Monoterpene, Sesquiterpene and Diterpene Alkaloids Monoterpene, Sesquiterpene and Diterpene alkaloids Monoterpene alkaloids Iridoid monoterpene-derived alkaloids have already been discussed as indole alkaloids. However, there are a number of other monoterpene alkaloids, most are derived from iridoid monoterpenes. These compounds are essentially iridoid monoterpenes with a nitrogen, usually of obscure origin, inserted into the structure.
Examples are actinidine, b - skytanthine, and boschniakine.
Gentianine may or may not be naturally occuring in any particular case. This substance has often been reported, but often arises from basicification of extracted mixtures with ammonium hydroxide. Some monoterpene alkaloids are derived from non-iridoid precursors. Gentianine is a sedative. Most of the alkaloids are related to picrotoxins.