Synthesis, separation and absolute configuration of all chiral compounds of the equol pathway with evaluation of commercial samples.

Daidzein, an isoflavone found in legumes, can undergo a series of enzymatic reductions to become equol. Equol has more potent bioactivity than daidzein. Not all humans have the necessary enzymes within the gut microbiome to convert daidzein to equol, thus missing out on health benefits like chemoprophylaxis and menopausal symptom relief. The intermediates between daidzein and equol are dihydrodaidzein and tetrahydrodaidzein, which are chiral like equol. An achiral HPLC method is presented that separates daidzein and its metabolites including O-desmethylangolensin, a molecule produced by individuals that cannot make equol. Chiral separation methods for all entities in the daidzein to equol pathway are presented including the absolute configuration of these analytes as determined using vibrational circular dichroism. This is the first instance of direct absolute configuration assignment of these molecules. Three commercially available equol supplements were analyzed using the developed methods and discrepancies between the label claims and results are discussed.