Legume proteinase inhibitors (PI/s) abrogate proteolytic activity of proteins and cause adverse effects on growth. In this study, two legume PIs - Archidendron ellipticum Trypsin Inhibitor (AeTI) and Derris trifoliata Trypsin Chymotrypsin Inhibitor (DtTCI) were purified and used along with standard, Soybean Trypsin Inhibitor (STI), either singly or in combination, as antiplasmodial agents against two Plasmodium forms (Pf 3D7/Pf FCR3). Both AeTI/DtTCI were purified to homogeneity by HPLC and showed over 98% trypsin/chymotrypsin inhibition, respectively. DtTCI severely arrested growth of both the Plasmodium forms (IC50 of 9.59 mu M, and 16.86 mu M, respectively). In addition, combination of DtTCl/AeTI had synergistic effect against both Pf3D7 (FIC-0.19) and Pf FCR3 (FIC-0.23). Combinations of DtTCl/STI and AeTI/STI showed additive effects for the parasite forms. Time-course studies indicated DtTCI and combination of DtTCl/AeTI, to be potent inhibitor of schizont rupture. Antiproteolytic action of the PIs on Pf Apical Merozoite Antigen 1 (AMA1) protein revealed that none of the inhibitors (singly/combinations) affected the primary proteolysis of PfAMA1 protein. Notably however, the normal secondary proteolysis of PfAMA1 was abrogated by both DtTCI (singly/combinations) and AeTI. Incidentally, the proteolytic processing of PfAMA1 remained unaffected following STI treatment. (C) 2017 Elsevier Ltd. All rights reserved.