Three new benzophenone glycosides with MAO-A inhibitory activity from Hypericum thasium Griseb.

Abstract

Purification of n-BuOH fraction from 80% ethanol extract of Hypericum thasium Griseb. resulted in the isolation of three new compounds 3′,4,5′-trihydroxy-6-methoxy-2-O-α-l-arabinosylbenzophenone (1), 3′,4,5′,6-tetrahydroxy-2-O-α-l-arabinosylbenzophenone (2), and 3′,4-dihydroxy-5′-methoxy-2-O-α-l-arabinosyl-6-O-β-d-xylosylbenzophenone (3) along with a known flavonoid glycoside quercetin-3-O-α-l-arabinofuranoside (4). The structures of the new compounds were elucidated by 1D and 2D NMR analysis as well as HRESIMS. The isolated compounds (1–4), as well as quercetin, and kaempferol previously isolated from EtOAc fraction were screened against MAO-A inhibitory activity. When tested against the MAO-A quercetin and kaempferol displayed IC50 values of 19.6, and 17.5μM, respectively. The IC50 values for MAO-A inhibition by compounds (1–4) were 310.3, 111.2, 726.0, and 534.1μM, respectively. Standard inhibitor (clorgyline) exhibited MAO-A inhibition with an IC50 value of 0.5μM.