A New Purine Derivative from the Roots of Phyllanthus flexuosus

A new purine derivative, 1-methyl-3-isopentenylisoguanine (1), together with six known compounds (2-7), was isolated from the roots of Phyllanthus flexuosus. The newly isolated structure was established by means of extensive spectroscopic analysis and single-crystal X-ray diffraction experiment. All isolates were evaluated for their in vitro cytotoxicities against two human hepatocellular carcinoma cell lines (HepG2 and SMMC-7721) by CCK-8 assays. Among them, three cleistanthane diterpenes (2–4) exhibited different levels of cytotoxicities against these cells with IC 50 values ranging from 27.34 to 53.28 μM. Furthermore, acetylcholinesterase inhibitory effect for the new purine derivative was also assessed.