Antidiabetic Ellagitannins from Pomegranate Flowers: Inhibition of α‑Glucosidase and Lipogenic Gene Expression

Abstract

Two new ellagitannins containing a rare 3-oxo-1,3,3a,8b-tetrahydrofuro[3,4-<i>b</i>]benzofuran moiety, namely punicatannins A (<b>1</b>) and B (<b>2</b>), were isolated from pomegranate (<i>Punica granatum</i>) flowers. Their structures with absolute configuration were determined by detailed analysis of spectroscopic data, electronic circular dichroism (ECD) calculation, and chemical hydrolysis. A plausible biogenetic route involving a key enzymatic 1,4-Michael addition is proposed. Punicatannin A showed potent inhibition of α-glucosidase and lipogenic gene expression