A light-sensitive yellow ommochrome pigment from the house fly

A light-sensitive pigment (lambda max at 430 and 340 nm), extracted in acidic methanol from the Musca domestica heads, showed, in the absorption curve, a plateau at 480-500 nm and a new maximum at 400 nm, after visible light irradiation. The light-sensitive house fly pigment showed spectroscopic and chemical properties of the ommochrome pigments (Butenandt and Schäfer: Recent Progress in the Chemistry of Natural and Synthetic, Colouring Matters and Related Fields, Academic Press, New York, pp 13-33, 1962; Bolognese and Scherillo: Experientia 30:225-226, 1974). The treatment of the extracted pigment with a methanol-HClsat. mixture afforded some coloured compounds; two main products were identified by comparison of their chromatographic and spectral properties with authentic samples of 1-oxo-2H-3-carbomethoxy-5-methoxy-11-(fumaroyl-methylester)-pyrido [3,2-a] phenoxazine (compound 7) and 1-oxo-2H-3-carbomethoxy-5-methoxy-9-chlorine-11-(fumaroyl-methylester )-pyrido [3,2-a] phenoxazine (compound 8), obtained from the oxidation mixture of 3-hydroxykynurenine methylester (compound 9).