Drug toxicology is a required new course for students majoring in pharmacy.The summary of teaching practice of the course,based on its characteristics and actual teaching conditions,will be benificial to establishing teaching models and teaching methods suitable for pharmaceutical specialty.

Aim To isolate, purify, and chemically characterize a polysaccharide showing inhibition of the six-?-helix bundle formation of HIV-1 envelope glycoprotein gp41 from cultured broth of a streptomyces sp.strain. Methods Ethanol was used to precipitate polysaccharides and macromolecules from the broth.Proteins in the precipitate were removed by sevage method.Purification was carried out by DEAE-Cellulose and sephadex G-25 column chromatography. The chemical structure of the polysaccharide was determined with the combined application of HPLC,UV,IR and 1H-NMR spectroscopy, and the methods of periodate oxidation and Smith degradation,etc. Activity of anti-HIV-1 ~gp41 six-?-helix bundle formation was assayed withsandwich ELISA method.Results The purified polysaccharide,designated as SMP for Streptomyces polysaccharide,is neutral with a molecular weight of approximately 4855 Daltons. Sugar analysis showed SMP contains glucose and fructose residues in an approximate molar ratio of 22∶1 (10.96 to 0.48). The glycosidic linkages were estimated to be (1→4)-?-D-pyranoside as its main chain, and 1→6 linkage was attached to the main chain. Activity analysis revealed SMP markedly inhibited the six-?-helix bundle formation of HIV-1 glycoprotein gp41 and the IC_~50 was (145.48?7.25) mg?L~-1 .Conclusion Streptomyces polysaccharide SMP showing inhibition of the six-?-helix bundle formation of HIV-1 envelope glycoprotein gp41 was isolated and purified.