RESUMO
Objective: This study was conducted to investigate the mechanisms of action of Eurycoma longifolia in rat corpus cavernosum
Materials and Methods: Tincture of the roots was concentrated to dryness by evaporating the ethanol in vacuo. This ethanolic extract was partitioned into 5 fractions sequentially with hexane, dichloromethane [DCM], ethyl acetate, butanol, and water. The corpus cavernosum relaxant activity of each fraction was investigated
The DCM fraction which showed the highest potency in relaxing phenyleph-rine-precontracted corpora cavernosa was purified by column chromatography. The effects of the most potent DCM subfraction in relaxing phenylephrine-precontracted corpora cavernosa, DCM-I, on angiotensin I- or angiotensin ll-in-duced contractions in corpora cavernosa were investigated. The effects of DCM-I pretreatment on the responses of phenylephrine-precontracted corpora cavernosa to angiotensin II or bradykinin were also studied. An in vitro assay was conducted to evaluate the effect of DCM-I on angiotensin-converting enzyme activity
Results: Fraction DCM-I decreased the maximal contractions [100%] evoked by angiotensin I and angiotensin II to 30 +/- 14% and 26 +/- 16% [p < 0.001], respectively. In phenylephrine-precontracted corpora cavernosa, DCM-I pretreatment caused angiotensin II to induce 82 +/- 27% relaxation of maximal contraction [p < 0.01] and enhanced [p < 0.001] bradykinin-induced relaxations from 47 +/- 8% to 100+/-5%. In vitro, DCM-I was able to reduce [p < 0.001] the maximal angiotensin-converting enzyme activity to 78 +/-0.24%
Conclusion: Fraction DCM-I was able to antagonize angiotensin ll-induced contraction to cause corpus cavernosum relaxation via inhibition of angiotensin II type 1 receptor and enhance bradykinin-induced relaxation through inhibition of angiotensin-converting enzyme