Thin-layer chromatographic investigation of plant pigments in selected juices and infusions of cosmetological importance and their antioxidant potential

ABSTRACT

Fruit preparations (e.g., fruit juices and nectars) are rich in plant pigments and of great demand by the alimentary and pharmaceutical industry, basically not only due to their health-enhancing properties, but also due to their attractive colors and an overall high esthetic valor. Anthocyanins and anthocyanidins are an interesting group of plant pigments, and in this study, a thin-layer chromatographic detection was carried out of two anthocyanins (cyanin and keracyanin) and two anthocyanidins (pelargonidin and delphinidin) in a selection of the commercial and homemade fruit juices and the infusions prepared of dried plants. Moreover, the same preparations were evaluated for their antioxidant properties by means of two spectrophotometric methods (based on the 2,2′-azino-di-[3-ethylbenzthiazoline] sulfonate (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) tests, respectively) and by the dot-blot test (based on DPPH). Finally, an effort was undertaken to correlate the chromatographically established occurrence of plant pigments in the investigated fruit preparations with their antioxidant properties. However, this correlation was not straightforward, and for at least two reasons. First, the four plant pigments considered are not the only secondary plant metabolites which exert an antioxidant activity. Second, different chemistries stand behind the two spectrophotometric antioxidant activity tests (ABTS vs. DPPH), and the different measuring techniques (spectrophotometry vs. dot blot) are assumed. Nevertheless, it was established that the juices and infusions with the highest detected numbers of plant pigments characterize with the high antioxidant activities also (with blueberries, chokeberries, and hibiscus flower on the top positions). In that way, confirmation of the antioxidant potential of the plant pigments was obtained. Moreover, the presence of certain plant pigments in fruit juices and plant infusions was reported for the first time.     

Solvent optimization in normal-phase liquid chromatography of selected steroids

Summary Resolution (R_s) is a function of three factors: efficiency, retentivity and selectivity. A procedure for optimization of mobile phase selectivity was demonstrated using a reversed-phase (RP) separation of compounds with various functionalities. In this paper, the same procedure is used with normal bonded-phase (NP) chromatography to develop a separation of structurally similar steroids. The optimization of mobile-phase selectivity provided increased problem-solving capability and decreased the analysis time.A brief summary of this work has been published in September 1981, in the form of a du Pont Application Study.     

Solvent effects in copolymerization

Extension of the Mayo-Lewis Model of copolymerization concerning solvent effects in free-radical polymerization is discussed on the basis of the bootstrap and penultimate unit effects.     

Solvent effects in dense gases

The effects of perturber gases, partial pressures in the range 0–50 atm, on the absorption spectra of high-n Rydbergs, n ≥ 10, in methyl iodide and benzene have been investigated. The perturbers were rare gases and H₂. It has been shown that the spectroscopic energy shift Δ = Δ(ρ, n) is given by Δ = Δ°ρ, where ρ is the number density of the perturber, for n ≥ 10. The shift data can be interpreted using a Fermi model, and values of scattering lengths for perturbers can be extracted. These scattering lengths are internally consistent, independent of the absorber, and in excellent agreement with electron-swarm results. Given that the Fermi model is nonspecific and microscopic, scattering shifts and lengths for mixtures of perturber gases can be predicted. These predictions, having been verified by experiment for He/Ar mixtures, provide a means of “tailoring” any required scattering length. Finally, it is shown empirically that the determinative scattering parameter is the polarizability of the perturber, and a universal relationship a = ?0.26α + 1.18 between scattering length a, in Bohr radii, and polarizability α is found to exist.     

Solvent effects in lipase-catalysed transesterification reactions

Porcine pancreatic lipase-catalysed transesterifications of 2,2,2-trifluoroethyl butyrate with racemic 2-octanol and 1-phenylethanol have been studied in different organic solvents. Solvent hydrophobicity (log P -1.1 to 3.3) has only a minor effect on the reaction rate. Independently of the solvent used as the reaction medium, both (R)-2-octyl and (R)-1-phenylethyl butyrates were obtained in high optical purity (ee greater than 90%). Candida cylindracea lipase is active only in the most hydrophobic solvents studied.     

