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It has been reported previously that Pisum Sativum (the common field pea) acts as a contraceptive. A series of animal experiments on white rats were performed and the results published (Sanyal, 1950–55) demonstrating its contraceptive effect due to the inhibition of the peripheral action of progesterone and consequent prevention of nidation of a fertilized ovum. Subsequently the active substance was located in the oil of the seeds, isolated in the pure state and its chemical nature determined. The synthesis of the active principle was also effected. The results of animal experiment on white rats with the synthetic active principle, m-xylohydroquinone, corroborated the previous experimental results. Further spectrophotometric studies in vitro as well, demonstrated that m-xylohydroquinone alone, and not its isomers, can interfere with progesterone. But in the language of Professor Swyer of the University College Hospital, London (England), to argue from rats to human beings is rather a risky procedure.

The finding of Professor N. C. Nag that the feeding of the seeds of Pisum Sativum, Linn to rats greatly reduced their production of offspring¹ led to the testing of an oil extracted from the seeds as a monthly intramuscular injection for women.² When this proved successful in postponing pregnancy, the active principle was isolated and its chemical nature was determined to be m-xylohydroquinone. When this compound was tested on rats, along with its four analogs, m-xylohydroquinone was found to be most protective and least toxic.³ In ovariectomized rats it prevented an increase in the weight of the uterus and also the development of the endometrial glands after the administration of progesterone. It was thought, therefore, that it would be most effective if administered shortly before the menstrual period.

For a clinical test the metaxylohydroquinone was prepared from meta-xylidene (2,6 dimethyl aniline) secured from Distillation Products Inc.

m-Xylohydroquinone, which is being used as an oral contraceptive by quite a large number of women patients, is showing very encouraging results. The dosage is only 300 to 350 mg. taken orally twice a month. The attendance of voluntary patients at the clinic is gradually increasing. A large number of private patients, about 800 in number, have taken and are taking the medicine for various periods and no undesirable effects have as yet been reported. Had there been any such effects, the number of voluntary patients would certainly have decreased rapidly. It is apparent that the medicine has no toxic effect on the human system. Still doubts have been expressed in some quarters as to its possible cumulative toxic effects when used for prolonged periods. For a scientific answer to this, the present work was undertaken at the instance of Dr. Clarence J. Gamble, M. D. of Boston, Mass., U.