Kosaku Takeda

Phytochemistry: structure of the blue cornflower pigment.

The same anthocyanin pigment makes roses red but cornflowers blue, a phenomenon that has so far not been entirely explained. Here we describe the X-ray crystal structure of the cornflower pigment, which reveals that its blue colour arises from a complex of six molecules each of anthocyanin and flavone, with one ferric iron, one magnesium and two calcium ions. We believe that this tetrametal complex may represent a previously undiscovered type of supermolecular pigment.

A blue pigment complex in flowers of Salvia patens

Abstract A blue pigment complex, protodelphin, was isolated from the blue flowers of Salvia patens. The absorption spectrum of its aqueous solution has two maxima in the visible region and the blue complex is stable in neutral or acidic aqueous solution. Protodelphin was shown to be composed of delphinidin 3-(6″-p-coumaroylglucoside)-5(6″-malonylglucoside), apigenin 7,4′-diglucoside and magnesium. This was confirmed by the in vitro synthesis of protodelphin from its component parts, malonyl awobanin, apigenin 7,4′-diglucoside and magnesium. The yield of the blue pigment was to a certain extent proportional to the amount of magnesium added to the reaction mixture and the stable blue complex was not obtained without this element. Similar blue complexes were formed by the use of manganese, cobalt, nickel, zinc and cadmium instead of magnesium. The results show the true blue colour of the flowers is manifested by the metallo-anthocyanin which contains magnesium as chelating metal and is a similar complex to commelinin.

Stable blue complexes of anthocyanin-aluminium-3-p-coumaroyl- or 3-caffeoyl-quinic acid involved in the blueing of Hydrangea flower

Abstract In a comparison of the behaviour of three esters of p -coumaroylquinic acid, only 3- p -coumaroylquinic acid formed a stable blue complex with hydrangea anthocyanin (delphinidin-3-glucoside) and aluminium; the 4- and 5-isomers were ineffective. Complex formation was almost identical with that occurring with 3-caffeoylquinic acid. Solutions of both ternary complexes were very stable at pH 3.7 at room temperature. Similar colour augmentation occurred with 3- p -coumaroylquinic acid, aluminium and cyanidin 3-glycoside but not with pelargonidin or malvidin glucosides. It is proposed that aluminium conjugates with the ortho -dihydroxy group of the anthocyanin B ring and the carboxyl and α-hydroxyl groups of the quinic acid moiety and that the complexes are stabilized in the manner of acylated anthocyanins.

Copigments in the blueing of sepal colour of Hydrangea macrophylla

Abstract From blue sepals of Hydrangea macrophylla , copigments which show a blueing effect on the hydrangea anthocyanin were isolated and identified as 3- p -coumaroylquinic acid and 3-caffeoylquinic acid. 5-Caffeoylquinic acid (chlorogenic acid) which was also found in the blue sepals, however, did not show such a blueing effect though it acted as a copigment. Likewise, the 4-esters of p -coumaroyl- and caffeoylquinic acids (not found in sepals) produced purple rather than blue colours. The facts suggest that the stereostructures of 3- p -coumaroyl- and 3-caffeoylquinic acids are effective for molecular interaction between the p -coumaroyl or caffeoyl residue in the compounds and the anthocyanin. The anthocyanin in red and blue sepals of hydrangea was confirmed to be delphinidin 3-monoglucoside.

Cell cultures of Centaurea cyanus produce malonated anthocyanin in UV light

Abstract Callus cultures which produce anthocyanin under continuous irradiation of UV and white light were derived from the stem of blue-flowered Centaurea cyanus . From the callus a suspension culture, in which anthocyanin synthesis can be induced by UV light, was obtained. The pigment in the cell cultures was identified as cyanidin 3-(6″-malonylglucoside) which occurs in the leaf, but not the flowers, of the parent plant.

Flavonoid cellobiosides from Salvia uliginosa

Abstract Two new flavone glycosides with an unusual interglycosidic linkage have been isolated from the petals of Salvia uliginosa and identified by NMR spectroscopy as apigenin 7-O- β- d -glucopyranosyl-(1→ → 4″)-β- d -glucopyranoside and apigenin 7-O- β- d -glucopyranosyl-(1→ → 4″)-β- d -glucopyranoside -4′-O- β- d -glucopyranoside . The NMR and UV spectra of these compounds were compared with those of the known compound, apigenin 7,4′-O,O- di-β- d -glucopyranoside , which was isolated from the same source.

A malonylated anthocyanin and flavonols in blue Meconopsis flowers

The structures of the major anthocyanin and two flavonols from the blue flowers of Meconopsis were identified by NMR spectroscopy as being cyanidin 3-O-[(6-O-malonyl-2-O-B-D-xylopyranosyl)-beta-D-glucopyranoside]-7-O-beta-D-glucopyranoside, kaempferol 3-O-(6-O-beta-D-glucopyranosyl)-beta-D-glucopyranoside and kaempferol 3-O-(6-O-beta-D-glucopyranosyl)-beta-D-galactopyranoside respectively.

Anthocyanin composition of Sinapis alba, light induction of enzymes and biosynthesis

Abstract The two major pigments of light-grown mustard (Sinapis alba) seedlings were identified as cyanidin 3-sambubioside 5-glucoside and cyanidin 3-sambubioside 5-sophoroside esterified with malonic, p-coumaric, ferulic, and sinapic acids. The activities of the enzymes (2S)-flavanone 3-hydroxylase and (+) dihydroflavanol 4-reductase and anthocyanin accumulation were determined in mustard seedlings at various times after illumination with red light (λmax = 660 nm). Both enzymes showed a drastic increase in activity after illumination and reached their maxima at the time of rapid anthocyanin accumulation. The results are consistent with the involvement of these enzymes in anthocyanin biosynthesis.

Identification of malonated anthocyanins in the Liliaceae and Labiatae

Abstract The pigment of bluebells, previously reported as delphinidin 3-p-coumarylglucoside-5-glucoside, has been shown to be malonated and it has been identified as malonylawobanin. A cyanidin derivative present in several members of the Labiatae, has been characterized as the related 3-p-coumarylglucoside-5-malonylglucoside.

Pelargonidin 3-(6″-succinyl glucoside)-5-glucoside from pink Centaurea cyanus flowers

A new anthocyanin acylated with succinic acid has been isolated from pink flowers of Centaurea cyanus. It has been identified as pelargonidin 3-(6″-succinylglucoside)-5-glucoside.