RESUMEN
Gallotannins are phenolic natural products containing galloyl moieties connected to polyhydric alcohol cores, e.g., D-glucose. Some gallotannins are reported to have antidiabetic properties, such as α-glucosidase inhibitory activity. In this study, fourteen unnatural gallotannin derivatives with 1,5-anhydroalditol and inositol as the cyclic polyol cores were synthesized to investigate how their structures affected antioxidative and α-glucosidase inhibitory activities. Tannic acid demonstrated the most potent antioxidative activity (EC50 = 2.84 µM), with potency increasing proportionally to the number of galloyl moieties. Synthetic inositol derivatives outperformed 1,5-anhydroalditol derivatives in rat α-glucosidase inhibitory activity. Pentagalloyl glucose, a natural compound, demonstrated the highest activity (IC50 = 0.336 µM).
Asunto(s)
Antioxidantes/farmacología , Productos Biológicos/farmacología , Inhibidores de Glicósido Hidrolasas/farmacología , Taninos Hidrolizables/farmacología , alfa-Glucosidasas/metabolismo , Animales , Antioxidantes/síntesis química , Antioxidantes/química , Productos Biológicos/síntesis química , Productos Biológicos/química , Compuestos de Bifenilo/antagonistas & inhibidores , Inhibidores de Glicósido Hidrolasas/síntesis química , Inhibidores de Glicósido Hidrolasas/química , Taninos Hidrolizables/síntesis química , Taninos Hidrolizables/química , Conformación Molecular , Picratos/antagonistas & inhibidores , RatasRESUMEN
Twenty-one natural and unnatural phenolic compounds containing a carbohydrate moiety were synthesized and their structure-activity relationship (SAR) was evaluated for α-glucosidase inhibition and antioxidative activity. Varying the position of the galloyl unit on the 1,5-anhydro-d-glucitol (1,5-AG) core resulted in changes in the α-glucosidase inhibitory activity and notably, particularly strong activity was demonstrated when the galloyl unit was present at the C-2 position. Furthermore, increasing the number of the galloyl units significantly affected the α-glucosidase inhibition, and 2,3,4,6-tetra-galloyl-1,5-AG (54) and 2,3,4,6-tetra-galloyl-d-glucopyranose (61) exhibited excellent activities, which were more than 13-fold higher than the α-glucosidase inhibitory activity of acertannin (37). Moreover, a comparative structure-activity study suggested that a hemiacetal hydroxyl functionality in the carbohydrate core and a biaryl bond of the 4,6-O-hexahydroxydiphenoyl (HHDP) group, which are components of ellagitannins including tellimagrandin I, are not necessary for the α-glucosidase inhibitory activity. Lastly, the antioxidant activity increased proportionally with the number of galloyl units.