Planar Chromatographic Study of Flavonoids and Soyasaponins for Validation of Fingerprints of Desmodium adscendens of Different Origin

JPC – Journal of Planar Chromatography – Modern TLC - The flavonoid and triterpenoid soyasaponin content of the aerial parts of Desmodium adscendens from four geographical origins of...     

Plant drug analysis by planar chromatography

Optimal performance laminar chromatography and automated multiple development chromatography are relatively recent techniques of planar chromatography that can be applied with success in plant material analysis. Therefore, these methods are used to study plant extracts and constituents belonging to different chemical classes of secondary metabolism: heterocyclic oxygen compounds (coumarins, flavonoids, and anthocyanins), alkaloids and quaternary ammonium salts, cannabinoids, essential oils, ginsenosides, and cardiac heterosides. Generally, the results obtained with these methods are good, and in most cases they compare with those of thin-layer chromatography.     

Isoregic Thienylene‐Phenylene Polymers: The Effects of Structural Variation and Application to Photovoltaic Devices

Isoregic conjugated polymers composed of thiophene and dialkoxybenzene units were designed to harvest incident light in the mid‐visible energy range (band gap of 2.1 eV). Poly(1,4‐bis(2‐thienyl)‐2,5‐diheptoxybenzene) (PBTB(OC₇H₁₅)₂) and poly(1,4‐bis(2‐thienyl)‐2,5‐didodecyloxybenzene) (PBTB(OC₁₂H₂₅)₂) have shown significant photovoltaic performance as an electron donor when used in tandem with the electron acceptor [6, 6]‐phenyl C₆₁‐butyric acid methyl ester (PCBM) in bulk hetero‐junction photovoltaic devices. Photovoltaic devices incorporating PBTB(OC₇H₁₅)₂ and PCBM have shown AM1.5 efficiencies of ～0.6% with a short circuit current density of 2.5 mA/cm², an open circuit voltage of 0.74 V, and a fill factor of 0.32. Incident Photon‐to‐Current Efficiency (IPCE) of the device was found to be ca. 16% at 410 nm. In order to examine the relationship between the molecular structure of the polymers and their electronic energy levels, and to correlate this with photovoltaic performance, optoelectronic and electrochemical results are discussed in relation to the I‐V characteristics of the devices. Additionally, a computer‐aided simulation is used to gain further insight into the effect of polymer structure on the energetic relationships in the bulk heterojunction devices.     

Separation and identification of cannabis components by different planar chromatography techniques (TLC, AMD, OPLC)

The use of cannabis is illicit in numerous countries, and the increasing consumption has led to a multiplication of scientific studies. New methods of planar chromatography such as automated multiple development (AMD) and optimum performance laminar chromatography (OPLC) techniques can be used as a substitute for the traditional thin-layer chromatography for the identification and quantitation of the Indian hemp components. Each method offers its own advantage: high resolution with neither diffusion nor spot stretching for AMD and speed, efficiency, and the possibility of working in the semipreparative mode for OPLC.     

Automated multiple development thin-layer chromatography for separation of opiate alkaloids and derivatives

There are three types of opiate alkaloids. First, the poppy alkaloids: morphine, codeine, thebaine, noscapine and papaverine; then, the semi-synthetic and synthetic derivatives used in therapy as antitussives and analgesics, such as pholcodine, ethylmorphine and dextromethorphan; at last narcotic compounds, diacetylmorphine (heroin) and opiates employed as substitutes in treatment of addiction: buprenorphine and methadone. For classical thin-layer chromatography (TLC) of opium alkaloids, it is necessary to use complex eluents with strong alkaline substances to obtain a clean separation between morphinan and isoquinoline compounds. This study purposes the planar chromatographic analysis of these substances by the automated multiple development (AMD) compared with results obtained by classical TLC method. The aim of this work was to achieve the best separation of these opiate alkaloids and derivatives by this modern technique of planar chromatography. The AMD system provided a clean separation for each of three opiates groups studied and the best results have been obtained with universal gradient: methanol 100, methanol-dichloromethane 50/50, dichloromethane 100, dichloromethane 100, hexane 100 for opium alkaloids and with gradient A: 5% of 28% ammonia in methanol 100, acetone 100, acetone 100, ethyl acetate-dichloromethane 50/50, dichloromethane 100 for antitussives and substitutes. Two reagents were used for the detection of alkaloids by spraying: Dragendorff and iodoplatinate reagents. The detection limits with these two reagents were 1 microg for ethylmorphine, thebaine, papaverine, codeine, and 2 microg for morphine and noscapine and other alkaloids.     

