Abstract:
Inhibition of starch-degrading enzymes, α-amylase and α-glucosidase, provides a measure to
ameliorate type II diabetes mellitus (T2D) by limiting the amount of glucose produced from dietary
starch that would subsequently be absorbed into the bloodstream. This study investigated the
inhibitory potential of cellobiose in amylolytic enzymes alone and also assessed its synergistic
effects when combined with the gold AGI standard, acarbose. Firstly, the pharmacokinetic
properties prediction and gastrointestinal digestibility simulation of cellobiose were investigated.
Following, in silico molecular docking, in vitro enzyme inhibition, and UV spectroscopy were then
used to investigate the inhibitory potential of cellobiose. Lastly, single and combined acarbose and
cellobiose were investigated for their inhibition of the amylolytic enzyme cocktail. Cellobiose
showed drug-likeness properties and did not possess any toxicity. In addition, it was found to
remain stable under gastrointestinal simulated conditions. Acarbose (-7.3 kcal/mol and -8.2
kcal/mol) had the highest binding affinity than cellobiose (-6.0 kcal/mol and -7.5 kcal/mol) for
both α-amylase and α-glucosidase, respectively. Upon binding of the compounds to the targets in
vitro, acarbose (Ki = 0.012 mM) is a reversible uncompetitive inhibitor, while cellobiose (Ki = 2.2
mM) is a reversible non-competitive inhibitor of α-amylase. On the other hand, both acarbose (Ki
= 0.08 mM) and cellobiose (Ki = 14 mM) are reversible competitive inhibitors of α-glucosidase. A
combination of acarbose and cellobiose in different ratios resulted in more synergistic results than
antagonistic or additive effects, with a 0.005: 1.25 mM (acarbose: cellobiose) being the best
combination. The results of the study showed that although cellobiose is not a better inhibitor of
amylolytic enzymes, its combination with acarbose leads to synergism which may reduce side
effects presented by the gold AGI standard and, as a result, both have the potential to be used for
T2D treatment.
