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Chelidonine, also named ranunculine, is a benzophenanthridine alkaloid isolated from the whole plant of Chelidonium majus. L. It has been used as a painkiller in clinical treatment based on its morphine-like analgesic effect. Pharmacological researches in recent years have demonstrated that chelidonine played a role in antitumor, antibacterial, spasmolysis activities, and so on. And the antitumor activity is drawing more and more attention. However, its mechanisms of function remain unclear, which needs to be clarified in the future.
Chelidonine is an alkaloid fundamental parent, a benzophenanthridine alkaloid and an alkaloid antibiotic. Chelidonine is an isolate of Papaveraceae with acetylcholinesterase and butyrylcholinesterase inhibitory activity .

Chelidonine is the major alkaloid component of Chelidonium majus. Chelidonium majus L. is the only species of the tribe Chelidonieae of the Papaveraceae family. The Papaveraceae family is rich in specific alkaloids. C. majus contains various isoquinoline alkaloids with protopine, protoberberine and benzophenanthridine structures. This benzophenanthridine alkaloid can induce apoptosis in some transformed or malignant cell lines. D-Chelidonine, the main alkaloid of Chelidonium majus, was first isolated in 1839. 
Chelidonine is a major bioactive, isoquinoline alkaloid ingredient in Chelidonium majus. Benzylisoquinoline alkaloids (BIAs) are a structurally diverse group of plant specialized metabolites with a long history of investigation. A restricted number of enzyme families have been implicated in BIA metabolism. Whereas some enzymes exhibit a relatively broad substrate range, others are highly substrate specific. A small number of plant species, including opium poppy (Papaver somniferum) and other members of the Ranunculales, have emerged as model systems to study BIA metabolism. Recently, the emergence of transcriptomics, proteomics and metabolomics has expedited the discovery of new BIA biosynthetic genes.

Chelidonine is an isolate of Papaveraceae with acetylcholinesterase and butyrylcholinesterase (a nonspecific cholinesterase) inhibitory activity. AChE (acetylcholinesterase) inhibitors or anti-cholinesterases inhibit the cholinesterase enzyme from breaking down ACh, increasing both the level and duration of the neurotransmitter action. According to the mode of action, AChE inhibitors can be divided into two groups: irreversible and reversible. Reversible inhibitors, competitive or noncompetitive, mostly have therapeutic applications, while toxic effects are associated with irreversible AChE activity modulators. Reversible AChE inhibitors play an important role in pharmacological manipulation of the enzyme activity. These inhibitors include compounds with different functional groups (carbamate, quaternary or tertiary ammonium group), and have been applied in the diagnostic and/or treatment of various diseases such as: myasthenia gravis, AD, post-operative ileus, bladder distention, glaucoma, as well as antidote to anticholinergic overdose. In general, methyltransferases of BIA metabolism accept a wide variety of alkaloid substrates with diverse backbone structures, with some showing more flexibility than others with respect to substrate range.