Coumestans are oxidation products of pterocarpan[2] that are similar to coumarin.

Coumestans, including coumestrol, a phytoestrogen, are found in a variety of plants.

Food sources high in coumestans include split peas, pinto beans, lima beans, and especially alfalfa and clover sprouts.

[3] Coumestrol has about the same binding affinity for the ER-β estrogen receptor as 17β-estradiol, but much less affinity than 17α-estradiol, although the estrogenic potency of coumestrol at both receptors is much less than that of 17β-estradiol.

[4] Because of the estrogenic activity of some coumestans, a variety of syntheses have been developed that allow the preparation of coumestans so that their pharmacological effects can be explored.