Enhanced phytochemical composition and biological activities of grape (Vitis vinifera L.) Stems growing in low altitude regions

Abstract

The influence of altitude (ranging from 120−730 m) on different grape stem samples of the Região Demarcada do Douro (Portugal), upon their chemical and biological properties, was studied over two consecutive vintages.Grape stem samples revealed a significantly higher phenolic concentration at lower altitude regions (ranging from 78.02 ± 0.70–103.49 ± 4.36 mg of Gallic Acid g−1 in contrast to concentrations between 32.35 ± 3.35 and 88.32 ± 1.75 mg of Gallic Acid g−1), and, consequently, higher antioxidant activities (0.73 ± 0.00 - 0.85 ± 0.04 against 0.24 ± 0.06 - 0.75 ± 0.01 mmol Trolox g−1) regardless of the vintage. Furthermore, and as expected, a year-to-year variation was verified as there was a significant increase of these parameters from 2017 to 2018, except for the antimicrobial activity, which demonstrated not to be severally affected by the climate conditions of each year of study, however, the high altitude generally induced a lower activity in the samples, which was confirmed by the multivariate analysis.Altitude, along with the season, demonstrated a major impact on secondary metabolites of grape stems, inducing their concentrations at low altitude sites, related to higher environmental stress levels, such as, precipitation, whereby these factors must always be taken into consideration in future industrial applications.