Brassica nigra and cuminum cyminum: Inhibitors of food borne pathogens.

ABSTRACT

Dried seeds of spices namely Brassica nigra (mustard) and Cuminum cyminum (cumin) were screened independently, in culture media, in their different forms (aqueous extracts, essential oils and powders) against some bacterial strains of spoilage and health significance. Test microorganisms included one gram+ve bacterial strain i.e. Bacillus cereus (MTCC 430) and three gram-ve bacterial strains viz. Enterococcus faecalis (MTCC 439), Psuedomonas aeruginosa (MTCC 1688) and Shigella sonnei (MTCC 2957). Spice agar method was opted for screening antibacterial activities of powdered forms of aforementioned spices at their different concentration levels (0.0, 0.1, 0.2, 0.4, 0.6, 0.8, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0 (% (w/v)). B.nigra more effectively inhibited bacterial strains in culture media. Minimum inhibitory concentrations (MIC) of powdered form of B.nigra were also determined. It was the concentration of spice which arrested the growth of bacterial strain upto 80% level of the total incubation period of 30 days. Agar-well assay was followed for antibacterial screening of aqueous extracts and essential oils of test spices. Aqueous extracts of reference spice samples did not exhibit growth inhibitory zones towards any test bacterial strains. On the other hand, essential oils of B.nigra and C.cyminum showed distinct growth inhibitory zones against all the bacterial strains under observation. Results obtained from agar well assay revealed that essential oil of B.nigra was more potent in inhibiting bacterial strains followed by C. cyminum . It was also noticed that B. cereus (gram+ve) was inhibited at lower concentrations of test substances as compared to all the other three gram-ve bacterial strains under investigation.