Antiproliferative Butyrolactones from Mezilaurus crassiramea

Bioassay-guided fractionation of the ethanol extract from the leaves of Mezilaurus crassiramea , which was toxic to Artemia salina larvae, afforded 3′-acetylrubrenolide ( 1 ), 2′,3′-diacetylrubrenolide ( 2 ), and rubrenolide ( 3 ) from the active dichloromethane soluble fraction. Compound 1 is new, while 2 and 3 are first reported from a natural source and in the Mezilaurus genus, respectively. Compound 3 showed significant cytotoxicity against UACC-62, MCF-7, HT-29, and PC-3 human cancer cell lines, with GI 50 values ranging from 3.3 to 9.9 µg/mL, while 1 and 2 exhibited marginal activities against at least five of the six investigated cell lines. The structures of 1 – 3 were established on the basis of 1D- and 2D-nuclear magnetic resonance analyses, high-resolution electrospray ionization mass spectrometry data and specific optical rotation values.