The use of tebuconazole as a fungicide to protect the library

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The use of tebuconazole as a fungicide to protect the library

Fungicides, i. e. all fungiactive and fungistatic chemical substances, used not only in agricultural and plant protecting practice, but also as disinfectants, can be divided in two following groups:

- surfactants active only on the surface without penetrating plant tissues. Their task is to block the cellular respiration and stop the metabolism of the cells. This group includes: copper - and sulphur fungicides, thiocarbonyl derivates, ditiocarbamates, aromatic hydrocarbons derivates, dicarboxymide fungicides;

- inner acting fungicides with systemic performance, that causes disturbance in development of pathogens and stopping the destruction of paper. This group contains: benzimidazole compounds, triazol compounds, phenyloamids and anilinopyrimidines.

Tebuconazole (triazoles group), which shows high fungicide efficacy and simultaneously low damage to books and other printed materials was the main substance used for this particular examination. For that reason the tebuconazole is used in fast interventions. It is also non toxic for the environment and provides no carcinogenic activity. The mechanism of biological activity of this fungicides' group lies in their ability to inhibit the synthesis of sterolic alcohol called ergosetrol, which is responsible for selectivity of cytomembrane. This selectivity is broken by the lack or insufficiency of the sterol in the cell's environment.

The main aim of this study was to carry out an initial experiment to check, whether triazoles could be used to fight microbiological hazards of antique library collections and separate printed materials. The construction of old prints causes variety of microbiological dangers, mainly with viral and fungal infections. For this particular study tebuconazole was chosen as a model example of the active substance and pathogen called Penicillium chrysogenum was the tested fungal material. The tebuconazol is a racemic solid substance, soluble in polar organic solvents, photo - and thermal stable in alcohols. The examined substance is usually obtained by reaction of 2-i-butylo-2 - (4-chlorofenyloetylo) - oxirane with 1,2,4 - triazole in dimethyl sulfoxide in the presence of a base (Pic. 1). On the market it is known as Tebu 250 EW and Horizon 250 EW.

For its high fungicidal activity the tebuconazol is very often used and added to other plant protection agents and what is more it is indeed the most popular of all triazole fungicides.

To relate the impact of fungicidal activity of tebuconazol on old prints and other historic materials, that would need preservation in the library, the ED50 factor was to be determined before the right investigation. The biological activity of the fungicides was referred in the ancient book preservation process, involving the appointment of the so - called ED50 coefficients, i. e. how big amount of the substance is needed to destroy half of the fungal pathogens' population. The ED50 ratio is used to determine the concentration of working solution, which should be sprayed on the surfaces of the protected material: paper, parchment, leather or fabric, providing the required protective efficacy.

To get the correct ratio a set of concentration series, consisting of isopropanolic solutions of tebuconazol was prepared. In the next stage, the solutions in the volume of 1 cm were mixed 50 cm³ of nutrient that consisted of agar-agar solved in wort and then put into Petri dish. On the set nutrient the test material, i.e. spawns of fungus Fungicidal activity, were placed. The concentration of the active substance in reference to 1 cm³ of nutrient were set in the range from 10⁵ to 10² ng/cm³. The linear growth of the fungus was measured every 24 h until the tested fungus totally covered the control dish, which included the set nutrient with 1 cm³ of isopropanol.

The fungicidal activity of tebuconazol on Fungicidal activity is given as ED50 ratio and the results are presented below in the Table 1.

Table 1. Fungicidal activity of examined substances