From Rinorea oblongifolia fruits, 3-Nor-4β-friedelan-24-ol (1) and 3-decyl-6,7,8-trimethoxy-2H,5H-furo[4,3,2-de]isochromene-2,5-dione (4), new derivatives alongside, 28-hydroxyfriedelan-3-one (2), friedelin (3), 3,3',4,4',5'-pentamethylcoruleoellagic acid (5), hexamethylcoruleoellagic acid (6), 3',4,4',5,5'-pentamethylcoruleoellagic acid (7), and fatty compounds 8-11 were isolated and characterized using HRESIMS, EIMS, 1D and 2D NMR. In vitro enzyme inhibition of compounds 1, 2, 4, 5, 6 and 7 were evaluated on acetylcholinesterase (AChE), butyrylcholinesterase (BChE), α-glucosidase, urease and tyrosinase. Against AChE and BChE, the phenolic compounds 4, 5, 6, and 7 had good activity probably due to the phenolic nature and methoxy substituents. Compounds 4, 5, 6 and 7 exhibited good α-glucosidase inhibition especially compound 4 whose IC50 = 42.45 ± 0.46 µg/mL was close that of acarbose (IC50 = 20.52 ± 0.84 µg/mL) standard drug. Urease and tyrosinase were appreciably inhibited by the compounds. Overall results of enzyme inhibitory assays indicate Rinorea oblongifolia, fruits and its constituents as potential remedy for enzymatic disorders.
Keywords: Rinorea oblongifolia; anticholinesterase; coruleoellagic acid derivatives; enzyme inhibition; triterpenoids; α-glucosidase inhibition.