Study of the Effect of Lampeni (Ardisia humilis Vahl.) Planting Condition toward the Alpha-glucosidase Inhibition Activity in vitro

Abstract

Background: The quality of a medicinal plant is influenced by agronomic conditions and harvesting time. Objective: This study aimed to evaluate the effect of planting method (open-air (OA) and shedding house (SH)) and harvesting time (2, 4, 6 months) of Lampeni (Ardisia humilis Vahl.) toward the inhibitory activity of alpha-glucosidase. Methods: The Lampeni seedling were placed under controlled light conditions (SH) and on direct sun exposure (OA). Harvesting of the leaves was carried out at the age of 2, 4, and 6 months after plantation (2m, 4m, and 6m). Each leaves dry powder was refluxed with methanol 70% and followed by liquid-liquid partition using n-hexane, ethyl acetate (EtOAc), and water. All samples were evaluated toward inhibition of the alpha-glucosidase enzyme in vitro. Total phenol levels were determined using Folin-Ciocalteu reagent. Results: The results showed that EtOAc fractions of both plantation techniques exhibited the highest inhibition of alpha-glucosidase. The highest activity was demonstrated by the 4m-OA-EtOAc fraction (IC50, 93.50 ppm) and followed by the 6m-OA-EtOAc fraction (IC50, 98.13 ppm). Based on the kinetic study, the inhibition type of the two most active samples were categorized as a non-competitive type. Total phenolic contents were decreased in the following order: 6m-SH-EtOAc > 4m-OA-EtOAc > 6m-OA-EtOAc > 4m-SH-EtOAc fraction. It was shown that there was no positive correlation between the strength of inhibition with total phenolic content. Conclusions: This study concluded that Lampeni at open-air plantation harvested on fourth months demonstrated the highest alpha-glucosidase inhibitory activity, although there was no positive correlation between the inhibition activity and phenolic content.