Scientists have isolated a number of alkaloids from the tuber of corydalis, including corydaline, tetrahydropalmatine (THP), dl-Tetrahydropalmatine (dl-THP), protopine, tetrahydrocoptisine, tetrahydrocolumbamine, and corybulbine.³ Of the full range of 20 alkaloids found in the plant, THP is considered to be the most potent. In laboratory research, it has been shown to exhibit a wide number of pharmacological actions on the central nervous system, including analgesic and sedative effects.⁴ dl-THP has been found to exhibit a tranquilizing action in mice. Scientists have suggested that dl-THP blocks certain receptor sites (e.g., dopamine) in the brain to cause sedation.⁵

In addition to its central nervous system effects, studies in the laboratory have shown the alkaloids from corydalis also have cardiovascular actions. For example, dl-THP has been shown to both decrease the stickiness of platelets and protect against stroke,⁶ as well as lower blood pressure and heart rate in animal studies.⁷ Additionally, it seems to exert an anti-arrhythmic action on the heart. This was found in a small double-blind clinical trial with patients suffering from a specific type of heart arrhythmia (e.g., supra-ventricular premature beat or SVPB).⁸ People taking 300–600 mg of dl-THP per day in tablet form, had a significantly greater improvement than those taking placebo pills.

Other human clinical trials on dl-THP have shown the ability to fall asleep was improved in people suffering from insomnia after taking 100–200 mg of dl-THP at bedtime. No drug hangover symptoms such as morning grogginess, dizziness or vertigo were reported by people taking the alkaloid extract.⁹

Reports from Chinese researchers also note that 75 mg of THP daily was effective in reducing nerve pain in 78% of the patients tested.¹⁰ Painful menstruation (dysmenorrhoea), abdominal pain after childbirth, and headache have also been reported to be successfully treated with THP.¹¹

Extracts of the herb may also be useful in the treatment of stomach ulcers. In a large sample of patients with stomach and intestinal ulcers or chronic inflammation of the stomach lining, a 90–120 mg extract of the herb per day (equal to 5–10 grams of the crude herb) was found to improve healing and symptoms in 76% of the patients.¹²