In Vitro Mammalian Alpha-glucosidase Inhibitor Screening of Selected Plant Materials from Siba-o, Calabanga, Camarines Sur

Abstract

Background and Objectives: Diabetes mellitus type 2 (DM2) remains a health threat to Filipinos. According to the International Diabetes Federation 2014, the Philippines is one of the emerging DM2 hotspots with an estimated prevalence rate of around 3.2 million cases (5.9%) between 20 to 79 years old. In line with the acceptance of Filipino patients with the utilization of herbal medicine as an effective alternative for treatment of their ailments, some of the selected plant materials from Siba-o, Calabanga, Camarines Sur were explored for mammalian intestinal alpha-glucosidase inhibition in vitro to develop new herbal drug candidates that are effective, safe, and more affordable.

Methodology: Exhaustive maceration using absolute ethanol was performed to extract the phytoconstituents from the plant matrix. In vitro alpha-glucosidase inhibition assay using spectroscopic method (96 well plates) was carried out to analyze the mammalian α-glucosidase inhibition of the different plant samples, IC₅₀ was determined from the generated linear regression extrapolated from concentrations-% inhibitions plot. Thin Layer Chromatography (TLC) bioautography was employed to identify the presence of flavonoids, tannins, essential oil, reducing sugar, coumarin, anthraquinones, anthrones, steroids, alkaloids, and peptides.

Results: From the 98 crude plant samples extracted, the ethanolic extracts of Melothria sp. stem with leaves showed a concentration-dependent inhibition activity towards mammalian α-glucosidase from rat intestine acetone powder with IC₅₀ values of 49.24 ppm. Tannins, flavonoids, essential oils, and indoles were detected from TLC bioautography that may be responsible for the bioactivity.

Conclusions and Recommendations: The results demonstrated the potential utilization of some plant samples as an alternative herbal drug. However, only Melothria sp. crude leaves and stem extract (SB32LS) showed a concentration-dependent activity and further studies must be done to isolate the metabolites responsible for the activity through activity-guided isolation.