Phenolic composition and antioxidant potential of Vitis vinífera leaves of six varieties harvested in Northeast of Portugal
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abstract
In the present work it was intended to study the phenolic composition and antioxidant potential of Vitis vinifera leaves of six varieties: white – Carrega Branco, Chardonnay and Viosinho, and red – Bastardo, Tinta Gorda and Touriga Francesa. All varieties were harvested in the NE of Portugal (Trás-os-Montes region). The phenolic composition of aqueous extracts was determined by HPLC-DAD and the antioxidant potential was evaluated by the total reducing capacity (TRC), reducing power, DPPH radical scavenging and hydroxyl radical-scavenging activity assays.
Six phenolic compounds were detected, namely: trans-caffeoyltartaric acid, trans-coumaroyltartaric acid, myricetin-3-O-glucoside, quercetin-3-O-glucoside, quercetin-3-O-galactoside and kaempferol-3-O-glucoside. The sum of these compounds varied between 23918 and 36859 mg/kg extract (dry basis) for the white varieties and 29706 and 43325 mg/kg extract (dry basis) for the red varieties. Regarding TRC, the white and red varieties displayed the following antioxidant capacities: 203 to 550 and 222 to 360 mg GAE/g extract, respectively. Some differences among the six varieties were observed in what concerns the reducing power and DPPH radical scavenging capacity. The highest values of reducing power were observed for Chardonnay (white) and Touriga Francesa (red) varieties. On contrary, the highest DPPH radical scavenging capacities were observed for the Viosinho (white) and Tinta Gorda (red) varieties. All extracts presented hydroxyl radical scavenging activity, being the Carrega Branco (white) variety the one that presented the highest potential.
