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.