Legume seeds are proven to contain high degrees of PI, such as for instance those from the Kunitz and BowmanBirk type people. Kunitz type inhibitors are proteins of AP26113, with minimal cysteine content and a single reactive site, although the BowmanBirk type inhibitors have Mrs 810 kDa, with large cysteine content and two reactive web sites. Several serine PI have already been demonstrated to work on platelet aggregation, blood coagulation, fibrinolysis and infection. For this reason, place Kunitz inhibitors are useful as tools in the study of those biochemical processes. PI is now well established as a class of cancer chemopreventive agents. Soybean Bowman Birk trypsin inhibitor. The absolute most studied, is an efficient anti tumoral agent because it stops and inhibits malignant transformation in vitro and carcinogenesis in vivo in a wide selection of programs. This chemical is under clinical Papillary thyroid cancer trials and studies on human populations are increasingly being considered. Several other plant or synthetic PI have been proved to be associated with growth arrest, cytotoxicity, and metastasis elimination or invasiveness inhibition of transformed cells. Lately, we described the isolation of a inhibitor from the seeds of Peltophorum dubium Taub. G. dubium is a tree from the Leguminosae family which grows in Argentina, Brazil, Uruguay and Paraguay. Its leaves, fruits and roots are employed in popular medicine and methanolic extracts showed antimicrobial activity. Nevertheless, no protein had been known. We separated Imatinib 152459-95-5 PDTI by affinity chromatography on a trypsin agarose order, it was active against bovine trypsin and chymotrypsin, and its amino terminal sequence was much like that of professional Kunitz kind soybean trypsin inhibitor. We indicated that both PDTI and SBTI exhibited a like action detected by hemagglutination of rabbit erythrocytes, which was inhibited by sialic acid containing compounds. We also showed evidence that PDTI and SBTI caused apoptosis of Nb2 rat lymphoma cells and had no effect on normal mouse splenocytes or lymphocytes, although apoptosis was caused by them on concanavalin A stimulated mouse lymphocytes. Although SBTI is the archetypical Kunitz sort trypsin inhibitor and has been thoroughly studied, these properties had remained unknown. More over, PDTI was also been shown to be active against trypsinlike proteases extracted from different lepidopteran larvae. Taking this into account, it had been especially interesting to evaluate PDTI and SBTI influence on human lymphocytes. Here, we describe for the very first time that both trypsin inhibitors encourage human Jurkat leukemia cell apoptosis, shown by a loss of cell viability followed by DNA fragmentation and no cell cycle profile amendment.