The quincyte pigments: Fossil quinones in an eocene clay mineral

Abstract An unusual series of quinone pigments in a pink Eocene ( c . 45x10 6 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 substituents (C 1 –C 3 ) 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.