Piper marginatum (Piperaceae), popularly known as "caapeba-cheirosa", "nhandi" or "malvarisco", provides an essential oil with a yield of about 1.5%. Several specimens already worked on by our group show a differentiated chemical composition, with a predominance of the following constituents: 3,4-methylenedioxypropiophenone (30-40%), anisole (20-30%), safrole (50-60%) and ?3-carene (30-40%). This species is used in folk medicine as a stimulating tonic, on external wounds and ulcers, in the treatment of erysipelas, and to relieve pain and itching caused by insect bites. Previous works have demonstrated that this oil has cercaricidal, insecticidal, anti-inflammatory and analgesic activity. The present work aimed to study the essential oil of Piper marginatum (OEPm), the chemical type rich in 3,4-methylenedioxypropiophenone, to evaluate its spasmogenic activity. OEPm did not alter basal tone, however, at concentrations of 100 to 1000 lIWm,1 it triggered spontaneous rhythmic movements of this muscle. It was also able to block acetylcholine- and histamine-induced submaximal responses with CI50 of 6.49 + 1.6611Wml(n= 4) and 11.50 + 2.1711Wml (n=5), respectively. OEPm also reversed 60mM K+-induced contracture, with CI50 of 46.34 + 8.5611Wml(n=6). These results suggest that the studied P. margínatum essential oil possesses antispasmodic activity with a more selective action on muscarinic and histaminergic receptors of ileal smooth muscle. Support: MCT-PPG7/European Community.
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