Chem. Pharm. Bull. 54(4) 542—545 (2006)

in southwest of China. Its stems were used in folk medicine for the treatment of rheumatism, traumatic injury, ulcer with pyogenic infections, stomachache and neurasthenia. Previous phytochemical investigation revealed that this plant mainly contained lignans and triterpenoids. As a part of our search for bioactive materials, the petroleum ether extract of the stems of S. propinqua showed cytotoxic activity against tumor cell lines during preliminary screening (HepG2, IC50 206 mg ·ml ; Bel-7402, IC50 191 mg ·ml ). Subsequent chromatographic separation and purification led to the isolation of one new triterpene, schisanterpene B (1) as well as 5 dibenzocyclooctadiene lignans, propinquanin E (2), schisantherin G (3), propinquanin F (4), schisantherin F (5) and Kadsurarin II (6). Compounds 2 and 4 are first reported occurrence from a natural source. In addition, octadecanoic acid, 2,3-dihydroxypropyl ester (7) and b-sitosterol (8) were isolated. This paper deals with the isolation and the characterization of the new triterpenoid and the two new natural products. The evaluation of the cytotoxic activity of the isolates by MTT assay was also described herein.