High-Resolution MS/MS Characterization of Vine Leaf Flavonols and Flavanonols of Fungal-Resistant Varieties

In viticulture, major challenges such as the effects of climate change and the use of phytochemicals to control grapevine pathogens can be mitigated by using vine varieties that are highly tolerant to fungal diseases and suitable for cultivation in hot and dry areas. There is significant interest in identifying natural sources of phenolic compounds due to their biological activities. Numerous flavonoids have been identified in various vine plant tissues (roots, wood, canes, stems, and leaves), with flavonols and flavanonols being the predominant glycosidic derivatives in leaves. These compounds were characterized by UHPLC/QTOF in the leaves of two resistant vine varieties. Using targeted and MS/MS suspected target approaches, 42 flavonoids were identified, 18 of which were detected in vine leaves for the first time. Cabernet Volos leaves exhibited higher biosynthesis of rutinoside derivatives, such as rutin and kaempferol-rutinoside, while Sauvignon Rytos leaves were richer in kaempferol, quercetin, syringetin, and isorhamnetin glucosides. No unique flavonols/flavanonols that could serve as variety markers were identified. This study provides the first insights into the leaf composition of fungal-resistant vine varieties, which is largely unexplored and warrants further research.