Membrane Separation and Concentration of Pigeon Pea Leaf Extract

Purification of the extract from pigeonpea leaves was studied. Multi-stage membrane separation and concentration using microfiltration, ultrafiltration, and nanofiltration membranes were conducted on the extract at room temperature. Concentrations of the major active ingredients in the filtrates were determined. The results indicated that 15.78% of the total flavonoids in the extract could be retained by the microfiltration membrane, 62.52% by the ultrafiltration membrane, and 97.92% by the nanofiltration membrane. By combining the membranes, the multi-stage filtration could remove as much as 50% of the solvent yielding a concentrated extract containing 50.13% flavonoids. The ultrafitration alone retained a vitexin concentration of 0.069 mg·g^-1 and isovitexin of 4.31 mg/g, as determined by HPLC. It appeared that the multi-stage membrane filtration could significantly improve the efficiency of pigeon pea extract separation resulting in a highly concentrated filtrate as well as desired energy conservation.