Sesquiterpene lactones are an extensive group of natural sesquiterpene derivatives (aliphatic mono-, di-, or tricyclic terpenes) derived mainly from the germacran (germacran type of sesquiter terpenes), eudesman (eudalin), guaian (guaianolide) and pseudoguaian. Of the more than2000 representatives of this group of substances, a large part is found in plants, mainly in representatives of the family of Asteraceae, more rarely in Magnoliaceae, liver mosses and others. Sesquiterpenlactones have a wide range of biological and pharmacological effects. In plants they act mainly as antibodies. They are toxic to bacteria, fungi, worms (e.g. santonin from Artemisia cina) and other parasites.
The spectrum of effects on humans is described as antitumoral, antimicrobial, antirheumatic and antiphlogistic(helenalin from Arnica montana). The pharmacological effect of sesquiterpene lactones is thought to be due to the alkylation of proteins (enzymes) characterized by exposed sulfhydryl (SH) groups.
Some representatives have properties that make them objects for pharmacological research. For example, sesquiterpene lactones(helenalin, dihydrohelenalin) and their esters are considered to be the essential principle of action in the action of arnica extracts. Arnica extracts have analgesic, antiseptic and above all antiphlogistic effects. The mechanism of action is assumed to be an inhibition of inflammatory cytokines and cyclooxygenase.
Sesquiterpenlactones play a major role in contact allergic reactions.