Enrichment of polyphenolic compounds from grape leaf extract (Vitis vinifera L.) using macroporous resin and investigating its adsorption kinetics and dynamics

Vitis vinifera L., with the common name grape , is native to Mediterranean region and widely grown in different climatic conditions all over the world. Grape leaves are also a rich source of important polyphenolic compounds that have been recognized for their diverse promising health benefits and therapeutic properties. In this study, the adsorption/desorption process on LXA-10 resin was investigated to enrich polyphenolic compounds in the prepared hydroalcoholic extract of grape leaves. The extract was obtained using ultrasound-assisted probe with water and ethanol (50:50) with an extraction yield of 26.4%. The pH value of the extract for maximum adsorption was optimized at 3.26. According to the findings of this study, the kinetic adsorption fitted well with pseudo-second-order model (R^2 = 0.99). Moreover, the dynamic study revealed the adsorption capacity and required solvent for polyphenolic desorption being 42 mL and six-bed volume (BV), respectively. In the enriched powder, the amount of quercetin-3-O-glucuronide and quercetin-3-O-glucoside increased from the ranges of 19.43 to 45.92 mg.g^-1 and 41.244 to 72.88 mg.g^-1, respectively. The antioxidant activity of enriched polyphenols also increased from 252.37 in the initial grape extract to 408.03 mM iron (II).mg^-1.