Short Review
Redox reactions of heme proteins with flavonoids

https://doi.org/10.1016/j.jinorgbio.2020.111095Get rights and content

Highlights

  • Heme peroxidases, cytochromes P450 and met-globins catalytically oxidize flavonoids.

  • Cytochrome c is reduced by flavonoids.

  • Catalase is converted into inactive Compound II by flavonoids.

  • Flavonoids may act as heme enzymes inhibitors.

Abstract

Proteins containing heme groups perform a variety of important functions in living organisms. The heme groups are involved in catalyzing oxidation/reduction reactions, in electron transfer, and in binding small molecules, like oxygen or nitric oxide. Flavonoids, low molecular weight plant polyphenols, are ubiquitous components of human diet. They are also components of many plant extracts used in herbal medicine as well as of food supplements. Due to their relatively low reduction potential, flavonoids are prone to oxidation. This paper provides a review of redox reactions of various heme proteins, including catalase, some peroxidases, cytochrome P450, cytochrome c, myoglobin, and hemoglobin with flavonoids. Potential biological significance of these reactions is discussed, in particular when flavonoids are delivered to the body at pharmacological doses.

Graphical abstract

Redox reactions of various heme proteins, performing important functions in living organisms, with flavonoids are reviewed. Potential biological significance of these reactions is discussed.

Unlabelled Image
  1. Download : Download high-res image (78KB)
  2. Download : Download full-size image

Introduction

Heme proteins perform a variety of important functions in living organisms, including catalysis (e.g. catalase, heme peroxidases, cytochromes P450), electron transfer (e.g. cytochrome c), oxygen transport and storage (e.g. myoglobin and hemoglobin), and signaling (e.g. NO receptor, soluble guanylate cyclase). Heme proteins contain FeII or FeIII protoporphyrin IX (or a derivative of this species) in their active sites, and these prosthetic groups are bound to a polypeptide backbone via histidine, tyrosine, methionine, cysteine or lysine residues [1,2].

Flavonoids are a large group of low molecular weight plant polyphenolic compounds whose structure is based on the flavan skeleton (Scheme 1).

The properties and reactivity of flavonoids depend on their chemical structures and according to them they are divided into several classes including catechins, flavonols, flavones, flavanones, antocyanidins and isoflavones ([3] and references therein). Widely distributed in fruits, vegetables, seeds, nuts and beverages, such as tea and wine, they are ubiquitous components of the human diet. In vitro studies have shown that flavonoids are powerful antioxidants. Due to the polyphenolic structure, these compounds may efficiently scavenge free radical species and other oxidants. Flavonoids also effectively chelate transition metal ions ([4] and references therein), which can prevent adverse reactions caused by these ions, such as. Fenton reaction. After consumption of flavonoids containing food, the maximal concentration of flavonoids in human plasma does not exceed several micromoles per liter and their half-life time in plasma is relatively short. Long-term consumption of flavonoid-rich food does not result in their accumulation in plasma (steady-state concentration of quercetin is below 1 μM) [5]. Thus steady-state flavonoids concentration is significantly lower than steady-state concentration of other low-molecular antioxidants present in plasma, like ascorbate or urate ([5] and references therein). On the other hand, it has been demonstrated that red blood cells as well as mitochondria are reservoirs of biologically active quercetin (and most likely of other flavonoids) [6,7]. The other important flavonoid reservoir is the intestine, where flavonoids concentration has been estimated to be several tens of micromoles per liter [8]. In these parts of human body, the role of flavonoids in the antioxidant defense system seems to be significant. Flavonoids can also act as prooxidants. This activity is connected with reactive oxygen species (mainly O2•- and H2O2) formed during flavonoid (auto)oxidation and with the reactivity of oxidized flavonoids towards thiols and nucleic acids ([9] and references therein). Autoxidation primarily occurs in an alkaline environment when flavonoids are partially deprotonated. However, in the case of several flavonoids (e.g. myricetin, quercetin, epigallocatechin gallate (EGCG)) this process is observed already at neutral pH, and time-dependent increase of H2O2 concentration in the solution is detected [10,11]. In some cases, prooxidant activity of flavonoids can be beneficial due to upregulation phase II detoxification enzymes and antioxidant enzymes [[12], [13], [14]].

