The oestrogenic isoflavones of subterranean clover

A number of strains of subterranean clover has been examined for isoflavone content in an attempt to explain the differences of oestrogenic potency in sheep and cattle under field conditions. A method of thin-layer chromatography has been developed which allows a rapid semiquantitative estimation of the main isoflavones present in this species. The isoflavones are present in a combined form, probably as glycosides, and the free isoflavones are rapidly released after crushing the leaf. The percentages of formononetin, genistein, and biochanin A in the leaves are very much higher than reported by earlier workers and vary widely between strains. Moreover, the ratios of the isoflavones differ greatly among strains. The relevance of these plant data to the oestrogenic potency in the animal is discussed.