In Vitro Antimicrobial and Anti-Tumor Activities of Intracellular and Extracellular extracts of Aspergillus niger and Aspergillus flavus var. columinaris

Fungi are known to produce a vast array of secondary metabolites that are gaining importance for their biotechnological applications. In the present study, the crude methanolic extracts of Aspergillus niger and Aspergillus flavus var. columinaris were tested by the disc diffusion method and minimal inhibitory concentration (MIC) determination for detection of antimicrobial activity against ten species of microorganisms: Escherichia coli ATCC 25922, Klebsiella pneumoniae ATCC 31488, Pseudomonas aeruginosa ATTC 27853, Shigella dysenteriae ATCC 13313, Proteus vulgaris ATCC 6380, Salmonella typhimurium (LIO, locally isolated organism), Bacillus cereus ATCC 11778, Enterococcus faecalis (LIO), Staphylococcus aureus ATCC 25923 and Candida albicans ATCC 10231 and by the sulforhodamine B (SRB) assay method to test their in vitro anti-tumor activity. The extracellular extracts of both fungi showed their activity against Gram-negative bacteria only. The antibacterial activity of extracellular extract of Aspergillus flavus var. columinaris was higher than that of extracellular extract of Aspergillus niger. Candida albicans was sensitive to the intracellular extract of Aspergillus flavus var. columinaris. The extracellular extracts of both isolated fungi were having more cytotoxic effect than their intracellular extracts. IC50 (concentration of extract required to reduce cell survival by 50%) of extracellular extract of Aspergillus niger was the most reducible one (0.905 μg/ml) followed by the extracellular extract of Aspergillus flavus var. columinaris (1.48 μg/ml). The IC50 of the intracellular extracts was approximately similar among two isolates (3.50 μg/ml for Aspergillus niger and 3.03 μg/ml for Aspergillus flavus var. columinaris). In conclusion, the extracellular extract of Aspergillus flavus var. columinaris possesses antibacterial activity against Gram-negative bacteria. While the extracellular extracts of Aspergillus niger and Aspergillus flavus var. columinaris have in vitro anti-tumor activity, which support their use in medicines. It is hoped that this study would lead to the establishment of some extracts that could be used to formulate new and more potent antimicrobial and anticancer drugs.