Effect of Aqueous Cinnamon Extract on the Postprandial Glycaemia Levels in Type 2 Diabetes Mellitus: a Randomized Controlled Trial

Type 2 diabetes mellitus (DM2) subjects aged between 35-77 years were recruited into this study through nutrition appointment, Holon Pharmacy from Lisbon and Portalegre, Portugal. After the approval of the Ethics Committee, 36 individuals, were selected and invited to participate in this study. After eligibility criteria applied, a randomized controlled clinical trial, blind to participants, was conducted to 36 DM2 subjects. Participants were randomly assigned to intervention (n=18) or control group (n=18). The first participant of the study was randomly allocated to intervention or control group and the following participants were systematically allocated in each group. The anonymity and the confidentiality of the participants data collected were guaranteed through a code attributed to each participant. The control group was given a glucose solution to oral glucose tolerance test (OGTT) and the intervention group was given a glucose solution to OGTT followed by a cinnamon aqueous extract. The glucose solution consist in a glucose drink with 75g of anhydrous D-Glucose dissolved in 200 mL of water at room temperature, as prescribed by ADA. The blood glucose levels were measured before intervention at fasting (t0) and after 30 (t30), 60 (t60, 90 (t90) and 120 (t120) minutes after intervention from both groups.

Aqueous cinnamon extract was prepared by Cinnamomum burmannii bark (from Sucrame Company, Portugal) with Indonesia origin. Sticks of cinnamon (60 g) were soaked into 1000 mL of water. After 24 h at room temperature, cinnamon solution was heated for 30 min at 100°C and then filtered at room temperature. After the cinnamon tea preparation a 100 mL individual dose was distributed to each participant. For chemical analysis, a hydromethanolic extract (50 : 50) was performed with aqueous cinnamon extract previously obtained.

Anthropometric paraments and pharmacological therapy data were collected at the beginning of the study. At day before the intervention, a 24-hour food recall questionnaire was employed to participants of the study and carefully instructed by an investigator to complete the food record. The Food Processor SQL (10.14.2. version) programme was applied to analysed the nutritional composition of meals, such as, total energy intake (Kcal), proteins (g), lipids (g), carbohydrates (g), dietary fibre (g) and soluble fibre (g). It were also estimated the glycemic index and glycemic load of food intake.

Based on the blood glucose values, the blood glucose incremental area under the curve (AUCi) of each participant was defined using the GraphPad Prism program (version 5.0). Maximum concentrations (Cmax) and variations of maximum concentrations (ΔCmax) were determined by comparing with its respective baseline glycemia levels values.

The total phenolic concentration in the C. burmanni extract was determined according to Folin-Ciocalteu method employing gallic acid as standard. For the determination of antioxidant activity two methods were performed: FRAP and DPPH, adapted by Thaipong et al. The FRAP method for determination of ferric reducing effect was based on the reduction, at low pH, employing a colourless ferric complex (Fe3+) to a blue-coloured ferrous complex (Fe2+) by electron-donating antioxidants action in 2,4,6-tri(2-pyridyl)-s-triazine (TPTZ) presence.