Stopped flow corroborated by UV-vis measurements allowed for the calculation of the copigmentation constants of delphinidin 3--glucoside with the neutral (CP) and negatively charged CP(-) forms of chlorogenic acid. Solutions of delphinidin 3--glucoside in the absence and presence of the copigment were equilibrated at several pH values in the acidic region, pH < 6, and reverse pH jumps monitored by stopped flow were carried out by adding sufficient acid to give flavylium cation at pH ≤ 1. This procedure allows for the separation of three contributions: (i) all flavylium cation and quinoidal base species, (ii) all hemiketal species, and (iii) all -chalcone species.
View Article and Find Full Text PDFThe first protecting group-free synthesis of N-glycosyl carbamates has been developed through reaction of d-glucose with n-butyl carbamate in acidic aqueous media. The structures of the N-glucosyl carbamates were unambiguously determined by comparison with authentic samples, prepared using the isocyanide method. With this protective group-free method for synthesis of N-glycosyl carbamates in hand, an anomeric pair of N-xylopyranosyl carbamates were prepared and used to assess the anomeric effect of nitrogen in the carbamate group.
View Article and Find Full Text PDFThe bluish-purple petals of Chinese bellflower, (kikyo in Japanese), contain platyconin () as the major anthocyanin. Platyconin () 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.
View Article and Find Full Text PDFThe color of food is critical to the food and beverage industries, as it influences many properties beyond eye-pleasing visuals including flavor, safety, and nutritional value. Blue is one of the rarest colors in nature's food palette-especially a cyan blue-giving scientists few sources for natural blue food colorants. Finding a natural cyan blue dye equivalent to FD&C Blue No.
View Article and Find Full Text PDFBiosci Biotechnol Biochem
January 2021
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.
View Article and Find Full Text PDFProc Jpn Acad Ser B Phys Biol Sci
July 2024
Hydrangea (Hydrangea macrophylla) is a unique flower because it is composed of sepals rather than true petals that have the ability to change color. In the early 20th century, it was known that soil acidity and Al content could intensify the blue hue of the sepals. In the mid-20th century, the anthocyanin component 3-O-glucosyldelphinidin (1) and the copigment components 5-O-caffeoylquinic, 5-O-p-coumaroylquinic, and 3-O-caffeoylquinic acids (2-4) were reported.
View Article and Find Full Text PDFHydrangea 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 (Al ). We show the color mosaic is a result of graded differences in intravacuolar factors.
View Article and Find Full Text PDFThe seed coat of mature black soybean, Glycine max, accumulates a high amount of cyanidin 3-O-glucoside (Cy3G), which is the most abundant anthocyanin in nature. In the pod, it takes two months for the seed coat color change from green to black. However, immature green beans rapidly adopt a black color within one day when the shell is removed.
View Article and Find Full Text PDFTitanbicus (TB), a hybrid of Hibiscus moscheutos × H. coccineus (Medic.) Walt.
View Article and Find Full Text PDFCatechinopyranocyanidins 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.
View Article and Find Full Text PDFAn amendment to this paper has been published and can be accessed via a link at the top of the paper.
View Article and Find Full Text PDFAn efficient conversion of rutin to the corresponding anthocyanin, cyanidin 3--rutinoside, was established. Clemmensen-type reduction of rutin gave a mixture of flav-2-en-3-ol and two flav-3-en-3-ols, which were easily oxidised by air to give the anthocyanin. The interconversion reactions of these flavonoids provide insight into their biosynthetic pathway.
View Article and Find Full Text PDFThe small red bean, Vigna angularis, is primarily used to produce the "an-paste" component of Japanese sweets. Through the manufacturing process, the red seed-coat pigment is transferred to the colorless "an-particles", imparting a purple color. However, the major pigment in the seed coat has not yet been identified, although it is historically presumed to be an anthocyanin.
View Article and Find Full Text PDFflower petals change color during senescence. When in full bloom, the flowers of are white and those of and are yellow. However, the colors change to pink and orange, respectively, when the petals fade.
View Article and Find Full Text PDFAll equilibrium and rate constants of heavenly blue anthocyanin (HBA 1) as well as the derivatives with two (HBA 2) or none (HBA 3) acylated units were determined. The three acylated units of the sugar in position 3 of the peonidin chromophore of HBA 1 are essential to confer the peculiar stability of its purple and blue colors. The sugars generate an efficient protective environment around position 2 (and 4) of the flavylium cation, through an intramolecular sandwich-type stacking that retards 35-fold the hydration reaction ( k) and increases 8.
