Polyphenolic diversity in Vitis sp. leaves

We identified and quantified the main constitutive polyphenolic compounds of the leaves of seven Vitis species and of one interspecific cross, analysing leaf blades and veins separately, to spread light on the strategic localization of polyphenols in leaf tissues. To the best to our knowledge, the main leaf constitutive polyphenols of V. candicans, V. coignetiae, V. vinifera sylvestris and Börner were never described. V. riparia and V. rupestris (belonging to the same botanical series of Ripariae) displayed similar flavan-3-ol and dimeric proanthocyanidin concentration and similar percentage incidence of caftaric acid over total phenolic acids. V. riparia distinguished respect to the other genotypes for its high flavonol content, the highest percentage incidence of myricetin derivatives and an important diversification in the type of accumulated flavonol. V. berlandieri (series Cinereae) and Börner (hybrid of V. riparia x V. cinerea) accumulated low amounts of flavonol-glucosides comparing to the other species, but they showed a wide profile diversification, as well. However, it was V. v. sylvestris, the wild ancestor of Vitis vinifera subsp. sativa that displayed the widest flavonol profile diversification. The differences in the flavonol profile could be related to the genus Vitis evolution: in fact, with domestication, the flavonoid biosynthetic pathway underwent a progressive simplification; for this, the highest flavonol diversity found in Vitis v. sylvestris is probably a demonstration of its reduced or nil level of domestication. V. amurensis, known for its cold tolerance and resistance to downy mildew, anthracnose and white rot, markedly differentiated respect to the other genotypes, for its high concentration of polyphenols, particularly of vein flavonols and flavanonols. Moreover, V. amurensis leaves generally presented a constantly high concentration of constitutive polyphenols throughout the season that probably contributes to protect against adverse environmental condition. The abundance of polyphenols in V. amurensis leaves emphasizes that this species is a source of natural bioactive compounds that could find application for nutraceutical and pharmacological uses. V. berlandieri and Börner markedly distinguished respect to the other studied species for their exclusive capability to accumulate flavones (mainly orientin, isoorientin, vitexin and isovitexin) in blades and in veins, in considerable amounts. Knowledge about these subjects could contribute to shed light on the identification of species-related molecules involved in the plant-defense mechanisms, to the chemotaxonomy of the genus Vitis, to the possibility of identifying specific natural bioactive compounds to use in plant-based preparation for nutraceutical, cosmetic, feed/food-additive purposes.