SYMPATHOMIMETIC EFFECTS OF SCOPARIA-DULCIS L AND CATECHOLAMINES ISOLATED FROM PLANT-EXTRACTS

The herb Scoparia dulcis L. is used in Brazilian folk medicine to trea t bronchitis, gastric disorders, haemorrhoids, insect bites and skin w ounds, and in oriental medicine to treat hypertension. A previous stud y has shown that extracts of S. dulcis have analgesic and anti-inflamm atory properties in this work the sympathomimetic activity of an ethan olic extract of Scoparia dulcis L. has been investigated in rodent pre parations in-vivo and in-vitro. Administration of the extract (0.5-2 m g kg(-1), i.v.) to anaesthetized rats produced dose-related hypertensi on blocked by the alpha-adrenoceptor antagonist prazosin (1 mg kg(-1)) . Partition of the extract in chloroform-water yielded an aqueous phas e 20 times more potent than the extract; this produced hypertension in either reserpine-treated or pithed rats. in untreated and reserpine-t reated rats the same fraction (1-3 x 10(3) mu g mL(-1)) produced conce ntration-dependent contractions of the vas deferens musculature parall el to those obtained with noradrenaline (10(-8)-10(-4) M). Prazosin (1 0(-7) M) reduced the maximum contractile effect of the aqueous fractio n, and shifted the concentration-response curves for noradrenaline to the right. The aqueous fraction (25 and 50 mu g mL(-1)) increased the inotropism of electrically driven left atria of rats, the effect being blocked by propranolol (0.4 mu g mL(-1)). in preparations of guinea-p ig tracheal rings the aqueous fraction (1-3 x 10(3) mu g mL(-1)) relax ed the muscle contraction induced by histamine (10(-4) M) in proportio n to the concentration. The effect was antagonized competitively by pr opranolol (1.5 mu M), High-performance liquid-chromatographic analysis of the aqueous fraction revealed the presence of both noradrenaline a nd adrenaline in the plant extract. The results indicated that both ca techolamines may account for the hypertensive and inotropic effects ob tained after parenteral administration of S. dulcis extracts. This sym pathomimetic activity is, however, unrelated to the previously reporte d analgesic and anti-inflammatory properties of the plant extract, but may explain its effectiveness upon topical application in the healing of mucosal and skin wounds.