G.C.H. Derksen

Analysis of anthraquinones in Rubia tinctorum L. by liquid chromatography coupled with diode-array UV and mass spectrometric detection

A liquid chromatographic (LC) method for the separation of both anthraquinone glycosides and aglycones in extracts of Rubia tinctorum was improved. For on-line MS detection atmospheric pressure chemical ionisation as well as electrospray ionisation (ESI) were used. The glycosides were ionised in both positive and negative ionisation (NI) mode, the aglycones only in the NI mode. With ESI ammonia was added to the eluent post-column to deprotonate the compounds. The efficiency of mass detection of the hydroxyanthraquinone aglycones was found to depend on the pKa value of the component. LC-diode-array detection and LC-MS provide useful complementary information for the identification of anthraquinones in plant extracts, which was proven with the identification of munjistin and pseudopurpurin.

High-performance liquid chromatographic method for the analysis of anthraquinone glycosides and aglycones in madder root (Rubia tinctorum L.).

A HPLC method has been developed for the simultaneous characterisation of anthraquinone glycosides and aglycones in extracts of Rubia tinctorum L. The anthraquinones are separated on an end-capped C18-RP column with a water–acetonitrile gradient as eluent and measured with UV detection at 250 nm. With this method the glycosides lucidin primeveroside and ruberythric acid and the aglycones lucidin, alizarin, purpurin, quinizarin and 2,6-dihydroxyanthraquinone can be analysed. Lucidin which is not commercially available was synthesised starting from resorcinol and phthalic anhydride. The glycosides ruberythric acid and lucidin primeveroside are commercially available as a mixture and were separated by droplet counter-current chromatography in ascending flow with chloroform–methanol–water as eluents prior to their use as standards.

Rubia tinctorum L.

Abstract The roots of Rubia tinctorum L. (madder) are the source of a natural dye. In this review for the first time all the different information on Rubia tinctorum available in the literature is summarised. The dye components are anthraquinones whichprobably contribute to the resistance of the plant against fungi in the soil. Madder roots have been used to dye textiles in many parts of the world since ancient timesand an overview of the historical development, cultivation, harvesting and dyeing techniques of madder is given. The anthraquinone alizarin, the hydrolysis product of ruberythric acid, is supposed to be the main dye component of Rubia tinctorum . The chemical synthesis of alizarin and the biosynthesis of the anthraquinones in Rubia tinctorum are described. As far as the purification, structure elucidation and structures of isolated compounds are concerned, the review confines itself to the anthraquinones of madder. Finally the pharmacology and medicinal uses of madder and pure anthraquinones are discussed. This review supplements and updates earlier partial reviews on madder or anthraquinones by Schweppe, Thomson and Wijnsma.