α-Glucosidase Inhibitory Xanthones from the Roots of Garcinia fusca.

Two new compounds, fuscaxanthones J (1) and K (2), together with eight known xanthones (3 - 10) were isolated from an ethyl acetate extract of the roots of Garcinia fusca. Their structures were determined using spectroscopic methods, mainly 1D- and 2D-NMR. α-Glucosidase inhibitory activity of the isolated compounds was evaluated and fuscaxanthone J (1) showed the most significant effect with an IC50 value of 8.3 ± 1.8 µm (compared with acarbose, IC50 = 214.5 ± 2.3 µm).

Highly potent cholinesterase inhibition of geranylated xanthones from Garcinia fusca and molecular docking studies.

Three new oxygenated xanthones, fuscaxanthones L-N (1-3), and 14 known xanthones 4-17, together with the other known metabolites 18-20 were isolated from the stem barks of Garcinia fusca Pierre. Their chemical structures were determined based on NMR and MS spectroscopic data analysis, as well as single X-ray crystallography. The geranylated compounds, cowanin (13), cowagarcinone E (15), norcowanin (16) and cowanol (17) exhibited potent inhibitions against acetylcholinesterase (AChE) (IC50 0.33-1.09 µM) and butyrylcholinesterase (BChE) (IC50 0.048-1.84 µM), which were more active than the reference drug, galanthamine. Compound 15 was highly potent BChE inhibitor (IC50 0.048 µM) and was 76-fold more potent than the drug. Structure-activity relationship studies indicated that the C-2 prenyl and C-8 geranyl substituents in the tetraoxygenated scaffold are important for high activity. Molecular docking studies revealed that the leads 13 and 15-17 showed similar binding orientations on both enzymes and very well-fitted at the double binding active sites of PAS and CAS with strong hydrophobic interactions from both isoprenyl side chains.