Chemical and enzymatic hydrolysis of anthraquinone glycosides from madder roots

Abstract

For the production of a commercially useful dye extract from madder, the glycoside ruberythric acid has to be hydrolysed to the aglycone alizarin which is the main dye component. An intrinsic problem is the simultaneous hydrolysis of the glycoside lucidin primeveroside to the unwanted mutagenic aglycone lucidin. Madder root was treated with strong acid, strong base or enzymes to convert ruberythric acid into alizarin and the anthraquinone compositions of the suspensions were analysed by HPLC. A cheap and easy method to hydrolyse ruberythric acid in madder root to alizarin without the formation of lucidin turned out to be the stirring of dried madder roots in water at room temperature for 90 min: this gave a suspension containing pseudopurpurin, munjistin, alizarin and nordamnacanthal. Native enzymes are responsible for the hydrolysis, after which lucidin is converted to nordamnacanthal by an endogenous oxidase.

Isolation and extraction of ruberythric acid from Rubia tinctorum L. and crystal structure elucidation

“…to date, 15 of these adding to the colouring properties of the plant (Baghalian et al, 2010;Henderson et al, 2013). The two most abundant colorants in untreated madder roots are the glycosides lucidin primeveroside (1) and ruberythric acid (2) (Derksen et al, 2003;Henderson et al, 2013). These glycoside compounds are often overlooked as colorant compounds in madder roots as they are acid sensitive, and many extraction and analytical techniques hydrolyse them to the corresponding aglycons.…”

Characterization of Organic Natural Dyes by Electrospray Mass Spectrometry Coupled with HPLC and/or Capillary Electrophoresis

“…Anthraquinones and flavonoids are present in plants mostly as polar glycosides; for these colouring agents classical extraction with hot aqueous methanol [19][20][21] or ethanol [21] was proved to be the most appropriate. Chemical hydrolysis is usually performed at elevated temperatures (80-100°C) or by refluxing with hydrochloric acid, [6][7][8][27][28][29][30][31][32][33][34][35][36][37] occasionally with sulfuric acid, [38][39][40] hydrofluoric acid, [41] or even in the presence of enzymes. [22][23][24][25][26] However, in the case of fibre analysis, bonds between colourant and metal ion or ground must be destroyed, and the extraction procedure has to be combined with acid hydrolysis in order to improve recovery.…”

Biosynthesis of food constituents: Natural pigments: Part 1

“…via hydroxymethyl, formyl, and carboxyl groups) then yields 2-methylanthra-9,10-quinone, which is oxidised to alizarin. The aglycone alizarin is then bound to the β-anomer of primeverose (6-O-β-d-xylopyranosyl-d-glucopyranose) building up ruberythric acid (Derksen et al 2003). The polyketide pathway forms anthraquinones with both rings hydroxylated.…”