Development and Validation of Analytical Methods for Quantifying Isoflavones and Equol in Biological Matrices

Abstract

Isoflavones are natural plant substances that attract widespread interest because of their association with a large variety of beneficial effects on human health. When they are ingested by animals or humans, most of these compounds are metabolized by bacteria present in the digestive system. Among the isoflavone microbial metabolites, equol is probably the most widely studied because it seems to have numerous health benefits. In the human population, however, not everyone is able to produce equol. Equol enrichment of some food, such as cow's milk, could be an alternative strategy for making equol’s health benefits available to everyone.

The main objective of the present thesis was to develop analytical tools for quantifying these compounds in several biological matrices, thus contributing to the feasibility study being conducted on producing milk naturally enriched with equol. For this purpose, four analytical procedures, using ultra performance liquid chromatography coupled with tandem mass spectrometry (UPLC^®-MS/MS), were developed and fully validated. The analytical tools were then applied successfully in two original exploratory studies that sought to quantify equol concentrations in commercial cow's milk in Belgium and study the evolution of isoflavone concentration in red clover (Trifolium pratenseL.) silage in laboratory-scale silos.

This thesis describes new and reliable analytical tools that will help to improve current knowledge about the feasibility of producing cow's milk naturally enriched with equol and to study isoflavone metabolization in dairy cow.