Grapevine leaves as a source of natural antioxidants
2008
Amarowicz, R. | Narolewska, O. | Karamac, M. | Kosinska, A.,Polish Academy of Sciences, Olsztyn (Poland). Inst. of Animal Reproduction and Food Research, Div. of Food Science | Weidner, S.,University of Warmia and Mazury, Olsztyn (Poland). Dept. of Biochemistry
The crude extracts of phenolic compounds were obtained from grapevine leaves using 80 percent acetone and 80 percent methanol (v/v). The content of total phenolic and condensed tannins was determined using Folin and Ciocalteau's phenol reagent, vanillin/HCl reagent, and protein precipitation method. The antioxidant properties of the extracts were investigated using the total antioxidant activity (TAA), DPPH radical scavenging activity and reducing power. The content of individual phenolic acids was determined using the HPLC method. The content of total phenolics in grapevine leaves and their extracts determined in this study was high (257 mg/g acetone extract and 232 mg/g methanolic extract). The content of condensed tannins in acetone extract was higher than in the methanolic one. Antiradical activity of both extracts against DPPH radical and reducing power were similar and strong. The acetone and methanolic extracts exhibited TAA of 1.37 and 1.44 mmol Trolox/g, respectively. Vitis vinifera leaves extracts were observed to contain gallic, caffeic, and p-coumaric acid. Gallic acid was a dominant phenolic acid. The majority of phenolic acids were found in the form of esters
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