New triterpenoids from Kadsura heteroclita and their cytotoxic activity.

Phytochemical investigations of the stem of Kadsura heteroclita (Roxb) Craib (Schizandraceae) resulted in the isolation and structure elucidation of six new triterpenoidal compounds named heteroclitalactones A-E (1-5) as well as heteroclic acid (6) and heteroclitalactone F (7), which was isolated for the first time from a natural source, and the six known compounds schisanlactone E (8), cycloartenone (9), schisandronic acid (10), nigranoic acid (11), changnanic acid (12) and schisanlactone B (13), respectively. The structures of these compounds were characterized by extensive 1D and 2D NMR spectral analyses. The majority of these triterpenoids showed moderate cytotoxic activity against the human tumor cell lines Bel-7402, BGC-823, MCF-7 and HL-60. Among the compounds tested, heteroclitalactone D (4) showed the strongest cytotoxic activity against the HL-60 cells with an IC50 of 6.76 microM.