Isolation and Characterization of Protease Inhibitors with Antimicrobial Activity from Sirisa (Albizia lebbeck) Seed Protein Extract

The present study aimed to identify protease inhibitors (PIs) with antimicrobial activity from sirisa (Albizia lebbeck) seed protein extracts that may be a natural alternative to overcome multi-drug resistance, toxicity, and side effects of existing antimicrobial drugs. The crude PIs were extracted from seeds of A. lebbeck in 1% PVP and further partially purified by ammonium sulphate (NH4)2SO4 fractionation. The total protein content was found to be high in 0-30 % (NH4)2SO4 saturated protein fraction F1 (7.3 ± 0.17 mg/ml). Reasonably high PI activity towards trypsin was observed in 60–90 % (NH4)2SO4 saturated fraction F3 assessed by the agar well diffusion method and in vitro solution assay. Electrophoretic profiling of proteins from the F3 fraction showed nine bands on the gel with differential mobility. The presence of a zone of inhibition (ZOI) for different concentrations of F3- 60–90 % (NH4)2SO4 saturated PIs on agar plate demonstrated antimicrobial activity against E.coli, S. aureus, and P. aeruginosa with MIC values of 100 ± 5 µg/ml, 100 ± 4 µg/ml, and 90 ± 3 µg/ml respectively. Our results indicate that PIs from seeds of sirisa display potent antimicrobial activity against the tested microorganisms and could be investigated further in the future use in designing or formulating natural antimicrobial drugs to treat microbial infection-related diseases.