Novel metabolites of the mammalian lignans enterolactone and enterodiol inhuman urine

Enterolactone (ENL) and enterodiol (END) are found in high concentrations i n human body fluids after ingestion of flaxseed and whole-grain products. A lthough much interest is presently focused on these mammalian lignans becau se of their putative beneficial health effects, little is known about their metabolic fate in humans. We have now identified nine novel metabolites of ENL and END in the urine of female and male humans ingesting flaxseed for five days. The chemical structures of six ENL metabolites and of three END metabolites were elucidated by GC/MS analysis and comparison with authentic reference compounds obtained by chemical synthesis. The six identified met abolites of ENL were the products of monohydroxylation at the para-position and at both ortho-positions of the parent hydroxy group of either aromatic ring. Likewise, the three END metabolites were formed through aromatic mon ohydroxylation at the para- and ortho-positions. The biological significanc e of these metabolites remains to be established. (C) 1999 Elsevier Science Ltd. All rights reserved.