Isolation of hypotensive compounds from Solanum sisymbriifolium Lam.

The crude hydroalcoholic root extract (CRE) of Solanum sisymbriifolium Lam. has formerly been shown to have hypotensive activity both in normo-and hyp ertensive rats. Hypotensive activity-guided fractionation of the CRE was pe rformed in anaesthetized normotensive rats, which led to the isolation of t he active principles. The intravenous (i.v.) and intraperitoneal (i.p.) val ues of the CRE in mice were found to be, respectively, 343 and 451 mg/kg, a nd no lethal effect was caused by doses up to 5.0 g/kg when administered by oral route. Depression of locomotion, increase of breathing rate and piloe rection was observed in a general behavior test with doses up to 200 mg/kg i.p., and 1000 mg/kg p.o., respectively. Increase in the gastrointestinal t ransit was found using 0.1 g/kg, whereas at doses of 0.5 and 1 g/kg, no sig nificant activity was observed in comparison with the control mice. Hexanic and butanolic fractions induced a remarkable hypotension in anaesthetized normotensive rats in doses of 1, 5, 7.5 and 10 mg/kg i.v. Two compounds iso lated from the butanolic fraction induced a significant decrease of the blo od pressure, HR, amplitude of the ECC and breathing rate when injected in a dose of 1 mg/kg i.v; and both systofic and diastolic, blood pressures were affected in a proportional mode. The hypotensive effect of the two compoun ds were not influenced by pretreatment with atropine and propranolol; and t he presser response to noradrenaline was not affected by any of them which suggests that neither a direct muscarinic activity, beta-adrenoceptor activ ation nor decrease of sympathetic vascular tone (sympatholitic activity) ar e probably involved in the mechanism of hypotension. The present study show s that the CRE of S. sisymbriifolium contains at least two hypotensive comp ounds whose characterization is under way. (C) 2000 Elsevier Science Irelan d Ltd. All rights reserved.