Saponins contained in alfalfa act on the cardiovascular, nervous, and digestive systems ⁽¹⁾. The hypocholesterolemic and hemolytic activity of the leaves and sprouts of alfalfa are attributed to a steroidal saponin fraction which, along with fiber contained within the plant, binds to cholesterol in vitro. Alkaloids such as stachydrine and l-homo-stachydrine found in the seed are thought responsible for alfalfa’s ability to promote menstrual discharge and for its lactogenic activity ⁽²⁾. Biochanin-A, an isoflavonoid constituent, blocks NF-κB activation by preventing phosphorylation and degradation of IκBα, leading to decreased expression of inducible nitric oxide synthase, thus preventing proliferation and inflammation ⁽¹⁷⁾.

Extracts from alfalfa preferentially served as agonists for estrogen receptor beta, and alfalfa increased estrogen-dependent MCF-7 breast cancer cell proliferation even more than did estradiol ⁽⁹⁾. The non-protein amino acid constituent, L-canavanine, constitutes 1.5% of the dry weight of alfalfa seeds and alfalfa sprouts. It has been shown to affect human T cells in vitro and induce hematologic and serologic abnormalities characteristic of systemic lupus erythematosus in monkeys ⁽¹³⁾. This is the proposed mechanism by which systemic lupus erythematosus relapse occurs in humans as well ⁽⁷⁾, although some researchers question whether L-canavanine concentrations in alfalfa are sufficient to cause this effect ⁽⁸⁾.