View Article and Find Full Text PDFpenia-O-Methylquercetin (2) was prepared by permethylation of quercetin (1). Selective demethylation of 2 using either BBr or BCl3/TBAI (tetrabutylammonium iodide) gave five O-methylquercetins (3-6), with satisfactory yields. The reaction can be easily scaled-up.
View Article and Find Full Text PDFJ Agric Food Chem
September 2015
Anthocyanins exhibit various vivid colors from red through purple to blue and are potential sources of food colorants. However, their usage is restricted because of their instability, especially as a blue colorant. The blue sepal color of Hydrangea macrophylla is due to a metal complex named "hydrangea-blue complex" composed of delphinidin 3-O-glucoside, 1, 5-O-caffeoylquinic acid, 2, and/or 5-O-p-coumaroylquinic acid, 3, as copigments, and Al(3+) in aqueous solution at approximately pH 4.
View Article and Find Full Text PDFWe aimed to identify the main compounds responsible for low temperature-induced yellow pigmentation of the bracts of Zantedeschia aethiopica 'Wedding March'. On the basis of the area ratios estimated from absorbance at 400 nm in HPLC analyses, we identified two flavonoids, isoorientin and swertiajaponin, as such compounds. We also identified two additional flavonoids, isovitexin and swertisin, which do not contribute considerably to the yellow pigmentation.
View Article and Find Full Text PDFBiosci Biotechnol Biochem
February 2012
A new tetraglycosyl flavonol, 3-O-[2-O-xylosyl-6-O-(3-O-glucosyl-rhamnosyl) glucosyl] kaempferol was isolated from pale purplish-pink petals of Wabisuke camellia cv. Tarokaja with three known flavonols. It was named urakunoside after the species name of Tarokaja, Camellia uraku.
View Article and Find Full Text PDFBiosci Biotechnol Biochem
October 2009
3-Di-p-coumaroylsophoroside-5-malonylglucoside and its demalonyl derivative were isolated from blue petals of Veronica persica Poiret. Blue, violet and purple cells coexist in the petal. These colors might be due to the varying pH of the vacuole between 5 and 7 unit.
View Article and Find Full Text PDFBlue flower colors are primarily due to anthocyanin, a flavonoid pigment. Anthocyanin itself is purple in neutral aqueous solutions, ans its color is very unstable and quickly fades. Therefore, the mechanism of blue color development in living flower petals is one of the most intriguing problems in natural product chemistry.
View Article and Find Full Text PDFProc Jpn Acad Ser B Phys Biol Sci
August 2009
Petal color change in morning glory Ipomoea tricolor cv. Heavenly Blue, from red to blue, during the flower-opening period is due to an unusual increase in vacuolar pH (pHv) from 6.6 to 7.
View Article and Find Full Text PDFTo clarify the cause of the difference in blue and red color development of hydrangea sepals, Hydrangea macrophylla, we analyzed the organic and inorganic components in the colored cells. To obtain colored protoplasts, each blue and red sepal tissue was treated with a combination of cellulase and pectinase, and then from the suspension of the olored and colorless protoplast mixture colored cells of the same hue were collected with a micro-pipette. The content of organic components (delphinidin 3-glucoside, chlorogenic acid, neochlorogenic acid and 5-O-p-coumaroylquinic acid) and Al(3+) in each colored cell was quantified respectively by semimicro-HPLC and graphite furnace atomic absorption spectroscopy (GFAAS).
View Article and Find Full Text PDFPhytochemistry
December 2008
A metalloanthocyanin, cyanosalvianin, was found in blue petals of Salvia uliginosa. Cyanosalvianin consisted of 3-O-(6-O-p-coumaroylglucopyranosyl)-5-O-(4-O-acetyl-6-O-malonylglucopyranosyl) delphinidin, 7,4'-di-O-glucopyranosylapigenin and magnesium ion. We reproduced the same blue color as the petals by mixing the three components together.
View Article and Find Full Text PDFThe sepal color of a chameleon hydrangea, Hydrangea macrophylla cv. Hovariatrade mark 'Homigo' changes in four stages, from colorless to blue, then to green, and finally to red, during maturation and the senescence periods. To clarify the chemical mechanism of the color change, we analyzed the components of the sepals at each stage.
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