A reliable and validated HPLC method was established for the assay of trypsin inhibitors(TI)and it was used in the investigation of the active TI components inMomordica cochinchinensis(Cucurbitaceae family).The underlying principle of the assay is the measurement of the decrease in trypsin activity due to the presence of TI in analyzed samples,which was achieved by using HPLC separation and quantification of p-nitroanilide that was generated by tryptic hydrolysis of N-α-benzoyl-DL-arginine -4-nitroanilide.The results showed that the HPLC method had higher selectivity than conventional spectrophotometric assay.