Solvent effects in microemulsion electrokinetic chromatography

The contribution of organic solvents to the mechanisms responsible for separation in microemulsion electrokinetic chromatography (MEEKC) is reviewed. Organic solvents are needed as constituents of microemulsions for a series of reasons. (i). A water-immiscible organic substance is used to form the actual oil phase of the microemulsion, (ii). a less hydrophobic solvent is commonly employed as a so-called co-surfactant, and (iii). in many cases an organic modifier is added to influence the solubility of the analytes in the aqueous phase of the microemulsion. All these organic solvents do not only participate in the separation in their actual function, but also interact with each other and the analytes. Variations in separation selectivities triggered by changes in the nature and/or concentration of these organic solvents present in microemulsions suitable for MEEKC are discussed in this work.     

Solvent effects in gold-catalysed A-coupling reactions

Gold-catalysed A³-reactions proceed efficiently when conducted in 2,2,2-trifluoroethanol as solvent. The rates of these reactions are accelerated considerably when conducted in a microwave reactor.     

A spectrophotometric method for plant pigments determination and herbs classification

Twenty herbs, showing medicinal benefits on human life, like Taraxacum officinale, Plantago lanceolata, Hypericum perforatum, Ocimum basilicum, Melissa officinalis, Mentha piperita, and others, were tested. The percentage content of pigments, i.e. chlorophylls, carotenoids, and flavonoids, in the chosen herbs was determined. The spectrophotometric method, which is quick and readily available, was used. Measurements required pigment extraction with a solvent. Ethanol was used for the determination of chlorophylls and carotenoids, and acetone for the determination of flavonoids. Hierarchical agglomerative cluster analysis was performed in order to confirm the experimental results. The study of flavonoids content showed an interesting regularity which can be used for the classification of herbs. Plants belonging to the Lamiaceae family showed the flavonoids content in the range from 0.18 % to 0.68 %, whereas those belonging to the Apiaceaehas family showed the flavonoids content in the 0.75–1.20 % range.     

Chromatographic and electrophoretic procedures for analyzing plant pigments of pharmacologically interests

The achievements in the use of chromatographic and electrophoretic techniques including thin-layer chromatography, high-performance liquid chromatography and capillary electrophoresis for the separation and quantitative determination of pharmacologically interesting plant pigments in various sample matrices such as medicine, plant, foods and food products, etc. are surveyed and critically evaluated.     

离子对内电子转移型染料阴离子-翁盐阳离子光敏体系中的溶剂效应和结构效应

本文研究了溶剂效应和结构效应对染料碘翁盐光物理, 光化学性质的影响。观察到在溶剂中离子对可以各种形式存在, 如紧密离子对、溶剂分隔离子对或溶剂化的自由离子, 溶剂的极性不仅影响各种存在形式的光谱性质, 而且影响它们之间的平衡关系, 进而影响离子对体系的物理化学性质。染料母核和碘翁阳离子的结构均对离子对体系的性质有影响。光诱导电子转移反应的热力学驱动力越大, 反应速度越快。用分子模拟技术(Molecular Modeling)对离子对体系的立体结构进行了研究, 为理解离子对体系的各种物理化学行为提供了重要的参考。     

Solvent effects in molecular complexes of porphyrins and metalloporphyrins

The apparent stability constants for porphyrin and metalloporphyrin complexes with an electron acceptor have been determined in mixed solvents. The variation of the apparent stability with solvent composition is evaluated in terms of solvation of the complex and reactant species and in terms of the exclusion of the solvent from the solvation sheath of the reactants, according to the equilibrium AS _a +DS _b =CS _x +yS.     

Solvent effects on tautomerism equilibria in heterocycles

. High-level ab initio quantum mechanical methods have been used to analyze the tautomeric preferences in the gas phase and in aqueous solution of three important five-member heterocycles: 4-(5-)methylimidazole, 5-hydroxyisoxazole, and 3-hydroxypyrazole. Solvent effects have been introduced by means of self-consistent reaction field (SCRF) calculations at the ab initio level using our parametrized version of the polarizable continuum model developed by Miertus, Scrocco and Tomasi (MST), including geometry relaxation upon solvation. The extent to which the MST model, and SCRF methods in general, are suitable for the study of processes of this type is discussed.     

