MVA and related precursors are incorporated at least 100 times more efficiently than in monoterpenes and sesquiterpenes. This is not as surprising as it once was, not that it has been established that monoterpenes and some sesquiterpenes are derived by another pathway. The two most important types of triterpenes are derived by orientation of the precursor squalene epoxide in two distinct arrangements followed by condensation. One type leads to triterpenes and to steroids. Phytosterols Steroids are derivatives of triterpenes with 26 or more carbon atoms that have undergone a characteristic type of rearrangement.
Cholesterol is an important sterol in animals.
This compound is an intermediate in the synthesis of other steroids in plants, but is rarely, if ever, accumulated in plants. They are found in a large number of plant species. Prostagens Progestagens are derived from cholesterol in plants and animals. Most reports of progestagens from plants are probably not valid however. Progestagens are mostly C 21 - compounds.