Antibacterial and Cytotoxic activities of Callistemon citrinus leaves.

Abstract

The aim of this study was to evaluate the antibacterial and cytotoxic activities of the methanolic extract of Callistemon
citrinus leaves. Disc diffusion method was carried out to evaluate antibacterial activity using kanamycin as standard. The
methanolic leaf extract showed potential antibacterial activity against both gram positive and gram negative pathogenic
bacteria. This extract showed highest activity against Bacillus megaterium and Escherichia coli with 29 mm and 27 mm
zone of inhibition. The minimum inhibitory concentration (MIC) of the extract was determined that showed potential
efficacy against the bacteria. The extract exhibited MIC with 64 ?g/ml and 64 ?g/ml for B. megaterium and E. coli
respectively. The cytotoxicity of the leaf extract was investigated by brine shrimp lethality bioassay using vincristine sulfate
as standard. The extract showed significant cytotoxicty with LC50 value of 9.84 ?g/ml as compared with LC50 value of 6.05
?g/ml of standard.