Abstract
Six sesquiterpene lactones (I-VI) were isolated and characterized as constituents of Chloranthus japonicus (Chloranthaceae). The lactones chloranthalactone A-E (I-V) were found to be lindenane derivatives, and the lactone VI was identified as atractylenolide III. The structure of chloranthalactone C (III) was determined by X-ray crystallographic analysis of a crystal of III in conjunction with the negative Cotton effect in the optical rotatory dispersion (ORD) curve and negative circular dichroism curve of the ketoalcohol (XII) prepared from III. The stereostructures of chloranthalactone A and B (I and II) were deduced from the ORD curves of the degradation products (VII and X). The cytotoxicities of these lactones against mouse lymphosarcoma L-5178Y cells were determined in comparison with that of helenalin, and they were found to show moderate cytotoxic effects.
