Inhibitory effects of Piper umbellatum Linn. leaf extracts on α-amylase and α-glucosidase activities

Abstract

Background:  Alpha-amylase and alpha-glucosidase are essential enzymes in converting food into energy inside the body. However, the proper management of these enzymes is needed to maintain normal blood glucose levels in the body. Thus, inhibiting these carbohydrate-hydrolyzing enzymes is necessary for managing hyperglycemia and alleviating Type 2 Diabetes Mellitus complications. Studies have reported that the Piper species have inhibitory properties on these digestive enzymes. However, the locally cultivated P. umbellatum has not yet been studied.

Objectives:  The study evaluated the inhibitory potentials of the locally grown P. umbellatum leaf extracts against α-amylase and α-gluiosidase.

Methodology: The P. umbellatum leaf extracts were screened for in vitro inhibitory α-amylase and α-glucosidase tests. The most active crude extract was subjected to semi-purification and fractions were subjected to inhibitory enzymatic tests. Qualitative and quantitative phytochemical analyses were conducted.

Results: Among all crude extracts, the KMB-HE exhibited the highest activities comparable to that of the acarbose standard (p>0.05). The KMB-HE showed inhibitions of 81.01%±1.66 and 89.51%±3.03 on α-amylase and α-glucosidase at 250 μg/mL, respectively. In addition, it contained the highest phenolic (195.00 ±3.60 GAE mg/gram) and flavonoid (4.55±0.06 QE mg/gram) contents that may be linked to the observed activities. The semi-purification of KMB-HE collected 24 fractions with PF10 demonstrating inhibitions of 68.07%±13.48 and 74.21%±2.22 in α-amylase and α-glucosidase, respectively. Also, the PF10 contained the highest phenolic (204.75±2.42 GAE mg/gram) and flavonoid (4.00±0.07 QE mg/gram) compounds among all the active fractions tested. The PF10 satisfied the recommended criteria for plant natural inhibitors: a moderate-to-low α-amylase and stronger α-glucosidase inhibitory activity.

Conclusion:  The P. umbellatum exhibited good inhibitory activities on carbohydrate-hydrolyzing enzymes.  These may lead to further analysis of the P. umbellatum for future development of a safer, locally available natural remedy in managing Type 2 Diabetes Mellitus.