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The structure of commelinin, a blue plant pigment, has been determined using X-ray crystallographic analysis. Commelinin, which belongs to the anthocyanin group of pigments, is present in the blue flowers of the plant Commelina communis. The crystalline form of commelinin indicates that the blue in the plant's petals derives from the 4'-keto anhydrobase anion of the anthocyanidin nucleus and that this anion is made stable by metal complexing to Mg2+, which is produced by powerful molecular association.

Summary: Hydrangea sepals exhibit a wide range of colors, from red, through purple, to blue; the purple color is a color mosaic. However, all of these colors are derived from the same components: simple anthocyanins, 3‐O‐glycosyldelphinidins, three co‐pigment components, acylquinic acids and aluminum ions (Al3+). We show the color mosaic is a result of graded differences in intravacuolar factors.In order to clarify the mechanisms of mosaic color, we performed single‐cell analyses of vacuolar pH, and anthocyanin, co‐pigment and Al3+ content. From the sepals, a protoplast mixture of various colors was obtained. The cell color was evaluated by microspectrophotometry and vacuolar pH then was recorded by using a pH microelectrode. The organic and Al3+ contents were quantified by micro‐HPLC.We found that the bluer the cell, the greater the ratio of 5‐O‐acylquinic acids and Al3+ to anthocyanins. Furthermore, reproducing experiments were conducted by mixing the components under various pH condition; all the colors could be reproduced in the various mixing conditions.Based on the above, we provide experimental evidence for cell color variation in hydrangea. Our study demonstrates the expression of phenotypic differences without any direct genomic control. [ABSTRACT FROM AUTHOR]

Corydalis ambigua (Japanese name, Ezoengosaku) flowers bloom with blue to purplish petals in early spring in Hokkaido prefecture. In this study, a mechanism for blue petal coloration by ferric ions and keampferol glycoside was elucidated. Blue petals and cell sap exhibited similar visible (Vis) spectra, with λmax at approximately 600 nm and circular dichroism (CD) with positive exciton-type Cotton effects in the Vis region. Analysis of the organic components of the petals confirmed cyanidin 3- O -sambubioside and kaempferol 3- O -sambubioside as the major flavonoids. Mg, Al, and Fe were detected in petals using atomic emission spectroscopy. Color, Vis absorption, and CD consistent with those of blue petals were reproduced by mixing cyanidin 3- O -sambubioside, kaempferol 3- O -sambubioside, and Fe3+ in a buffered aqueous solution at pH 6.5. Both Fe3+ and flavonol were essential for blue coloration. [ABSTRACT FROM AUTHOR]

Catechinopyranocyanidins A and B (cpcA and cpcB) are two purple pigments present in the seed‐coat of red adzuki bean, Vigna angularis, of which cpcA is the major pigment, containing two chiral carbons in the catechin part. Their absolute configurations were determined by comparison of their experimental and quantum chemical calculated electronic circular dichroisms (ECDs). These purple pigments are labile on light irradiation and easily decompose to photo‐degraded catechinopyranocyanidins A and B (pdcpcA and pdcpcB), while retaining the stereostructure of the catechin residue. We applied modified Mosher's method for determining the chirality of the secondary alcohol in pdcpcA. Hexamethylation of pdcpcA by diazomethane followed by esterification using (S)‐ and (R)‐MTPACl gave (R)‐ and (S)‐MTPA esters, respectively. By analysis of the NMR spectra of (R)‐ and (S)‐MTPA esters of tetramethylated (+)‐catechin, the chirality of pdcpcA was determined to be 2R, 3S, same as the absolute configuration of cpcA. [ABSTRACT FROM AUTHOR]

The experimental data on the kinetic and thermodynamic acidities of pentacarbonyl(cyclobutenylidene)chromium complexes in acetonitrile. Results of the gas phase ab initio calculations indicate that in the gas phase, the effect of antiaromaticity on the thermodynamic acidities is large but strongly attenuated in acetonitrile.

A study conducted revealed that a homogeneous two-component polycondensation reaction without strict stoichiometric balance could lead to polymers of high molecular weight by catalysis if certain structural reactivity criteria are met in the monomers.

