Quassinoids

Quassin is a white, bitter, crystalline substance that is the prototypical example of the family of quassinoids. It can be extracted from the quassia tree, from which it gets its name. It was first isolated in 1937, and its chemical structure was elucidated in 1961.

Ailanthone is a quassinoid allelochemical produced by the tree Ailanthus altissima (commonly known as tree of heaven). It is a key agent behind the tree's strong allelopathic effects, which inhibit the growth of competing plants by suppressing seed germination and disrupting root elongation. Native to China, Ailanthus altissima has become one of the worst invasive species in North America and Europe, where ailanthone is known to contribute significantly to its competitive spread.