A comprehensive study of ground-roasted coffee beans from <i>Coffea liberica</i> as dipeptidyl peptidase IV inhibitors

Abstract Type 2 diabetes mellitus (T2DM), a degenerative disease characterized by insulin resistance, has been reported as a serious healthcare problem, especially in low-to-middle-income countries. Dipeptidyl peptidase IV (DPP4) inhibition is a potential solution to overcome T2DM-related problems. Liberica coffee ( Coffea liberica ) was reported to have several health benefits due to the bioactive compounds it contains, such as phenolics, flavonoids, and alkaloids. This study aimed to provide a comprehensive evaluation of ground-roasted coffee beans (GRCB) from C. liberica, including in vitro evaluation, metabolite fingerprinting using LC-HRMS, and authentication analysis using Fourier transform infrared (FTIR) spectroscopy combined with chemometric techniques. In vitro evaluation proved the inhibitory activity of GRCB solution (with a percentage inhibition of 92.09%), which was comparable to sitagliptin used as a positive control. Metabolite identification revealed the presence of caffeine and chlorogenic acid isomers, namely cryptochlorogenic acid and isochlorogenic acid, as potential markers for further investigation. Chemometric techniques, namely principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA), were used to perform exploratory data analysis and authentication study, respectively. The PCA results generated the plot observation, capturing 99.4% of the total variance within the first two components. It also facilitated the functional group identification by evaluating wavenumbers as the variables in the model construction. An authentication study using PLS-DA was also carried out, and it successfully differentiated GRCB with the presence of starch as an adulterant with the area under the curve-receiver operating characteristic (AUC-ROC) outcome of 1.