Open Access
Impact of extraction conditions on the phenolic composition and antioxidant capacity of grape stem extracts
(MDPI, 2019) Jiménez Moreno, Nerea; Volpe Sainz, Francesca; Moler Cuiral, José Antonio; Esparza Catalán, Irene; Ancín Azpilicueta, Carmen; Zientziak; Estatistika, Informatika eta Matematika; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Estadística, Informática y Matemáticas; Gobierno de Navarra / Nafarroako Gobernua
The use of grape stems for the extraction of bioactive compounds to be used in the pharmaceutical, food, and cosmetic industries is a promising objective. The aim of this work is to determine the influence of the different extraction conditions (temperature, ethanol concentration, and ratio of sample/solvent) on phenolic composition and antioxidant capacity of Mazuelo stem extracts. In general, the ethanol concentration of the extraction solvent was the factor that had the greatest influence on the extraction of different bioactive compounds. The greatest content of total phenolic compounds and the highest antioxidant activity of the extracts were obtained with 50% ethanol and at 40 °C. The most abundant compound found in the different extracts obtained from Mazuelo grape stem was (+)-catechin, but appreciable concentrations of gallic acid, a quercetin derivative, and stilbenes (trans-resveratrol and trans-ε-viniferin) were also extracted. Quercetin and malvidin-3-glucoside showed the highest correlation with the antioxidant capacity of the extracts, while stilbenes did not present such relation. The maximum concentration of gallic acid was extracted with water but the extraction of most of the compounds was maximum on using 50% ethanol. Consequently, the selection of the extraction method to be used will depend on the particular compound to be extracted in greatest quantity.
Open Access
Phenolic composition of grape stems from different Spanish varieties and vintages
(MDPI, 2021) Esparza Catalán, Irene; Moler Cuiral, José Antonio; Arteta, Maite; Jiménez Moreno, Nerea; Ancín Azpilicueta, Carmen; Zientziak; Estatistika, Informatika eta Matematika; Institute for Advanced Materials and Mathematics - INAMAT2; Ciencias; Estadística, Informática y Matemáticas; Gobierno de Navarra / Nafarroako Gobernua
Grape stems are a by‐product from the wine industry that has been underused to date despite having great potential for the agro‐food and cosmetic industries. The aim of the present work was to characterize grape stem extracts obtained from different grape varieties from two vintages (2016 and 2018). Both spectrophotometric and chromatographic methods were used for sample characterization. The results showed that there exist significant differences in antioxidant activity, total phenolic content (TPC) and total flavonoid content (TF) among grape stems from different varieties in each vintage and from different vintage for the same variety. Catechin was the most abundant phenolic compound in all extracts from both vintages. In general, Mazuelo presented higher concentration values of the different phenolic compounds than Garnacha and Tempranillo. It was observed than extreme temperatures and accumulated precipitations, which were higher in the 2016 vintage, had an impact on the polyphenol synthesis. Therefore, grape stems from the 2018 vintage presented higher TPC and TF values than their counterparts from the 2016 vintage. In addition, the statistical analysis revealed that the influence of environmental factor such as light, temperature and precipitations have different impact on the synthesis of polyphenols depending on the family of the specific compound.

Moler Cuiral, José Antonio

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