Abstract This study aimed to optimize the extraction solvents for Bordo grape (Vitis labrusca) seeds by response surface methodology regarding to the antioxidant activity (AA) and trans-resveratrol content. Fatty acids (FA) and AA of the oil obtained by pressing cold method were also determined. The extraction optimization was determined by the statistical simplex-centroid mixing scheme, enabling the analysis of solvents effects (water, ethanol and acetone) and their mixtures on the responses. AA was performed by DPPH, ABTS and FRAP methods, and by total phenolic compounds and flavonoids. FA were determined by GC and trans-resveratrol by HPLC. The extracts containing ternary fraction of solvents showed greater AA, increasing about 20 times compared to pure solvent. The composition that showed the best response ranged between 45-48% of water, 14-20% of ethanol and 35-38% of acetone for both grape seeds, with polarity ranged from 0.705 to 0.706. The oil from seeds showed high concentrations of PUFA, particularly linoleic acid. The optimized extraction method improved the use of this residue as a potential antioxidant source for food industry.

Abstract The presence of PUFA (polyunsaturated fatty acids) in cow milk, including conjugated linoleic acids (CLA) isomers, makes milk susceptible to lipid oxidation, and may lead to the formation of volatile products responsible for a rancid smell. Consequently, including natural antioxidants in the diet of dairy cattle can assist in preventing lipid oxidation. In this study, soybean oil (a source of PUFA) and different ethanolic extracts of Brazilian propolis were included in the cows' feed, and the antioxidant activity and lipid oxidation of the animals' milk was assessed. Antioxidant activity was analyzed using the DPPH method, potassium ferricyanide reduction and chelating ability. Total phenolic compounds and flavonoids were also determined. Lipid oxidation was assessed by determining conjugated dienes and the production of aldehydes (propanal, pentanal, hexanal and octanal). Increased antioxidant activity was seen in the samples of milk from cows receiving propolis. Similarly, the addition of ethanolic extract of propolis to the diet of dairy cattle increased milk protection for two treatments with propolis against lipid oxidation in terms of production of propanal and hexanal. These results confirm the positive effect of applying this natural additive to the diet of lactating cows, improving the nutritional quality of the milk produced.

Resumo As atividades antioxidante e antibacteriana, e a toxicidade de produtos naturais podem mudar de acordo com a variedade vegetal, bem como a parte da planta que é analisada. Neste estudo, foram analisadas cascas, polpas e sementes de quatro variedades de abacate (Quintal, Fortuna, Margarida e Hass) no que tange às propriedades antioxidantes e antibacterianas, e à toxicidade. Existem poucos estudos na literatura comparando essas três primeiras variedades. A atividade antioxidante foi medida utilizando-se os métodos DPPH (2,2-diphenyl-1-picrylhydrazil), ABTS [2,2'-azino-bis- (3-ethylbenzothiazoline-6-sulfonic acid)] e FRAP (Ferric Reducing Ability Power), juntamente com o conteúdo de compostos fenólicos e flavonoides. A análise de componentes principais foi aplicada para testes antioxidantes. A atividade antibacteriana contra patógenos alimentares foi avaliada pelos testes de concentração inibitória mínima e concentração bactericida mínima. A toxicidade foi avaliada contra Artemia salina e também pela atividade hemolítica. O extrato etanólico da casca da variedade Quintal apresentou a maior atividade antioxidante e antibacteriana. Este mesmo extrato não mostrou toxicidade nos testes preliminares e mostra grande potencial de aplicação na indústria de alimentos como um aditivo alimentar.

Abstract The antioxidant and antibacterial activity and toxicity of natural products can change according to plant variety, as well as the part of the plant which is analyzed. In this study, peel, pulp and seed of four avocado varieties (Quintal, Fortuna, Margarida, and Hass) were analyzed for antioxidant and antibacterial properties and toxicity. There are few studies in the literature comparing these three first varieties. Antioxidant capacity was measured using the DPPH (2,2-diphenyl-1-picrylhydrazil), ABTS [2,2'-azino-bis- (3-ethylbenzothiazoline-6-sulfonic acid)], and FRAP (Ferric Reducing Ability Power) methods, along with the content of phenolic compounds and flavonoids. Principal component analysis was applied for antioxidant tests. Antibacterial activity against food pathogens was assessed by the minimum inhibitory concentration and minimum bactericidal concentration tests. Toxicity was evaluated against Artemia salina and also by hemolytic activity. The ethanolic extract of Quintal variety peel presented the greatest antioxidant and antibacterial activity. This same extract showed no toxicity in the preliminary tests, and shows great potential for food industry application as an additive.