Two New Phloroglucinol Derivatives with Phosphodiesterase Inhibitory Activity from the Leaves of Eucalyptus robusta

The leaves of Eucalyptus robusta Smith (Myrtaceae) are used in China to prepare the anti-malari­ al traditional medicine “Da Ye An” [1], Previous work on the extract of the leaves has yielded the bisphloroglucinol robustaol [21 as well as the robustadials A and B [3], The known phenols euglobal la, and Ia2, originally reported from E. globulus [4], were also isolated [3]. In a broad screening for biological activity, the crude ethanol extract of the leaves showed phosphodiesterase inhibitory activi­ ty. Using this bioassay to guide the isolation, two simple, though to the best of our knowledge pre­ viously unreported, phloroglucinols, 1 and 2, were isolated from the crude ethanol extract.