Alkaloids derived from diterpenes (e.g., KAURANES; CLERODANES) often containing the nitrogen bridge structures. These alkaloids may be divided into C18-, C19-, C20- and bis-diterpene types depending on the number of carbon atoms in their central framework. They are found most often in RANUNCULACEAE (e.g., ACONITUM and DELPHINIUM) and may possess analgesic, antiarrhythmic and anti-inflammatory activities. Some are cardiotoxic by blocking L-TYPE CALCIUM CHANNELS.