Antioxidants play a pivotal role in promoting health by neutralizing harmful free radicals and reducing oxidative stress, which is linked to chronic diseases and aging. This research explores the chemistry of antioxidants and their potential to enhance the nutritional value of functional foods through chemical modification. We delve into various types of antioxidants, including phenolic compounds, flavonoids, and carotenoids, emphasizing their mechanisms of action and stability. Chemical modifications such as esterification, glycosylation, and polymerization are examined for their ability to improve the bioavailability and efficacy of these compounds. By altering chemical structures, we can enhance antioxidant properties, optimize stability under different conditions, and improve overall nutritional benefits. The study also investigates the impact of these modifications on the sensory attributes of functional foods, including taste, texture, and colour. Additionally, we review the latest advancements in analytical techniques used to assess antioxidant activity and bioavailability. The findings underscore the potential of chemical modification as a tool for developing functional foods with enhanced health benefits. This approach offers promising prospects for creating nutritionally superior products that can better contribute to disease prevention and overall well-being.