Recently, fish consumption has been increasing; subsequently, the number of by‐products has also increased. However, generated residues are frequently discarded, and an appropriate management is necessary to properly use all fish by‐products. Fishery by‐products are well known for their content of bioactive compounds, such as unsaturated fatty acids, amino acids, minerals, peptides, enzymes, gelatin, collagen, and chitin. Several studies have reported that fishery by‐products could provide significant properties, including antioxidant, antihypertensive, antimicrobial, anti‐inflammatory, and antiobesity. Consequently, fish discards are of considerable interest to different industrial sectors, including food, nutraceuticals, medical, and pharmacology. In the food industry, the interest in using fishery by‐products is focused on hydrolysates as food additives, collagen and gelatin as protein sources, chitin and chitosan to form edible films to protect food during storage, and oils as a source of Omega‐3 and useful as antioxidants. Although different studies reported good results with the use of these by‐products, identifying new applications in the food sector, as well as industrial applications, remains necessary.

Sinami (Oenocarpus mapora H. Karst), a native fruit found in the Amazon region of South America, has high nutritional value and is rich in lipids. However, the processing of sinami generates a large volume of agro-industrial waste, mainly composed of seeds. Our research comprises a proximal analysis of the sinami seed and its phenolic compounds and their antioxidant activity. The chemical analysis revealed high moisture but low protein, fiber, and lipid content. Furthermore, the extracts showed high in vitro antioxidant activity against 1,1-diphenyl-2-picrylhydrazyl radical IC₅₀ (0.34 ± 0.001 mg/mL) and ABTS IC50 (0.10 ± 0.0002 mg/mL) free radicals. Based on this previous assessment, a gel exfoliant was developed. Since sinami seed powder is a novel ingredient, different formulations were evaluated to determine future incorporation into the cosmetic market. The best exfoliant gel prototype was studied under normal and stressed conditions (40 °C) for 3 months, maintaining a pH value of 5.25 and final viscosities of 700–800 mPa.s and 600–500 mPa.s under normal and stress conditions, respectively. Although unexplored, the sinami seed could be considered a raw material for the cosmetic industry.