Investigation of Anti-Diabetic Properties of Ceylon Cinnamon Bark Extracts by In-Vitro α-Amylase and α-Glucosidase Inhibition, Molecular Modeling, and Postprandial Blood Glucose Regulation for Potential Nutraceuticals
Authors: Sandaruwan Chanaka , Kusal Thusitha , Siriwardhana Asitha , Lankathilake Wasantha , Purasinhala Kosala , Gunarathne Sahan , Rodrigo Sanjeewa , Gunawardene Manju , Karunaratne Veranja , Amaratunga Gehan A.J. 
Published: May 2024

Background:

Diabetes Mellitus (DM) can appear due to the absence of insulin (DM1-
type 1) or poor response of cells to insulin (DM2-type 2). Even though DM1 cannot be controlled
using general treatments, DM2 can be easily controlled or prevented using pharmaceuticals,
nutraceuticals, or dietary practices. Ceylon cinnamon (Cinnamomum zeylanicum) is one such natural
remedy that has been consumed against elevated blood glucose levels in the past. Cinnamon and
different types of cinnamon extracts have been scientifically tested for their activities on the inhibition
of α-amylase and α-glucosidase enzymes that are responsible for carbohydrate metabolism and
are effective in blood glucose regulation. However, the combined effect of aqueous and ethanol
extracts of cinnamon bark on blood glucose regulation is still lacking. In this study, Water Extract
of Cinnamon (CWE), Ethanol Extracts of Cinnamon (hot ethanol extract of cinnamon-CHEE, cold
ethanol extract of cinnamon-CEE, and 50% ethanol extract of cinnamon- CEE-50) were studied for
their sugar-controlling properties.

Objectives:

This study was performed to identify the efficacy of different cinnamon extracts on the
inhibition of α-amylase and α-glucosidase enzymes, followed by animal studies to confirm the use
of the extracts in nutraceutical formulations.

Methods:

Water and ethanol-based extraction method was used to prepare cinnamon extracts. These
extracts have been scientifically tested for their activities on the inhibition of α-amylase and α-glucosidase
enzymes. Molecular docking studies were used to identify the binding of the active molecules
to the substrate binding sites of α-amylase and α-glucosidase. In-vivo time dependence postprandial
blood glucose regulation studies have been performed with healthy Wistar male rats.

Results:

Yields of the CHEE, CEE, and CWE were 14±2%, 12±2%, and 8±1% respectively. According
to the LCMS data, the major component in the CEE was cinnamaldehyde. Both CWE and
CEE were subjected to the Total Polyphenol assay (TPC) and Total Flavonoids (TFC) assays. The
TPC of CWE and CEE were 117±1 mg (Gal)/g and 170±10 mg (Gal)/g, while the TFC of CWE and
CEE were 359±1 mg (Qc)/g and 254±4 mg (Qc)/g, respectively. In the α-amylase inhibition assay,
Acarbose; a known α-amylase inhibitor, and CEE showed IC50 values of 65.4 ppm and 2.6 ppm,
while CWE failed to show inhibition against α-amylase. In the α-glucosidase inhibition assay, Acarbose;
a known α-amylase inhibitor, CEE, and CWE showed IC50 values of 312 ppm, 4.5 ppm, and
1.3 ppm, respectively. In-vivo time dependence postprandial blood glucose regulation studies that
have been performed with healthy Wistar male rats showed a lowering of blood glucose concentrations
by 22%, 11%, and 10% of glucose at 30 min, 60 min, and 90 min compared to the control
group.

Conclusion:

The CEE contains polyphenols and flavonoids and is effective in inhibiting both α-
amylase and α-glucosidase. The CWE also contains polyphenols and a comparatively higher level
of flavonoids and is effective in inhibiting α-glucosidase while not affecting α-amylase inhibition.
Overall, the IC50 data, TPC data, and TFC data proposed that the inhibition of carbohydrate hydrolyzing
enzymes by polyphenols may depend on the polarity of particular polyphenols. Based on the
rat trials, it can be concluded that the 1:1 combination of CWE and CEE may be useful in formulating
postprandial blood glucose level-regulating nutraceuticals.