Researchers discover novel coffee diterpenoids with anti-diabetic potential
Researchers have identified six novel diterpene esters in roasted Arabica coffee beans using an innovative bioactivity-oriented analytical approach that combines 1D NMR spectroscopy with LC-MS/MS molecular networking. The compounds demonstrate moderate α-glucosidase inhibitory activity, suggesting potential applications in managing blood glucose levels.
Activity-guided discovery yields three major compounds
A research team from the State Key Laboratory of Phytochemistry and Natural Medicines at Kunming Institute of Botany, Chinese Academy of Sciences, successfully isolated three new coffee diterpene esters from roasted Coffea arabica beans. The compounds, designated caffaldehydes A-C (1-3), were identified through a systematic three-step dereplication strategy designed to reduce solvent use and analytical time whilst improving compound discovery efficiency.
The study addressed a significant challenge in coffee chemistry research. “Because coffee roasted beans are a very complex mixture system, whether there are other novel active coffee diterpenes in it is a question worth exploring in depth,” the authors stated in their publication.
The research utilised silica gel column chromatography to separate a diterpene extract (80.7 g) into 19 fractions. These fractions underwent 1H NMR analysis and α-glucosidase activity screening, with results analysed using cluster heatmap methodology to identify active groups.
Structural characterisation reveals distinctive features
Compound 1 (caffaldehyde A) was obtained as a colourless oily liquid with molecular formula C36H56O5. Analysis revealed characteristic signals including an aldehyde proton at δH 10.18, three olefinic protons, and one oxidation methylene signal. The 13C-DEPT NMR spectrum confirmed 36 carbon atoms, including the diterpene skeleton first reported by De Lucia et al. in 2009, esterified with palmitic acid.
Compounds 2 and 3 exhibited similar spectral characteristics to compound 1, with their 13C NMR and HRESIMS data indicating esterification with stearic acid (18:0) and arachidic acid (20:0) respectively. Two-dimensional NMR analysis of compound 2 confirmed the esterification location at C-17 through HMBC correlation from δH 4.26 to δC 174.0.
Biological activity assessment demonstrates enzyme inhibition
The isolated compounds displayed significant α-glucosidase inhibitory activity, a key parameter for anti-diabetic potential. Caffaldehyde A demonstrated an IC50 value of 45.07 ± 3.16 μM, whilst caffaldehydes B and C showed enhanced activity with IC50 values of 24.40 ± 0.33 μM and 17.50 ± 2.86 μM respectively. These values compared favourably with the positive control acarbose (IC50: 60.71 ± 16.45 μM).
“Research has shown that C&K can exhibit anti-cancer effects through various pathways. Additionally, C&K may potentially lower blood sugar levels by stimulating insulin secretion and increasing glucose uptake,” the researchers note, referring to previously studied coffee diterpenes cafestol and kahweol.
Molecular networking identifies trace compounds
To explore additional trace active diterpenoids, the research team employed LC-MS/MS-based molecular networking through the Global Natural Products Social Molecular Networking (GNPS) platform. This approach successfully identified three additional novel coffee diterpene esters (compounds 4-6) without requiring chromatographic purification.
The molecular network analysis revealed that compounds 1-3 shared characteristic fragment ion peaks at m/z 313, 295, 277 and 267. Adjacent nodes representing compounds 4-6 displayed identical fragmentation patterns, indicating structural similarity. Through molecular formula analysis, the fatty acid moieties were determined to be margaric acid (17:0), octadecenoic acid (18:1) and nonadecanoic acid (19:0) respectively.
Implications for food science and functional ingredients
The research demonstrates significant advances in natural product discovery methodology applicable to complex food matrices. The authors explained: “In the experimental design of this study, it is hoped that the scheme will take into account several aspects: Assist in the discovery and separation of active compounds; Direct identification of trace novel compounds without chromatographic purification; Avoid chromatographic separation as much as possible to reduce the use of solvents and consumables; Reduce the difficulty of spectrum analysis and shorten the research time.”
This efficient analytical strategy offers particular relevance for the functional food sector, where rapid identification of bioactive compounds can accelerate product development. The presence of multiple novel diterpene esters with varying fatty acid chains suggests greater chemical diversity in roasted coffee than previously recognised.
The findings contribute to understanding coffee’s potential health benefits beyond its caffeine content. Coffee diterpenoids represent approximately 99.6% of coffee oil’s diterpene content, with Arabica coffee generally containing higher levels compared to Robusta varieties.
The study’s multi-spectral approach, integrating NMR spectroscopy, mass spectrometry and molecular networking, provides a template for investigating bioactive compounds in other complex food systems. This methodology enables both targeted isolation of abundant active compounds and direct identification of trace components, maximising research efficiency whilst minimising resource consumption.
Reference
Hu, G., Quan, C., Al-Romaima, A., et. al. (2025). Bioactive oriented discovery of diterpenoids in Coffea arabica basing on 1D NMR and LC-MS/MS molecular network. Beverage Plant Research, 5, e004. https://doi.org/10.48130/bpr-0024-0035
