In the context of sustainable viticulture and circular bioeconomy, this study investigated the valorization potential of vineyard pruning by-products (leaves), gathered during two seasonal defoliation events across eight Vitis vinifera varieties (Vinhão, Touriga Nacional, Padeiro de Basto, Alvarinho, Sauvignon Blanc, Loureiro, Moscatel Galigo Branco and Arinto).
Removing leaves from plants before they naturally dry out and fall is a useful wine-growing practice for controlling yield and improving grape quality. This technique can reduce the number and compactness of bunches and improve the cold resistance and composition of grapes. However, the time of year and the amount of defoliation are crucial, since excessive leaf removal can negatively affect vine performance.
This study aimed to evaluate the polyphenolic composition of two defoliation timings (May and June) from hydroalcoholic extracts of dried leaves.
Identification and quantification of catechin, epigallocatechin gallate (EGCG), gallic acid, quercetin, rutin, ellagic acid and 3-O-methylellagic acid (3-MEA) were performed using high-performance liquid chromatography (HPLC) with a diode array detector (DAD).
Based on the obtained results, the 50% ethanol solution resulted in a higher content of phenolic compounds for vine leaves in the second defoliation. In the leaves of the early defoliation, the phenolic composition showed the main accumulation of gallic acid and catechin, while the content of quercetin and 3-MEA was higher in the second defoliation.
Higher contents of quercetin were obtained in leaf extracts from the Vinhão variety (53 mg/100g). 3-MEA, an ellagic acid derivative, was found exclusively in leaves collected during the second defoliation, revealing significant differences between cultivars.
This research provides information about the phenolic profile evolution of vineyard pruning by-products (leaves), contributing to a more environmentally friendly and waste-reducing food system. Valorization of this pruning waste presents a possible alternative to disposal, in line with sustainable and health-promoting food innovation goals and enhancing a circular economy.
