POLYPHENOL ACCUMULATION IN VITIS SPECIE LEAVES DURING THE VEGETATIVE SEASON

Grapevines produce a large number of secondary metabolites and the most abundant are polyphenols. In grapevine vegetative organs, polyphenols represent the main actors of plant adaptation to diverse environmental conditions. Leaves, in particular, are the most exposed part of the plant and leaf polyphenols help the plant to cope with environment and with biotic and abiotic stressors. Besides, grapevine leaves are commonly used as a food product, both in fresh and brined preparations, representing a potential source of natural bioactive phenolic compounds. The knowledge about phenolic compounds accumulation in various Vitis species leaves is scarce and the accumulation trend during the vegetative season has not been fully investigated. We have undertaken a study regarding the quantification and identification of main polyphenols in the healthy leaves of a number Vitis species during the vegetative season. Moreover, to widen knowledge on tissue specific polyphenols, leaves were divided into two parts, blades and veins. Leaf extract polyphenols were analyzed spectrophotometrically and by targeted analytical approach using HPLC-DAD and HPLC-ESI-MS. In this work we present data on Vitis amurensis (Asian specie) and Vitis berlandieri (American specie), known to have a limited susceptibility to some pathogens. In leaf blades concentration of hydroxycinnamoyl derivatives decreased during the vegetative season, regardless the specie and similarly to what was assessed in Vitis vinifera leaves; on the contrary, flavonol and proanthocyanidin accumulation were different among species. The concentration of flavan-3-ols was higher in both non vinifera species than in vinifera, moreover Vitis amurensis showed the highest concentrations of total polyphenols and flavonols. In Vitis berlandieri leaves vitexin, a glycosylated flavone with anti-microbial and anti-viral capacity, was detected and identified for the first time.