Purification of Isoflavone from Soybean Hypocotyls using Various Resins

Isoflavone was extracted with various concentration of aqueous methanol using whole hypocotyls as the starting material. Whole hypocotyls were preferred as the raw material because the residue could be easily removed from the solvent after the extraction process. Extraction yield was almost constant at the methanol concentration of $20-80\%$. Most of the isoflavone was extracted within 1 hr, and the extraction yield remained almost constant thereafter. When the concentration of methanol was $80\%$, the content of total solid was reduced due to the reduced extraction of contaminating protein as the result of protein insolubilization. Among resins tested, Diaion HP-20, Amberlite XAD-16, and Amberlite IRC-50 showed the highest capacity to absorb the compound. Open column chromatography with Diaion HP-20 showed that $80\%$ aqueous ethanol was most efficient as the eluting solvent with final recovery of the phytochemical being more than $95\%$. Maximum adsorption of the phytochemical occurred at the acidic pH 2-4. When the spatial velocity was increased to 15 and more, the degree of adsorption was decreased, whereas below spatial velocity of 15, the adsorption capacity of isoflavone to the resin was almost constant. The purity of the isoflavone purified by column chromatography was $78\%$.