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Related Concept Videos

Oxidation of Phenols to Quinones01:17

Oxidation of Phenols to Quinones

In the presence of oxidizing agents, phenols are oxidized to quinones. Quinones can be easily reduced back to phenols using mild reducing agents. The electron-donating hydroxyl group enhances the reactivity of the aromatic ring, enabling oxidation of the ring even in the absence of an α hydrogen.
o-hydroxy phenols are oxidized to o-quinones and p-hydroxy phenols to p-quinones. Such redox reactions involve the transfer of two electrons and two protons. The reversible redox property is crucial in...
Radical Autoxidation01:20

Radical Autoxidation

The oxidation of an organic compound in the presence of air or oxygen is called autoxidation. For example, cumene reacts with oxygen to form hydroperoxide. Autoxidation involves initiation, propagation, and termination steps. Many organic compounds are susceptible to autoxidation—especially ethers in the presence of oxygen, which form hydroperoxides. Even though this reaction is slow, old ether bottles contain small amounts of peroxide, which leads to laboratory explosions during ether...
Phase II Reactions: Glucuronidation01:24

Phase II Reactions: Glucuronidation

Glucuronidation, a pivotal phase II biotransformation process, involves the coupling of glucuronic acid to a drug or xenobiotic. Given its widespread occurrence and critical role in drug metabolism, it's considered the most crucial phase II reaction. It enhances the water solubility of substances, aiding their expulsion from the body. The driving force behind these reactions is a group of enzymes known as UDP-glucuronosyltransferases (UGTs). UGTs facilitate the transfer of a glucuronic acid...
Drug Metabolism: Phase II Reactions01:14

Drug Metabolism: Phase II Reactions

Phase II reactions are essential for the detoxification and elimination of drugs from the body. These reactions involve the conjugation of parent drugs or their phase I metabolites with endogenous molecules, resulting in more hydrophilic drug conjugates. The primary conjugation reactions in this phase are sulfation and glucuronidation. Both sulfation and glucuronidation typically produce biologically inactive metabolites. However, in some cases involving prodrugs, active metabolites may be...
Pharmacokinetics in Geriatric Patients: Effect of Age on Drug Metabolism01:18

Pharmacokinetics in Geriatric Patients: Effect of Age on Drug Metabolism

Geriatric patients show significant variation in how their bodies process medications, which can change how effective and safe treatments are. The liver is the primary organ where drug metabolism occurs, involving two main types of chemical reactions: phase I and II. Phase I metabolism is driven by the cytochrome P450 enzyme system, which includes key types such as CYP3A, CYP2D6, and CYP2C9. Research indicates that while aging doesn't notably alter the levels or activity of these enzymes, it...
Bioactivation and Tissue Toxicity01:25

Bioactivation and Tissue Toxicity

Bioactivation is a metabolic process that transforms less reactive substances into highly reactive metabolites, initiating tissue toxicity. This transformation can lead to various toxic effects, including carcinogenesis and teratogenesis. Reactive metabolites are classified into two main types: electrophiles and free radicals.Electrophiles are electron-deficient species and are produced primarily by the enzyme cytochrome P-450 during the metabolism of compounds containing carbon, nitrogen, or...

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Mitochondrial Respiration Quantification in Yeast Whole Cells
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Glucuronidated metabolites of the flavonoid quercetin do not auto-oxidise, do not generate free radicals and do not

Federica Lodi1, Rosario Jiménez, Carmen Menendez

  • 1Department of Pharmacology, School of Medicine, Universidad Complutense de Madrid, Spain.

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Quercetin metabolites, mainly glucuronides, do not show pro-oxidant effects unlike quercetin itself. This suggests circulating quercetin forms are safer, impacting dietary flavonoid research.

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Area of Science:

  • Biochemistry
  • Pharmacology
  • Nutritional Science

Background:

  • Quercetin, a common dietary flavonoid, impacts blood pressure and endothelial function.
  • Quercetin is rapidly metabolized into various forms (methylated, sulfated, glucuronidated) during absorption.
  • Quercetin's effects can be either antioxidant or pro-oxidant depending on conditions.

Purpose of the Study:

  • To investigate the pro-oxidant effects of quercetin and its major circulating metabolites.
  • To compare the auto-oxidation, superoxide radical generation, and nitric oxide (NO) scavenging of quercetin and its metabolites.

Main Methods:

  • Analyzed auto-oxidation and O(2)(-) release using absorption spectra and chemiluminescence.
  • Measured NO scavenging using an amperometric electrode.
  • Assessed the biological activity of NO in rat aortic rings.

Main Results:

  • Quercetin, isorhamnetin, and quercetin 3'-sulfate auto-oxidized and generated superoxide radicals.
  • Quercetin scavenged NO, while its glucuronide metabolites did not.
  • Quercetin inhibited NO biological activity, but quercetin 3-glucuronide did not.

Conclusions:

  • Quercetin's main circulating forms, glucuronides, do not exhibit pro-oxidant effects.
  • Metabolism significantly alters the pro-oxidant activity of quercetin.
  • Dietary quercetin's safety profile may be influenced by its metabolic transformation.