Spectroscopic studies and chemical degradation experiments of zooxanthellatoxin-A, (ZT-A), a member of macrolide group of compounds, indicate its structure to contain a 62-membered lactone ring, as confirmed by the formation of the corresponding seco acid. One methylene group contains a heteroatom, which is revealed by the HMQC spectrum of ZT-A in CD30D. Two sets of high-field proton resonances and C-H coupling data suggest a spiroacetal structure of ZT-A.

Electrospray ionization mass spectroscopy helps evaluate the molecular weight of the supramolecular pigment commelinin without any solvent. Spectral data reveal that water molecules are removed without dissociation of supramolecules during ionization in a chamber. Commelinin consists of six anthocyanin molecules, malonylawobanin, six flavone molecules, flavocommelin and two magnesium ions, (M6F6Mg2)(6-).

Sodium borohydride reduction of the products generated from the oxidation of zooxanthellatoxin-A using periodate yielded two fragments, one 47-carbon long, the other consisting of 56 carbon atoms. The latter fragment has a polyhydroxylated and polyunsaturated structure with sulfate ester and diepoxide functionality as revealed by spectral data. Zooxanthellatoxins also contain a few ethereal rings which together with the high degree of unsaturation make this group of marine toxins unique.

The blue color of the petals of Ipomoea tricolor is caused by the very high vascular pH in the petals. The blue color in petals of flowers is usually caused by metal complexation or vascular pH or both. The vascular pH is influenced by the quinonoidal anion of anthocyanin, called anhydrobase.

Covering: 1992 to 2007 [ABSTRACT FROM AUTHOR]

The article presents a study on the color development and variation of hydrangea macrophylla sepal cells. It discusses how the sepals of the flowering plant hydrangea obtain its blue and red color variation. It states that colored cells of hydrangea sepals are located at the second layer from the surface and are obtained by treating with cellulase and prectinase. Based on the aluminum analysis, there is a high aluminum concentration in the blue protoplast compared to the red ones.

Abstract: The dicaffeoyl anthocyanin, phacelianin, was isolated from blue petals of Phacelia campanularia. Its structure was determined to be 3-O-(6-O-(4′-O-(6-O-(4′-O-β-d-glucopyranosyl-(E)-caffeoyl)-β-d-glucopyranosyl)-(E)-caffeoyl)-β-d-glucopyranosyl)-5-O-(6-O-malonyl-β-d-glucopyranosyl)delphinidin. The CD of the blue petals of the phacelia showed a strong negative Cotton effect and that of the suspension of the colored protoplasts was the same, indicating that the chromophores of phacelianin may stack intermolecularly in an anti-clockwise stacking manner in the blue-colored vacuoles. In a weakly acidic aqueous solution, phacelianin displayed the same blue color and negative Cotton effect in CD as those of the petals. However, blue-black colored precipitates gradually formed without metal ions. A very small amount of Al3+ or Fe3+ may be required to stabilize the blue solution. Phacelianin may take both an inter- and intramolecular stacking form and shows the blue petal color by molecular association and the co-existence of a small amount of metal ions. We also isolated a major anthocyanin from the blue petals of Evolvulus pilosus and revised the structure identical to phacelianin. [Copyright &y& Elsevier]

Abstract: Blue sepal-color of Hydrangea macrophylla might be due to a supramolecular metal-complex pigment consisting of delphinidin 3-glucoside ( 1 ), co-pigments (5-O-caffeoylquinic acid ( 2 ), and/or 5-O-p-coumaroylquinic acid ( 3 )) and Al3+ in an aqueous solution around pH4.0. To clarify the mechanism of blue sepal-color development of hydrangea, we tried to reproduce the blue color in vitro by mixing 1 with designed synthetic co-pigments in the presence of Al3+ at pH4.0. We at first succeeded in clarifying the essential functional structure in the co-pigment that could form the stable blue solution. Here, we present the structure of the blue pigment caused by an Al-complex coordinating of 1 at ortho-dihydroxyl groups of the B-ring, 1-hydroxy, 1-carboxylic acid, and the carbonyl residue in the ester at 5-position of 2 and/or 3 . The hydrophobic interaction between the aromatic acyl residue at 5-position and the nucleus of 1 may also contribute to stabilize the complex. [Copyright &y& Elsevier]