The flavan phenolic nucleus of flavonoids is favourable to molecular interaction with other compounds, including proteins. Generally, flavonoid-protein interactions obey reversible non-covalent bonds (including electrostatic and hydrophobic interactions), redox reactions and covalent bond formation. In the latter two cases one- or two-electron oxidation of flavonoid precedes flavonoid-mediated protein oxidation/reduction or flavonoid-protein covalent coupling (conjugation with cysteine residue) [15]. It is believed that many beneficial health effects of flavonoids are due to their interactions with proteins. These flavonoid-protein interactions include both a direct molecular contact, and flavonoid-mediated regulation of gene expression for specific proteins ([15] and references therein). Flavonoid binding to proteins may influence biological activity of the latter. It has been reported that flavonoids inhibit a wide variety of enzymes, among others those involved in the biotransformation of procarcinogens, in the mitochondrial electron transfer, or in the pathogenesis of cardiovascular diseases [15,16].

The observed positive health effects in humans using a flavonoid-rich diet (reviewed in [17]) caused an increase in the interest in herbal medicine as well as food supplements containing flavonoids. It should be underlined, however, that flavonoids in pharmacological doses (i.e. when their plasma concentration increases from several to several dozen times compared to the control group [18,19]), can alter proteins expression and/or function (vide supra), which can change, among others, the metabolism of conventional drugs [[20], [21], [22], [23]].

In this review we focus mainly on some redox reactions occurring between flavonoids and representative heme proteins, including catalase, some heme peroxidases, cytochrome P450, cytochrome c, myoglobin and hemoglobin. It should be noted, however, that these reactions are preceded by the non-covalent binding of flavonoids to the protein molecule. The binding constants for flavonoid-heme protein (non-covalent) complexes obtained from in vitro measurements are of the order of 104–105 M−1 [[24], [25], [26], [27]], and are comparable with the values obtained for non-heme proteins. To the best of our knowledge, no redox interactions of heme center of soluble guanylate cyclase, nitric oxide synthase, and heme oxygenase with flavonoids are known.

Section snippets

Hydrogen peroxide scavenging enzymes, catalases and peroxidases

Catalases, enzymes present in almost all aerobically respiring organisms, catalyze decomposition of hydrogen peroxide (H2O2) to water and molecular oxygen. Catalases are homotetramers containing a heme group with ferric iron (FeIII) within each subunit. The catalytic cycle proceeds in two steps:Catalase+H2O2CompoundI+H2OCompoundI+H2O2Catalase+H2O+O2where Compound I (Cpd I) is an oxoferryl porphyrin (por) π-cation radical, two-electron oxidation product of a heme group (por•+FeIV = O) [28].

Conclusions

Heme proteins perform many physiological functions depending, among others, on the redox potential, binding site of the heme group as well as its protein environment. Due to their relatively low reduction potential, flavonoids are regarded as efficient reducing agents. Heme enzymes, like peroxidases or CYPs oxidize flavonoids in the catalytic cycle. Hypervalent forms of globins, which can be formed under oxidative stress, are reduced by flavonoids to their ferric, and even ferrous forms.

Abbreviations

    Cpd I

    Compound I of catalase/peroxidase

    Cpd II

    Compound II of catalase/peroxidase

    CYPs

    cytochromes P450

    Cytc

    cytochrome c

    EC

    epicatechin

    ECG

    epicatechin gallate

    EGC

    epigallocatechin

    EGCG

    epigallocatechin gallate

    ferrylHb(Mb)

    analog of Compound II of catalase/peroxidase

    Hb

    hemoglobin

    HRP

    horseradish peroxidase

    LPO

    lactoperoxidase

    Mb

    myoglobin

    MetHb(Mb)

    methemoglobin/metmyoglobin

    MPO

    myeloperoxidase

    OxyHb(Mb)

    oxygenated hemoglobin/myoglobin

    (Per)ferrylHb(Mb)

    analog of Compound I of catalase/peroxidase with the difference that

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declaration of competing interest

None.

