Alternanthera sessilis leaf fractions possess in vitro inhibitory activities in mammalian α-amylase and α-glucosidase

Diabetes is a metabolic disorder characterized by high blood glucose levels. With its increasing prevalence leading to a global burden, the search for new sources of antidiabetic agents are needed. Plant extracts and their fractions are essential in the management of diabetes due to numerous scientific evidences of their antidiabetic activity through various mechanisms. In this study, fractions from Alternanthera sessilis (Philippine variety) was investigated for their ability to inhibit key carbohydrate-degrading enzymes related to type-2 diabetes, specifically, α-amylase and α-glucosidase. The crude methanol extract of A. sessilis leaf was fractionated with three solvents of different polarities: water, ethyl acetate and hexane. These fractions were screened for mammalian α-amylase and α-glucosidase inhibitory activities in vitro, and for the presence or absence of phytochemicals. All fractions displayed inhibitory activities in porcine α-amylase and intestinal rat α-glucosidase, with the highest activity observed in the ethyl acetate fraction (IC50 amylase = 0.52 ± 0.072 mg/mL; IC50 glucosidase = 2.82 ± 0.21 mg/mL). This fraction also demonstrated no significant difference but lower inhibitory activity relative to acarbose (IC50 amylase = 0.0025 ± 0.00045 mg/mL, p=0.72, α=0.05; IC50 glucosidase = 0.36 ± 0.063 mg/mL, p=0.26, α=0.05). Phytochemical screening of this fraction showed the presence of carbohydrates, lipids, tannins, triterpenoids, flavonoids, and glycosides, as well as berberine and quercetin, which may have accounted for the observed enzyme inhibitory activity. In summary, A. sessilis fractions may be used as potential sources of α-amylase and α-glucosidase inhibitors, with the ethyl acetate fraction as the most potent.