Vasorelaxing Activity of Two Coumarins from Murraya paniculata Leaves

In the search for novel chemical scaffolds leading to potential antihypertensive agents, the methanol extract of Murraya paniculata leaves was assessed for its effects on isolated rat aorta rings. The vasorelaxing effect of the chloroform fraction of the methanol plant extract was the most potent for its vasorelaxing activity on rat aorta rings contracted by 60 mm K+ (K60). Two coumarins were isolated from the chloroform fraction: the novel kimcuongin (1) and the known murracarpin (2). Their structures were determined from spectroscopic evidences including H-1- and C-13-NMR, correlation spectroscopy (COSY), nuclear Overhauser effect spectroscopy (NOESY), heteronuclear multiple bond correlation (HMBC), heteronuclear single quantum correlation (HSQC), and high resolution mass spectrometry (HR-MS). Kimcuongin and, to a lesser extent, murracarpin, showed vasorelaxing activity with IC50 values of 37.7 mu m and 139.3 mu m, respectively. The coumarins kimcuongin and murracarpin may thus represent a novel class of vasodilators of natural source.