Anthocyanin composition and extraction from Grenache noir (<em>Vitis vinifera</em> L.) vine leaf using an experimental design. I - By ethanol or sulfur dioxide

Abstract

<p style="text-align: justify;"><strong>Aim</strong>: Anthocyanins are water soluble pigments mainly located in grape skin; however, these phenolic compounds are also located in vine leaves. The aim of this work was to identify, quantify and determine for the first time the anthocyanin composition in Grenache noir (<em>Vitis vinifera</em>) leaves.</p><p style="text-align: justify;"><strong>Methods and results</strong>: Five anthocyanins were identified and quantified in Grenache noir leaves by HPLC-UV-MS. Of these, cyanidin-3-<em>O</em>-glucoside and peonidin-3-<em>O</em>-glucoside were the main anthocyanins and represented 44 and 37%, respectively, while delphinidin-3-<em>O</em>-glucoside, petunidin-3-<em>O</em>-glucoside and malvidin-3-<em>O</em>-glucoside accounted for only 6, 5 and 8%, respectively. A multi-factorial design experiment was used to build a mathematical model to estimate the best extraction condition (highest anthocyanin extraction yield from leaf extract) for both SO<sub>2</sub> and ethanol in the aqueous extraction solvent. For SO<sub>2</sub>, the optimal extraction parameters were an extraction time ranging between 5.77 and 6 h, a temperature ranging between 20 and 23.7°C and a concentration of 500 ppm of SO<sub>2</sub> in the aqueous extraction solvent. Using the hydro-alcoholic extraction solvent, the optimal extraction parameters were an extraction time ranging between 3 and 4.37 h, a temperature set at 20°C and an ethanol concentration in the extraction solvent ranging between 32 and 40%.</p><p style="text-align: justify;"><strong>Conclusion</strong>: Only the five mono-glucoside anthocyanins usually detected in grapes have been detected, indentified and quantified in Grenache noir leaves by HPLC-UV-MS. Using a multi-factorial design experiment the optimum conditions for the extraction of these anthocyanins were obtained in hydro-alcoholic solution (i.e., extraction time ranging between 3 and 4.37 h, a temperature set at 20°C and an ethanol concentration ranging between 32 and 40%) and in water with SO<sub>2</sub> (i.e., extraction time ranging between 5.77 and 6 h, a temperature ranging between 20 and 23.7°C and a concentration of 500 ppm of SO<sub>2</sub> in water).</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: Five anthocyanins were detected, identified and quantified in Grenache noir leaves by HPLC-UV-MS and the main anthocyanin were with cyanidin-3-<em>O</em>-glucoside and peonidin-3-<em>O</em>-glucoside. The</p>