Flavone dyes

Flavone [525-82-6 Flavone dyes Flavone synthase Flavonoids... 

Flavone-type dyes occur in all the higher plants in the leaves, roots, bark, fmits, poUen, and flower petals. None have been found in fungi, mosses, or hchens. The most widespread flavone dyes are quercetin [117-39-5] (12) and kaempferol [520-18-3] (13) ... 

Flavone dyes having these stmctures are hydroxylated and methoxylated derivatives. The degree of hydroxylation varies from two in chrysin [480-40-0] (17) to six in gossypetin [489-35-0] (18). Those dyes containing not more than three hydroxyls are generally termed flavones whereas those containing up to and including six are flavonols. 

When the historic textile material to be investigated contains a red that has hardly faded, we should start by testing this red dyeing, because this is the simplest and quickest way to obtain a result. In the first place, we need a smaller sample for the identification of red anthraquinone dyes than for identifying yellow flavone dyes, and in addition, it is then usually possible to identify the dyer s plant or dye insects that have been used for the red shade. 

When the dyeing treated in this manner is heated with tin, aluminum, iron, copper, and uranyl salts after it has been washed out with water, flavone dyes that contain luteolin as the main component can be identified fairly easily from the color of the lakes. In such cases, one can assume that dyer s plants such as dyer s rocket and dyer s greenwood (both C.I. Natural Yellow 2) were mainly used. 

Flavone dye extracted from the seeds, stems, and leaves of Reseda luteola L (Dyer s Rocket)... 

Flavones. These compounds are the most widely distributed natural coloring matter formerly used as dyestuffs. The term flavone was first suggested in 1895 (69), and is indicative of their yellow color ijlavus, Latin for yellow). They have lost their commercial value as dyes since the advent of synthetic dyes in 1856. 

In general, the dyes occur as glycosides, the most common sugar being glucose. Some flavones contain more than one sugar. Their role as dyes in the plant is not definitely known a common suggestion is that they protect the plant from harm fill uv radiation. 

The basic unit of the flavone-type dyes is 2-phenyIbenzopyrone (14) which unsubstituted is flavone [525-82-6], isoflavone [574-12-9] is (15) and flavonol [577-85-5] is (16). 

The flavone, isoflavone, and flavonol-type dyes owe their importance to the presence of an o-hydroxy carbonyl stmcture within the molecule. Positions 4 and 5 can chelate with different metallic salts to give colored, insoluble complexes. In other words, these dyes require a mordant in order to fix them onto the fiber. Perkin was able to predict the stmcture of unknown flavones by comparing the color of their complexes with the color of known complexes (70). For example, ferric chloride gives a green color with 5-hydroxyflavones and a brown one with 3-hydroxyflavones (71). 

Fig. 3.7 Anodic SWV curves of flavones (1 and 2, reversible processes), an anthraquinone dye (3, a quasireversible process) and a pyran dye (4, a totally irreversible process). Scans from open-circuit potential toward positive potentials (reprinted from [186] with permission)...

Flavone or 2-Phenylchromone, C15H10°2> and other flavones are the parents of a > number of yel natural dyes found in plants, leaves, fruits and flowers. The natural materials contain OH groups and occur un combined or as glucosides. Nitration occurs in 2-phenyl group giving a mixture of 2y- ... 

The a- and y-methylene groups of pyrylium salts condense with pyranones and ben-zopyranones when the salts are heated in acetic anhydride or phosphorus oxychloride. Some of the resulting compounds are potentially interesting as dyes, for example the tripyran (110) (68JOC4418). In hot acetic anhydride equimolar amounts of the salt (111) and flavone condense to give a green-coloured salt (112) (78AP236). 

The flavonoids, derivatives of flavone (353) and of isoflavone (354), are widely distributed among plants of many kinds. They provide colour (from pale yellow to orange) in flowers and their potential as dyes is being revived now that awareness of the toxicity of some synthetic dyes is increasing, for example morin (355 CI. Natural Red) is one of many... 

The flavone morin (700) (Natural Yellow C.I. 75660) dyes wool yellow, the actual shade being determined by the mordant which is used. It has also been mentioned as a spot test reagent for salts of aluminum, beryllium, zinc and other metals (B-54MI22401). 

The basic unit of the flavune-type dyes is 2-phenylbenzopyrone (4) which unsubstiluted is flavone (4) isoflavone is (5) and flavonol (6) is... 

When rare-earth-metal ions such as Eu and Tb are bound to polyelectrolyte membranes such as poly(sodium acrylate) and poly(sodium ethene-sulphonate) their fluorescence intensities are considerably enhanced this is associated with the formation of asymmetric bonds between the rare-earth ions and the acrylate/S03 groups in the polymers. This was confirmed by the addition of EDTA to the Tb -poly(sodium acrylate) complex which, because of its preferential binding to the polymer, displaced Tb ions and resulted in reduced fluorescence of the latter. Stokes shifts of fluorescent dyes in different polymer systems have been related more to mobility effects in the polymer than polarity,and the fluorescence of hydrolysed aspirin has been found to be affected by the nature of different polymer supports.The luminescence properties of cis-(2,2 -bipyridyl)ruthenium(ii) complexes have been found to be influenced by binding the complex to a polymer matrix,as have the luminescence properties of flavones and l-octadecyl-3,3-dimethyl-6 -nitrospiro(indoline-2,2 -2H-benzopyran). Other studies of interest in-... 

The naturally occurring llavones are yellow and are very widely distributed in plants. They accumulate in almost any part of a plant, from the roots to the flower petals. Unlike the anthocyanins, which are too reactive and short-lived, the much more stable llavones have, from time immemorial, been used as dyes, for they impart various shades of yellow to wool. As an example, the inner bark of one of the North American oaks, Quercus velutina, was a commercial material known as quercitron bark and much used in dyeing it contains quercetrin. The corresponding aglycone, quercetin, is one of the most widely occurring flavones, found, for example, in Chrysanthemum and Rhododendron species, horse chestnuts, lemons, onions and hops. 

Other polyhydroxy flavones exist in plants [51], These flavones are usually combined as glucosides or rhamnosides and are generally yellow. These materials have been used for dyeing cloth and hair, and they are usually mordanted with chromium, tin, or iron salts for dyeing cloth. This mordanting process changes the color as well as the binding character of the dye. 

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