Complex Formation and Flower Colors

Abstract

520 535 544 532 543 542The pigment of the blue cornflower, protocyanin, is a complex of high molecular weight. Iron(III) and aluminum ions combine with the anhydro base of the cyanin to form deep-blue complexes, which are stable in the physiological p H range. Complexes of this type also have been synthesized. Alkali iiretal salts play no part in blue flower pigments. Formation of blue complexes can be prevented by sequestration of the metal ions with stronger complexing agents, e.g. flavonols. The variuticn of flower colurs can be explained to a large extent on the basis of the complex formation of anthocyanins. In delphinidin glycosides, the color base or airhydro base is stable even in slightly acidic media.

An Anthocyanin Complex Isolated From the Syrup of Canned Blueberries

“…In the past, color variations of this type have been attributed to complex formation between anthocyanins and inorganic ions and also to "copigmentation" of anthocyanins with other polyphenols. However there has been an increasing number of isolations (see for example: Mitsui et al, 1959;Saito et al, 1961;Hayashi and Takeda, 1962;Bayer et al, 1966;Asen and Jurd, 1967) of rather special pigments from certain blue-colored flowers. It should be emphasized that flowers are the only forms of plant material from which these pigments have been isolated.…”

Isolation Techniques for Flavonoids

“…It is of particular use in the isolation of high molecular weight flavonoids (and tannins) which are water soluble and are mixed with sugars or soluble inorganic material in the crude extract. Markharn (1972) found dialysis useful in the separation of a flavone-polysaccharide compound (MW about 3000) from an aqueous plant extract of Monoclea forsteri, and considerable use has been made of this technique in the isolation of high molecular weight blue flavonoid 'complexes' from cornflower (MW 6200) (Bayer et al, 1966), Commelina communis (Takeda et al , 1966) and Professor Blaauw iris (Asen et al , 1970), all of which were non-dialysable through a cellulose membrane. Flavonoids produced on hydrolysis of the non-dialysable commelinin (Takeda et al, 1966) were dialysable under the same conditions.…”

“…Flavonoids must be ionized or complexed with a metal ion to be mobile in an electric field and for this reason the technique is admirably suited to the isolation of flavonoids which occur naturally in these states, e.g. patuletin 7-potassium bisulphate (which was readily separated from the 7-glucoside) (Saleh et al, 1971), the pectin-metal-anthocyanin cornflower pigment (Bayer et al, 1966) and the metallo-anthocyanin-flavone Commelina pigment (Take da et al, 1966). In each of these cases acidic acetate buffers were used in conjunction with high voltages (3000 V, 110 V and 400 V respectively) to produce migration of the flavonoids to the anode.…”

Intermolecular binding of blueberry pectin-rich fractions and anthocyanin

“…Researchers who studied anthocyanins in flowers as color pigments found that pectin formed large non-dialyzable, co-pigment complexes with anthocyanin (Asen, Stewart, Norris, & Massie, 1970;Bayer, Egeter, Fink, Nether, & Wegmann, 1966). More recent studies report that pectin solubilized anthocyanin-metal chelate complexes and prevented pigment precipitation in aqueous environments, making anthocyanin a potential natural blue colorant for beverage applications (Buchweitz, Carle, & Kammerer, 2012a;Buchweitz, Nagel, Carle, & Kammerer, 2012b).…”