References (114)

  • P. Nicholls et al.

    Enzymology and structure of catalases

    Adv. Inorg. Chem.

    (2000)
  • M. Alfonso-Prieto et al.

    The reaction mechanisms of heme catalases: an atomistic view by ab initio molecular dynamics

    Arch. Biochem. Biophys.

    (2012)
  • J. Krych et al.

    Catalase is inhibited by flavonoids

    Int. J. Biol. Macromol.

    (2013)
  • D. Majumder et al.

    Catalase inhibition an anti cancer property of flavonoids: a kinetic and structural evaluation

    Int. J. Biol. Macromol.

    (2017)
  • H.M. Awad et al.

    Peroxidase-catalyzed formation of quercetin quinone methide-glutathione adducts

    Arch. Biochem. Biophys.

    (2000)
  • G. Galati et al.

    Peroxidative metabolism of apigenin and naringenin versus luteolin and quercetin: glutathione oxidation and conjugation

    Free Radic. Biol. Med.

    (2001)
  • G. Galati et al.

    Prooxidant activity and cellular effects of the phenoxyl radicals of dietary flavonoids and other polyphenolics

    Toxicology.

    (2002)
  • D. Metodiewa et al.

    Quercetin may act as a cytotoxic prooxidant after its metabolic activation to semiquinone and quinoidal product

    Free Radic. Biol. Med.

    (1999)
  • I.M.C.M. Rietjens et al.

    Flavonoids and alkenylbenzenes: mechanisms of mutagenic action and carcinogenic risk

    Mutat. Res. Fundam. Mol. Mech. Mutagen.

    (2005)
  • W. Wang et al.

    The biological activities, chemical stability, metabolism and delivery systems of quercetin: a review

    Trends Food Sci. Technol.

    (2016)
  • H. Spalteholz et al.

    Kinetic evidence for rapid oxidation of (−)-epicatechin by human myeloperoxidase

    Biochem. Biophys. Res. Commun.

    (2008)
  • T. Kirchner et al.

    (−)-Epicatechin enhances the chlorinating activity of human myeloperoxidase

    Arch. Biochem. Biophys.

    (2010)
  • J. Gau et al.

    Flavonoids as promoters of the (pseudo-)halogenating activity of lactoperoxidase and myeloperoxidase

    Free Radic. Biol. Med.

    (2016)
  • R. Ihalin et al.

    Origin, structure, and biological activities of peroxidases in human saliva

    Arch. Biochem. Biophys.

    (2006)
  • J. Gau et al.

    Reactivation of peroxidase activity in human saliva samples by polyphenols

    Arch. Oral Biol.

    (2018)
  • S. Karkola et al.

    The binding of lignans, flavonoids and coumestrol to CYP450 aromatase: a molecular modelling study

    Mol. Cell. Endocrinol.

    (2009)
  • V.P. Androutsopoulos et al.

    Comparative CYP1A1 and CYP1B1 substrate and inhibitor profile of dietary flavonoids

    Bioorg. Med. Chem.

    (2011)
  • V.M. Breinholt et al.

    In vitro investigation of cytochrome P450-mediated metabolism of dietary flavonoids

    Food Chem. Toxicol.

    (2002)
  • P. Hodek et al.

    Flavonoids-potent and versatile biologically active compounds interacting with cytochromes P450

    Chem. Biol. Interact.

    (2002)
  • R. Dutour et al.

    Inhibitors of cytochrome P450 (CYP) 1B1

    Eur. J. Med. Chem.

    (2017)
  • Y.J. Moon et al.

    Dietary flavonoids: effects on xenobiotic and carcinogen metabolism

    Toxicol. in Vitro

    (2006)
  • H. Doostdar et al.

    Bioflavonoids: selective substrates and inhibitors for cytochrome P450 CYP1A and CYP1B1

    Toxicology

    (2000)
  • V.P. Androutsopoulos et al.

    Dietary flavonoids in cancer therapy and prevention: substrates and inhibitors of cytochrome P450 CYP1 enzymes

    Pharmacol. Ther.

    (2010)
  • V.P. Androutsopoulos et al.

