Phenolic profile of leaves obtained from autochthonous grapevine cultivars in Isparta Province of Türkiye.

In the current age, nutrition is a widely discussed topic, with foods rich in antioxidants being advocated to support healthy living. Phenolic compounds, which are used in treating various diseases due to their antimicrobial properties, have health-promoting properties. Consequently, producing extracts from grape cultivars with high phenolic content for use in pharmaceuticals, food supplements, and cosmetics is essential for health and the economy. It is well established that grape leaves are rich in phenolic compounds. However, they are not currently utilized to their full potential and are considered mainly waste. This study was conducted in vineyards in Isparta, located in Türkiye's Mediterranean Region, in 2018. The study utilized four autochthonous leaf varieties: two red (Vitis vinifera cv. 'Burdur Dimriti' and Vitis vinifera cv. 'Siyah Gemre') and two white (Vitis vinifera cv. 'Razaki' and Vitis vinifera cv. 'Tilki Kuyruğu'). Total phenolic and flavanol content, as well as the presence of other phenolic compounds, were determined in the grape leaves. The study's findings indicated significant variations in the phenolic content of different grapevine leaf cultivars. Total phenolic content ranged from 3.25 to 7.38 mg CE·g-1, while total flavanol content ranged from 67.66 to 120.24 mg CE·g-1. Phenolic compounds identified in the leaves included gallic acid, ferulic acid, caffeic acid, chlorogenic acid, catechin, quercetin, epicatechin, rutin, p-Coumaric acid, ο-Coumaric acid, protocatechuic acid, hesperidin, vanillin, kaempferol, luteolin, and tannic acid, which were found to vary among the cultivars. Leaves from white cultivars had higher phenolic content than red cultivars. 'Razaki' is the most bioactive cultivar because it has the richest flavonols. 'Razaki' and 'Tilki Kuyruğu' could be an important resource for the development of functional products.