Effect of circulating forms of soy isoflavones on the oxidation of low density lipoprotein

Turner, Rufus, Baron, Tobias, Wolffram, Siegfried, Minihane, Anne-Marie ORCID: https://orcid.org/0000-0001-9042-4226, Cassidy, Aedin, Rimbach, Gerald and Weinberg, Peter D (2004) Effect of circulating forms of soy isoflavones on the oxidation of low density lipoprotein. Free Radical Research, 38 (2). pp. 209-216. ISSN 1071-5762

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Abstract

Soy isoflavones are thought to have a cardioprotective effect that is partly mediated by an inhibitory influence on the oxidation of low density lipoprotein (LDL). However, the aglycone forms investigated in many previous studies do not circulate in appreciable quantities because they are metabolised in the gut and liver. We investigated effects of various isoflavone metabolites, including for the first time the sulphated conjugates formed in the liver and the mucosa of the small intestine, on copper-induced LDL oxidation. The parent aglycones inhibited oxidation, although only 5% as well as quercetin. Metabolism increased or decreased their effectiveness. Equol inhibited 2.65-fold better than its parent compound daidzein and 8-hydroxydaidzein, not previously assessed, was 12.5-fold better than daidzein. However, monosulphated conjugates of genistein, daidzein and equol were much less effective and disulphates completely ineffective. Since almost all isoflavones circulate as conjugates, these data suggest that despite the increased potency produced by some metabolic changes, isoflavones may not be effective antioxidants in vivo unless they are deconjugated again.

Item Type:	Article
Uncontrolled Keywords:	adult,copper,electrophoretic mobility shift assay,humans,isoflavones,lipoproteins, ldl,male,molecular structure,oxidation-reduction,soybeans,spectrophotometry
Faculty \ School:	Faculty of Medicine and Health Sciences > Norwich Medical School
UEA Research Groups:	Faculty of Medicine and Health Sciences > Research Groups > Nutrition and Preventive Medicine Faculty of Medicine and Health Sciences > Research Groups > Cardiovascular and Metabolic Health Faculty of Medicine and Health Sciences > Research Centres > Lifespan Health
Depositing User:	Pure Connector
Date Deposited:	20 Jan 2014 14:42
Last Modified:	19 Oct 2023 01:16
URI:	https://ueaeprints.uea.ac.uk/id/eprint/47345
DOI:	10.1080/10715760310001641854

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