Optimization of Polyphenol-Rich Extracts from Defatted Avocado Peel and Seed Residues Using Ultrasound-Assisted RSM: Antioxidant Potential and Valorization Prospects

It is well known that a significant amount of processed avocado fruit, specifically peel and seed, is treated as waste. During this study, these by-products were valorized through a two-step approach combining lipid profiling and optimized antioxidant extraction. Initially, oil was extracted and analyzed via GC-FID, revealing distinct fatty acid compositions: peel oil was rich in oleic (32.0%), linoleic (21.9%), and α-linolenic acids (9.7%), while seed oil was dominated by oleic (48.0%) and palmitic acids (20.7%), with moderate linoleic content (24.0%). Following defatting, the dried residues were subjected to ultrasound-assisted extraction, which was optimized by response surface methodology (RSM) to maximize the recovery of antioxidant-rich fractions. Peel extracts exhibited the highest total polyphenolic content (105.98 mg GAE/g), FRAP (673.89 μmol AAE/g), and ascorbic acid (17.9 mg/g), while seed extracts showed superior DPPH activity (1071.31 μmol AAE/g). Regression modeling identified optimal conditions for each antioxidant metric, highlighting matrix-specific bioactivity. The combined analysis of lipid and polar fractions underscores the multifunctional potential of avocado residues as sustainable sources of natural antioxidants. These findings support their application in food, cosmetic, and nutraceutical formulations, contributing to circular bioeconomy strategies.