The Effects of Preservation Methods of Grapevine Leaves on Total Phenols, Total Flavonoids and Antioxidant Activity

Abstract

Preservation methods may affect total phenols, flavonoids contents, and antioxidant capacity of many vegetables and fruits. These effects may cause degradation of antioxidant compounds, formation of new products, or destruction of the active metabolites. This study investigated the effects of different preservation methods, such as canning and freezing, on total flavonoids, total phenols, and antioxidant activity on grapevine leaves, which can be consumed either as medicine or food. Phytochemical screening was performed by using standard analytical methods; antioxidant activity was assayed by using 2, 2-diphenyl-1-picryl-hydrazyl-hydrate reagent method; and total flavonoids and total phenols content were determined by using the rutin reference standard method and by Folin-Ciocalteu’s method, respectively. The phytochemical content of all the studied grapevine leaf extracts were same. Fresh leaf extract showed the highest antioxidant capacity as well as total phenols and flavonoids contents. This was followed by the frozen leaf extract, while the canned leaf extract showed lower antioxidant capacity and reduced phenolic and flavonoids contents. Canning and freezing preservation methods of these leaves had no deleterious effects on total antioxidant capacity as well as total phenols and flavonoid contents. Therefore these methods can be used for preparing nutraceutical, cosmeceutical, and pharmaceutical supplements. However, the preservation of V. vinifera leaves by canning is economically and environmentally favored over freezing. In addition the storing, handling, and maintenance of canned leaves is easier than fresh and frozen leaves.