Production and purification of bioactive compounds with potent antimicrobial activity from a novel terrestrial fungus Aspergillus sp. DHE 4
Ahmed S.Abdel-Razeka,b, Dina H.El-Ghonemyb, MohamedShaabana,c
Department of Organic and Bioorganic Chemistry, Faculty of Chemistry, University of Bielefeld, D-33501, Bielefeld, Germany.
Steep declines in the development of antimicrobial agents have been reported in recent years; however, there has been an increase in both the number of antibiotic resistant pathogenic bacteria and immunocompromised patients susceptible to opportunistic pathogens. Therefore, the development of antimicrobial agents with new modes of action became vital to address the threats posed by the advent of bacteria that are resistant to current therapeutic agents. Nowadays, filamentous fungi are regarded as a source of novel pharmacologically beneficial bioactive compounds. In the current study the crude extracts of three locally isolated fungal strains were biologically evaluated for their antimicrobial activity using a paper disk diffusion method. A fungal isolate genetically identified as a new Aspergillus sp., showed potent antimicrobial activity against various pathogenic microorganisms; mainly Gram-positive bacteria and yeast. Solid-state fermentation on Rice solid medium followed by working up and purification using a series of diverse chromatographic techniques afforded various bioactive compounds namely; 4-hydroxy-4-methyl-tetrhydo-pyrone; R(−)-mevalonolactone] (1), three proposed alternative structures (2a, 2b or 2c) for a novel poly-hydroxysterol, kojic acid (3) and α-/β-glucoside mixture (4a/4b). The chemical structures of these compounds were confirmed by 1D and 2D NMR and ESI HR mass spectrometry and compared with literature data. These findings represent the first report on the production of polyhydroxy sterol and R(−)-mevalonolactone from a new Aspergillus sp., suggesting the producing fungus as a talented source for investigation of promising drug leads.
Keywords: Aspergillus sp. DHE 4, Antimicrobial activity, Bioactive compounds, NMR and ESI HR mass spectrometry.