Investigating Matcha as an Amylase Inhibitor for Postprandial Hyperglycaemia in Gestational Diabetes

Gestational diabetes affects more than 1 in 7 pregnancies globally, and poses significant risks to both maternal and fetal health. Postprandial hyperglycaemia associated with gestational diabetes significantly increases the risks of such complications including preeclampsia, macrosomia and the development of long term diabetes mellitus (Plows et al., 2018). A key contributor to postprandial glucose spikes is the digestive enzyme α-amylase, which catalyzes the breakdown of dietary starch into glucose. While pharmacological glucosidase inhibitors are commonly used in type II diabetes to reduce α-amylase activity, such medications remain largely unprescribed for gestational diabetes due to limited safety data during pregnancy (Yilmazer-Musa et al., 2012). Such gaps underscore the need for alternative therapeutic strategies to safely control postprandial hyperglycemia in gestational diabetes.

Natural compounds derived from plants have been increasingly investigated for the potential of regulating carbohydrate digestion. Green tea derived from Camellia Sinensis contains a high concentration of polyphenolic compounds known as catechins, particularly gallated catechins such as epigallocatechin gallate. Such compounds directly interact with α-amylase enzymes, reducing catalytic activity and slowing the hydrolysis of starch molecules (Hara & Honda, 1990).

Aim: This study aimed to evaluate the efficacy of Camellia Sinensis (matcha green tea) as an inhibitor of α-amylase activity for the potential therapeutic use to manage the postprandial hyperglycaemia associated with gestational diabetes.

Preliminary Trials

Current studies of (Gao et al., 2013) and (Miao et al., 2015) isolate catechins from matcha as an inhibitor, while this study aims to investigate whole matcha and concentrations safe for consumption during pregnancy. Given the recommended daily caffeine intake during pregnancy is limited to ≤ 200–300 mg (Qian et al., 2019), preliminary trials of (0.00, 0.50, 1.00, 1.50 (%v/v)) matcha extract were conducted to establish a concentration range that reflects realistic consumption. Based on the preliminary trials, concentrations of 0.00% and 0.50% demonstrated greatest consistency, thus the experimental range of (0.0, 0.10, 0.25, 0.40, and 0.50 (v/v%)) was selected.

Amylase Starch Assay

An in vitro enzymatic assay was conducted to measure α-amylase activity in the presence of increasing concentrations of matcha extract (0.0, 0.10, 0.25, 0.40, and 0.50 (v/v%)). Trials were conducted at a consistent temperature of 21°C, with 1% amylase solution and 1% starch solution stained with iodine. Amylase activity was quantified by measuring change in initial and final light absorbance over a 5 minute reaction period using a colorimeter, reflecting the rate of starch breakdown.

Temperature Change

The amylase starch assay was replicated at 37°C to investigate inhibitory effects of matcha on the enzymatic activity of amylase at physiologically accurate temperature conditions.

Varying Starch Concentrations

Varying starch concentrations of (1.0%, 2.0%, 3.5%, 5.0%, 6.5%) were tested at a consistent temperature of 37°C, with 1% amylase solution and 0.5% matcha solution to measure amylase inhibition at differing levels of starch consumption.

21°C vs 37°C Amylase Starch Assay

Two-way ANOVA was performed with Bonferroni-adjusted post hoc analysis, which identified significant differences between temperatures at 0.0% and 0.1% matcha extract (p < 0.05), while higher concentrations showed no significant differences between temperature groups.

Within each temperature condition, pairwise comparisons revealed multiple significant differences between matcha extract concentrations, as indicated in the figure 2 legend.

Linear regression indicates a significant and strong (r2 0.83, p<0.0001) relationship.

Varying Starch Concentrations

A one-way ANOVA revealed statistically significant differences among starch concentrations, with Bonferroni-adjusted multiple comparisons identifying specific pairwise differences. Statistically significant differences were observed between lower and higher concentrations, with 1.00%, 2.00% and 3.50% differing significantly from both 5.00% and 6.50%. While remaining comparisons between starch concentrations are all not statistically significant.

Linear regression indicates a significant (r2 0.6075, p <0.0001) relationship.

The results demonstrate a dose-dependent inhibitory effect of matcha on α-amylase activity in vitro, with increasing concentrations producing statistically significant reductions in reaction rate. Importantly, this inhibitory effect is maintained at physiological temperature (37 °C), indicating that the observed mechanism is robust under biologically relevant conditions. While temperature significantly increased baseline enzyme activity at lower concentrations (0.00–0.10%), it did not diminish inhibition at higher concentrations, suggesting that matcha’s inhibitory properties persist even at higher enzymatic activity and are unaffected under physiologically relevant conditions.

Statistically significant differences between starch concentration comparisons indicate that enzyme saturation was not reached within the tested range (up to 6.5%), as reaction rates continued to respond to increasing substrate availability.

Collectively, the results suggest that bioactive compounds in matcha reduce starch digestion by limiting α-amylase activity in a dose-dependent manner. Given the role of α-amylase in driving postprandial hyperglycemia, this inhibitory effect highlights the potential of matcha as a practical α-amylase inhibitor to control postprandial spikes. In the context of gestational diabetes, these findings provide a mechanistic basis for further investigation into apply novel safe and accessible interventions for glycemic control during pregnancy.

Further Investigations

Testing varying pH levels, exploring matcha as an inhibitor for pancreatic and salivary amylase to observe differences in respective physiological environments. Further testing if inhibition properties remain under stomach pH levels, to evaluate efficacy through the digestive system.

In-vivo testing to determine if this mechanism translates to a reduction in postprandial blood glucose levels in a biological system.

Testing whole foods with starch, such as bread or potatoes to evaluate practical relevance.

I would like to thank my biology teacher Mr. Persaud for supervising the experimental process of this project. Thank you so much Irena Rebalka and Catharine Bowman for all your support, answers to my questions and valuable feedback in preparation for CWSF. Thank you BASEF as a whole for planning, organizing and offering this incredible opportunity to youth in our community.

References

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