Bioautography direct

Homans, A. L., Fuchs, A. Direct bioautography on thin-layer chromatograms as a method for detecting fungitoxic substances. J Chromatogr 1970 5(2) 327-3299. 

Dellar et al. (55) isolated the antifungal sesquiterpenes aristolen-2-one (Compound 9) and prostantherol (Compound 10) from two species of Prostanthera (Labiatae). Activity was assessed and tracked through the separation procedure by the use of direct bioautography with Cladosporium cucumerinum as the target fungus. 

In direct bioautography there is usually no need for diffusion from the adsorbent to the agar medium. Both water-soluble and lipid-soluble substances are in direct contact with the bacteria and the growth medium on the surface of the adsorbent particles. There is no dilution and diffusive loss of the separated substances, and this results in low detection limits. 

However, the planar chromatographic adsorbent material is, not always suitable for microbial studies. If the test bacterium requires special conditions (e.g., extremely long incubation time) the advantages of the method may not be exploited. The main factors influencing the evaluation of direct bioautography will be discussed below. 

The direct bioautography process can be divided into three steps (1) growing test bacteria cultures for... 

The antibacterial activity of waltherione-A, isolated from Waltheria douradinha (Sterculiaceae) (Table IX) and its O-methylated derivative were evaluated by means of direct bioautography in a TLC bioassay. The former alkaloid was not active against all bacteria tested (S. aureus. Streptococcus epidermidis. Micrococcus luteus, Klebsiella pneumoniae. Salmonella setubal, and E. coli), while its O-methyl derivative was active against all of them. The detection limits were 25.0, 3.5, 6.5, 12.5, 12.5, and 6.5 pg, respectively (170). 

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