Alkaloids with Human δ-Opioid Receptor Binding Affinity from the Australian Rainforest Tree Peripentadenia mearsii

Abstract

Three new pyrrolidine alkaloids, peripentonine A - C (2-4), one known pyrrolidine alkaloid peripentadenine (1) and one novel indolizidine alkaloid mearsamine (5) were isolated from the leaves of Peripentadenia mearsii and their structures determined by 1D and 2D NMR spectroscopy. Peripentonine A (2) and B (3) were isolated as a 1:1 mixture of inseparable diastereomers. Mearsamine (5) contains a novel tricyclic ring system. Peripentadenine, peripentonine A/B and C showed receptor binding affinity for the human d-opioid receptor with IC50 values of 11.4, 69.2 , and 30.9 卬 respectively. Mearsamine did not bind to the d-opioid receptor.