Hydroalcoholic extraction of polyphenol compounds assisted by a microwave digester from residues of vine pruning

The interest on the valorization of by-products from the wine industry has significantly increased over the years due to environmental and economic issues1 . Among these by-products, residues obtained from the pruning of vine are lignocellulosic materials with an important percentage of extractives composed by bioactive compounds as phenolic compounds13. In this context, the objective of this work was the extraction optimization of phenolic compounds from vine pruning residues (VPR) using microwave heating. For that, the variables studied were: temperature (60-120 °C), extraction time (5-40 min) and ethanol concentration (0-60 %) at fixed solid/solvent ratio of 40:1 (mL/g). The Total phenolic contents were quantified following the Folin-Ciocalteu method. The phenolic compounds were also identified and quantified by UHPLC. In addition, antioxidant activity of VPR extracts was determined by the following methods: FRAP, DPPH and ABTS expressed as Trolox equivalents (TE). For the extraction of total phenolic compounds, the most significant variable was the percentage of ethanol. At optimized conditions (120°C, 5 min, and 60% ethanol-water) 2.26 g/100g of phenolic compounds were obtained. Under theses conditions, the phenolic acids, stilbenes and flavanols were found in higher concentration achieving a concentration of 185.15 and 118.15 mg per 100 g of VPR for ellagic acid and apigenin, respectively. The antioxidant activity was 7.53, 4.33 and 3.41 g per 100 g of VRP for FRAP, DPPH and ABTS, respectively, which can be positively compared with values reported in literature 3,4 . This work shows an environmentally friendly extraction technique to obtain bioactive compounds which could improve the integral valorization of VPR. [1] Jesus et al. (2017) J Clean. Prod. 168: 74-86. [2] Sánchez-Gómez et al. (2017) Ind. Crops Prod. 2017, 97, 120127. [3] Gullón et al. (2017) Ind. Crops Prod. 2017, 107, 105113. [3] Cebrián et al. (2017) Ind. Crops Prod. 2017, 109, 730736 [4] Karacabey et al. (2012) Food Bioprocess Technol. 5: 359-371.