Uranyl extraction by beta-diketonate ligands to SC-CO2: theoretical studies on the effect of ligand fluorination and on the synergistic effect of TBP

We report theoretical investigations on the effect of H --> F substitution in acetylacetonate ligands in order to understand why fluorination promotes the extraction of uranyl to supercritical CO(2) with a marked synergistic effect of tri-n-butyl phosphate "TBP". The neutral LH and deprotonated L(-) forms of the ligand, and the uranyl complexes UO(2)L(2) and UO(2)L(2)S (S = H(2)O versus trimethyl phosphate "TMP" which mimics TBP) are studied by quantum mechanics (QM) in the gas phase, whereas the ligands LH and their UO(2)L(2) and UO(2)L(2)S complexes are studied by molecular dynamics (MD) in SC-CO(2) solution as well as at a CO(2)-water interface. Several effects are found to favor F ligands over the H ligands. (i) First, intrinsically (in the gas phase), the complexation reaction 2 LH + UO(2)(2+) --> UO(2)L(2) is more exothermic for the F ligands, mainly due to their higher acidity, compared to the H ligands. (ii) The unsaturated UO(2)L(2) complexes with F ligands bind more strongly TMP than H(2)O, thus preferentially leading to the UO(2)L(2)(TMP) complex, more hydrophobic than UO(2)L(2)(H(2)O). (iii) Molecular dynamics simulations of SC-CO(2) solutions show that the F ligands and their UO(2)L(2) and UO(2)L(2)S complexes are better solvated than their H analogues, and that the UO(2)L(2)(TBP) complex with F ligands is the most CO(2)-philic. (iv) Concentrated solutions of UO(2)L(2)(TBP) complexes at the CO(2)-water interface display an equilibrium between adsorbed and extracted species, and the proportion of extracted species is larger with F- than with H- ligands, in agreement with experimental observations. Thus, TBP plays a dual synergistic role: its co-complexation by UO(2)L(2) yields a hydrophobic and CO(2)-philic complex suitable for extraction, whereas TBP in excess at the interface facilitates the migration of the complex to the supercritical phase.     

Succinobucol's new coat--conjugation with steroids to alter its drug effect and bioavailability

Synthesis, detailed structural characterization (X-ray, NMR, MS, IR, elemental analysis), and studies of toxicity, antioxidant activity and bioavailability of unique potent anti-atherosclerotic succinobucol-steroid conjugates are reported. The conjugates consist of, on one side, the therapeutically important drug succinobucol ([4-{2,6-di-tert-butyl-4-[(1-{[3-tert-butyl-4-hydroxy-5-(propan-2-yl)phenyl]sulfanyl}ethyl)sulfanyl]phenoxy}-4-oxo-butanoic acid]) possessing an antioxidant and anti-inflammatory activity, and on the other side, plant stanol/sterols (stigmastanol, β-sitosterol and stigmasterol) possessing an ability to lower the blood cholesterol level. A cholesterol-succinobucol prodrug was also prepared in order to enhance the absorption of succinobucol through the intestinal membrane into the organism and to target the drug into the place of lipid metabolism-The enterohepatic circulation system. Their low toxicity towards mice fibroblasts at maximal concentrations, their antioxidant activity, comparable or even higher than that of ascorbic acid as determined by direct quenching of the DPPH radical, and their potential for significantly altering total and LDL cholesterol levels, suggest that these conjugates merit further studies in the treatment of cardiovascular or other related diseases. A brief discussion of succinobucol's ability to quench the radicals, supported with a computational model of the electrostatic potential mapped on the electron density surface of the drug, is also presented.     

Choquet-based optimisation in multiobjective shortest path and spanning tree problems

This paper is devoted to the search of Choquet-optimal solutions in finite graph problems with multiple objectives. The Choquet integral is one of the most sophisticated preference models used in decision theory for aggregating preferences on multiple objectives. We first present a condition on preferences (name hereafter preference for interior points) that characterizes preferences favouring compromise solutions, a natural attitude in various contexts such as multicriteria optimisation, robust optimisation and optimisation with multiple agents. Within Choquet expected utility theory, this condition amounts to using a submodular capacity and a convex utility function. Under these assumptions, we focus on the fast determination of Choquet-optimal paths and spanning trees. After investigating the complexity of these problems, we introduce a lower bound for the Choquet integral, computable in polynomial time. Then, we propose different algorithms using this bound, either based on a controlled enumeration of solutions (ranking approach) or an implicit enumeration scheme (branch and bound). Finally, we provide numerical experiments that show the actual efficiency of the algorithms on multiple instances of different sizes.