Cholinesterase, α-glucosidase, tyrosinase and urease inhibitory activities of compounds from fruits of Rinorea oblongifolia C.H. Wright (Violaceae).

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 IC 50 = 42.45 ± 0.46 µg/mL was close that of acarbose (IC 50 = 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.