Biosynthetic evolution of galloilated polyphenols in Tannat grapes during ripening, potential applications of grape thinning

Abstract

Galloylated flavan-3-ols are a class of polyphenolic compounds present in various plants, including grape seeds. These compounds are formed through the condensation of flavan-3-ols, such as catechins, although the precise mechanism by which gallic acid is incorporated into the molecule remains unclear. The biosynthesis of galloylated flavan-3-ols in grape seeds is a subject of ongoing debate, reflecting the complexity of the metabolic pathways involved in polyphenolic compound production [1]. Flavan-3-ol gallate transferase (F3’5’GT) is a key enzyme in the biosynthesis of galloylated proanthocyanidins (GPCs), which are naturally occurring compounds found in grape seeds and other plant tissues. Research has demonstrated that the expression of the F3’5’GT gene is significantly higher in the seeds of Vitis vinifera cv. Tannat compared to other grape varieties [2]. This elevated gene expression may explain the higher levels of GPCs observed in Tannat grapes.

In this study, we present a comprehensive analysis of galloylated flavan-3-ol profiles by HPLC-MS/MS across three vintages, combined with an assessment of enzyme gene expression at multiple sampling points throughout the ripening process [4]. Our findings reveal a distinct peak in F3’5’GT expression at veraison, consistent with previous data from our research group. Notably, as ripening progresses, there is a significant decline in both enzyme activity and GPC concentration in grapes.

Furthermore, our investigation highlights the influence of environmental factors, such as temperature and light intensity, on F3’5’GT expression, reinforcing prior indications of their regulatory role. While GPCs are not only found in wine but also available through dietary supplements, our findings have important implications for supplement production [4]. They underscore the potential benefits of extracting GPCs from immature grapes obtained during berry thinning, optimizing their use in nutraceutical applications.

References

[1] Boido, E., García-Marino, M., Dellacassa, E., Carrau, F., Rivas-Gonzalo, J. C., Escribano-Bailón, M. T. (2011). Aust. J. Grape Wine Res., 17, 383-393.

[2] Da Silva, C., Zamperin G., Ferrarini, A., Minio, A., Dal Molin, A., Venturini, L., Buson, G., Tononi, P., Avanzato, C., Zago, E., Boido, E., Dellacassa, E, Gaggero, C., Pezzotti, M., Carrau, F., Delledonne, M. (2013). The Plant Cell, 25, 4777-4788.

[3] Dellacassa, E. Biosynthetic dynamics of galloylated polyphenols during the ripening of Tannat grapes: oenological significance and value as functional components in wine. sectoral commission for scientific research (CSIC). Project CSIC 2125.

[4] Fernández-Fernández, A.M., Iriondo-DeHond, A., Nardin, T., Larcher, R., Dellacassa, E., Medrano-Fernandez, A. del Castillo, M.D. (2020. Foods, 9, 1575; https://doi.org/10.3390/foods9111575