Short Lecture "Chemical characterisation of glucosyl- hydroxydihydrochalkonesulfites occurring in red grape pomace extract and red wine"

Grape pomace is a highly abundant side-product of winemaking. Due to their high content of different classes of bioactive polyphenols, grape pomace extracts are widely used for pharmaceutical, functional food and cosmetic purposes [1]. In an anthocyanin-enriched grape pomace extract, hitherto unknown sulfur- containing compounds were detected by LC-HRMS analysis. Fractionation of the extract by various chromatographic methods allowed the preparative isolation of four compounds. 1D- and 2D-NMR spectroscopy and HRMS allowed their structural elucidation as new glucosyl- hydroxydihydrochalkonesulfites ([Fig. 1]), differing in substitution pattern at position 6 of the sugar moiety. The fact that the isolated compounds were easily degraded to respective anthocyanins in the presence of acid indicates that they are structurally closely linked to this compound class. The compounds were most likely formed during grape pomace extraction which had been performed under sulfite addition. However, it remains to be clarified, from which progenitors and by which mechanism they are formed. Interestingly, some of the newly isolated compounds could also be detected when various commercially available red wines were analysed by LC-HRMS analysis, indicating that they are also formed during red wine production and are constituents of commercially available red wine.

Fig. 1 Structures of compounds isolated from red grape pomace extract.

Acknowledgements NAWI Graz is thanked for supporting Central Lab Environmental, Plant & Microbial Metabolomics. We thank Breko GmbH & Grap’SUD Group for providing the grape pomace extract.

 

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• References

• 1 Anda M, Popitiu M, Fierascu I. et al. Grapevine Wastes: A rich source of antioxidants and other biologically active active compounds. Antioxidants 2022; 11: 393

Publication History

Article published online:
16 November 2023