Planta Med 2001; 67(4): 306-311
DOI: 10.1055/s-2001-14334
Original Paper
Pharmacology
© Georg Thieme Verlag Stuttgart · New York

Interaction of Various Piper methysticum Cultivars with CNS Receptors in vitro

Long Doan Dinh1 , Urs Simmen1,*, Karin Berger Bueter1 , Bernd Bueter2 , Kenneth Lundstrom3 , Willi Schaffner1
  • 1 Institute of Pharmaceutical Biology, University of Basel, Witterswil, Switzerland
  • 2 Vitaplant AG, Witterswil, Switzerland
  • 3 F. Hoffmann-La Roche AG, Research Laboratories, Basel, Switzerland
Further Information

Publication History

June 6, 2000

October 29, 2000

Publication Date:
31 December 2001 (online)

Abstract

Methanolic leaf and root extracts of the Hawaiian kava (Piper methysticum Forst.) cultivars, Mahakea, Nene, Purple Moi and PNG, were tested on binding affinities to CNS receptors including GABAA (GABA and benzodiazepine binding site), dopamine D2, opioid (μ and δ), serotonin (5-HT6 and 5-HT7) and histamine (H1 and H2). HPLC analysis was carried out in order to determine the amount of the main kavalactones kavain, 7,8-dihydrokavain, methysticin, 7,8-dihydromethysticin, yangonin and 5,6-demethoxyyangonin. The most potent binding inhibition was observed for leaf extracts to GABAA receptors (GABA binding site) with IC50 values of approximately 3 μg/ml, whereas root extracts were less active with IC50 values ranging from 5 μg/ml (Nene) to 87 μg/ml (Mahakea). Since the leaf extracts generally contained lower amounts of the kavalactones than the root extracts, there might exist additional substances responsible for these activities. Leaf extracts also inhibited binding to dopamine D2, opioid (μ and δ) and histamine (H1 and H2) receptors more potently than the corresponding root extracts with IC50 values ranging from 1 to 100 μg/ml vs. ≥ 100 μg/l, respectively. Significant differences in the potential of binding inhibition were also observed between cultivars. Binding to serotonin (5-HT6 and 5-HT7) and benzodiazepine receptors was only weakly inhibited by both root and leaf extracts of all four cultivars. In conclusion, our investigation indicates that the GABAA, dopamine D2, opioid (μ and δ) and histamine (H1 and H2) receptors might be involved in the pharmacological action of kava extracts. Since the cultivars contained similar amounts of kavalactones, while their pharmacological activities differed markedly, other constituents may play a role in the observed activities. Additionally, leaves generally exhibited more potent binding inhibition than roots, therefore leaf of P. methysticum might be an interesting subject for further pharmacological studies.

Abbreviations

BHK:baby hamster kidney

CHO:Chinese hamster ovary

CNS:central nervous system

DMY:5,6-demethoxyyangonin

DHM:7,8-dihydromethysticin

DHK:7,8-dihydrokavain

GABA:γ-aminobutyric acid

3H-LSD:3 H-lysergic acid diethylamide

HPLC:high performance liquid chromatography

IC50:50 % inhibitory concentration

SFV:Semliki Forest Virus

References

Dr. Urs Simmen

Institute of Pharmaceutical Biology

University of Basel

Benkenstrasse 254

4108 Witterswil

Switzerland

Email: usimmen@datacomm.ch

Fax: ++41 61 721 52 19

Phone: ++41 61 721 52 16