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- Antimicrobial activity of pomegranate peel extracts performed by high pressure and enzymatic assisted extractionPublication . Alexandre, Elisabete M. C.; Silva, Sara; Santos, Sónia A. O.; Silvestre, Armando J. D.; Duarte, Maria F.; Saraiva, Jorge A.; Pintado, ManuelaThis study aimed to assess the effect of high pressure (300 and 600 MPa) and enzymatic extraction (pectinase and cellulase) on the phenolic compounds profile, antioxidant capacity and antimicrobial activity of extracts from pomegranate by-products. Antimicrobial activity against eight different strains of pathogenic and contaminant bacteria and against five beneficial bacteria including Lactobacillus and Bifidobacterium strains were determined. The maximum level of total phenolic content, as well as antioxidant capacity were observed at 300 MPa, however enzymatic extraction did not improve the extraction yields. Punicalagin isomers and bis-hexahydroxydiphenoyl-glucoside isomer were the most abundant phenolic compounds found in the extracts. All pomegranate peel extracts demonstrated selective antimicrobial activity against all pathogenic bacteria without affecting beneficial ones. Pressurized extracts presented lower minimum inhibitory concentration against Bacillus cereus and Pseudomonas aeruginosa and lower minimum bactericidal concentration against B. cereus, while, enzymatic extracts presented lower minimum bactericidal concentration for Staphylococcus aureus, Methicillin-resistant Staphylococcus aureus and Listeria monocytogenes. Principal component analyses reveled that antioxidant activity and phenolic compounds content were strongly related with antimicrobial activity. Pomegranate peels extracts obtained by high pressure extraction could so be used as a source of high added-value bioactive compounds for antioxidant and antimicrobial applications.
- Experimental design, modeling, and optimization of high-pressure-assisted extraction of bioactive compounds from pomegranate peelPublication . Alexandre, Elisabete M. C.; Araújo, Paula; Duarte, Maria F.; Freitas, Victor de; Pintado, Manuela; Saraiva, Jorge A.Pomegranate peels are very rich in bioactive compounds, particularly antioxidants, that when properly extracted, may be used for different applications such as food, cosmetics, and pharmaceutics. In this paper, we studied the effect of high-pressure extraction on antioxidant activity and bioactive compounds (total phenolics, tannins, flavonoids, and anthocyanins) of pomegranate peel, using a Box-Behnken design to evaluate the effects of pressure, extraction time, and ethanol concentration to estimate the optimum extraction conditions by response surface methodology (RSM). Individual phenolics, tannins, and anthocyanins were also identified and quantified using the optimum extraction conditions identified by RSM. The results indicated that a quadratic polynomial model could be used to optimize high-pressure extraction of bioactive compounds from pomegranate peel (R (2) higher than 0.90). Ethanol concentration was the variable with higher impact and high pressure increased in average 13% the extraction amount of bioactive compounds. The optimum extraction conditions were similar for all compounds (except for anthocyanins) ranging between 356 and 600 MPa, 32 and 56% of ethanol, and 30 min of extraction time. A pressure of 492 MPa, extraction time of 30 min, and an ethanol concentration of 37% were found to result in the highest amount of the quantified individual compounds. Analysis of variance indicated a high goodness of fit of the used models and adequacy of response surface methodology for optimizing high-pressure extraction. The pomegranate peels are industrial by-products that are rich in bioactive compounds and the results obtained in this work show that high pressure is a promising process for scale up of extraction processes. However, pilot plant tests at higher scale will be necessary to ponder the economic viability of the process.