Reversible hepatic black pigmentation and enzyme alteration induced by prolonged feeding of high dose of crocin dyes in rats.

Crocin dyes, isolated from Gardenia jasminodes, did not affect hepatic function when they were orally administered to rats in a daily dose of 50 mg/kg for 8 days, but could induce acute hepatic discoloration. A high dosage of 100 mg/kg for 2 weeks could induce both hepatic damage and black pigmentation, but a lower dose of 100 mg/kg for 40 days did not. Rats fed on diet containing 1% of crocin dyes for four months were shown to have mild hepatic functional disorders and pigmentation. The black pigmentation of the liver and the acute hepatic damage associated with the discoloration were completely reversible. During the period of hepatic pigmentation caused by high dose of crocin dyes, the urine had abnormally increased porphyrin excretion and tended to display a blackish green color. The skin also appeared purplish black. The mechanism of black pigmentation seemed to correlate with the gradual accumulation of crocin dyes. In summary, the crocin dyes have a very low toxicity in rats even in high experimental dosage which would hardly happen in human practice. It is therefore suggested that the crocin dyes are safe for coloring foods.