A cardiogenin major isomer is obtained from a methanol extract of Geum japonicum and separated from its minor isomer. The separation of the two isomers can be achieved by chiral phase chromatography, e.g., using a Chiralpak® IC™ column. The purity of the isolated cardiogenin major isomer can be further increased by crystallization, yielding isolated cardiogenin major isomer having HPLC purity as high as 98.97% (a/a) at 210 nm and a potency of 95.50%) (w/w).