α-Glucosidase Inhibitory Activity of Tannat Grape Phenolic Extracts in Relation to Their Ripening Stages

Auriane Dudoit (1) , Nawel Benbouguerra (1) , Tristan Richard (2) , Ruth Hornedo-Ortega (2) , Josep Valls-Fonayet (2) , Gaëlle Coussot (3) , Cédric Saucier (1)

1 SPO - Sciences Pour l'Oenologie
2 ISVV - Institut des Sciences de la Vigne et du Vin [Villenave d'Ornon]
3 IBMM - Institut des Biomolécules Max Mousseron [Pôle Chimie Balard]

The present study aimed to screen grape extracts as novel α-glucosidase inhibitors to prevent type-2 diabetes and hyperglycemia. The total polyphenol content (TPC) was measured by Folin-Ciocalteu assay and the stilbene, anthocyanin and flavan-3-ol compounds were measured by Ultra High-Performance Liquid Chromatography coupled to Mass Spectrometry (UHPLC-MS). The α-glucosidase inhibitory of seed and skin Tannat grape extracts at four ripening stages were investigated. The highest TPC values were measured in seeds at the “veraison stage” (65.29 ± 5.33 g of Gallic Acid Equivalent (GAE) per kilogram of Fresh Weight (FW)). This was in accordance with the high flavan-3-ol contents measured for these two extracts (43.22 ± 2.59 and 45.45 ± 6.48 g/kg of seeds FW, respectively). The skin and seed extracts at the first stage of ripening exerted strong α-glucosidase inhibition, exceeding 95% (p < 0.05). A high linear correlation (R = 0.723, p ≤ 0.05) was observed between flavan-3-ol contents and the α-glucosidase inhibitory activity. The stilbene contents and this activity were moderately to strongly anti-correlated (R = –0.828, p ≤ 0.05 for trans-resveratrol). The enzyme kinetic studies revealed a mixed type of inhibition. This study brings promising results for the therapeutic potential of seed and skin Tannat grape extracts as a functional food product with anti-diabetic activity.

Mots clés: anti-diabetes; grape; ripening; α-glucosidase; phenolic compounds

Domaines: Chimie thérapeutique; Endocrinologie et métabolisme

Auriane Dudoit, Nawel Benbouguerra, Tristan Richard, Ruth Hornedo-Ortega, Josep Valls-Fonayet, et al.. α-Glucosidase Inhibitory Activity of Tannat Grape Phenolic Extracts in Relation to Their Ripening Stages. Biomolecules, 2020, 10 (8), pp.1088. ⟨10.3390/biom10081088⟩. ⟨hal-02948324⟩