Abstract The use of whole fruits and vegetables, including the parts usually discarded during food processing, is an alternative to reduce the quantity of agro-industrial wastes. This study aimed to evaluate papaya seeds' nutritional and bioactive potential in two ripening stages. The seeds in the stages 0 and 5 of ripening were analyzed regarding their physicochemical composition, while the oil and the hydroethanolic extracts of the seeds were studied in respect of their fatty acid profile, total phenolic content, antioxidant and antimicrobial capacities. The seeds in both ripening stages show good nutritional quality, because they are sources of protein, fiber, and oil. The oil extracted from the seeds is majorly composed by oleic fatty acid (around 70%). The seeds extracts did not present antimicrobial activity against Salmonella enteritidies, Escherichia coli e Staphylococcus aureus. However, they presented high contents of total phenols (58.1 and 36.0 mg GAE⁄g dry extract for seeds in the ripening stages 0 and 5, respectively) and good antioxidant capacity, according to the FRAP and ABTS●+ assays. Papaya seeds provide nutrients and bioactive compounds and their use is a promising alternative to reduce the disposal of food wastes in the environment.

Resumo Folhas de oliveira contêm oleuropeína, um composto fenólico conhecido por seu potencial antioxidante, antimicrobiano, anti-inflamatório, entre outros. Este trabalho teve como objetivo estudar a extração da oleuropeína, utilizando solvente hidroalcoólico. Folhas de oliveira (FO) foram maceradas a 25 °C com um solvente (S), formado por uma mistura de etanol e água (70:30 v/v), nas proporções FO:S iguais a 1:8, 1:6 e 1:3, em massa, com ou sem a presença de ácido acético. Observou-se que o maior teor de oleuropeína no extrato liofilizado (18 g/100 g, aproximadamente) foi obtido no procedimento utilizando a razão FO:S = 1:3, com ácido acético. Por fim, foi realizado um teste para verificar o efeito do extrato liofilizado sobre o tempo de indução em amostras de azeite de oliva extravirgem e refinado, verificando-se um aumento de três e duas horas, respectivamente. Concluiu-se que é possível obter extratos de folhas de oliveira utilizando solventes renováveis e que a oleuropeína pode atuar como um antioxidante natural no azeite, melhorando sua estabilidade oxidativa.

Abstract Olive leaves contain oleuropein, a substance known for its antioxidant, antimicrobial and antiinflammatory potentials, amongst others. The objective of this work was to study the extraction of oleuropein using a hydroalcoholic solvent. Olive leaves (OL) were macerated at 25 °C with a solvent (S) consisting of a mixture of ethanol and water (70:30 v/v), with OL:S mass ratios equal to 1:8, 1:6 and 1:3, with or without the presence of acetic acid. The highest oleuropein content found in the freeze dried extract (approximately 18 g/100 g) was obtained from the procedure using an OL:S ratio = 1: 3, in the presence of acetic acid. Finally, a test was carried out to verify the effect of the freeze dried extract on the induction time in samples of extra-virgin and refined olive oil, and increases of 3 and 2 hours, respectively, were observed. It was concluded that it is possible to obtain olive leaf extracts using renewable solvents, and that oleuropein can act as a natural antioxidant in olive oil, improving its oxidative stability.