Chemical Constituents from Diospyros discolor Willd. and their Acetylcholinesterase Inhibitory Activity

Background: Diospyros discolor is commonly known as ‘buah mentega’ and traditionally used to treat various diseases. Many compounds especially triterpenes in Diospyros sp. were reported to inhibit acetylcholinesterase (AChE) and butyrylcholinesterase enzymes in vitro and in vivo. D. discolor was reported to contain triterpenes, yet to be investigated for their AChE inhibitory activity. D. discolor leaves extract showed high (95.80 ± 1.57 %) AChE inhibitory activity at the concentration of 100 μg/mL. Objective: The aim of the present study is to identify chemical constituents from D. discolor and their AChE inhibitory activity. Materials and Methods: The leaves and stem barks of D. discolor were air dried, powdered and successively extracted using n-hexane, dichloromethane and methanol. The solvents were evaporated to obtain dried crude extracts. The compounds were purified using exhaustive chromatographic procedures and their structures were determined by analyses of spectral data. The AChE inhibitory activity was carried out using Ellman’s method. Results: A new flavonol, 7,4’-dihydroxy-5,3’,5’-trimethoxyflavonol (1), along with five known flavonoids (2-6) and six known triterpenes (7-13) were isolated from the leaves and stem barks of D. discolor. Selected compounds were evaluated for AChE inhibitory activity, in which stigmast-4-ene- 3-one (7) showed the lowest inhibition concentration with an IC₅₀ value of 11.77 ± 2.11 μM. Conclusion: A new flavonol (1) and twelve known compounds were identified and characterized. Even though D. discolor extracts showed high percent inhibition against AChE enzyme, the isolated compounds showed moderate inhibition.