Fate of (14C)xanthotoxin (8-methoxypsoralen) in laying hens and lactating goats

Abstract

The metabolism of xanthotoxin, a naturally-occurring furanocoumarin photosensitizer, was studied in laying hens and lactating goats treated with a single oral dose equivalent to 10 mg xanthotoxin/kg of body weight. Within 48 hours, essentially all of the administered radiocarbon was eliminated in the excreta of the laying hens, while 92% and 3% were excreted in the urine and feces, respectively, of the goats. Of the different tissues collected, only the liver and blood of the laying hens; and the liver, blood, and muscle of the goats contained >.01% of the administered dose 7 days after treatment. Radiocarbon residues in the milk, egg white, egg yolk and egg shell were low. In the egg yolk and white, >95% of the radiocarbon present was identical in TLC behavior to xanthotoxin. Unmetabolized xanthotoxin, xanthotoxol, 6-(7-hydroxy-8-methoxycoumaryl)-acetic acid (HCA) and 6-(7-hydroxy-8- methoxycoumaryl)-hydroxy acetic acid (HCHA) were isolated and identified in the excreta of laying hens. Xanthotoxin is thus metabolized in the laying hens by O-demethylation, hydrolysis, and oxidation of the furan ring. In the goat, xanthotoxin is metabolized by O-demethylation, hydroxylation, reduction, oxidative cleavage of the furan ring, hydrolysis of the lactone ring, and conjugation to HCA, HCHA, xanthotoxol, 5,8-dihydroxypsoralen, psoralenquinone, 5-hydroxy-8- methoxypsoralen and 3{5-(6-hydroxy-7-methoxybenzofuryl]}-propanoic acid.