Harmonine is a defensive chemical produced by Harmonia axyridis, the Asian harlequin ladybug, aka the multicolored Asian lady beetle. It is one of the compounds in the insect’s hemolymph (circulatory system fluid) that helps it ward off predators.
Almost 100 years ago, H. axyridis was introduced into the United States and Europe because it controls aphids in crops better than native ladybug species. But the Asian species can damage crops, and it carries a parasite that kills native ladybugs. Harmonine not only helps protect the Asian bug from the parasite, but its foul taste makes it unpalatable to birds and other predators.
In 2012, A. Vilcinskas and co-workers at Justus Liebig University (Giessen, Germany) discovered that harmonine is active against the pathogens responsible for malaria and tuberculosis. They are working to create harmonine-based drugs that can prevent or combat these diseases.
Learn more about this molecule from CAS, the most authoritative and comprehensive source for chemical information.