The quincyte pigments: Fossil quinones in an eocene clay mineral

Article abstract of DOI:10.1016/S0040-4020(01)80947-9

An unusual series of quinone pigments in a pink Eocene (c. 45x10⁶ yr) sepiolite (quincyte, France) has been characterised by spectroscopy. The structure of the major pigment (c. 75% of total), 2,8-di-isopropyl-peri-xanthenoxanthene-4,10-quinone, was confirmed by synthesis. Spectroscopy revealed six minor related components with various oxygenated C-2 substitutents (C₁-C₃) and, generally, a C-8 isopropyl group. Although the origin of the pigments is unknown, they (or their precursors) appear to have been biosynthesised by the acyl-malonate pathway.