Sedative Effects of California Poppy and Corydalis

Sedative Effects of California Poppy and Corydalis

Reference: Schafer HL, Schafer W, Schneider W, Elstner EF. Sedative action of extract combination of Eschscholtzia californica and Corydalis cava. Arzneim Forsch Drug Res 1995; 45: 124-26.

Summary & Comments/Opinions: While valerian (Valerian officinalis), passion flower (Passiflora incarnata) and hops (Humulus lupulus) are phytotherapeutic agents commonly employed for insomnia and anxiety, recent investigations by Dr. Schafer and his colleagues from the Technical University in Munich, Germany, have highlighted other more obscure medicinal plants falling into this category. This includes California poppy (Eschscholtzia californica) and corydalis (Corydalis cava). Both plants belong to the family of Papaveraceae and are rich in isoquinoline alkaloids. In the case of California poppy, the main alkaloid is protopine, although six other major categories of alkaloids have been isolated. The total alkaloid content in the root is 2.7% whereas the content in the herb ranges from 0.06 to 0.29%. The flower contains up to 5% rutin.

Although protopine is quite similar structurally to the narcotic morphine, it does not have the same addictive properties or mechanism of action. Protopine alkaloids increase the binding of GABA to GABA receptors comparably to benzodiazepines. In fact, the authors comment that in vitro animal experiments have demonstrated that at a concentration of 10 umol/L, diazepam increased GABA binding by 39% whereas the California poppy alkaloids increased it by 24 to 31%. How these figures compare to traditional sleep promoting agents like valerian would make an interesting study.

Like California poppy, corydalis has a long historical lineage as a sleep inducing herb. The tubers of the plant contain 6% total alkaloids, with one of the primary alkaloids called bulbocapnine representing about 20 to 35% of this total. Bulbocapnine seems to work with the dopaminergic neuronal transmitter system. Dr. Schafer notes "...that bulbocapnine possesses a selective action on the dopaminergic receptors, but by the interaction on the dopaminergic system it also influences other neurotransmitter systems, e.g. the serotinergic and cholinergic systems, in experiments with rats and mice." Several in vitro rat trials employing corydalis extract have demonstrated a sedative effect.

Although the authors give an extensive list of alkaloids for this plant, there is no mention of tetrahydropalmatine. Tetrahydropalmatine from the Chinese species Corydalis yanhuso has been extensively studied and found to be an effective analgesic, sedative, and tranquilizer. DL-tetrahydropalmatine has been given to patients with insomnia and was successful in alleviating the problem at a dose of 100 to 200 mg given at bedtime. Reported side effects included vertigo, fatigue, and occasional nausea.

From these preliminary studies it seems that both medicinal plants have an important role to play in helping patients with insomnia. Although at present they lack comprehensive human clinical trials to confirm their efficacy, it is hoped that some of the larger phytopharmaceutical companies will investigate these herbs in greater detail.

Natural Product Research Consultants, Inc.


By R. Reichert

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