Benzoic and cinnamic acid derivatives as antioxidants: structure-activity relation

Area of Science:

• * Chemistry
• * Biochemistry
• * Nutritional Science

Background:

• * Antioxidants play a crucial role in combating oxidative stress.
• * Benzoic and cinnamic acid derivatives are common phenolic compounds with potential antioxidant properties.
• * Understanding structure-activity relationships is key to developing effective antioxidants.

Purpose of the Study:

• * To compare the antioxidant activity of benzoic acid and cinnamic acid derivatives.
• * To investigate the impact of different aromatic substitutions on antioxidant efficacy.
• * To evaluate antioxidant potential using both kinetic and lipoprotein oxidation models.

Main Methods:

• * Assessed antioxidant capacity via a competition kinetic test measuring peroxyl radical quenching.
• * Evaluated in vitro oxidative modification of human low-density lipoprotein (LDL).
• * Utilized 2,2'-azobis(amidinopropane) dihydrochloride and Cu(II) to initiate LDL oxidation.

Main Results:

• * Cinnamic acid derivatives demonstrated superior antioxidant activity compared to benzoic acid counterparts.
• * In kinetic tests, antioxidant activity increased with substitution: p-hydroxy < p-hydroxymethoxy < dihydroxy < p-hydroxydimethoxy.
• * In the LDL system, dihydroxy acids showed equal or greater antioxidant capacity than p-hydroxydimethoxy acids.

Conclusions:

• * Cinnamic acids are more effective antioxidants than their benzoic acid analogs.
• * Aromatic substitution patterns significantly modulate antioxidant activity, with varying effects across different assay systems.
• * The study highlights the importance of both the core structure and substitution pattern in determining antioxidant potential.