Oligomeric Proanthocyanidin Complex from Avocado Seed as A Promising alpha-glucosidase Inhibitor: Characteristics and Mechanisms

Although considered an abundant source of agricultural byproducts, avocado (Persea americana Mill.) seed, with several biological activities and bioactive components, might become a promising resource for phytopharmaceutical development. In this study, through bioassay-guided isolation of the main alpha-glucosidase inhibitors in avocado seed, we discovered the major alpha-glucosidase inhibitor to be avocado seed oligomeric proanthocyanidin complex (ASOPC). Thiolysis and UPLC-DAD-HRESIMS showed the presence of A- and B-type procyanidins, and B-type propelargonidin with (epi)afzelechin as extension unit. Mean degree of polymerization (mDP) of ASOPC was calculated as 7.3 +/- 1. Furthermore, ASOPC appeared to be a strong, reversible, competitive inhibitor of alpha-glucosidase, with IC50 value of 0.1 mu g/mL, which was significantly lower than Acarbose (IC50 = 75.6 mu g/mL), indicated that ASOPC is a potential natural alpha-glucosidase inhibitor. These findings would contribute to the direction of utilizing avocado seed bioactive components with the possibility to be used as natural anti-diabetic agents.