Quassinoids

Quassinoids are a class of natural products, primarily highly oxygenated terpenoid lactones derived from plants in the Simaroubaceae family. The best known source is Quassia amara, but related species such as Simarouba and Eurycoma longifolia also produce quassinoids. Chemically, quassinoids are diverse, but they share a common triterpenoid-derived framework with one or more lactone rings and extensive oxygenation. They display a range of oxidation patterns and substituents, giving many structural variants that are studied for their biological activities.

These compounds occur mainly in wood and bark extracts and are responsible for some of the bitter flavors associated with quassia species. Quassinoids range from simple to highly complex polycyclic structures, and some members are among the most bitter natural products known, contributing to traditional uses as bitter tonics and insect deterrents.

Biological activity is broad and predominantly studied for medical and agricultural applications. Quassinoids have shown antifeedant and insecticidal effects, as well as cytotoxic, antiviral, antimicrobial, and antimalarial activities in various assays. Several members, such as bruceantin and quassin, have attracted research attention for potential anticancer and antiparasitic properties, though their toxicity and pharmacokinetic profiles pose challenges for therapeutic use.

Research continues to explore structure–activity relationships, biosynthesis, and potential applications, while recognition of their toxicity underscores the need for careful evaluation in any practical setting.