Antimicrobial Activity of a Protease Inhibitor Isolated From the Rhizome of Curcuma Amada

Abstract

Objective: Protease inhibitors (PIs) are effective antimicrobial agents, and this study was aimed to study the antibacterial efficacy of a PI isolated from the rhizome of Curcuma amada.Methods: A proteinaceous protease inhibitor was isolated from the rhizome of C. amada and purified by Sephadex G-50 gel permeation chromatography. The purified inhibitor was denoted as Curcuma amada protease inhibitor (CAPI). The antibacterial effect of CAPI against Gram-positive and Gramnegative bacteria, the minimal inhibitory concentration (MIC), and minimal bactericidal concentration (MBC) of CAPI was studied in vitro, and the membrane disruption activity of CAPI was also analyzed.Results: CAPI was effective against both Gram-positive and Gram-negative bacteria, with slightly higher concentrations required for Gram-negative bacteria. The MIC ranged from 75 to 100 µg/ml and the MBC ranged from 100 to 125 µg/ml of CAPI. The study of membrane disruption by CAPI revealed the release of cell contents, namely, reducing sugars and proteins from the bacterial cell. Conclusion:A PI was effectively isolated from the rhizome of C. amada, and the isolated inhibitor proved to be a promising antibacterial agent.