Redox properties of individual quercetin moieties

Heřmánková, Eva; Zatloukalová, Martina; Biler, Michal; Sokolová, Romana; Bancı́řová, Martina; Tzakos, Andreas G.; Křen, Vladimı́r; Kuzma, Marek; Trouillas, Patrick; Vacek, Jan

doi:10.1016/j.freeradbiomed.2019.08.001

Cited by 50 publications

(33 citation statements)

References 64 publications

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“…Actually, the solvent might not only affect the splitting intensities but also affect the distribution of UE. Calculation shows that, in Q • , with only one deprotonated hydroxyl group in the gas phase, the UE of Q • is largely localized on the negative charged oxygen [21], while, in a polar solvent, the UE is not concentrated on the negatively charged oxygen [22]. Our calculations also show that the delocalization of the UE in the gas phase differs from that in water (data not shown).…”

Section: Discussionmentioning

confidence: 62%

Delocalization of the Unpaired Electron in the Quercetin Radical: Comparison of Experimental ESR Data with DFT Calculations

Moalin

Zhang

et al. 2020

IJMS

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In the antioxidant activity of quercetin (Q), stabilization of the energy in the quercetin radical (Q•) by delocalization of the unpaired electron (UE) in Q• is pivotal. The aim of this study is to further examine the delocalization of the UE in Q•, and to elucidate the importance of the functional groups of Q for the stabilization of the UE by combining experimentally obtained spin resonance spectroscopy (ESR) measurements with theoretical density functional theory (DFT) calculations. The ESR spectrum and DFT calculation of Q• and structurally related radicals both suggest that the UE of Q• is mostly delocalized in the B ring and partly on the AC ring. The negatively charged oxygen groups in the B ring (3′ and 4′) of Q• have an electron-donating effect that attract and stabilize the UE in the B ring. Radicals structurally related to Q• indicate that the negatively charged oxygen at 4′ has more of an effect on concentrating the UE in ring B than the negatively charged oxygen at 3′. The DFT calculation showed that an OH group at the 3-position of the AC ring is essential for concentrating the radical on the C2–C3 double bond. All these effects help to explain how the high energy of the UE is captured and a stable Q• is generated, which is pivotal in the antioxidant activity of Q.

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Section: Discussionmentioning

confidence: 62%

Delocalization of the Unpaired Electron in the Quercetin Radical: Comparison of Experimental ESR Data with DFT Calculations

Moalin

Zhang

et al. 2020

IJMS

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“…The in vitro antioxidant activity of caffeine was measured with the DPPH assay as previously described ( Kumar and Mandal, 2017 ; Hermankova et al, 2019 ). Briefly, a 2-mL aliquot of each sample solution was added to 2 mL of DPPH solution in a quartz cuvette, yielding final solutions with different concentrations of caffeine (32–4,096 μM) and 0.2 mM DPPH.…”

Section: Methodsmentioning

confidence: 99%

Caffeine Targets SIRT3 to Enhance SOD2 Activity in Mitochondria

Gan

Gao

et al. 2020

Front. Cell Dev. Biol.

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Caffeine is chemically stable and not readily oxidized under normal physiological conditions but also has antioxidant effects, although the underlying molecular mechanism is not well understood. Superoxide dismutase (SOD) 2 is a manganesecontaining enzyme located in mitochondria that protects cells against oxidative stress by scavenging reactive oxygen species (ROS). SOD2 activity is inhibited through acetylation under conditions of stress such as exposure to ultraviolet (UV) radiation. Sirtuin 3 (SIRT3) is the major mitochondrial nicotinamide adenine dinucleotide (NAD +)-dependent deacetylase, which deacetylates two critical lysine residues (lysine 68 and lysine 122) on SOD2 and promotes its antioxidative activity. In this study, we investigated whether the antioxidant effect of caffeine involves modulation of SOD2 by SIRT3 using in vitro and in vivo models. The results show that caffeine interacts with SIRT3 and promotes direct binding of SIRT3 with its substrate, thereby enhancing its enzymatic activity. Mechanistically, caffeine bound to SIRT3 with high affinity (K D = 6.858 × 10 −7 M); the binding affinity between SIRT3 and its substrate acetylated p53 was also 9.03 (without NAD +) or 6.87 (with NAD +) times higher in the presence of caffeine. Caffeine effectively protected skin cells from UV irradiation-induced oxidative stress. More importantly, caffeine enhanced SIRT3 activity and reduced SOD2 acetylation, thereby leading to increased SOD2 activity, which could be reversed by treatment with the SIRT3 inhibitor 3-(1H-1,2,3-triazol-4-yl) pyridine (3-TYP) in vitro and in vivo. Taken together, our results show that caffeine targets SIRT3 to enhance SOD2 activity and protect skin cells from UV irradiation-induced oxidative stress. Thus, caffeine, as a small-molecule SIRT3 activator, could be a potential agent to protect human skin against UV radiation.

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“…In vitro, according to our results, aglycons exert higher activity versus heterosides. In this sense, quercetin has five hydroxyl groups (Figure 6) capable of interacting with the receptor binding site, and one of them is in the most active position: the C3-OH on ring C [47]. Due to these structural characteristics, quercetin has shown an intense and wide inhibitory effect on whole-blood production of TNF-α at all assayed concentrations.…”

Section: Assay Of Il-1β Tnf-α Il-6 and Il-8 Production In Lps-stimulated Whole Bloodmentioning

confidence: 99%

Potential Therapeutic Anti-Inflammatory and Immunomodulatory Effects of Dihydroflavones, Flavones, and Flavonols

et al. 2020

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Systemic inflammation, circulating immune cell activation, and endothelial cell damage play a critical role in vascular pathogenesis. Flavonoids have shown anti-inflammatory effects. In this study, we investigated the effects of different flavonoids on the production of pro-inflammatory interleukin (IL) 1β, 6, and 8, and tumor necrosis factor α (TNF-α), in peripheral blood cells. Methods: We studied the whole blood from 36 healthy donors. Lipopolysaccharide (LPS)-stimulated (0.5 μg/mL) whole-blood aliquots were incubated in the presence or absence of different concentrations of quercetin, rutin, naringenin, naringin, diosmetin, and diosmin for 6 h. Cultures were centrifuged and the supernatant was collected in order to measure IL-1β, TNF-α, IL-6, and IL-8 production using specific immunoassay techniques. This production was significantly inhibited by quercetin, naringenin, naringin, and diosmetin, but in no case by rutin or diosmin. Flavonoids exert different effects, maybe due to the differences between aglycons and glucosides present in their chemical structures. However, these studies suggest that quercetin, naringenin, naringin, and diosmetin could have a potential therapeutic effect in the inflammatory process of cardiovascular disease.

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Redox properties of individual quercetin moieties

Cited by 50 publications

References 64 publications

Delocalization of the Unpaired Electron in the Quercetin Radical: Comparison of Experimental ESR Data with DFT Calculations

Delocalization of the Unpaired Electron in the Quercetin Radical: Comparison of Experimental ESR Data with DFT Calculations

Caffeine Targets SIRT3 to Enhance SOD2 Activity in Mitochondria

Potential Therapeutic Anti-Inflammatory and Immunomodulatory Effects of Dihydroflavones, Flavones, and Flavonols

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