Effect of Oil of Wintergreen on Spontaneous Tumors of the Mammary Gland in Mice: VI. The Different Effect of Two Fractions Obtained by the Distillation of the True Oil

Abstract

In a series of papers (1–5) data have been presented dealing with the effect of oil of wintergreen on spontaneous carcinoma of the mammary gland in mice. The fourth and fifth papers are of particular interest for a full understanding of the present data. In the fourth paper it was pointed out that the redistilled synthetic methyl salicylate had very little, if any, effect on the growth of such tumors. In the fifth paper, on the other hand, it was shown that the true or natural oil of wintergreen administered in the diet had a pronounced effect, slowing up the growth of spontaneous tumors in mice and enhancing certain retrogressive changes in the tumors. The survival time of the treated animals after the onset of malignancy was not influenced, however. Histologically tumors in treated animals showed, to a great extent, exaggeration of the retrogressive changes recorded by different observers in spontaneously receding tumors. These changes include large areas of necrotic tissue, pyknotic nuclei, and an enhancement of the connective tissue of the tumor. Several of the tumors in treated animals had completely regressed. These effects were brought about when treatment was initiated after the malignant tumors had been discovered. Except for the presence of impurities in small amounts, there is chemically very little to account for this difference in effect of the two oils. The true oil of wintergreen consists of more than 95 per cent methyl salicylate. While it is well known that the true oil of wintergreen is more stable than the synthetic methyl salicylate, due perhaps to the impurities contained in the former, it is questionable whether this could determine the different effect on malignant tumor growth.