Phytochemical analysis of Cotinus coggygria heartwood. Identification of isolated colorants in historical art objects

The heartwood of Cotinus coggyria Scop. (Anacardiaceae) has been used since the antiquity [1] as a source of a yellow dye known as young fustic. Although young fustic had been used in art objects for centuries, its exact chemical consistency is not well studied [2].

Phytochemical investigation of the methanol extract of the heartwood led to the isolation and structure elucidation by NMR and MS of several phenolic compounds, mainly aurones, chalcones, dihydroflavones and dihydroflavonols. Among them, the most abundant were sulfuretin (1) as well as 7,3',4'-trihydroxy-dihydroflavone (2), 5,7,4'-trihydroxy-dihydroflavone (3), 4,2',4'-trihydroxychalcone (4), 3,7,3',4'-tetrahydroxy-dihydroflavone (5), 3,5,7,3',4'-pentahydroxy-dihydroflavone (6), fisetin (7) and methyl gallate (8). Compounds 2-6 are described for the first time as constituents of young fustic.

The isolated compounds were used as standards for the development of an analytic methodology using HPLC-DAD. HPLC analysis of the organic colorants extracted by acid hydrolysis from a series of ecclesiastical garments of the post-Byzantine period has led to the identification of most of the isolated compounds coming from Cotinus coggyria, along with other natural dyes. Prior to the analysis of the historical yarns, the ability of the extraction procedure to recover the dye components was tested by using reference dyed fibers. It was concluded that both extraction procedure and HPLC methodology are effective and can be used for the unambiguous identification of young fustic in historical textiles.

Acknowledgement: The project was funded by the General Secreteriat for Research and Technology of Greece (Program PENED).

References: [1] Baumann H (1993) Greek Wild Flowers and Plant Lore in Ancient Greece, Herbert Press: London. [2] Westenburg, H. et al. (2000) J. Nat. Prod. 63: 1696–1698.