A novel strain of Chromobacterium sp. NIIST (MTCC 5522) producing high level of purple blue bioactive compound violacein was isolated from clay mine acidic sediment. During 24 h aerobic incubation in modified Luria Bertani medium, around 0.6 g crude violacein was produced per gram of dry weight biomass. An inexpensive method for preparing crystalline, pure violacein from crude pigment was developed (12.8 mg violacein/L) and the pure compound was characterized by different spectrometric methods. The violacein prepared was found effective against a number of plant and human pathogenic fungi and yeast species such as Cryptococcus gastricus, Trichophyton rubrum, Fusarium oxysporum, Rhizoctonia solani, Aspergillus flavus, Penicillium expansum, and Candida albicans. The best activity was recorded against Trichophyton rubrum (2 -g/ml), a human pathogen responsible for causing athlete-s foot infection. This is the first report of antifungal activity of purified violacein against pathogenic fungi and yeast.
Diarrhea is one of the leading causes of morbidity and mortality in humans in developed and developing countries. Furthermore, increased resistance to antibiotics has resulted in serious challenges in the treatment of this infectious disease worldwide. Therefore, there exists a need to develop alternative natural or combination drug therapies. The aim of the present study was to investigate the synergistic effect of curcumin-1 in combination with three antibiotics against five diarrhea causing bacteria. The antibacterial activity of curcumin-1 and antibiotics was assessed by the broth microdilution method, checkerboard dilution test, and time-kill assay. Antimicrobial activity of curcumin-1 was observed against all tested strains. The MICs of curcumin-1 against test bacteria ranged from 125 to 1000 μg/mL. In the checkerboard test, curcumin-1 markedly reduced the MICs of the antibiotics cefaclor, cefodizime, and cefotaxime. Significant synergistic effect was recorded by curcumin-1 in combination with cefotaxime. The toxicity of curcumin-1 with and without antibiotics was tested against foreskin (FS) normal fibroblast and no significant cytotoxicity was observed. From our result it is evident that curcumin-1 enhances the antibiotic potentials against diarrhea causing bacteria in in vitro condition. This study suggested that curcumin-1 in combination with antibiotics could lead to the development of new combination of antibiotics against diarrhea causing bacteria.
The aim of this study is to investigate the antimicrobial compounds present in the lichen Usnea albopunctata. Ethyl acetate extract was purified by silica gel column chromatography to obtain a major compound and the chemical structure was characterized by 1 H-NMR, 13 C-NMR, DEPT, 1 H-1 H COSY, HMQC, HMBC, UV, and HR-MS spectroscopic methods as protolichesterinic acid. The antimicrobial activity was estimated by determination of the minimal inhibitory concentration by the broth microdilution method and agar disc diffusion method against thirteen human pathogenic bacterial and four fungal strains. Protolichesterinic acid recorded significant broad spectrum antimicrobial property. The best antibacterial activity was recorded against K. pneumonia (0.25 g/mL) and V. cholerae (0.5 g/mL). Significant antifungal activity was recorded against T. rubrum (0.12 g/mL), which is significantly better than the standard antifungal agent. Protolichesterinic acid is reported for the first time from Usnea albopunctata. Antifungal activity of protolichesterinic acid against medically important fungi is also reported for the first time. Thus the results of the present study suggest that protolichesterinic acid has significant antimicrobial activities and has the strong potential to be developed as an antimicrobial drug after further clinical evaluation.
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