Anti-microbial and cytotoxic activity of ZzAMP, a serine protease inhibitor (SPI) with nutraceutical potential from rhizomes of medicinal plant, Zingiber zerumbet.

Serine protease Inhibitors (SPIs) abundantly reported in plant storage organs constitute important candidate molecules for antimicrobial and anticancer therapeutics. Our earlier studies had identified antimicrobial protein/or peptides (AMP) from Zingiber zerumbet rhizomes designated ZzAMP inhibiting serine protease (SP) of necrotrophic phytopathogen, Pythium myriotylum. Considering the high ethno-medicinal applications of Z. zerumbet rhizomes, present study evaluated the anti-bacterial, anti-oxidant and cytotoxic properties of ZzAMP. Though ZzAMP displayed low radical scavenging activity (IC50 1000 µg/ml), it exhibited considerable anti-bacterial activity towards the nosocomial pathogen Klebsiella pneumonia (93%), which produced maximal extracellular protease (30.6 ± 1.47 U/ml) amongst the pathogens screened. Evaluation of cytotoxic activity of ZzAMP revealed decrease in viability of cancer cell line, HeLa (IC50 115.09 μg/ml) compared to normal cells, L929 (IC50 299.95 μg/ml). Present experiments showing antimicrobial and cytotoxic activities of ZzAMP with minimal damage to normal cells are indicative of its potential as a promising nutraceutical protein.