Short ReviewRedox reactions of heme proteins with flavonoids
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.
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:where 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)
- et al.
Flavonoids—chemistry, metabolism, cardioprotective effects, and dietary sources
J. Nutr. Biochem.
(1996) - et al.
Consumption of flavonoid-rich foods and increased plasma antioxidant capacity in humans: cause, consequence, or epiphenomenon?
Free Radic. Biol. Med.
(2006) - et al.
Mitochondria accumulate large amounts of quercetin: prevention of mitochondrial damage and release upon oxidation of the extramitochondrial fraction of the flavonoid
J. Nutr. Biochem.
(2010) - et al.
Chemical features of flavonols affecting their genotoxicity. Potential implications in their use as therapeutical agents
Chem. Biol. Interact.
(2000) - et al.
Antioxidant and prooxidant properties of flavonoids
Fitoterapia
(2011) - et al.
Potential toxicity of flavonoids and other dietary phenolics: significance for their chemopreventive and anticancer properties
Free Radic. Biol. Med.
(2004) - et al.
Nrf2-ARE signaling pathway and natural products for cancer chemoprevention
Cancer Epidemiol.
(2010) - et al.
Bioavailability and bioefficacy of polyphenols in humans. I. Review of 97 bioavailability studies
Am. J. Clin. Nutr.
(2005) - et al.
Probing the binding of flavonoids to catalase by molecular spectroscopy
J. Mol. Struct.
(2007) - et al.
A structure-differential binding method for elucidating the interactions between flavonoids and cytochrome-c by ESI-MS and molecular docking
Talanta
(2013)
Enzymology and structure of catalases
Adv. Inorg. Chem.
The reaction mechanisms of heme catalases: an atomistic view by ab initio molecular dynamics
Arch. Biochem. Biophys.
Catalase is inhibited by flavonoids
Int. J. Biol. Macromol.
Catalase inhibition an anti cancer property of flavonoids: a kinetic and structural evaluation
Int. J. Biol. Macromol.
Peroxidase-catalyzed formation of quercetin quinone methide-glutathione adducts
Arch. Biochem. Biophys.
Peroxidative metabolism of apigenin and naringenin versus luteolin and quercetin: glutathione oxidation and conjugation
Free Radic. Biol. Med.
Prooxidant activity and cellular effects of the phenoxyl radicals of dietary flavonoids and other polyphenolics
Toxicology.
Quercetin may act as a cytotoxic prooxidant after its metabolic activation to semiquinone and quinoidal product
Free Radic. Biol. Med.
Flavonoids and alkenylbenzenes: mechanisms of mutagenic action and carcinogenic risk
Mutat. Res. Fundam. Mol. Mech. Mutagen.
The biological activities, chemical stability, metabolism and delivery systems of quercetin: a review
Trends Food Sci. Technol.
Kinetic evidence for rapid oxidation of (−)-epicatechin by human myeloperoxidase
Biochem. Biophys. Res. Commun.
(−)-Epicatechin enhances the chlorinating activity of human myeloperoxidase
Arch. Biochem. Biophys.
Flavonoids as promoters of the (pseudo-)halogenating activity of lactoperoxidase and myeloperoxidase
Free Radic. Biol. Med.
Origin, structure, and biological activities of peroxidases in human saliva
Arch. Biochem. Biophys.
Reactivation of peroxidase activity in human saliva samples by polyphenols
Arch. Oral Biol.
The binding of lignans, flavonoids and coumestrol to CYP450 aromatase: a molecular modelling study
Mol. Cell. Endocrinol.
Comparative CYP1A1 and CYP1B1 substrate and inhibitor profile of dietary flavonoids
Bioorg. Med. Chem.
In vitro investigation of cytochrome P450-mediated metabolism of dietary flavonoids
Food Chem. Toxicol.
Flavonoids-potent and versatile biologically active compounds interacting with cytochromes P450
Chem. Biol. Interact.
Inhibitors of cytochrome P450 (CYP) 1B1
Eur. J. Med. Chem.
Dietary flavonoids: effects on xenobiotic and carcinogen metabolism
Toxicol. in Vitro
Bioflavonoids: selective substrates and inhibitors for cytochrome P450 CYP1A and CYP1B1
Toxicology
Dietary flavonoids in cancer therapy and prevention: substrates and inhibitors of cytochrome P450 CYP1 enzymes
Pharmacol. Ther.
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.
Oxidative modification of quercetin by hemeproteins
Biochem. Biophys. Res. Commun.
Complex I and cytochrome c are molecular targets of flavonoids that inhibit hydrogen peroxide production by mitochondria
Biochim. Biophys. Acta Bioenerg.
Anthocyanins block ischemia-induced apoptosis in the perfused heart and support mitochondrial respiration potentially by reducing cytosolic cytochrome c
Int. J. Biochem. Cell Biol.
5,7,3′,4′-Hydroxy substituted flavonoids reduce the heme of cytochrome c with a range of rate constants
Biochimie
Heme protein radicals: formation, fate, and biological consequences
Free Radic. Biol. Med.
Detection and reactions of the globin radical in hemoglobin
Biochim. Biophys. Acta
Ferrylmyoglobin: formation and chemical reactivity toward electron-donating compounds
Methods Enzymol.
A novel antioxidant role for hemoglobin. The comproportionation of ferrylhemoglobin with oxyhemoglobin
J. Biol. Chem.
Protective effects of rutin against haemoglobin oxidation
Biochem. Pharmacol.
Structural analysis of heme proteins: implication for design and prediction
Heme enzyme structure and function
Chem. Rev.
Properties and applications of flavonoid metal complexes
RSC Adv.
Human red blood cells as a natural flavonoid reservoir
Free Radic. Res.
Interactions of quercetin with iron and copper ions: complexation and autoxidation
Free Radic. Res.
Flavonoid-induced conversion of catalase to its inactive form - compound II
Free Radic. Res.
Pro-oxidant activity of flavonoids induces EpRE-mediated gene expression
Chem. Res. Toxicol.
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