OBJECTIVE

We conducted this study to evaluate the pregnancy interceptive activity of the roots of Calotropis gigantea Linn. in colony-bred adult Sprague-Dawley rats when administered during the preimplantation and/or peri-implantation periods.

METHODS

The ethanolic extract of the roots of C. gigantea Linn. and its hexane, chloroform, n-butanol-soluble and n-butanol-insoluble fractions were administered to rats on Day 1, Days 1-5, Days 1-7 or Days 5-7 postcoitum. Rats from the control group received an equal volume of the vehicle (Tween 80 in glass distilled water) only. At autopsy on Day 10 postcoitum, the final body weight and number as well as status of the corpora lutea and implantations in each animal were recorded. For estrogen agonistic and antagonistic activities, 21-day-old immature rats ovariectomized 7 days earlier were treated orally with the test agent or the vehicle for 3 days. In the case of estrogen antagonistic activity, the rats also received 0.05 mg/kg of 17alpha-ethinyl estradiol for 3 days. At autopsy 24 h after the last treatment, uterine fresh weight was taken and premature opening of the vagina as well as the extent of vaginal cornification, if any, were recorded.

RESULTS

The ethanolic extract of the roots of C. gigantea Linn. exhibited 100% pregnancy interceptive activity in rats when administered as a single oral dose of 100 mg/kg on Day 1 postcoitum. The extract also exhibited 100% efficacy at the dose of 12.5 mg/kg when administered in the Days 1-5 and 1-7 postcoitum schedules. When administered during the peri-cum-early postimplantation period (i.e., Days 5-7 postcoitum at 250 mg/kg), most of the implantations showed signs of resorption. On fractionation, the chloroform fraction showed 100% activity at 100 mg/kg in the single-day (Day 1 postcoitum) schedule, whereas the hexane, n-butanol-soluble and n-butanol-insoluble fractions were found to be inactive at this dose. At autopsy on Day 10 postcoitum, 7-25% loss in body weight was recorded at the minimum effective contraceptive dose (MED) in rats treated with the ethanolic extract as well as its chloroform-soluble fraction on Days 1-7, 1-5 and 1 postcoitum, in comparison with the 6-7% increase in body weight observed in vehicle control rats. There was however no mortality in any of the treatment groups. The active ethanolic extract and its chloroform fraction were devoid of any estrogen agonistic or antagonistic activity at their respective MEDs in the ovariectomized immature rat bioassay. Efforts are being made to isolate the active principles devoid of effect on body weight.

CONCLUSIONS

The findings suggest the potential for developing products of this plant as contraceptives for human use and welfare. In addition, characterization of the agents responsible for body weight decrease and evaluation of their mechanism of action and safety profile, with or without contraceptive efficacy, might have added advantage for the management of obesity.