Impact of Extraction Conditions on the Phenolic Composition and Antioxidant Capacity of Grape Stem Extracts

Abstract

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.

Reducing SO2 Doses in Red Wines by Using Grape Stem Extracts as Antioxidants

“…This difference suggests that the antioxidant potential of flavonoids is much greater than that of the stilbenes. In previous work, it was also found that the antioxidant capacity of resveratrol and viniferin is low in comparison to that of quercetin or malvidin-3-glucoside, probably due to structural features of these molecules [ 35 ].…”

“…The grape stem extract was obtained through an extraction using GRAS solvents and stems of grapes from the Mazuelo variety harvested in the 2016 vintage [ 35 ]. Among the different varieties harvested in the 2016 vintage (Mazuelo, Tempranillo, Garnacha, and Graciano), the stems of Mazuelo grapes were chosen because they presented the highest antioxidant capacity and phenolic content.…”

Unravelling the Biological Potential of Pinus pinaster Bark Extracts

“…If the ethanol concentration used on the extractive process is higher (90% v/v), the extracts contain lower amounts of these secondary metabolites. Other research works also reported higher phenolic compounds extraction when intermediate ethanol concentrations are used as solvents for other extraction matrices [32,33]. Jiménez-Moreno and co-workers [32] studied different extraction conditions to obtain grape stem extracts rich in polyphenols, and their results showed that using 50% ethanol the extraction is maximized and the extracts show greater antioxidant activity.…”

“…Other research works also reported higher phenolic compounds extraction when intermediate ethanol concentrations are used as solvents for other extraction matrices [32,33]. Jiménez-Moreno and co-workers [32] studied different extraction conditions to obtain grape stem extracts rich in polyphenols, and their results showed that using 50% ethanol the extraction is maximized and the extracts show greater antioxidant activity. Recently, Tanase et al [34] gathered bibliographic information on the extraction of phenolic compounds from the bark of woody plants and their potential biological activity, showing that several solvents are used to obtain phenolic compounds.…”

“…In this review, the authors report that the mixture of water with ethanol has been widely used to maximize the extraction of these compounds derived from lignocellulosic matrices, such as the Pinus species. This may have to do with the ability of the solvent to penetrate the cell wall, allowing the phenolic compounds to escape [32].…”