Cotinus coggygria Wood: Novel Flavanone Dimer and Development of an HPLC/UV/MS Method for the Simultaneous Determination of Fourteen Phenolic Constituents

Phytochemical investigations of Cotinus coggygria Scop. wood, a medicinal and tinctorial plant used since antiquity, resulted in the isolation and structure elucidation of the novel C-3/C-3 '' dimer of butin (3',4',7-trihydroxyflavanone) and other known compounds: gallic acid and its methyl ester; catechin; profisetinidins: fisetinidol-(4 alpha -> 8)-(+)-catechin and epifisetinidol-(4 beta -> 8)-(+)-catechin; flavanonols: fustin and dihydroquercetagetin; flavanones: butin and eriodictyol; flavonols: fisetin and quercetin; the chalcone butein and the aurone sulfuretin. The isolated compounds were used for the development and validation of a HPLC-method which enables the determination of these bioactive substances in C. coggygria extracts. Separation was possible on an ether-linked phenyl column material, using as mobile phase mixtures of water, methanol, and acetonitrile with 0.02% trifluoroacetic acid. Sensitivity, selectivity, linearity, precision, accuracy, and repeatability of the method were verified and assured suitability for its intended use. LC-MS experiments performed in positive and negative electrospray ionization mode confirmed the identity of analytes and allowed unambiguous assignment of all peaks of interest. The analysis of different C. coggygria samples revealed that sulfuretin (0.38-0.69%) and fustin (0.33-0.59%) dominated, followed by dihydroquercetagetin (0.12-0.35%), a rare flavanonol derivative with a 5,6,7-trihydroxysubstituted A-ring. The new natural compound C-3/C-3 '' flavanone dimer occurred in concentrations of 0.03-0.06%; the two latter compounds could represent valuable markers for the identification and quality control of C. coggygria wood.