The title compound, 6-C-glucopyranosyl-7-O-methylapigenin dihydrate, C22H22O10·2H2O, is a natural C-glucosylflavone. The flavone skeleton is almost planar, the dihedral angle between the pyran moiety and the 4-hydroxyphenyl ring being 9.8 (3)°. The basal plane of the pyranosyl ring of the glucose moiety is almost perpendicular to the benzopyran ring system. The flavone skeletons are stacked along the a axis, forming layers parallel to (001). Between these hydrophobic layers, the glucose groups and water molecules of crystallization are connected via O-H…O hydrogen bonds, forming hydrophilic layers. [ABSTRACT FROM AUTHOR]

The article presents a study which examined stereoselective bulk polymerization of racemic lactide (rac-LA) for stereoblock polyracemic lactide using an achiral aluminum complex. Poly(-L-lactide) (PLLA) is a renewable and environmentally benign polymer with biodegradable and biocompatible features. PLLA is commercially synthesized via the ring-opening polymerization of L-lactide with high enantiomeric purity, because the polymerization of lactide with low optical purity using conventional catalysts affords amorphous polylactide due to its stereoirregularity. The industrial block bulk process for the synthesis of PLLA adopts a high reaction temperature to keep the reaction mixture molten for direct extrusion from the reactor. In this process, the amount of the catalyst must be reduced to a minimum level as a consequence of minimizing the contaminates in the product, therefore, a high catalytic activity is one of the essential components for the development of an industrial polymerization catalyst. In the study, the highly reactive and stereoselective polymerization of rac-LA in bulk at 130-180°C using an achiral aluminum complex to produce the crystalline isotactic poly(rac-LA), in which the Tm values are comparable to that of homochiral PLLA. All manipulations were carried out using standard Schlenk-line techniques. Molecular weights of the polymers were estimated by size-exclusion chromatography using polystyrene standards. For the preparation of the catalysts, a solution of each ligand (0.50 mmol) in toluene (0.50 mL) was added 0.10 M Et3 Al in toluene (0.50 mL, 0.050 mmol) under N2 at room temperature. The clear solution was stirred at 70°C for 3h (0.050 M catalyst).

The bluish-purple petals of Chinese bellflower, Platycodon grandiflorum (kikyo in Japanese), contain platyconin (1) as the major anthocyanin. Platyconin (1) is a polyacylated anthocyanin with two caffeoyl residues at the 7-position, and its color is stable in a diluted, weakly acidic aqueous solutions. HPLC analysis of the fresh petal extract showed the presence of several minor pigments. Photo-diode array detection of minor pigments suggested that some of these were polyacylated anthocyanins. To establish the relationship between structure and stability of the acylated anthocyanins and to obtain information on their biosynthetic pathways, minor pigments were isolated from the petals, and their structures were determined by MS and NMR analyses. Four known (2–5) and three new anthocyanins (6–8) were identified, which contained a delphinidin chromophore, and four of these (5–8) were diacylated anthocyanins, in which the acyl-glucosyl-acyl-glucosyl chain was attached at the 7-O-position of the delphinidin chromophore. These diacylated anthocyanins exhibited a bluish-purple color at pH 6, which was stable for more than a week. [ABSTRACT FROM AUTHOR]

The article focuses on a study that analyzes the urakunoside, a major flavonol component in the Tarokaja petals. It notes that Tarokaja is one of the oldest Wabisuke cultivars and is thought to be the origin of many other Wabisuki camellia cultivars. It adds that its various physiological and morphological characteristics have drawn interests from the horticultural industry, prompting to explore more on its chemical components.

The article presents a study on the anthocyanin components of blue veronica flowers and its procedure for color development by photodide array detection analysis. It states that demalonyl derivative of 3-Di-p-coumaroylsophoroside-5-malonylglucoside was separated from the blue petals of the flowers. It reveals that the colors blue, violet and purple coexist in the petal because of the changing pH level of vacuole. Meanwhile, only the demalonylated pigment was discovered in the blue anthers.