Purpose: To investigate the inhibitory effect of
S. alata
leaf extracts on α-amylase and α-glucosidase,
and its potential for reducing postprandial blood glucose level of rats.
Methods: The α-amylase and α-glucosidase inhibitory potentials of acetone, ethylacetate and hexane
extracts of
S. alata were investigated by reacting different concentrations (0.63 – 10.0 mg/mL) of the
extracts with the enzymes and substrates while the mode(s) of inhibition of both enzymes were
determined using the Lineweaver-Burk plot. The effect of oral administration of the hexane extract (with
lowest IC
50 for α-glucosidase) of the plant in sucrose-induced hyperglycemic rats was also determined
by evaluating fasting blood glucose levels.
Results: The acetone extract of
S. alata displayed the highest inhibitory activity against α-amylase (IC
50
= 6.41 mg/mL) while hexane extract exhibited highest inhibitory effect on α-glucosidase (IC
50 = 0.85
mg/mL). Both acetone and hexane extracts inhibited α-amylase and α-glucosidase in a competitive and
uncompetitive manner respectively. The hexane extract of
S. alata also caused significant reduction (p <
0.05) in the postprandial blood glucose level of sucrose-loaded rats within two hours.
Conclusions: It can be suggested that one of the mechanisms of anti-diabetic action of
S. alata leaf is
the inhibition of intestinal α-glucosidase.
