A tissue culture method is described for callus formation from Galphimia glauca (Mapighiaceae) in MS (Murashige & Skoog) medium supplemented with various growth regulators. Best induction was achieved when using hypocotyls as explants in medium supplemented with 2 mg/l of 2,4-dichlorophenoxyacetic acid (2,4-D). Major cellular growth of calluses was obtained with naphthaleneacetic acid (2 mg/l) + kinetin (1 mg/l). Subcultivation of calluses using various concentrations of 2,4-D allowed the production of the sedative nor-seco-triterpenoid, galphimine B and a new related compound. The structure of the new constituent was elucidated as 6-acetoxygalphimine B. The highest accumulation of active constituent 1 (1.5 × 102- dry weight) was achieved when 4 mg/l of the hormone were used, and this experimental condition allowed the detection of only galphimine B. A preliminary screening of the methanolic extracts prepared from calluses, using the isolated guinea-pig ileum as a general test system for pharmacological effects, demonstrated that the most active material was the one with the highest concentration of galphimine B. Total accumulation of this sedative triterpene, in the optimized tissue culture conditions, was in the same order of magnitude as the value quantified for wild plants (4.5 × 102- dry weight). 1 This work was taken in part from the Ph.D. thesis of Lidia Osuna