Mutagenicity studies of urine and faecal samples from rats treated orally with the food colourings Brown FK and Red 2G.

Urine and faecal extracts from rats given Brown FK or Red 2G orally (800 mg/kg body weight) were investigated for mutagenicity. Extracts were subjected to liquid fluctuation and plate incorporation assays with Salmonella typhimurium strains TA98 and TA100 in the presence and absence of liver microsomes and/or a beta-glucuronidase-sulphatase preparation. Urine from Red 2G-treated rats only exhibited direct activity when coloured fractions from polyamide-column concentrates were tested with TA100. All other urines, as well as aqueous and ether faecal extracts from animals receiving either colouring, were no more mutagenic than the respective control extracts obtained from the same animals prior to dosing.