New arylalkanones from Horsfieldia macrobotrys, effective antidiabetic agents concomitantly inhibiting α-glucosidase and free radicals

In search of effective antidiabetic agents having therapeutic effect by inhibiting a-glucosidase and preventive effect by scavenging free radicals, Horsfieldia macrobotrys showed promising bioactivity required for the proposed criteria. Bioassay-guided isolation of the stem bark extract resulted in two new arylalkanones named horsfieldone A (1) and maingayone D (2), together with a new flavanone C-glucoside named 8-C-beta-D-glucopyranosylpinocembrin (3). Their structures and stereochemistry were determined by spectroscopic techniques as well as Mosher's method. Of isolated compounds, maingayone D (2) was the most potent inhibitors against both alpha-glucosidases and free radicals. The presence of additional phenolic moieties in 2 clearly indicated their critical roles in inhibitory effects. Further investigation on mechanism underlying alpha-glucosidase inhibition indicated that maingayone D (2) could retard the enzyme function by both competitive and noncompetitive manners. (C) 2015 Elsevier Ltd. All rights reserved.