Metabolic fate of gallic acid orally administered to rats

The metabolic behavior of orally administered gallic acid was investigated by HPLC and 4-O-methyl gallic acid was found to be the main metabolite in r at peripheral blood and urine, After oral administration of garlic acid, ma ximum concentration in portal vein and inferior vena cava occurred at 15 an d 30 min, respectively. In portal vein, gallic acid was preferentially dete cted relative to 4-O-methyl gallic acid, whereas gallic acid and 4-O-methyl gallic acid were equally detected in inferior vena cava. On the other hand , 4-O-methyl gallic acid but not gallic acid was found in liver. The conten ts of gallic acid and 4-O-methyl gallic acid in urine were nearly 100 times higher than those in blood. The ratio of 4-O-methyl gallic acid to total g allic acid metabolites in urine nas from 0.55 to 0.76, indicating that a co nsiderable amount of gallic acid was excreted without being metabolized. In this study we found that gallic acid administered orally existed in the bl ood for 6 h at most, and more than half was metabolized to 4-O-methyl galli c acid, followed by excretion into urine.