Novel linear and step‐gradient counter‐current chromatography for bio‐guided isolation and purification of cytotoxic podophyllotoxins from Dysosma versipellis (Hance)

Dysosma versipellis (Hance) is a famous traditional Chinese medicine for the treatment of snakebite, weakness, condyloma accuminata, lymphadenopathy, and tumors for thousands of years. In this work, four podophyllotoxin‐like lignans including 4′‐demethylpodophyllotoxin (1), α‐peltatin (2), podophyllotoxin (3), β‐peltatin (4) as major cytotoxic principles of D. versipellis were successfully isolated and purified by several novel linear and step gradient counter‐current chromatography methods using the systems of hexane/ethyl acetate/methanol/water (4:6:3:7 and 4:6:4:6, v/v/v/v). Compared with isocratic elution, linear and step‐gradient elution can provide better resolution and save more time for the separation of photophyllotoxin and its congeners. Their cytotoxicities were further evaluated and their structures were validated by high‐resolution electrospray TOF MS and nuclear magnetic resonance spectra. All components showed potent anticancer activity against human hepatoma cells HepG2.