Isolation and extraction of lucidin primeveroside from Rubia tinctorum L. and crystal structure elucidation.

Madder (Rubia tinctorum L.) has been used as a dye for over 2000 years with alizarin and purpurin the major natural dyes analysed from extractions undertaken. The use of ethanol as the solvent in the extraction process produced an extract that yielded four anthraquinone compounds lucidin primeveroside, ruberythric acid, alizarin and lucidin-ω-ethyl ether. Gravitational separation of the extract was used to record the first crystal structure of lucidin primeveroside, which is also the first ever known crystal structure of a glycoside containing anthraquinone moiety. The crystal structure along with (1)H and (13)C NMR helped elucidate and confirm the structure of this overlooked natural dye which has been shown to be a major compound in R. tinctorum L.