Quercetin influences BSA alpha-helical structures of native, ACR- and NaNO2-modified BSAs

Abstract

Quercetin (QUE) is a plant flavonoid with a multifarious spectrum of properties. It is a prominent component of the human diet, considered to be safe and beneficial for human health. Acrylamide (ACR) and sodium nitrate III (NaNO 2) are also present in the diet and may demonstrate adverse and toxic effects on the macromolecules and tissues of the human organism. Albumin, the most abundant blood protein, is the most susceptible to the action of various exogenous factors, which may lead to structural damage and functional disturbances. The aim of this study was to estimate ACR-and NaNO 2-induced changes in the secondary structure of bovine serum albumin (BSA), using circular dichroism (CD), and to determine the impact of quercetin on these modifications. BSA was incubated with ACR and NaNO 2 solutions in the absence and presence of QUE in two different concentrations (3 mM and 500 µM), and changes in albumin alpha-helical structure were determined by CD. The BSA secondary structure was vulnerable to alterations upon treatment with acrylamide and NaNO 2 , as well as quercetin. QUE, depending on concentration and incubation time, caused a decrease of around 13-19% in the alpha helix content of BSA molecules, but also prevented the changes in the protein alpha-helical structure initiated by ACR and NaNO 2. The most spectacular inhibition was revealed for QUE in lower concentrations after 24 h of incubation with NaNO 2. Although QUE reveals a protective effect towards albumin modifications, it is difficult to unambiguously define whether this effect is advantageous, because quercetin itself causes alterations in BSA structure.