Coumestan is a heterocyclic organic compound. Coumestan forms the central core of a variety of natural compounds known collectively as coumestans. Coumestans are oxidation products of pterocarpan 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.
Coumestrol has a similar binding affinity for the ER-ò estrogen receptor as 17ò-estradiol, but much less affinity than 17ñ-estradiol, although the estrogenic potency of coumestrol at both receptors is much less than that of 17ò-estradiol.
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.