Review
Quercetin and iron metabolism: What we know and what we need to know
Section snippets
Quercetin primary sources and daily intake
Quercetin's name comes from the Latin quercetum, meaning oak forest, or Quercus (oak), and quercetin is the dietary flavonoid that has attracted the most attention from the scientific community. Because of its widespread dietary sources, quercetin accounts for approximately 75% of our total flavonol intake (Sampson et al., 2002). Quercetin provides colors to common fruits and vegetables because of its abundant distribution in rinds and barks. Of the vegetables, onions, the richest source of
Quercetin biochemistry
In flavonoids, different substitution patterns in the common diphenylpropane (C6-C3-C6) skeleton are responsible for their classifications and characterized biochemical activities (Cook and Samman, 1996) (Fig. 1A). More specifically, quercetin is a polyphenol that belongs to the flavonol subgroup of flavonoids. It is characterized by a phenyl benzo(c) pyrone-derived structure with five hydroxyl groups on its flavone backbone structure at the 3, 3Ź¹, 4Ź¹, 5, and 7 carbons (Mendoza-Wilson and
Iron homeostasis: roles of quercetin
As the second-most abundant metal on Earth, iron is so important that approximately 4 billion years ago, the first tellurian living organisms originated from the iron-rich oceans (Pietrangelo, 2015). Iron is an essential life-supporting micronutrient in the human diet, and it plays an irreplaceable role in many fundamental metabolic processes. Long before the occurrence of photosynthesis, iron-sulfur clusters acted as the earliest catalytic cofactors on Earth. They were used by the ancient
Quercetin and iron-catalyzed ROS-Formation
Quercetin's iron-chelating property and direct scavenging action against ROS (reactive oxygen species) are believed to be the essence of its antioxidant activity. In fact, its direct ROS-scavenging activity is at least partly responsible for quercetin's protective effects in the majority of the studies described above, in which its primarily function is iron chelation (Chander et al., 2005, Eybl et al., 2008, Li et al., 2016a, Morel et al., 1993, Singh et al., 2004, Zhang et al., 2006, Zhang et
Quercetin-iron complex: a seeded player with multiple biological functions
Numerous articles have shown that as a unique class of flavonoid derivatives, flavonoid-metal complexes, often exhibit a superior and broader spectrum of biological activities than their corresponding parent flavonoid alone. These activities include antioxidant, antimicrobial, anticancer, anti-inflammatory and anti-diabetic capacities (Havsteen, 2002, Li et al., 2008, Prajapati et al., 2010). This spectrum is attributed to the specific spatial configuration generated in the complex of the metal
Other interactions between iron and quercetin
The formation of ROS is closely related to the redox state of iron. The Fe2+-initiated production of superoxide anions by the reduction of one electron of oxygen initiates the formation of hydrogen peroxide and a subsequent Fenton reaction. This reaction is responsible for the generation of hydroxyl radicals, the most ānoxiousā oxidants among the ROS. With respect to quercetin, apart from its iron-chelating and ROS scavenging activities, the enhancement of the autooxidation of Fe2+, which thus
Conclusions and future perspectives
Among the essential dietary nutrients, iron is clearly worthy of special attention, because free iron is highly reactive. However, humans do not have effective excretory mechanisms to decrease excessive serum iron or to buffer the levels of the pro-oxidant iron forms in serum and cells. In this context, humans have developed intricately homeostatic regulation mechanisms to keep the iron concentrations within a narrow range to avoid excess or deficiency. Quercetin has long been extensively
Conflicts of interest
The authors declare that there are no conflicts of interest.
Acknowledgments
This work was supported in part by the National Natural Science Foundation of China (No. 81472979, 81172658, 81402673 and 81472979).
References (184)
- et al.
Chelating and free radical scavenging mechanisms of inhibitory action of rutin and quercetin in lipid peroxidation
Biochem. Pharmacol.
(1989) - et al.
Dietary intakes of flavonols, flavones and isoflavones by Japanese women and the inverse correlation between quercetin intake and plasma LDL cholesterol concentration
J. Nutr.
(2000) - et al.
Quercetin as a shuttle for labile iron
J. Inorg. Biochem.
(2012) - et al.
The effect of pH on yields of hydroxyl radicals produced from superoxide by potential biological iron chelators
Arch. Biochem. Biophys.
(1986) - et al.
Divalent metal-dependent regulation of hepcidin expression by MTF-1
FEBS Lett.
(2010) - et al.
A novel N491S mutation in the human SLC11A2 gene impairs protein trafficking and in association with the G212V mutation leads to microcytic anemia and liver iron overload
Blood Cells Mol. Dis.
(2011) - et al.
Phytoestrogens modulate hepcidin expression by Nrf2: implications for dietary control of iron absorption
Free Radical Biol. Med.
(2015) - et al.
Determination of the stability constants for the binding of sulfonated morin with Fe2+
Inorg. Chim. Acta.
(2007) - et al.
Intra- and intermolecular hydrogen bonding in 3-hydroxy- and 5-hydroxychromone
Tetrahedron Lett.
(2008) - et al.
Regulators of iron homeostasis: new players in metabolism, cell death, and disease
Trends Biochem. Sci.
(2016)