Cytotoxic 7,20-epoxy ent-kauranoids from Isodon xerophilus

Four 7.20-epoxy ent-kaurane diterpenoids. xerophilusins G (1) and I-K (2-4). were isolated from the leaves of Isodon xerophilus. along with four known ones, enanderianin C (5), rosthorin A (6), longikaurin B (7), and rabdoternin D (8). Their structures were determined primarily using NMR spectroscopic techniques. The structure and stereochemistry of 3 were confirmed by X-ray crystallography. Compounds 4 and 7 exhibited broad cytotoxicity against four kinds of human tumor cells (K562, HL-60, HCT, and MKN-28 cells) in the range of 2.23-15.35 and 0.30 8.61 mug/ml, respectively. (C) 2001 Elsevier Science Ltd. All rights reserved.