Flavan-3-ols in Vitis seeds: Their extraction and analysis by HPLC-ESI-MS/MS.

An orthogonal L1643 × 22 test design was applied to select the optimum conditions for extracting flavan-3-ols in grape seeds. Highest yield of flavan-3-ols was achieved with 80% methanol, a ratio [1:30 (g/mL)] of sample-to-solvent, sonication for 20 min, and extraction at 25 °C for 12 h in darkness. The optimized analytical method for HPLC separation was a multistep gradient elution using 1% formic acid (A) and acetonitrile containing 1% formic acid (B), at a flow rate of 0.6 mL/min in 36 min. Moreover, fourteen flavan-3-ols were separated and identified using HPLC-ESI-MS/MS, including four monomers ((+)-catechin, (-)-epicatechin, epigallocatechin gallate and epicatechin gallate) and ten oligomers (three dimers, four trimers, two tetramers and one pentamer). The optimized method was used to determine flavan-3-ols content and compositions among ten representative cultivars. The new wine grape - Beihong, had higher flavan-3-ols content and polymerization than classic wine grapes - Cabernet Sauvignon, Merlot, Semillon and Riesling.

Resveratrols in grape berry skins and leaves in vitis germplasm.

BACKGROUND: Resveratrol is an important stilbene that benefits human health. However, it is only distributed in a few species including grape and is very expensive. At present, grape has been an important source resveratrol. However, the details are scarce on resveratrol distribution in different Vitis species or cultivars. METHODOLOGY/PRINCIPAL FINDING: The composition and content of resveratrols were investigated by HPLC for assessing genotypic variation in berry skins and leaves of 75 grape cultivars, belonging to 3 species and 7 interspecific hybrids. Trans-resveratrol, cis-piceid and trans-piceid were detected in berry skins and leaves, but cis-resveratrol was not. Resveratrol content largely varied with genetic background as well as usage. In most cultivars, total resveratrol including the above three compounds was higher in berry skins than leaves. In berry skins of most cultivars and leaves of almost all cultivars, cis-piceid was the most abundant resveratrol; trans-resveratrol and trans-piceid were minor components. Some specific cultivars were found with extremely high levels of trans-resveratrol, cis- piceid, trans-piceid or total resveratrols in berry skins or leaves. In skins and leaves, rootstock cultivars had a higher content of total resveratrols, and the cultivated European type cultivars and their hybrids with V. labrusca had relatively low totals. There were no significant correlations of the amounts of total resveratrols or any individual resveratrol between berry skins and leaves. All 75 cultivars can be divided into four groups based on the composition of resveratrols and their concentration by principal component analysis. CONCLUSION: Resveratrol content of grape berries and leaves varied largely with their genetic background and usage. Rootstock cultivars had a higher content of total resveratrols than the other germplasm. Total resveratrols were lower in leaves than berry skins in most cultivars. Cis-piceid was the most abundant resveratrol in most cultivars, and trans-res and trans-pd were minor components.

Resveratrols in Vitis berry skins and leaves: their extraction and analysis by HPLC.

An orthogonal L(36) (6)(5) test design was applied to select the optimum conditions for extracting resveratrols from grape berry skins and leaves. Solvent choice was the most important factor in the extraction of resveratrols, and mixed methanol and ethyl acetate [50:50 (v/v)] had much higher extraction efficiency than the other five solvents tested. For extracting resveratrols, 1g of berry skins or leaf tissue extracted in 10 mL methanol and ethyl acetate [50:50 (v/v)] for 24h at 25°C in darkness was the optimized extraction condition. The optimized analytical method for HPLC was a multi-step gradient elution using acetonitrile and water. The optimized method was used to determine resveratrols among three different cultivars. The cultivar 'Zhi 168' had the highest total resveratrols in berry skins while 'Saint-Emilion' had the lowest resveratrols. The resveratrol content of 'Beta' was between that of 'Zhi 168' and 'Saint-Emilion'.