VINE SHOOTS FROM PORTUGUESE VINEYARDS AS A SUSTAINABLE SOURCE OF POLYPHENOLS: EXTRACTION AND CHARACTERIZATION

Abstract

Vine-shoots are an important waste in all viticulture areas that should be re-used with innovative applications [1,2]. The aim of the present study was to characterize the vine shoots from different Portuguese grape varieties (Touriga Nacional - TN and Tinta Roriz - TR) with a view to exploit their potential as a source of phenolic compounds. For this purpose, microwave-assisted extraction (MAE), subcritical water extraction (SWE) and conventional extraction (CE) were tested and compared in order to evaluate their efficiency for the recovery of the main polyphenols in vine shoots. The phenolic composition and antioxidant activity from the obtained extracts were quantified by liquid chromatography with UV detection and spectrophotometric analyses. Among the evaluated extraction methods, the highest yields were obtained by the MAE and SWE techniques. Concerning the differences in the vine shoots varieties, TR is richer in total phenolic compounds (32.9 ± 1.8 mgGAE/g) and total flavonoids (20.7 ± 0.4 mgEE/g), as well as in antioxidant activity. HPLC analysis enable to identify nine different polyphenols, with gallic and caffeic acids, catechin and epicatechin being the main contributors to the phenolic composition.