Roasted coffee may do more than wake you up for it could help to control blood sugar. Scientists from Kunming Institute of Botany, Chinese Academy of Sciences, have discovered several new coffee compounds that inhibit α-glucosidase, a key enzyme linked to type 2 diabetes.
Some of these molecules were even more potent than a common anti-diabetic drug. The study also introduced a faster, greener way to uncover health-boosting compounds in complex foods.
The compounds were found to strongly inhibit α-glucosidase, an enzyme that plays a central role in breaking down carbohydrates during digestion. Since this enzyme directly affects how quickly sugars enter the bloodstream, the discovery points to possible new functional food ingredients aimed at managing type 2 diabetes.
The discovery was made using more advanced analytical methods: nuclear magnetic resonance (NMR) and liquid chromatography-mass spectrometry (LC-MS/MS).
Research process
The scientists designed a three-step, activity-focused process to uncover bioactive diterpene esters in roasted Coffea arabica beans. The approach aimed to detect both common and extremely low-level compounds that could inhibit α-glucosidase, while also reducing solvent use and speeding up analysis.
With the first step of the analysis, the crude diterpene extract was separated into 19 fractions using silica gel chromatography. Each fraction was then analysed with ^1H NMR and tested for α-glucosidase inhibition. Second, by applying cluster heatmap analysis to the ^1H NMR data, the researchers identified Fr.9-Fr.13 as the most biologically active fractions based on distinctive proton signal patterns.
For the third step, analysis of a representative sample, Fr.9, using ^13C-DEPT NMR revealed the presence of an aldehyde group, confirming earlier findings. After purification with semi-preparative high performance liquid chromatography (HPLC), the scientists isolated three previously unknown diterpene esters, named caffaldehydes A, B, and C. Their chemical structures were verified through 1D and 2D NMR along with high-resolution mass spectrometry (HRESIMS).
Analysis
Although the three caffaldehydes differed in their fatty acid components (palmitic, stearic, and arachidic acids), all showed notable α-glucosidase inhibition. Their IC₅₀ values were 45.07, 24.40, and 17.50 μM respectively, indicating stronger activity than the comparison drug acarbose.
In order to uncover additional trace compounds that were difficult to detect using NMR or HPLC alone, the team applied LC-MS/MS to combined fraction groups. They then built a molecular network using GNPS and Cytoscape. This analysis revealed three more previously unknown diterpene esters (compounds 4-6) that were closely related to caffaldehydes A-C.
It was found that while they shared similar fragment patterns, these molecules contained different fatty acids (magaric, octadecenoic, and nonadecanoic acids). Searches of existing compound databases confirmed that these substances had not been reported before.
Thee results show that this integrated dereplication strategy is highly effective for identifying structurally diverse and biologically meaningful compounds in complex foods such as roasted coffee.
This could lead to new opportunities to develop coffee-based functional foods or nutraceuticals that support glucose control and may help manage diabetes.
The research appears in the journal Beverage Plant Research, titled “Bioactive oriented discovery of diterpenoids in Coffea arabica basing on 1D NMR and LC-MS/MS molecular network.”
