All steps tried either alone or in combination within the process of purification were carried out at 4-6°C unless specifically stated. Firstly, the powder from fresh bitter melon seeds was extracted in 0.15 M NaCl solution and then the pH of the solution was adjusted to 4.0. After simple centrifugation, the supernatant was neutralized and fractionated by 30%-65% ammonium sulfate. The precipitate was dialyzed against the pH 6.3, 0.05 M phosphate buffer. Secondly, the sample was applied onto a SP-Sepharose FF column and eluted with pH 6.3, 0.05 M phosphate buffer containing 0.15 M NaCl. The elution peak containing 30 kDa protein was collected. Thirdly, the portion was loaded onto a Sephacryl S-100 column and the elution peak with 30 kDa protein was pooled. Finally, the sample was applied onto a Macro-Cap-SP column. A linear gradient of 0-0.15 M NaCl in pH 7.0, 20 mM sodium phosphate buffer eluted the column and two peaks with 30 kDa proteins were respectively collected. 