Alkaloids and phenolic compounds from the trunks of Coffea canephora and their alpha-glucosidase inhibition

Introduction: Coffea canephora, known as Robusta coffee, is one of five coffee species grown in Vietnam. Continuous reporting of the chemical and bioactivity investigation of the Coffea canephora trunk, the isolation and spectroscopic analysis of alkaloids and phenolic glycosides, and their α-glucosidase inhibition were addressed. Method: The crude methanol extract was prepared from dried Coffea canephora trunk powder using the maceration method. The n-hexane and ethyl acetate extracts were separated from the crude extract by sequence soaking in n-hexane and then in ethyl acetate. From these extracts, five organic compounds and a mixture were isolated using various chromatographic methods, and their structures were elucidated by NMR spectroscopic and MS techniques. αGlucosidase inhibition assays were carried out by Apostolidis’s method. Results: Five compounds consisting of caffeine (1), uridine (2), 3,4,5-trimethoxyphenol (3), kelampayoside A (4), polystachyol (5), and a mixture of (±)-lyoniresinol 3 a -O-b-D-glucopyranoside (6) were isolated from the n-hexane and ethyl acetate extracts and structurally elucidated. αGlucosidase inhibition assays demonstrated that compounds 2, 4 and 5 showed better activity than acarbose. Conclusion: To the best of our knowledge, all isolated compounds except compound 1 were investigated from the Coffea genus for the first time. Compounds 2, 4 and 5 showed better activity than acarbose in the α-glucosidase inhibitory assay.