Solvent effects in the aza-Michael addition of anilines

The aza-Michael addition of functionally substituted anilines to enoates is significantly affected by the hydrogen bond donor ability of the solvent. Very polar protic fluorinated alcohols (hexafluoroisopropanol and trifluoroethanol) favor the addition of weak nucleophiles, whereas these solvents are no longer required for anilines bearing additional OH or NH₂ group.     

Solvent effects,species and extraction method effects,and coinitiator effects in the grafting of lignin

A general method of grafting lignin has been developed which allows solvent extracted lignin, steam exploded lignin, and kraft lignin to be converted to complex polymers. The lignins grafted have been obtained from aspen, poplar, oak, grasses, and pine. The lignins are research samples, pilot plant products, and commerical products from paper production. Nonionic copolymers of virtually any composition and molecular weight can be made from lignin and 2-propenamide by free radical reaction of 2-propenamide in the presence of the lignin. The water soluble product is a thickening agent and has limiting viscosity number in water at 30°C that vary from 0.1 to 2.0 dL/g. The grafting reaction is rapid and yields of 80 wt % or more can be obtained in as little as 30 min from reactions run in 1,4-dioxacyclohexane or dimethylsulfoxide. The reaction is initiated by a hydroperoxide, chloride ion, and lignin.     

Solvent effects in thermodynamically controlled multicomponent nanocage syntheses

The solvent effects on the condensation reaction between tetraformylcavitand 2 and ethylene-1,2-diamine 3 are reported. Earlier, it was found that the trifluoroacetic acid-catalyzed condensation of 2 and 2 equiv of 3 in CHCl(3) provides in 82% yield an octahedral nanocage 1 composed of 6 cavitands that are linked together by 12 -CH=N-CH(2)CH(2)-N=CH- linker groups (Liu, X.; Liu, Y.; Li, G.; Warmuth, R. Angew. Chem., Int. Ed. 2006, 45, 901). In tetrahydrofuran, the same reactants yield a tetrameric nanocage 4 (35% yield), which resembles a distorted tetrahedron built up from four cavitands that occupy the apexes. Each cavitand is doubly linked to one other cavitand and singly linked to the other two cavitands via -CH=N-CH(2)CH(2)N=CH- connectors. In CH(2)Cl(2), the reaction between 8 2 and 16 3 yields a square antiprismatic nanocage 5 (65% yield), in which each cavitand occupies one of the eight corners and is connected to four neighboring cavitands via -CH=N-CH(2)CH(2)-N=CH- linkers. Nanocage 5 is also the main product in CH(2)ClCH(2)Cl (26% yield) and CHCl(2)CHCl(2) (33% yield). Reduction of all imine bonds in 4 and 5 yields polyaminonanocontainers 7 and 8, respectively, which were isolated as trifluoroacetate salts. Contrary to the formation of larger capsules composed of four, six, or eight cavitands in the reaction between 2 and 3, the acid-catalyzed reaction of 2 with 2 equiv of H(2)N-X-NH(2) (X = (CH(2))(n)(=3,4,5), 1,3-C(6)H(4), 1,4-(CH(2))(2)C(6)H(4), or 1,3-(CH(2))(2)C(6)H(4)) quantitatively yields octaiminohemicarcerands 9-14, in which two cavitands are connected with four -CH=N-X-N=CH- linkers. The outcomes of these condensation reactions are rationalized with the different diamine structures and the relative orientation of cavitands in 1, 4, 5, and 9-14.     

Solvent effects on metal carbonyls and related compounds

The observed solvent effects on the CO and NO frequencies in metal carbonyls and related compounds are shown to be influenced by the solvent acceptor properties, as expressed by the acceptor number.With 6 Figures     

Solvent effects on the tautomerism of apigeninidin

Solvent effects are found to be responsible for the predominance in water solution of a highly unstable tautomer of apigeninidin in vacuo. We present free energy perturbation in molecular dynamics simulations and self-consistent reaction field calculations of the relative solvation of the anionic tautomers of apigeninidin.