Not a well-known supplemental ingredient, Celandine (Chelidonium majus) has been studied since the middle 1800s. The dried whole herb is the part used.
Celandine's long history of use to stimulate bile secretions has recently been confirmed by German researchers. It seems to act to stimulate the secretion only, and has not been shown to stimulate the synthesis of bile. This would be a good addition to bile producing, gall bladder, and liver formulations.
Celandine is available as a powder, or a powdered extract.