Comparative bioactivity of dhaman grass root extracts in different polar solvents against plant and human pathogens

Abstract

Background: Cenchrus ciliaris L. (Poaceae) is a very suitable and highly nutritive grass for environmental conditions of the desert; yet, no antimicrobial work has been done on this grass. Aim: To estimate in vitro the antibiotic activity of root extracts of C. ciliaris in various polar solvents to use the grass as a possible source for new antimicrobial compounds against important plant and human pathogens. Settings and Design: The antibiotic activity of C. ciliaris root extracts were evaluated against a few medically important pathogens including Gram-negative bacteria Proteus mirabilis, Klebsiella pneumoniae, Agrobacterium tumefaciens, and the fungi, Aspergillus niger. Materials and Methods: Dried, powdered, and weighted root material was successively extracted with different polar solvents [hexane, petroleum ether, toluene, benzene, isopropyl alcohol, chloroform, ethyl acetate, acetone, ethanol, glacial acetic acid (GAA), and water] using a Soxhlet assembly. Antibiotic activity was performed by using disc diffusion assay followed by determination of minimum inhibitory concentrations by broth dilution method, against sensitive bacteria (with good inhibition zone). Most of the extracts, at higher concentrations, showed varying degrees of inhibitory activity against selected bacteria. Statistical Analysis: Mean value and standard deviation were calculated for the test bacteria and fungi. Data were analysed by one-way analysis of variance (ANOVA) and P values were considered significant at P<0.05. Results and Conclusions: Results revealed that the highest antibiotic activity was exhibited by the water and GAA extracts against P. mirabilis, followed by isopropyl alcohol extract against K. pneumoniae and A. tumefaciens. Water extract was observed to be the most active extract with maximum zone of inhibition against A. tumefaciens (plant pathogen) as compared to all other extracts. Key words: Antibiotic activity, Cenchrus grass, minimum inhibitory concentration, one of inhibition