INHIBITION OF INTESTINAL MOTILITY AND SECRETION BY FLAVONOIDS IN MICEAND RATS - STRUCTURE-ACTIVITY-RELATIONSHIPS

Intraperitoneal administration of some flavonoids (apigenin, flavone, kaempferol, morin, myricetin, naringin and rutin; 12.5-50 mg kg(-1)) s ignificantly (P<0.05-0.01) reduced small (28-69%) and large (83-134%) intestinal transit in mice. Other flavanoids (naringenin, silibinin, s ilymarin and taxifolin, 100-200 mg kg(-1)) reduced (23-41%; P<05-0.01) intestinal transit at doses of 100-200 mg kg(-1) while hesperitin, ca techin and phroridzin (up to 200 mg kg(-1)) had no effect. This effect was antagonized by yohimbine (87-96%) and phentolamine (87-91%) but n ot by prazosin, propranorol, atropine, hexamethonium, mepyramine, cypr oheptadine and naloxone. Yohimbine (92-96%) also antagonized the inhib itory effect of flavonols (12.5-50 mg kg(-1)) (P<0.05-0.01) on intralu minal accumulation of fluid and diarrhoea induced by castor oil. By co ntrast, verapamil potentiated the flavonol effect. It is suggested tha t these effects, influenced by the structure of the molecules, are med iated by alpha 2-adrenergic receptors and calcium.