gelatins of different quality and origin were analysed including gelatin-containing final products like candies and meat products. In gelatins manufactured by stepwise extraction (first to fifth extract) with water of increasing temperature (ca. 55–95°C) amounts of 2.7–4.8% of D-aspartic acid (D-Asp) were determined in extracts obtained at ≤ 85°C. The amounts D-Asp were as high as 28.1% in fifth extracts obtained at 95°C (data corrected for 4.3% of D-Asp determined in native collagen as a result of acid-induced epimerisation of L-Asp during total hydrolysis). Epimerisation of aspartyl or asparaginyl residues of proteins in general on heating in water is assumed to proceed via formation of aspartyl succinimide, tautomerisation and release of D-Asp on total hydrolysis. The other AA residues of gelatin showed only a slight increase of epimerisation with increasing thermal treatment. Furthermore, amounts of 3–4% of cis-4-D-hydroxyproline, formed from native trans-4-L-hydroxyproline in collagen on hydrolysis, were detected in total hydrolysates of all gelatins. Received: 8 August 1997 / Revised version: 24 November 1997     

Chiral Stereoisomer Engineering of Electron Transporting Materials for Efficient and Stable Perovskite Solar Cells

A series of chiral stereoisomers of electron transporting materials with two chiral substituents is rationally designed and synthesized, and the influence of stereoisomerism on their physical and electronic properties is investigated to demonstrate highly efficient and stable perovskite solar cells (PSCs). Compared to mesomeric naphthalene diimide (NDI) derivatives, which have heterochiral side groups with centrosymmetric molecular packing of symmetric‐shaped conformers in the crystalline state, enantiomeric NDI derivatives have homochiral side groups that exhibit non‐centrosymmetric molecular packing of asymmetric‐shaped conformers in the crystalline state and exhibit better solution processability based on one order of magnitude higher solubility. A similar trend is observed in different rylene diimide stereoisomers based on larger semiconducting core perylene diimide. The PSCs based on NDI enantiomers with good film‐forming ability and a very high lowest phase transition temperature (T_lowest) of 321 °C exhibit a high and uniform average power conversion efficiency (PCE) of 19.067 ± 0.654%. These PSCs also have a high temporal device stability, with less than 10% degradation of the PCE at 100 °C for 1000 h without encapsulation. Therefore, chiral stereoisomer engineering of charge transporting materials is a potential approach to achieve high solution processability, excellent performance, and significant temporal stability in organic electronic devices.     

Diketopyrrolopyrrole Organic Thin‐Film Transistors: Impact of Alkyl Substituents and Tolerance of Ethylhexyl Stereoisomers

Bis(thiophen‐2‐yl)‐diketopyrrolopyrrole (DPP) dyes bearing various alkyl substituents at the amide positions (n‐butyl, n‐pentyl, n‐hexyl, n‐heptyl, n‐octyl, 2‐ethylhexyl) and chlorine (Cl), bromine (Br), or cyano (CN) substituents at the thiophene positions have been synthesized and investigated with regard to their molecular and semiconducting properties. Intense absorption, strong fluorescence, and reversible oxidation and reduction processes are common to all of these dyes. Their characterization as organic semiconductors in vacuum‐processed thin‐film transistors reveals p‐channel operation with field‐effect mobilities ranging from 0.01 to 0.7 cm² V^?1 s^?1. The highest mobility is found for the DPP dyes bearing the 2‐ethylhexyl substituents, which is surprising, considering that as a result of the chiral substituents, this material is a mixture of (R,R), (S,S), and (R,S) stereoisomers. The high carrier mobility in the films of the DPPs bearing stereoisomerically inhomogeneous ethylhexyl groups is rationalized here by single‐crystal X‐ray diffraction (XRD) analysis in combination with XRD and atomic force microscopy studies on thin films, which reveal the presence of slightly different 2D layer arrangements for the n‐alkyl and the 2‐ethylhexyl derivatives. For the cyano‐substituted DPPs possessing the lowest LUMO levels, ambipolar transport characteristics are observed.     

Quantitative high-resolution gas chromatographic determination of stereoisomeric composition of chiral volatile compounds in the picogram range by ec-detection

A gas chromatographic method using electron capture detection for determination of the stereochemical composition of chiralolatile compounds, e.g., pheromones, at the picogram level is described. Substances of interest are analyzed as pentafluorobenzoate derivatives on fused silica capillary columns coated with CP Sil-88. This method was developed primarily for the quantitative analyses of stereoisomerism of the pheromone precursor, diprionol, in female sawflies,Neodiprion sertifer. It was possible to separate the stereoisomers showing (2S, 3S, 7R) and (2S, 3S, 7S) configurations. Resolution of the (2S, 3S, 7S)- and (2S, 3R, 7R)-diastereomers was high enough to allow the quantification of these stereoisomers. A quantitative analysis of the diprionol production in individualN. sertifer females yielded 7.5–9.7 ng/female.     

Impact of packaging and storage conditions on colour and β-carotene retention of pasteurised mango purée

The effects of light and oxygen on β-carotene, vitamin A value, and colour stability of mango purée during storage were evaluated. Non-aseptic production at a pilot-plant scale, involving continuous high-temperature-short-time (HTST) heating, caused significant 13-cis-β-carotene formation, resulting in a pro-vitamin A retention of 82.3–89.6%, while peroxidase (POD) activity was reduced to residual levels of 0.4–2.6% in the pasteurised purée. Since oxygen removal from the package headspace by flushing with superheated steam or N₂ marginally affected β-carotene stability during storage, hot-filling was most crucial for exhausting the air. Irrespective of the packaging material, pro-vitamin A loss during storage was chiefly caused by oxidative degradation of β-carotene. Additional photo- isomerisation under exposure to light became manifest in the relative increase in 9-cis-β-carotene with associated decline in the 13-cis isomer portion. Despite photoisomerisation, pro-vitamin A retention was up to 90.9% in bottled purée after 168 days of light-exposed storage, with deaeration of the purée resulting from hot-filling. Marked colour loss mainly caused by accumulation of brown oxidation products was monitored by a rising degree of discolouration (Dd). Although additional headspace deaeration of cans and bottles improved colour retention, dissolved residual oxygen and other reactive compounds provoked browning and β-carotene degradation. As regards pro-vitamin A and colour, headspace minimisation was much more effective than its deaeration. Due to smaller headspace volumes, bottling proved superior to canning under the prevailing conditions, irrespective of light-exposed storage.