RESUMEN
The current work is an attempt to know that in which fraction(s) the relaxant constituents of Rosa moschata concentrate. Crude methanolic extract of Rosa moschata was prepared as per our reported procedure. Sub fractions of methanol extract were extracted with different solvents in increasing order of polarity i.e. n-hexane > chloroform > ethyl acetate > n-butanol > residual aqueous fractions. Different concentrations (0.01, 0.03, 0.1, 0.3, 1, 3, 5 and 10 mg/ml) of the fractions were tested on spontaneous contractions and KCl induced contractions on rabbits' jejunal preparations. Calcium Concentration Response Curves (CCRCs) in the presence and absence of the test fractions using verapamil were constructed to understand its mechanisms. EtOA fraction was more relaxant with EC50 values 0.812±0.149 mg/ml on spontaneous and 2.01±0.08 mg/ml on KCl induced contractions. we also found right shift in its EC50 values expressed as log [Ca++]M values. In presence of 0.3 mg/ml EtOA fraction, its EC50 value was -2.22±0.035 vs control EC50 -2.71±0.21. For n-BuOH fraction, EC50 value was -1.82±0.00 vs control with EC50 -2.28±0.049 at concentration of 0.3 mg/ml. Ethyl acetate fraction of Rosa moschata was more potent and is therefore can be a target for activity guided isolation of calcium channel antagonists.