Calycosin is an O-methylated isoflavone. It can be isolated from Astragalus membranaceus Bge. var. mongholicus and Trifolium pratense L. (red clover).
Isoflavone 3â²-hydroxylase uses formononetin, NADPH, H<sup>+</sup> and O<sub>2</sub> to produce calycosin, NADP<sup>+</sup> and H<sub>2</sub>O.
Calycosin has been shown to possess anti-cancer properties in vitro, and extracts of Astragalus membranaceus have been used to complement chemotherapy regimes in treatment of cancer in China.