Isolation and Characterization of Novel Benzoates, Cinnamates, Flavonoids, and Lignans from Riesling Wine and Screening for Antioxidant Activity

Abstract

A German Riesling wine has been fractionated with the aid of countercurrent chromatography. After purification by HPLC, the structures of 101 compounds were established by mass spectrometry and NMR spectroscopy. Seventy-three of the isolated compounds exhibited a phenolic or benzylic structure. Fifty-four compounds were reported for the first time as Riesling wine constituents. New compounds identified in this work included twelve benzoic and cinnamic acid derivatives. In addition to two isomeric (E)-caffeoyl ethyl tartrates, the glucose esters of (E)-cinnamic, (E)-p-coumaric, and (E)-ferulic acid, as well as the 4-O-glucosides of (E)- and (Z)-ferulic acid, have been identified for the first time in Riesling wine. The structures of two additional phenylpropanoids were elucidated as 3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-propan-1-one and 2,3-dihydroxy-1-(4-hydroxy-3-methoxyphenyl)-propan-1-one. Moreover, two ethyl esters, i.e., ethyl protocatechuate and ethyl gallate, as well as the glucose ester of vanillic acid, were newly detected in Riesling wine. Novel representatives in the flavonoid group were dihydrokaempferol, dihydroquercetin, and four dihydroflavonol glycoconjugates, i.e., the 3-O-glucosides of dihydrokaempferol and dihydroquercetin, as well as the 3-O-xyloside and the 3'-O-glucoside of dihydroquercetin. Additionally, six novel lignans, i.e., lariciresinol 4-O-glucoside, three isolariciresinol derivatives, and two secoisolariciresinols, as well as three neolignans were isolated. Structural elucidation of the newly isolated wine constituents is reported together with the determination of their antioxidant activity.

The Evolution of Polyphenols from Grapes to Wines

“…Various types of hydroxybenzoic acids (HBA) have been identified in both grapes and wines, among them parahydroxybenzoic, protocatechuic, vanillic, gallic and syringic acids (Figure 2) [12]. Gallic acid is considered the most important phenolic acid, being the precursor of all hydrolyzable tannins.…”

“…Flavonoids are grouped into several classes, differing from the oxidation degree of the central pyran ring, except of chalcones, including flavanols, flavonols, flavononols, flavones, flavanones, flavanes, anthocyanidins and anthocyanins, chalcones and dihydrochalcones ( Figure 3I) [12].…”

Wine and grape polyphenols—A chemical perspective

“…Hydroxycinnamic acids (HCA) are one of the most representative classes of phenolic acids found in both grapes and wine (Baderschneider & Winterhalter, 2001). para-Coumaric, caffeic, ferulic and sinapic acids (Fig.…”

Phenolic derivatives and other chemical compounds from Cochlospermum regium

“…All NMR experiments were performed on a Bruker DPX-300 instrument ( 1 H 300 MHz, 13 C 75 MHz) using CDCl 3 as a solvent and tetramethylsilane (TMS) as an internal standard. The chemical shifts are reported in δ units and coupling constants (J) in Hz.…”