Binding of STW 5 (Iberogast) and its components to intestinal 5-HT, muscarinic M3, and opioid receptors.

Clinical studies with the fixed herbal combination product STW 5 (Iberogast) have indicated an efficacy comparable to metoclopramide (5-HT(3) antagonist) and cisapride (5-HT(4) agonist) in functional gastro-intestinal diseases like functional dyspepsia (FD) and irritable bowel syndrome (IBS). Since serotonin (5-HT(3) and 5-HT(4)) and muscarinic M(3) receptors are known to play a central role in the etiology of FD and IBS, the extracts contained in STW 5 and several of their phytochemical components were studied in vitro for binding affinities to these receptors of the intestine. STW 5 inhibited the binding of (3)H-GR113808 and (3)H-4-DAMP to 5-HT(4) and M(3) receptors, respectively, about 10 times more potently than the binding of (3)H-GR65630 to 5-HT(3) receptors.

Interaction of various Piper methysticum cultivars with CNS receptors in vitro.

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 (mu and delta), 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.