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Senecionine is an organic compound with the chemical formula. It is produced by Senecio species and classified as a pyrrolizidine alkaloid. It has a core structure of retronecine which is further esterified by two Isoleucine to form a 12 member lactone ring.

Biosynthesis
In Senecio species, biosynthesis of Senecionine starts from L-Arginine or L-ornithine. Since plants don't have decarboxylase enzyme for L-ornithine, it must be first converted into L-Arginine, which can be readily converted to putrescine. Putrescine gains an aminopropyl group from spermidine in an NAD+ fashion to form homospermidine via homospermidine synthase. The detailed mechanism for this step isn't well understood and it is suspected that imine intermediate is involved. Homospermidine undergo a series of reactions to form the 2 five member rings structure of retronecine. Retronecine is further esterified by two L-isoleucine and modified through a couple of steps to senecionine.