Structure and Molecular Stacking of Anthocyanins—Flower Color Variation

Abstract

In 1913 Willstatter made the striking observation that the same pigment can give rise to different colors. Thus, the same pigment, cyanin, is found in the blue cornflower and in the red rose. Willstatter attributed the variety of flower colors to different pH values in solution. Indeed, anthocyanin changes its color with pH; it appears red in acidic, violet in neutral, and blue in basic aqueous solution. Willsfutter's pH-theory for explaining flower color variation is still to be found in major text books of organic chemistry. Very recently, however, reinvestigation has disclosed that the color variation and stabilization of anthocyanins in aqueous solution could have other causes, namely self-association, copigmentation and intramolecular sandwich-type stacking. The stacking would be mainly brought about by intermolecular or intramolecular hydrophobic interaction between aromatic nuclei such as anthocyanidins, flavones and aromatic acids. In addition, hydrogen bonds and charge transfer interactions may also be involved. The most interesting molecular complexes of anthocyanins are the metalloanthocyanins such as commelinin and protocyanin (blue cornflower pigment). These seemingly pure blue complexes each consist of six anthocyanin and six flavone molecules and two metal ions; their molecular weight is nearly 10000. A structure is proposed for commelinin.

Cytochrome P450 93G1 Is a Flavone Synthase II That Channels Flavanones to the Biosynthesis of Tricin O-Linked Conjugates in Rice

“…Among them, flavones are found extensively in land plants but are absent in almost all members of the Cruciferae (Martens and Mithöfer, 2005;Zhou and Ibrahim, 2010). In plants, flavones play important physiological roles, including UV protection (Schmitz-Hoerner and Weissenböck, 2003), interactions with other organisms (Peters et al, 1986;Kong et al, 2007), regulation of auxin transport (Mathesius et al, 1998), and copigmentation in flowers (Goto and Kondo, 1991). On the other hand, flavones as dietary constituents or supplements have become increasingly popular due to their health-beneficial effects, such as cancer prevention (Bontempo et al, 2007;Cai et al, 2007;Liu et al, 2007), antioxidation (Park et al, 2007), antiviral activities (Yarmolinsky et al, 2012), reduction of risks of cardiovascular diseases (Baek et al, 2009), and suppression of cholesterol levels (Dharmarajan and Arumugam, 2012).…”

Thermochromic Biopolymer Based on Natural Anthocyanidin Dyes

“…A homologous series with one to three hydroxyl groups on the B-ring evolves. The introduction of the hydroxyl groups also leads to the presence of adjacent hydroxyl groups in cyanidin chloride and delphinidin chloride, which is an essential condition for their ability to form chelate-complexes [15][16][17][18]. Increasing number of hydroxyl groups and the presence of adjacent hydroxyl groups should also stabilize the formation of PLA-dye complexes [19].…”

Sugar and anthocyanidin content of two processing‐grade sweet cherry cultivars and cherry products

“…Anthocyanins are susceptible to alteration of colour due to inter alia pH, metal ions, processing temperature (Timberlake 1981 ;Brouillard 1988), sucrose concentration , ascorbic acid (Poei-Langston & Wrolstad 1981), endogenous polyphenoloxidase (WescheEbeling & Montgomery 1990), and commercial pectinase treatment (Jiang et al 1990). However, Goto & Kondo (1991) suggested that the unexpected stability of anthocyanins in vivo could be the result of metal complexation, self-association, copigmentation, or molecular stacking. All four types of stabilisation have been demonstrated recently (Kondo et al 1992) in commelinin, a blue anthocyanin.…”