Cucurbitacins and cucurbitane glycosides: structures and biological activities

The natural cucurbitacins constitute a group of triterpenoid substances which are well-known for their bitterness and toxicity. Structurally, they are characterized by the tetracyclic cueurbitane nucleus skeleton, namely, 19-(10 -> 9 beta)-abeo-10 alpha-lanost-5-ene (also known as 9 beta-methyl-19-norlanosta-5-ene), with a variety of oxygen substitutions at different positions. According to the characteristics of their structures, cucurbitacins are divided into twelve categories. The biological effects of the cucurbitacins are also covered.