[Biotransformation of phenolglycosides leiocarposide and salicin]

Leiocarposide (1; 3-beta-D-glucopyranosyloxy-2-methoxy-6-hydroxy-benzoic acid -2'-beta-D-glucopyranosyloxybenzyl ester) is a phenolic glycoside from Solidago virgaurea L. After oral administration to rats it will be only poorly absorbed and mostly unchanged fecaly excreted. In the urine were found less than 10% as metabolites: leiocarpic acid (3; 3,6-dihydroxy-2-methoxy-benzoic acid, 2% of the administered dose), 3-conjugates (2%), salicylic acid (5; 0.5%), 5-conjugates (0.1%) and salicyluric acid (6; 0.5%). On the other hand salicin (2), structural part of 1, is good absorbed. In the urine were excreted 15% of the unchanged drug and the following metabolites: 0.1% saligenin (4), 30% 5, 5% 5-conjugates, 0.1% 6, 2% gentisic acid (7) and 0.1% 2,3-dihydroxy-benzoic acid (8). The different metabolic rates are explicable by the high stability of the ester bond of 1. It is hydrolyzed in artificial intestinal fluid only very slowly (t1/2 = 41.7 h).