Extensive fractionation of n-hexane extract from the dried powdered-trunks of Coffea canephora Pierre ex A.Froehner (Rubiaceae) led to the isolation of a new oleanane-skeleton triterpene, coffecanolic acid (1), along with three known analogues sumaresinolic acid (2), oleanolic acid (3), and 3-O-acetyloleanolic acid (4). The chemical structures were elucidated using FT-IR, 1D and 2D NMR and HR-ESI-MS data analysis. The isolated compounds were assayed for in vitro α-glucosidase inhibitory activity by determining their half-maximal inhibitory concentration (IC50, µM). Compounds 1-4 exhibited higher inhibitory activities when compared with acarbose, a positive control. Compound 1 was found to be the most potent molecule against α-glucosidase, with the IC50 = 83.0 ± 1.2 µM, which improved by 2.5-fold over acarbose (IC50 = 209.8 ± 0.3 µM) in this assay.[Formula: see text].
Keywords: Coffea canephora; NMR analysis; oleanane skeleton; triterpene; α-glucosidase inhibition.