Absolute configuration of naturally occurring glabridin

Glabridin is a species-specific biomarker from the roots Glycyrrhiza glabra L. (European licorice, Fabaceae). 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.