title: Absolute configuration of naturally occurring glabridin.
abstract: The title compound {systematic name: 4-[(3R)-8,8-dimethyl-3,4-dihydro-2H-pyrano[2,3-f]chromen-3-yl]benzene-1,3-diol, commonly named glabridin}, C20H20O4, is a species-specific biomarker from the roots Glycyrrhiza glabra L. (European licorice, Fabaceae). In the present study, this prenylated isoflavan has been purified from an enriched CHCl3 fraction of the extract of the root, using three steps of medium-pressure liquid chromatography (MPLC) by employing HW-40F, Sephadex LH-20 and LiChroCN as adsorbents. Pure glabridin was crystallized from an MeOH-H2O mixture (95:5 v/v) to yield colorless crystals containing one molecule per asymmetric unit (Z' = 1) in the space group P212121. Although the crystal structure has been reported before, the determination of the absolute configuration remained uncertain. Stereochemical analysis, including circular dichroism, NMR data and an X-ray diffraction data set with Bijvoet differences, confirms that glabridin, purified from its natural source, is found only in a C3 R configuration. These results can therefore be used as a reference for the assignment of the configuration and enantiopurity of any isolated or synthetic glabridin sample.
authors.affiliation: Department of Medicinal Chemistry and Pharmacognosy, and UIC/NIH Center for Botanical Dietary Supplements Research, MC-781, College of Pharmacy, University of Illinois at Chicago, 833 S. Wood Street, Chicago, IL 60612, USA.
authors.forename: Charlotte
authors.initials: C
authors.lastname: Simmler
authors.forename: Frank R
authors.initials: FR
authors.lastname: Fronczek
authors.forename: Guido F
authors.initials: GF
authors.lastname: Pauli
authors.forename: Bernard D
authors.initials: BD
authors.lastname: Santarsiero
mesh_terms: D002942:Circular Dichroism; D006035:Glycyrrhiza / Q000737:chemistry*; D007529:Isoflavones / Q000737:chemistry* / Q000302:isolation & purification; D010636:Phenols / Q000737:chemistry* / Q000302:isolation & purification; D010936:Plant Extracts / Q000737:chemistry* / Q000302:isolation & purification; D018517:Plant Roots / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D007529:Isoflavones; D010636:Phenols; D010936:Plant Extracts; C107601:glabridin
keywords: absolute configuration; crystal structure; glabridin; natural compounds