title: Phytoestrogens in milk: Overestimations caused by contamination of the hydrolytic enzyme used during sample extraction.
abstract: Isoflavones are natural phytoestrogens with antioxidant and endocrine-disrupting potencies. Monitoring of their levels is important to ensure the high quality and safety of food, milk, and dairy products. The efficiency and accuracy of phytoestrogen analyses in complex matrices such as milk depend on the extraction procedure, which often uses hydrolysis by means of the β-glucuronidase/sulfatase enzyme originating from Helix pomatia. The present study reveals that the commercially available hydrolytic enzyme is contaminated by several phytoestrogen isoflavones (genistein, daidzein, formononetin, and biochanin A) and their metabolite equol, as well as flavones (naringenin and apigenin) and coumestrol. We show that the concentrations of daidzein and genistein in the enzyme could have impaired the results of analyses of the main isoflavones in several previously published studies. Of 8 analyzed compounds, only equol was confirmed in the present study and it serves as a reliable marker of phytoestrogens originating from cow feed. Critical reassessment of phytoestrogen concentrations in milk is needed because several previously published studies might have overestimated the concentrations depending on the extraction procedure used.
authors.affiliation: Faculty of Science, Research Centre for Toxic Compounds in the Environment, Masaryk University, Kamenice 753/5, Building A29, CZ62500 Brno, Czech Republic.
authors.forename: L
authors.initials: L
authors.lastname: Bláhová
authors.affiliation: Faculty of Science, Research Centre for Toxic Compounds in the Environment, Masaryk University, Kamenice 753/5, Building A29, CZ62500 Brno, Czech Republic.
authors.forename: J
authors.initials: J
authors.lastname: Kohoutek
authors.affiliation: Faculty of Science, Research Centre for Toxic Compounds in the Environment, Masaryk University, Kamenice 753/5, Building A29, CZ62500 Brno, Czech Republic.
authors.forename: T
authors.initials: T
authors.lastname: Procházková
authors.affiliation: Faculty of Agronomy, Department of Morphology, Physiology and Animal Genetics, Mendel University, Zemědělská 1, CZ613 00 Brno, Czech Republic.
authors.forename: M
authors.initials: M
authors.lastname: Prudíková
authors.affiliation: Faculty of Science, Research Centre for Toxic Compounds in the Environment, Masaryk University, Kamenice 753/5, Building A29, CZ62500 Brno, Czech Republic. Electronic address: blaha@recetox.muni.cz.
authors.forename: L
authors.initials: L
authors.lastname: Bláha
mesh_terms: D000818:Animals; D002417:Cattle; D003375:Coumestrol; D005260:Female; D005966:Glucuronidase; D007529:Isoflavones; D008892:Milk / Q000737:chemistry*; D010063:Ovum; D048789:Phytoestrogens
chemical_list: D007529:Isoflavones; D048789:Phytoestrogens; D005966:Glucuronidase; D003375:Coumestrol
keywords: bovine milk; equol; mass spectrometry; phytoestrogen