TEAC antioxidant activity of 4-hydroxybenzoates

Area of Science:

• * Medicinal Chemistry
• * Computational Chemistry
• * Biochemistry

Background:

• * Antioxidants are crucial for combating oxidative stress.
• * Understanding the structure-activity relationship of antioxidants is essential for designing effective compounds.
• * 4-hydroxybenzoates are a class of compounds with potential antioxidant properties.

Purpose of the Study:

• * To investigate the influence of pH, electron donating capacity, and hydrogen atom donating capacity on the antioxidant potential of hydroxy and fluorine substituted 4-hydroxybenzoates.
• * To compare the antioxidant behavior of different forms of 4-hydroxybenzoates (nondissociated, monoanionic, dianionic).
• * To elucidate the role of fluorine and hydroxyl substituents in modulating antioxidant activity.

Main Methods:

• * Experimental investigation using the TEAC (Trolox Equivalent Antioxidant Capacity) assay.
• * Computational calculations to determine intrinsic electron and hydrogen atom donating capacities.
• * Synthesis of fluorobenzoate series for mechanistic comparison.

Main Results:

• * pH significantly affects antioxidant behavior; deprotonation increases radical scavenging ability.
• * Fluorine and hydroxyl substituents influence electron and proton donating abilities similarly.
• * Antioxidant behavior of monoanionic forms is primarily determined by hydrogen atom donating capacity, not electron donating capacity.
• * Number and position of hydroxyl groups quantitatively affect antioxidant behavior.

Conclusions:

• * The antioxidant potential of 4-hydroxybenzoates is pH-dependent and influenced by substituent type and position.
• * Hydrogen atom donation is the key mechanism for antioxidant activity in monoanionic forms.
• * This study provides a quantitative understanding of how structural modifications impact antioxidant properties.