NEW MATERIAL:A lignan derivative of the formula (R1 is OH, R2 is methyl or incorporate R1 to form methylene or R1 is methyl and R2 is H). EXAMPLE:Isoschizandrin. USE:Medicine, antiulcerative. It is used to treat gastric and duodenal ulcers. PREPARATION:Dried fruits of Schizandra chinensis Baill are subjected to extraction with lower hydrocarbon such as petroleum ether at moderate temperatures. The solvent is removed from the extract and the residue is suspended in water, subjected to steam distillation to remove the essential oil. The remaining non- essential oil fraction is subjected to repeated silica-gel chromatography for purification. The resultant fraction is chromatographed with a silica-gel thin layer, eluted with a solvent such as methanol and irradiated with an ultraviolet ray of 2536Angstrom wavelength to give the compound of the formula where R1 is hydroxy and R2 is methyl.