Identification of New Diterpenoids from the Pulp of <i>Coffea arabica</i> and Their α-Glucosidase Inhibition Activity
Abdulbaset Al-Romaima, Guilin Hu, Yanbing Wang, Chenxi Quan, Haopeng Dai, Ming‐Hua Qiu
Abstract
Six new ( 1, 2, 3, 5, 6, and 8 ) and seven known ( 4, 7, 9, 10, 11, 12, and 13 ) diterpenoids have been identified in the pulp of Coffea arabica . The structures of new diterpenoids were elucidated by extensive spectroscopic analysis, including 1D, 2D NMR (HSQC, HMBC, 1 H– 1 H COSY, and ROESY), HRESIMS, IR, DP4+, electronic circular dichroism, and X-ray crystallography analysis. Compound 1 is ent -labdane-type diterpenoid, whereas compounds ( 2 – 13 ) are ent -kaurane diterpenoids. The result of α-glucosidase inhibitory assay demonstrated that compounds ( 1, 3, 5, 7, and 10 ) have moderate inhibitory activity with IC 50 values of 55.23 ± 0.84, 74.02 ± 0.89, 66.46 ± 1.05, 49.70 ± 1.02, and 76.34 ± 0.46 μM, respectively, compared to the positive control (acarbose, 51.62 ± 0.21 μM). Furthermore, molecular docking analysis has been conducted to investigate the interaction between the compounds and the receptors of α-glucosidase to interpret their mechanism of activity. This study is the first investigation that successfully discovered the presence of diterpenoids within the coffee pulp.