VOLUME 18 (Supplement)

In vitro inhibition of α-glucosidase by Rubus rosifolius leaf and fruit extracts

Prickly-stemmed Rubus rosifolius is an endemic Philippine plant growing in the mountainous areas and bearing edible red berries reportedly rich in phenolic compounds with known antioxidant, anti-inflammatory, antimicrobial, and antidiabetic properties. However, planting elevation and climate change affect the fruit-bearing season and the quantity that can be harvested, leading to the exploration of the pharmacological properties of the leaves. This study aimed to compare the α-glucosidase inhibitory activities of the R. rosifolius leaf and fruit extracts to maximize the potential plant parts that can be further studied in managing insulin resistance in diabetic patients. Physicochemical characteristics, phytochemical screening, and α-glucosidase inhibitory assay of the methanolic leaf and fruit extracts were performed using acarbose and phosphate buffer solution as positive and negative controls. The R. rosifolius leaf and fruit extracts were abundant in reducing sugars, flavonoids, saponins, tannins, alkaloids, steroids, triterpenoids, and anthraquinone glycosides for the fruit extract only. Spectrophotometric analysis at 405 nm showed that the leaf extract can inhibit 93.86% of the enzyme at 62.5 μg/mL, 77.84% at 250 μg/mL for the fruit extract, and 59.13% at 500 μg/mL for acarbose. Statistical analysis using one-way ANOVA showed a significant difference (p-values < 0.05) in inhibiting α-glucosidase at various concentrations among the treatment groups, indicating better inhibitory activities of the leaf extract (IC₅₀ of 22.24 μg/mL) than the fruit extract (IC₅₀ = 195.32 μg/mL) and acarbose (367.96 μg/mL). In conclusion, the methanolic R. rosifolius leaf and fruit extracts are promising candidates in lowering postprandial plasma glucose levels.