Cow’s milk as a dietary source of equol and phenolic antioxidants: differential distribution in the milk aqueous and lipid fractions

Abstract

International audienceCow’s milk contains bioactive secondary phenolic compounds that are formed by bovine’s gut bacterial flora from plant phenolic compounds. Equol, a metabolite of daidzein, is one such secondary compounds of biological interest. The potential of phenolic compounds in milk as dietary antioxidants and their distribution within the milk matrix were examined. The equol concentrations, total phenolic contents, and antioxidant activity (Trolox equivalent antioxidant capacity and inhibition of F2-isoprostanes formation by human neutrophils in vitro) were measured and compared in commercial cow’s milk of varying lipid contents. The Trolox equivalent antioxidant capacity and ability to inhibit F2-isoprostanes formation in vitro increased with the concentrations of phenolic compounds and equol in the milk. Equol and total phenolic compound concentrations correlated positively with the milk lipid concentrations. Separate experiments using homogenized and non-homogenized milk showed that dairy equol and phenolic compounds distributed to larger extent in the lipid fraction than in the aqueous fraction of cow’s milk. Our results showed that cow’s milk may serve as a dietary source of unique phenolic compounds, such as equol. Skimming of cow’s milk may reduce the original amount of equol and phenolic compounds and thereby diminishes the overall nutritive value and functional properties of cow’s milk

Validating the use of an ultra-performance liquid chromatography with tandem mass spectrometry method to quantify equol in cow’s milk

“…This means that equol is not a particularly lipophilic compound and therefore has little affinity with the lipid milk fraction. This interpretation goes against a recent study, however, where the authors reported that equol is distributed to a larger extent in the lipid fraction than in the aqueous fraction and therefore that the skimming process reduces the amount of equol in cow's milk (Tsen et al 2014). More research is needed to clarify this situation, but this initial screening indicated that equol did not seem to be affected by the lipid fraction in milk.…”

“…An alternative strategy for making equol's health benefits available to everyone would be the supply of this molecule in the human diet via food of animal origin. From the range of foods commonly consumed by humans, milk from dairy cows is an interesting potential source of equol (Tsen et al 2014;Křižová et al 2011). In recent years, many studies have been conducted on how to assess equol in milk and on feeding strategies for increasing the content of this molecule in milk (Adler et al 2014;Kalač 2013;Höjer et al 2012;Andersen et al 2009;Mustonen et al 2009;Steinshamn et al 2008).…”

Concept, mechanism, and applications of phenolic antioxidants in foods

“…Some of these may also be formed from amino acids. Dairy milk is thus a good source of several PCs including equol and phenolic antioxidants (Tsen et al, 2014). These shown to improve milk quality when supplemented to the diet of dairy cows (Aguiar et al, 2014).…”

In vitro and in vivo antioxidant potential of milks, yoghurts, fermented milks and cheeses: a narrative review of evidence

“…In addition to a protein fraction, antioxidant peptides, uric acid, CLA and lipophilic vitamins, milk also contains bioactive secondary phenolic compoundssuch as equol, a metabolite of daidzeinwhich are formed from plant phenolics by the bacterial flora of the cow intestine (54) . Tsen et al (55) analysed five commercial whole milk, four commercial semi-skimmed milk and three commercial skimmed milk samples purchased from local supermarkets in Singapore and found that the antioxidant capacity and the ability to inhibit the formation of F 2 -isoprostanes increased with the concentrations of phenolic compounds and equol. However, differences in the antioxidant potential were not as marked as the differences in the equol concentration, indicating that other compounds contributed to the antioxidant potential.…”