title: Isolation and extraction of ruberythric acid from Rubia tinctorum L. and crystal structure elucidation.
abstract: Madder (Rubia tinctorum L.) has been exploited as a dye throughout history. The roots of the plant are very rich in the highly coloured glycosidic compounds ruberythric acid and lucidin primeveroside, alongside the corresponding aglycons which can be readily formed by deglycosylation, particularly during extraction. Supported by (1)H and (13)C NMR data, the conclusive X-ray crystal structure of the natural dye ruberythric acid is presented for the first time. The solid state structure revealed extensive intermolecular hydrogen bonding interactions between the sugar moieties in the unit cell, but only intramolecular hydrogen bonding through the hydroxyquinone groups. There is also some additional π-π stacking from the anthraquinone moiety.
authors.affiliation: School of Chemistry, University of Leeds, Leeds LS2 9JT, UK; Centre for Technical Textiles, University of Leeds, Leeds LS2 9JT, UK. Electronic address: cm10l2f@leeds.ac.uk.
authors.forename: Lauren
authors.initials: L
authors.lastname: Ford
authors.affiliation: School of Chemistry, University of Leeds, Leeds LS2 9JT, UK. Electronic address: c.m.rayner@leeds.ac.uk.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Rayner
authors.affiliation: Centre for Technical Textiles, University of Leeds, Leeds LS2 9JT, UK. Electronic address: r.s.blackburn@leeds.ac.uk.
authors.forename: Richard S
authors.initials: RS
authors.lastname: Blackburn
mesh_terms: D000880:Anthraquinones / Q000737:chemistry* / Q000302:isolation & purification*; D002851:Chromatography, High Pressure Liquid; D004396:Coloring Agents / Q000302:isolation & purification; D018360:Crystallography, X-Ray; D004187:Disaccharides / Q000737:chemistry / Q000302:isolation & purification*; D008968:Molecular Conformation; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D018517:Plant Roots / Q000737:chemistry; D045470:Rubia / Q000737:chemistry*
chemical_list: D000880:Anthraquinones; D004396:Coloring Agents; D004187:Disaccharides; C064333:ruberythric acid; C010078:alizarin; C039315:lucidin
keywords: Adsorption mechanism; Alizarin; Anthraquinone glycoside; Dye; Extraction; Madder; Purpurin; Ruberythric acid; Rubia tinctorum; X-ray crystal structure