| dc.description.abstract | Concentration of constituent of a modius, Ph, and age are known to influence the quality and quantity of metabolites produced by micro-organisms in media. The effects of variation of these parameters on the production of aflatoxin and its co-fluorescent metabolites by Aspargillus flavus link (U.I.81) in Yeast-extract-sucrose medium have been investigated. Ph 7 or 4.5, sucrose concentration 18%-25% and 2%-2.5% of yeast extract have been found conducive for adequate production of these metabolites. Optimum concentrations of these metabolites were obtained as from the 8th day of incubation.
The antibiotic properties of the aflatoxins and some of these other fluorescent metabolites have also been investigated. They were found to have a narrow spectrum of antibiotic action confined almost entirely to few gran-positive species of the Bacillus genus. Three strains of Bacillus brevis, two of Bacillus megaterium and one of Bacillus mycoides were found susceptible to one or more of these fluorescent metabolites. The following pathogenic bacteria were also found susceptible to some of these metabolites, i.e. Heisseria gonorrhooae, Neisseria meningitides, Haemophilius influenene, Staphylocooci evogenes, Corynebacterium diphtheria (inter-medium), Streptooocous viridans and Streptococous faecalin. Out of a total of 388 faecel bacteria, 12 mouth-swab bacteria got off a normal person resident in Nigeria and 258 faecal bacteria got off a normal individual resident in a temperate clients country but just arrived in Nigeria, not a single one was found sensitive to any of these compounds.
These metabolism in combination with one another and with common clinical antibiotic compounds have also been investigated. The combination B1–B5, G1-G5, B3-B4, B6-G6, exhibited synergism, while G4-G6 indicated antagonism. All other possible combinations between one another of these compounds gave additive action. Combinations: B1- Tetracycline, B1 – Novobiocin, G1 – tetracycline, G1 – Novobiocin, G6- Chloramphaniool and G6 – Novobiocin resulted in synergism. Combinations between the other fluorescent compounds and tetracycline, chloramphenicol, streptomycin, novobiocin and penicillin resulted in additive action. The only exceptions were the combinations between penicillin and B1, G3 and G6, which resulted in antagonism.
The modes of action of these compounds investigated show that they are bacteriostatic in action and slightly more effective during the exponential phase of growth of susceptible bacteria. Oxygen uptake was inhibited significantly in some susceptible bacteria even at as low a concentration as 5 µg/ml. DNA, RNA, and protein synthesis were also inhibited in susceptible bacteria. The compounds also showed ability to bind DNA, RNA, protein, cell-membrane, starch, cellulose, cellulose-acetate, cellulose-phosphate, ecteola-cellulose, methyl-carboxy-cellulose, and cellulose-acetate.
The chemistry of five of these co-fluoresecent metabolites of aflatoxin were also investigated. From melting point, iodine number, ultraviolet, infra-red, nuclear magnetic resonance, mass spectral and fluorescence data obtained, for these compounds, it can be concluded that they are probably hydroxylated unsaturated aromatic coumarin compounds containing the bio-dihydro or bio-tetrahydro-furan ronan. | en_US |
