This chapter provides an overview of the pharmacological studies and clinical applications of individual Gelsemium alkaloids or of the total alkaloids. The elegant synthesis starts from a Diels–Alder reaction between β-nitroacrylate and the tetrahydropyranyl enol ether to give a crystalline adduct easily separated from the reaction mixture. A new alkaloid was isolated from G.elegans by column chromatography and TLC. Its structure was identified, and it was designated as gelsenicine and humantenmine. Gelsenicine forms colorless cubic crystals from acetone, and is the most toxic alkaloid isolated so far from G.elegans Humantenidine is a colorless transparent resinous material. The toxicity of the alkaloids from G.elegans is studied much less extensively, but it has been found that the toxicity of the principal alkaloid koumine is comparable to that of gelsemine. The toxic Gelsemium alkaloids in crude form are used as analgesic and antispasm agents for a long time. It is also applied in traditional Chinese medicine as a remedy for dangerous skin ulcers, such as miliary vesicles under the nose. © 1988 Academic Press, Inc.