Peroxynitrite scavenging of flavonoids: structure activity relationship

Area of Science:

• Biochemistry
• Medicinal Chemistry
• Chemical Biology

Background:

• Peroxynitrite is a reactive nitrogen species implicated in various disease pathologies due to its oxidative and nitrosative damage to biomolecules.
• Understanding the mechanisms by which compounds can neutralize peroxynitrite is crucial for developing therapeutic strategies against associated diseases.

Purpose of the Study:

• To investigate the peroxynitrite scavenging capabilities of substituted phenols and various flavonoids.
• To elucidate the structure-activity relationships governing the efficacy of these compounds as peroxynitrite scavengers.

Main Methods:

• Evaluation of peroxynitrite scavenging activity using spectrophotometric assays.
• Correlation analysis between scavenging activity and electronic properties of substituted phenols (Hammett σ, E(HOMO)).
• Structure-activity relationship analysis of flavonoids based on their chemical structures and hydroxyl group positions.

Main Results:

• Phenol scavenging activity is enhanced by electron-donating substituents, correlating well with Hammett σ and E(HOMO) values.
• Flavonoids with a catechol group in ring B (e.g., rutin) or three hydroxyl groups in the AC-ring (e.g., galangin, kaempferol) demonstrated potent scavenging activity.
• The 3-hydroxyl group in the AC-ring was identified as a key reactive center, with its reactivity further boosted by electron-donating groups at the 5 and/or 7 positions.

Conclusions:

• Substituted phenols and specific flavonoids are effective peroxynitrite scavengers.
• Electronic and structural features, particularly hydroxyl group positioning and electron-donating substituents, significantly influence scavenging efficacy.
• These findings provide valuable insights for designing novel therapeutic agents targeting peroxynitrite-mediated diseases.