A Standard Addition Method to Assay the Concentration of Biologically Interesting Polyphenols in Grape Berries by Reversed-Phase HPLC

Abstract

A reversed-phase HPLC method which allows the simultaneous assay of (+)-catechin, (-)-epicatechin, trans-resveratrol, quercetin and quercetin glycosides in grape berries is described. Kromasil 100 served as stationary phase and a gradient of acetic acid, water and methanol was used. The analytical run requires 42 min for complete sample elution. Satisfactory peak resolution was achieved following a novel extraction process and direct injection of a 20 μL sample. The method was used for the analyses of eighteen samples. Linearities were in the range of 0.98 to 0.999 regression coefficient, for all phenolics, while detection limits ranged from 30 μg mL -1 for trans-resveratrol to 1.5 mg mL -1 for (+)-catechin. Recoveries ranged from 95.1 to 98.7% while the method provided good precision, with standard deviations between 3.5 and 6.1%, n=5.

Bioactive non-coloured polyphenols content of grapes, wines and vinification by-products: Evaluation of the antioxidant activities of their extracts

“…The monomers (+)-catechin and (À)-epicatechin were the most abundant, assayed in concentrations ranging from 9.58 to 22.40 mg/100 g and 3.94 to 13.53 mg/ 100 g, respectively. These results correlate well with previous findings on different Greek V. vinifera varieties (Sakkiadi, Georgiou, & Haroutounian, 2007). The flavonol aglycons quercetin and kaempferol were detected only in trace amounts and their quantification was not possible.…”

Grape stem extracts: Polyphenolic content and assessment of their in vitro antioxidant properties

“…The red variety Mandilaria and the white variety Asyrtiko, exhibited the highest concentrations of (þ)-catechin over the two successive vinification seasons. On the contrary, (À)-epicatechin, the isomer of (þ)-catechin, was detected in considerably lower amounts, in contrast to grape tissue and wine assays (Kallithraka, Tsoutsouras, Tzourou, & Lanaridis, 2006;Sakkiadi, Georgiou, & Haroutounian, 2007;Sakkiadi, Stavrakakis, & Haroutounian, 2001). It must be noted however, that previous findings on Merlot variety stems (Souquet, Labarbe, Le Guerneve, Cheynier, & Moutounet, 2000) also determined the presence of (À)-epicatechin in trace amounts, combined with lower concentrations of (þ)-catechin, as compared to our findings.…”

High-Throughput Quantification of 32 Bioactive Antioxidant Phenolic Compounds in Grapes, Wines and Vinification Byproducts by LC–MS/MS

“…The remaining bulk of the phenolic compounds consisted of flavan-3-ol monomers and their glycosides, with prevailing compounds monomers (+)-catechin and (–)-epicatechin, which were found in concentrations ranging, respectively, from 107 to 19 and 181 to 50 mg/kg of dry material, while only traces of the remaining flavonol monomers were detected. These results correlate well with previous findings for grapevines from the Greek islands [ 47 ]. On the contrary, only low amounts of flavonol glycosides were detected with the most abundant being epicatechin gallate and quercetin-3- β -glucoside.…”