Effects of Mulberry Leaf and Corn Silk Extracts Against α-Amylase and α-Glucosidase In Vitro and on Postprandial Glucose in Prediabetic Individuals: A Randomized Crossover Trial

TL;DR

This study tested how mulberry leaf and corn silk extracts affect blood sugar after meals in prediabetic people, finding some benefits in overweight individuals.

Contribution

The novel aspect is evaluating the extracts in a GOS milk matrix and identifying subgroup-specific effects on postprandial glucose.

Findings

Mulberry leaf and corn silk extracts inhibited α-amylase and α-glucosidase dose-dependently in vitro.

In overweight prediabetic individuals, GOS milk with the extracts reduced postprandial glucose levels significantly.

No significant overall effect was observed across all prediabetic individuals.

Abstract

Objective: Postprandial hyperglycemia is a major risk factor for type 2 diabetes and cardiovascular disease. Inhibition of α-amylase and α-glucosidase can attenuate postprandial glycemic response (PPGR). This study aimed to investigate the inhibitory effects of mulberry leaf and corn silk on these enzymes in vitro and their impact on postprandial glucose (PG) levels in prediabetic individuals using milk-based matrices. Research Design and Methods: In vitro, enzyme inhibition was assessed using the DNS method (α-amylase) and pNPG method (α-glucosidase). A randomized crossover trial was conducted in 11 prediabetic individuals with four interventions: pure milk; lactose-hydrolyzed milk; lactose-hydrolyzed milk with mulberry leaf, corn silk, and resistant dextrin; and GOS milk with mulberry leaf and corn silk. PPGR was assessed by area under the glucose curve, 1 and 2 h PG, maximum PG, and 2 h glucose excursion. Paired Wilcoxon signed-rank tests were used for comparisons. Results: Mulberry leaf and corn silk extracts inhibited both enzymes dose-dependently, with synergistic effects. No significant differences in PPGR indices were observed across interventions in the overall prediabetic individuals. However, in the overweight subgroup, the combination of GOS milk supplemented with mulberry leaf and corn silk significantly reduced 1 h PG (median difference [P25, P75]: −0.84 mmol/L [−1.05, −0.49]), maximum PG (−0.54 mmol/L [−0.75, −0.25]), and glucose excursion (−0.62 mmol/L [−0.75, −0.24]) compared to pure milk. Conclusions: Mulberry leaf and corn silk extracts inhibit α-amylase and α-glucosidase in vitro and may attenuate postprandial glucose excursions in overweight prediabetic individuals when delivered in a GOS milk matrix.

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