Silver enhances the in vitro antifungal activity of the saponin, CAY-1

Abstract

The fungicidal properties of purified CAY-1, dissolved silver ion and ethylenediamine tetraacetic acid (EDTA) separately were studied in vitro as were the abilities of silver and EDTA to enhance CAY-1 fungicidal properties. Non-germinated and germinating conidia of Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Fusarium verticillioides (Fusarium moniliforme), Fusarium oxysporum and Fusarium solani were incubated separately with CAY-1 (0-24.8 μg ml(-1)), silver (0-111.1 μg ml(-1)), and EDTA (0-2400 μg ml(-1)). Controls consisted of non-germinated or germinated conidia in test medium. To assess combined activity, compounds, based on the sub-lethal doses of each as defined in the initial experiments, were combined and tested in bioassays. Controls for the mixed sets consisted of non-germinated or germinated conidia only or with the sub-lethal CAY-1 test concentrations. The minimum inhibitory concentrations (MICs) for CAY-1 and silver, both separate and combined, were determined. Viability assays showed CAY-1 activity only against the germinating conidia of A. flavus, A. niger and F. solani. Silver was active against the germinating conidia of all fungi and the non-germinated conidia of F. oxysporum and F. solani. Combined silver and CAY-1 produced significant viability loss at concentrations not effective separately. EDTA was not fungicidal separately and did not enhance CAY-1 fungicidal properties. MIC data showed that CAY-1 plus silver had an additive effect. Results indicate that dissolved silver was fungicidal in vitro and enhanced the fungicidal properties of CAY-1 at concentrations ineffective when tested separately.

Fungicidal and antibacterial activity of the hydrogel compositions with silver

“…The estimated by diameter EC50 values (16.05.9 -86.439.0 ppm) for the compositions with colloidal silver were close to obtained estimations (1-50 up to 100 ppm) for silver nanoparticles in other studies [2,[11][12][13][14][15][16]. This is indicative of quite high fungicide and bactericide efficiency of similar PPA.…”

“…Traditional evaluation by the linear growth of the colony gives value EC50 from 16 to 32 ppm for Oomycete in the case of using any types of hydrogels with silver nanoparticles and EC50 from 14 to 35 ppm for Enterobacteria in the case of using any forms of silver (ionic or colloidal) with a hydrophilic type of hydrogels (Aquasorb or VUM-0). The same values were obtained by a similar laboratory microbiological methods (silver ions or nanoparticles in the composition of dense, gel-like agar medium or in the foams as saponins) in the studies [15] -EC50 from 30 to 50 ppm; [12] -diapason EC50-ECt up to 111 ppm; [13] -EC50-ECt from 50 to 100 ppm; [16] -EC50 from 13 to 50 ppm; [14] -EC50 from 10 to 15 ppm. Smaller doses were received only for aquaculture, or when using water solutions and dispersions of silver at the surface of agar medium for the growth of microbes as, for example, EC50 = 5-50 ppb of silver ions in Slade and Pegg [10], 2-8 ppm of silver nanoparticles in Min et al [11] or Ali et al [2].…”

“…Such causative agents as late blight and black leg of potato were used for the laboratory experiments. Unlike previous studies [2,[10][11][12][13][14], this research involves the assessment of non-water solutions such as gel compositions of the PPA with colloidal and ionic form of silver nitrate (AgNO3). These compositions improve the stability of the nanoparticles, and in the practical use guarantee fixation of PPA in the rhizosphere and its protection from leaching.…”

“…Two main objectives of the research are as follows: 1) to assess the antifungal and antibacterial effects of gel compositions with silver in order to determine the range of PPA doses for subsequent trials under field conditions; 2) to compare the effectiveness of different forms of silver and different types of hydrogels. Based on the previous studies [2,[10][11][12][13][14][15][16], the dose of silver should not exceed 100 ppm, which is economically sufficient considering an average price of silver 15-30$ per Trinity oz.. This study compared the efficiency of the two agents, as well as several types of hydrogels: a convenient "Aquasorb" based on polyacrylamide and new hydrogels produced at the Ural Chemicals Factory by our proprietary technology with the filling of the polymer matrix.…”

“…Two types of growth inhibitors were used, colloidal silver and ionic silver (chemically pure AgNO3) in the composition with three types of hydrogels (hydrophilic agent Aquasorb (France) based on polyacrylamide, acrylic gel VUM-0 with hydrophilic filler in the form of waste biocatalytic production of polyacrylamide and acrylic gel PM-1 with amphiphilic filler in the form of dispersed peat). The latter is an experimental product of the Ural Chemicals Factory from patent-pending technology [4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The colloidal silver is an experimental product "Zeroxxe" of AgroChimProm GC (http://tdahp.ru/en/,) that contains silver nanoparticles with a size of 10-70 nm superficially modified with environmentally safe biodegradable amphiphilic surfactant (tallow amphopolycarboxyglycinate-stabilizer [18].…”