Alizarin, soluble dyes from

Turkey Red.—Alizarin is the chief constituent of the coloring matter Turkey red, which has been known since ancient times and which was obtained from the root of the madder plant, Rubia tinctorum L. The substance is of special interest because the determination of its constitution was one of the early triumphs of organic chemistry and because it was the first natural dye to be synthetically prepared. The name is derived from the oriental name for the madder, viz., alizari. In the madder root it is present as a glucoside known as ruberythric acid, which, on hydrolysis by fermentation or by boiling with acids, yields glucose and alizarin. Alizarin is a solid which sublimes as orange red needles, m.p. 289°, insoluble in water but slightly soluble in alcohol. 

Novotnd et al. [261] studied a set of eight historical anthroquinone and naphthoquinone dyes (carminic acid, laccaic acid A and B, lawsone, juglone, alizarin, lapachol, emodin). They were well resolved in 12 min on a C]g column (A — 270 nm) using a 15-min exponential gradient from 40/60 -y 95/5 methanol/ water (0.1 M citrate pH 2.5). Separately, alizarin and purpurin were resolved on a C]g column (A = 245 ran) using a 72/25 methanol water (0.2 M acetate pH 4.3) mobile phase. Detection limits of 0.6-12 ng injected (analyte dependent) were reported. Linear curves up to the solubility limit of l mM were also used. 

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