PHOSPHOLIPASE-D INHIBITORS FROM A MYRSINE SPECIES

The phospholipase D-inhibitory activity of a methanol extract from the leaves of a New Zealand plant, Myrsine australis, has been attributed to two new saponins 1 and 2. Compound 1 was assigned as 3-O-(-beta-D- xylopyranosyl-(1 --> 2)-O-beta-D-glucopyranosyl-(-1 --> 4)-[O-beta-D-g lucopyranosyl-(1 --> 2)]-alpha-L-arabinosyl)-16 alpha-hydroxy-13 beta, 28-epoxyoleaneane and 2 as 3 beta-O-(-beta-D-rhamnopyranosyl-(1 --> 2) -O-beta-D-glucopyranosyl-(1 --> beta-D-glucopyranosyl-alpha-L-arabinop yranosyl]-16 alpha-hydroxy-13 beta,28-epoxyleanane. Compounds 1 and 2 showed IC50 values of 3 and 2 mu M, respectively, versus phorbol 12-my ristate-13-acetate-stimulated phopholipase D in human promyelocytic le ukemic (HL-60) cells. Compounds 1 and 2 also inhibited fMLP (formyl-Me t-Leu-Phe) stimulated phospholipase D with IC50 values of 8 and 24 mu M, respectively.