Multimodal α-Glucosidase and α-Amylase Inhibition and Antioxidant Effect of the Aqueous and Methanol Extracts from the Trunk Bark of Ceiba pentandra.

Postprandial hyperglycemia and oxidative stress are important factors that worsen the health condition of patients with type 2 diabetes. We recently showed that extracts from Ceiba pentandra mitigate hyperglycemia in dexamethasone- and high diet/streptozotocin-induced diabetes. Herein, we evaluated the postprandial regulatory properties and the antioxidant effects of the aqueous (AE) and methanol (ME) extracts from the stem bark of Ceiba pentandra. The phytochemical analysis of AE and ME was performed using the LC-MS technique and the total phenolic and flavonoid assays. Both extracts were tested for their ability to inhibit superoxide anion (O₂^•ـ), hydrogen peroxide (H₂O₂), protein oxidation, alpha-amylase, and alpha-glucosidase activities. The mode of enzyme inhibition was also determined in a kinetic study. AE and ME were both rich in phenolic and flavonoid compounds. ME was 2.13 and 1.91 times more concentrated than AE in phenolic and flavonoid compounds, respectively. LC-MS allowed the identification of 5 compounds in both extracts. ME and AE inhibited O₂^•ـ with IC₅₀ of 51.81 and 34.26 μg/ml, respectively. On H₂O₂, they exhibited IC₅₀ of 44.84 and 1.78 μg/ml, respectively. Finally, they exhibited IC₅₀ of 120.60 and 140.40 μg/ml, respectively, in the inhibition of protein oxidation induced by H₂O₂, while showing IC₅₀ of 39.26 and 97.95 μg/ml on the protein oxidation induced by AAPH. ME and AE inhibited alpha-amylase with IC₅₀ of 6.15 and 54.52 μg/ml, respectively. These extracts also inhibited alpha-glucosidase, demonstrating IC₅₀ of 76.61 and 86.49 μg/ml. AE exhibited a mixed noncompetitive inhibition on both enzymes, whereas ME exhibited a competitive inhibition on α-amylase and a pure noncompetitive inhibition on α-glucosidase. These results demonstrate that ME and AE scavenge reactive oxygen species and prevent their effects on biomolecules. Besides, ME and AE inhibit carbohydrate digestive enzymes. These properties may contribute to reduce postprandial hyperglycemia and regulate glycemia in diabetic patients.