    The flavonoids diosmetin and luteolin exert synergistic cytostatic effects in human hepatoma HepG2 cells via CYP1A-catalyzed metabolism, activation of JNK and ERK and P53/P21 up-regulation

    J. Nutr. Biochem.

    (2013)
  • E.M. Cherviakovsky et al.

    Oxidative modification of quercetin by hemeproteins

    Biochem. Biophys. Res. Commun.

    (2006)
  • R. Lagoa et al.

    Complex I and cytochrome c are molecular targets of flavonoids that inhibit hydrogen peroxide production by mitochondria

    Biochim. Biophys. Acta Bioenerg.

    (2011)
  • K. Skemiene et al.

    Anthocyanins block ischemia-induced apoptosis in the perfused heart and support mitochondrial respiration potentially by reducing cytosolic cytochrome c

    Int. J. Biochem. Cell Biol.

    (2013)
  • M. Rabago Smith et al.

    5,7,3′,4′-Hydroxy substituted flavonoids reduce the heme of cytochrome c with a range of rate constants

    Biochimie

    (2019)
  • C. Giulivi et al.

    Heme protein radicals: formation, fate, and biological consequences

    Free Radic. Biol. Med.

    (1998)
  • K.M. McArthur et al.

    Detection and reactions of the globin radical in hemoglobin

    Biochim. Biophys. Acta

    (1993)
  • C. Giulivi et al.

    Ferrylmyoglobin: formation and chemical reactivity toward electron-donating compounds

    Methods Enzymol.

    (1994)
  • C. Giulivi et al.

    A novel antioxidant role for hemoglobin. The comproportionation of ferrylhemoglobin with oxyhemoglobin

    J. Biol. Chem.

    (1990)
  • L.N. Grinberg et al.

    Protective effects of rutin against haemoglobin oxidation

    Biochem. Pharmacol.

    (1994)
  • T. Li et al.

    Structural analysis of heme proteins: implication for design and prediction

  • T.L. Poulos

    Heme enzyme structure and function

    Chem. Rev.

    (2014)
  • M.M. Kasprzak et al.

    Properties and applications of flavonoid metal complexes

    RSC Adv.

    (2015)
  • M. Fiorani et al.

    Human red blood cells as a natural flavonoid reservoir

    Free Radic. Res.

    (2003)
  • H. El Hajji et al.

    Interactions of quercetin with iron and copper ions: complexation and autoxidation

    Free Radic. Res.

    (2006)
  • J. Krych et al.

    Flavonoid-induced conversion of catalase to its inactive form - compound II

    Free Radic. Res.

    (2014)
  • Y.Y. Lee-Hilz et al.

    Pro-oxidant activity of flavonoids induces EpRE-mediated gene expression

    Chem. Res. Toxicol.

    (2006)
  • Cited by (11)

    • The effect of Luteolin on DNA damage mediated by a copper catalyzed Fenton reaction

      2022, Journal of Inorganic Biochemistry
      Citation Excerpt :

      From these observations, it can be concluded that the DNA damage is caused by a synergistic effect of singlet oxygen and superoxide radical anions. Luteolin is capable of interacting with a variety of metals and biomolecules [52–54]. In this work, the effect of luteolin on DNA damage in the copper catalyzed Fenton reaction has been studied.

    • Targeting flavonoids on modulation of metabolic syndrome

      2020, Journal of Functional Foods
      Citation Excerpt :

      Redox reactions of heme proteins with flavonoids and their potential biological significance were deeply discussed by (Gebicka, 2020), showing important observations on the role of flavonoids in reactions with hydrogen peroxide-scavenging enzymes, catalases and peroxidases (Procházková, Boušová, & Wilhelmová, 2011). Myricetin, for example, is recognized as a potent catalase inhibitor and more efficient than conventional compounds such as azide, while flavonoids are oxidized by heme peroxidases via the classical peroxidase mechanism, also acting as their competitive inhibitors (Gebicka, 2020). Thus, redox interaction of various heme proteins with flavonoids may produce beneficial or adverse effects, depending on specific physiological or pathological conditions (Gebicka, 2020).

    View all citing articles on Scopus
    View full text