Isoflavone contents of red and subterranean clovers

Abstract The concentrations of the isoflavones biochanin A, genistein, formononetin, pratensein and daidzein in leaves of four varieties of red clover and two of subterranean clover have been measured by a paper chromatographic‐spectrophotometric method. Biochanin A and formononetin are the predominant isoflavones in red clovers whereas biochanin A and genistein are the most abundant in subterranean clovers. For both species the isoflavone levels differed between varieties and between sampling dates. Higher levels were found during flowering for red clovers and before flowering for subterranean clovers. The isoflavone contents have been calculated to have oestrogenic activity equivalent to 2–17 μg. of stilboestrol (% dry wt.) for the red clover samples and 22–48 μg. of stilboestrol (% dry wt.) for the subterranean clover samples. The potency of some of these samples is much higher than potencies previously reported in the literature.