Two new ent-kaurane-type diterpene diastereomers isolated from Coffea canephora.

Phytochemical investigation of the trunks of Coffea canephora yielded two new ent-kaurane diterpene diastereomers, which have been named coffecanepholide A, ent-3ß,16ß,17-trihydroxykauran-18-al (1) and coffecanepholide B, ent-3ß,16ß,17-trihydroxykauran-19-al (2). Structural elucidation and configurational assignment were deduced from extensive spectroscopic NMR/HRESIMS analysis and by comparison with the spectral data of the literature relevant structures. The isolated compounds were assayed for in vitro inhibitory activities against α-glucosidase. Structure 2 showed the α-glucosidase inhibitory activity with an IC50 value of 294.7 ± 0.9 µM, while compound 1 exhibited inactivity. In addition, the docking results revealed that structure 2 can form more interactions with amino acid residues at the active site of α-glucosidase, which gave a more negative binding energy (-9.56 kcal/mol) compared with 1 (-8.60 kcal/mol). This observation might be responsible for a better activity of 2 against α-glucosidase.

Cafestol analogues from Coffea canephora: in vitro inhibition and molecular docking to α-glucosidase.

A new cafestol-type diterpenoid, 5ß-hydroxy-2-oxocafestol named coffecanepholide C (1) along with three known diterpenoids including cafestol (2), tricalysiolide A (3) and atractyligenin (4) were identified from the Coffea canephora trunks collected at Lam Dong province, Vietnam. Their structures were elucidated by HRESIMS and NMR spectroscopic analysis (1H, 13C, COSY, HSQC, HMBC, and NOESY NMR) as well as compared with data in the literature. Upon evaluation of the α-glucosidase inhibitory activity, compound 1 (IC50 = 142.0 ± 0.2 µM) and compound 3 (IC50 = 286.2 ± 1.2 µM) exhibited activity against α-glucosidase, while structures 2 and 4 showed no activity. Furthermore, the docking simulations revealed that the carbonyl groups of compounds 1 and 3 formed hydrogen bonds with Lys506 residue at the enzyme pocket, which may induce the α-glucosidase inhibitory activity.

A new oleanane-skeleton triterpene isolated from Coffea canephora.

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].