Green extraction optimization of antioxidant bioactives from Spondias tuberosa agroindustrial waste

Spondias tuberosa (umbu), a native species of the Caatinga biome, generates about 60% waste during food processing, mainly composed of peel and pulp. These by-products are rich in secondary metabolites, such as flavonoids, tannins, and anthocyanins, with recognized antioxidant activity and potential use as cosmetic raw materials. This study aimed to optimize the extraction of these compounds from umbu residues using a Design of Experiment (DOE). A 2 4 full factorial design was established for screening the preliminary extraction process, assessing the independent variables: extraction method (homogenizer-assisted extraction or ultrasound-assisted extraction), solvent (water or 50% v/v ethanol), residue type (fresh or dried), and extraction time (5 or 15 min). Meanwhile, for optimization, Central Composite Design (2 2 + 2 axials) was applied, in which the independent variables were solvent concentration (ethanol between 22% and 78%) and extraction time (3 and 17 min). The response variables, total solids (TS), DPPH assay, and total flavonoid content (TFC), were evaluated across preliminary and optimization stages. Dried residue and 50% ethanol outperformed other conditions, establishing homogenizer-assisted extraction (HAE) as the most efficient method. During screening, the values ranges from 0 to 23.8 mg/mL (TS), 14%–90% (DPPH), and 1.10–23.50 µg QE/mg (TFC). Optimization shifted these ranges to 9.82–32.71 mg/mL (TS), 82.6%–95.6% (antioxidant capacity), and 8.76–29.76 µg QE/mg (TFC). Overall, these findings highlight umbu residues as a valuable source of bioactives for green cosmetics, promoting agroindustrial by-product valorization and sustainability.