Comparison of Accelerated Methods for the Extraction of Phenolic Compounds from Different Vine-Shoot Cultivars

Abstract

Most research on the extraction of high-priced compounds from vineyard/wine byproducts has traditionally been focused on grape seeds and skins as raw materials. Vine-shoots can represent an additional source to those materials, the characteristics of which could depend on the cultivar. A comparative study of hydroalcoholic extracts from 18 different vineyard cultivars obtained by superheated liquid extraction (SHLE), microwave-assisted extraction (MAE), and ultrasound-assisted extraction (USAE) is here presented. The optimal working conditions for each type of extraction have been investigated by using multivariate experimental designs to maximize the yield of total phenolic compounds, measured by the Folin-Ciocalteu method, and control hydroxymethylfurfural because of the organoleptic properties of furanic derivatives and toxicity at given levels. The best values found for the influential variables on each extraction method were 80% (v/v) aqueous ethanol at pH 3, 180 °C, and 60 min for SHLE; 140 W and 5 min microwave irradiation for MAE; and 280 W, 50% duty cycle, and 7.5 min extraction for USAE. SHLE reported better extraction efficiencies as compared to the other two approaches, supporting the utility of SHLE for scaling-up the process. The extracts were dried in a rotary evaporator, reconstituted in 5 mL of methanol, and finally subjected to liquid-liquid extraction with n-hexane to remove nonpolar compounds that could complicate chromatographic separation. The methanolic fractions were analyzed by both LC-DAD and LC-TOF/MS, and the differences in composition according to the extraction conditions were studied. Compounds usually present in commercial wood extracts (mainly benzoic and hydroxycinnamic acids and aldehydes) were detected in vine-shoot extracts.

Comparison of the volatile profile of vine-shoots and oak chips by headspace-gas chromatography-mass spectrometry (HS-GC-MS)

“…2,3,11 Vine-shoots have been characterized as a potential source of phenols usually detected in wines. 18,19 The phenolic composition of extracts from vine-shoots was similar to that observed in extracts from oak wood. The aim of this research was to characterize the volatile fraction formed by heating different varieties of vine-shoots and oak chips.…”

Refining of wine lees and cheese whey for the production of microbial oil, polyphenol‐rich extracts and value‐added co‐products

“…Furthermore, (+)‐catechin (86.48 µg g −1 dry weight) is also a major phenolic compound in the extract of the solid phase of Merlot lees, but it is only contained in the liquid phases of Malagouzia and Merlot lees. Although the valorization of winery by‐products for the separation of high‐value compounds has mainly focused on grape seeds and skins, other streams such as wine lees and vine shoots could be exploited for this purpose creating holistic utilization of winery by‐products.…”

Intestinal anti-inflammatory activity of hydroalcoholic extracts of Phlomis purpurea L. and Phlomis lychnitis L. in the trinitrobenzenesulphonic acid model of rat colitis.

“…Extraction efficiency (expressed as percentage w/w) was 21% for P. lychnitis and 18% for P. purpurea. The polyphenolic content of the extracts was determined by the Folin-Ciocalteu method, as previously described (Delgado-Torre et al, 2012) using acid gallic as standard, and the results were expressed as equivalent to grams of gallic acid per 100 g of extract (%); these values were 12.8% for P. lychnitis and 13.8% for P. purpurea.…”