Interest in food colorants as shown by the number of patents has doubled in recent years with natural pigments outnumbering synthetics by five to one The natural colorant area can be subdivided into anthocyanins, betalains, chlorophylls, carotenoids, flavonoids, polyphenols, Monascus, hemes, quinones, biliproteins, safflower, turmeric, and miscellaneous All involve different groups of chemical compounds which may be used directly as colorants, or may be chemically modified to produce different hues or increased stability All usually involve a method of collection, extraction, purification, possibly stabilization, and formulation A variety of hues can be obtained ranging from green through yellow, orange, red, blue, and violet, depending on the source of colorant Similarly, water or oil‐soluble formulations can be prepared depending on the type of colorant

Food colorants: Anthocyanins

In mammals, cadmium is widely considered as a non-genotoxic carcinogen acting through a methylation-dependent epigenetic mechanism. Here, the effects of Cd treatment on the DNA methylation patten are examined together with its effect on chromatin reconfiguration in Posidonia oceanica. DNA methylation level and pattern were analysed in actively growing organs, under short- (6 h) and long- (2 d or 4 d) term and low (10 mM) and high (50 mM) doses of Cd, through a Methylation-Sensitive Amplification Polymorphism technique and an immunocytological approach, respectively. The expression of one member of the CHROMOMETHYLASE (CMT) family, a DNA methyltransferase, was also assessed by qRT-PCR. Nuclear chromatin ultrastructure was investigated by transmission electron microscopy. Cd treatment induced a DNA hypermethylation, as well as an up-regulation of CMT, indicating that de novo methylation did indeed occur. Moreover, a high dose of Cd led to a progressive heterochromatinization of interphase nuclei and apoptotic figures were also observed after long-term treatment. The data demonstrate that Cd perturbs the DNA methylation status through the involvement of a specific methyltransferase. Such changes are linked to nuclear chromatin reconfiguration likely to establish a new balance of expressed/repressed chromatin. Overall, the data show an epigenetic basis to the mechanism underlying Cd toxicity in plants.

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In Posidonia oceanica cadmium induces changes in DNA methylation and chromatin patterning

Blue flower color development by anthocyanins: from chemical structure to cell physiology

Anthocyanins occur widely in plants, being responsible for their blue, purple, violet, magenta, red and orange coloration; while betalains, consisting of red-violet betacyanins and yellow-orange betaxanthins, occur exclusively in families of the order Caryophyllales. The occurrence of these two classes of pigments is mutually exclusive. Their stability is markedly influenced by environmental and processing factors such as pH, temperature, O2, enzymes and condensation reactions. Due to their inherent instability these pigments, and betalains in particular, have not been widely used as food colorants. However, structural variants of the anthocyanins, i.e. polyacylated and copigmented species, have demonstrated remarkable stability and have great potential for use as stable natural colorants. Anthocyanin and betalain preparations can be used to colour a variety of foods and pharmaceuticals with compatible physicochemical properties, yielding highly coloured and high quality products. Their application could be enhanced, however, with new sources and stable structural variants, modification of current processes and foods, and technological advances (e.g. industry-scale extractions/purifications, microbial purifications, biotechnology) that would make purer and more stable preparations available. In this chapter the chemistry and biochemistry of anthocyanins and betalains—their structure and distribution, functions, biosynthesis, factors influencing their stability, methods of extraction and analysis, and current and potential sources and uses—are reviewed.

Anthocyanins and betalains

Flower colour results from the preferential absorption of part of the visible light by one, or several, chemical compound(s) synthesized by higher plants. Since plants cannot ‘see’ their own colours, it is conceivable that the colour signals emerging from flowers are messages interpretable by mammals as well as by birds and insects (Harborne, 1976). Thus colour is most likely a link between animals and plants, as are flower shape, scent and taste. In particular, insects and birds attracted by colour pollinate the flowers and aid the survival of plant species. In contrast to man, some insects, especially bees, can perceive in the near ultraviolet (340–380 nm) as well as in the visible.

Flavonoids and flower colour

Structure of gentiodelphin, an acylated anthocyanin isolated from Gentiana Makinoi, that is stable in dilute aqueous solution

Heavenly blue anthocyanin II trans-4-0-(6-0-(trans-3-0-(β -d-glucopyranosyl)caffeyl)-β-d-glucopyranosyl)- caffeic acid, a novel component in heavenly blue anthocyanin

Heavenly Blue Anthocyanin III.Structure of Bisdeacyl Heavenly Blue Anthocyanin, a Controlled Alkaline Hydrolysis Product of Heavenly Blue Anthocyanin

Structure of tris-deacyl heavenly blue anthocyanin was determined to be 3-O-(β-sophorosyl)-5-O-(β-glucosyl)peonidin by PMR analysis.

Structure confirmation of tris-deacyl heavenly blue anthocyanin, an alkaline hydrolysis product of heavenly blue anthocyanin obtained from flower of morning glory "heavenly blue"

Hiroyuki Imagawa

Papers

Structure of gentiodelphin, an acylated anthocyanin isolated from Gentiana Makinoi, that is stable in dilute aqueous solution

Heavenly blue anthocyanin II trans-4-0-(6-0-(trans-3-0-(β -d-glucopyranosyl)caffeyl)-β-d-glucopyranosyl)- caffeic acid, a novel component in heavenly blue anthocyanin

Heavenly Blue Anthocyanin III.Structure of Bisdeacyl Heavenly Blue Anthocyanin, a Controlled Alkaline Hydrolysis Product of Heavenly Blue Anthocyanin

Structure confirmation of tris-deacyl heavenly blue anthocyanin, an alkaline hydrolysis product of heavenly blue anthocyanin obtained from flower of morning glory "heavenly blue"