Antioxidant activity of grains

Area of Science:

• Food Science
• Nutritional Biochemistry
• Analytical Chemistry

Background:

• Whole grain consumption is linked to reduced chronic disease risk.
• Health benefits are attributed to phytochemicals, but their full content is often underestimated.
• Bound phytochemicals, previously overlooked, play a significant role.

Purpose of the Study:

• To investigate the complete phytochemical profiles (free, soluble conjugated, insoluble bound) in uncooked whole grains.
• To determine the antioxidant activities associated with these different phytochemical forms.
• To quantify the contribution of bound phytochemicals to overall antioxidant capacity.

Main Methods:

• Analysis of free, soluble conjugated, and insoluble bound phytochemicals in corn, wheat, oats, and rice.
• Quantification of total phenolic content using gallic acid equivalents.
• Measurement of total antioxidant activity using vitamin C equivalents.
• Identification of major phenolic compounds, focusing on ferulic acid.

Main Results:

• Corn exhibited the highest total phenolic content (15.55 µmol gallic acid equiv/g), followed by wheat, oats, and rice.
• The majority of phenolics were in bound forms (62-85%), contradicting previous literature focusing on free phenolics.
• Ferulic acid was the predominant phenolic compound, with bound forms vastly outweighing free and soluble-conjugated forms (ratio 0.1:1:100).
• Corn showed the highest total antioxidant activity (181.42 µmol vitamin C equiv/g), followed by wheat, oats, and rice.
• Bound phytochemicals were the primary contributors to total antioxidant activity (58-90%).

Conclusions:

• Whole grains possess substantial amounts of bound phytochemicals, significantly contributing to their total phenolic content and antioxidant activity.
• The high proportion of bound phytochemicals, particularly ferulic acid, and their resistance to digestion may explain the protective mechanisms of whole grains against chronic diseases like colon cancer.
• Future research should consider bound phytochemicals for a comprehensive understanding of whole grain health benefits.