MAO Inhibitory Activity of Xanthones from Dichloromethane Extract of Polygala supina

Eight xanthones as inhibitors of monoamine oxidase have been isolated from dichloromethane extract of aerial part and roots of Polygala supina Schreb. The isolated xanthones were characterized by spectroscopic methods such as 1D, 2D NMR, and MS data analyses as 6,8-Dihydroxy-2,3,4-trimethoxyxanthone (1), 2,4,6,8-Tetrahydroxy-3,7-dimethoxyxanthone (2), 2,3,7-Trimethoxyxanthone (3), 3,7-Dihydroxy-1,2-dimethoxyxanthone (4), 1,3,6-Trihydroxy-2,7-dimethoxyxanthone (5), 1,3,5-Trihydroxy-2,6,7-trimethoxyxanthone (6), 3,6,8-Trihydroxy-1,2-dimethoxyxanthone (7), 1,3,7-Trihydroxy-2,6-dimethoxyxanthone (8). MAO-A (monoamine oxidase-A) activity of isolated xanthones (1–8) from dichloromethane extract was assayed according to the method of Holt et al.¹ Compound 5 showed the best activity with IC₅₀ value of 0.24 mM, also 1 and 4 showed good activity with IC₅₀ values of 2.12 mM and 3.64 mM, respectively. The compounds 2, 6, and 7 showed mild activity with IC₅₀ values of 12.21, 43.80, and 23.98 mM. However, compounds 3 and 8 were not active.

References: 1. Holt A et al. (1997) Analytical Biochemistry 244: 384–392