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Evaluation of the Interference of Solvents Used in the Evaluation of Antimicrobial Activity of Liposoluble Natural Compounds
1 , 1 , 1 , * 2
2  Teacher Training Center (CFP) - Federal University of Campina Grande - Cajazeiras - Paraíba - Brazil.


Because it is an activity already consolidated throughout the ages, the use of compounds from plants has been well studied and tested for definition or proof of its antibacterial activity. Despite the difficulties encountered as the solubility of essential oils, there are compounds that help in experiments, they are called solvents and emulsifiers and the most used in phytotherapeutic tests are: ethyl acetate, acetone, ethyl alcohol, methyl alcohol, neutral detergent (phosphates free), dimethylsulfoxide (DMSO), triton X-I00 and polysorbate 80 (tween 80). In view of this fact, the present work seeks to identify concentrations of polysorbate 80 (Tween 80) and dimethylsulfoxide (DMSO) capable of performing an antibacterial activity, due to its wide use in the scientific environment, against the following bacterial strains: Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Pseudomonas aeruginosa ATCC 27853, Proteus mirabilis ATCC 25922 and Enterococcus faecalis ATCC 29212. The evaluation of the activity of the compounds was performed by the diffusion disc method. This method is the one recommended by the Clinical and Laboratory Standards Institute and is based on the diffusion through the agar of a reagent impregnated in a disc of filter paper and the diffusion of the same leads to the formation of a halo of inhibition of growth of the micro- organisms whose diameter is inversely proportional to the minimum inhibitory concentration. This method is qualitative, that is, it allows to classify the bacterial sample as susceptible, intermediate or resistant to antimicrobial. The tests were carried out with different concentrations of the reagents to determine the antimicrobial effect of the studied solvents. The experiments were run in triplicate at all concentrations using the compounds in combination (DMSO + Tween). The incubation was done in a greenhouse at 35 ± 2 ° C, for a period of 24 hours. The tests were performed and the results expressed in mm by the arithmetic mean of the diameter of the inhibition halos, formed around the discs. As results, no values ​​were determined that determined antimicrobial activity, and it is not possible to determine MIC when the formed halo is equal to or less than 6 mm or when there is no formation thereof. In view of the results, it can be observed that the compounds may not present activities against the microorganisms tested or, due to their physico-chemical characteristics, suffer some interference, such as the diffusion difficulty in the agar, its insolubility in water and chemical complexity.

Keywords: Antibacterial activity, DMSO, Tween 80, diffusion disk.