This study examined the effect of chitosan elicitor with four different concentrations (0, 0.2, 0.4 and 0.6 g/l) on physiological and biochemical properties of stevia under four levels of salinity stress (0, 50, 100, 150 mM level of NaCl). Salt stress caused reduction of chlorophyll a (Chl a), chlorophyll b (Chl b), total chlorophyll, carotenoid and total protein content. The increment of malondialdehyde (MDA) content was not significant in all NaCl levels, while the CAT and POX activities were increased as well as stevioside and rebaudioside A under salinity stress. On one side, chitosan treatments could compensate the reduction of physiological traits such as photosynthetic pigments and protein content. On the other side, chitosan caused multiple increases in malondialdehyde content, antioxidant enzymes activity (catalase and peroxidase), steviol glycosides (stevioside and rebaudioside A) under salt stress. We report for the first time, the potential of chitosan to enhance salinity-tolerant abilities in stevia through increment of the salt-adaptive factors and to diminish harmful damages caused by NaCl stress.
Background
Antibiotics have been widely used for the treatment of bacterial infections for decades. However, the rapid emergence of antibiotic-resistant bacteria has created many problems with a heavy burden for the medical community. Therefore, the use of nanoparticles as an alternative for antibacterial activity has been explored. In this context, metal nanoparticles have demonstrated broad-spectrum antimicrobial activity. This study investigated the antimicrobial activity of naked cerium oxide nanoparticles dispersed in aqueous solution (CNPs) and surface-stabilized using Pseudomonas aeruginosa as a bacterial model.
Methods
Gelatin-polycaprolactone nanofibers containing CNPs (Scaffold@CNPs) were synthesized, and their effect on P. aeruginosa was investigated. The minimum inhibitory and bactericidal concentrations of the nanoparticls were determined in an ATCC reference strain and a clinical isolate strain. To determine whether the exposure to the nanocomposites might change the expression of antibiotic resistance, the expression of the genes shv, kpc, and imp was also investigated. Moreover, the cytotoxicity of the CNPs was assessed on fibroblast using flow cytometry.
Results
Minimum bactericidal concentrations for the ATCC and the clinical isolate of 50 µg/mL and 200 µg/mL were measured, respectively, when the CNPs were used. In the case of the Scaffold@CNPs, the bactericidal effect was 50 µg/mL and 100 µg/mL for the ATCC and clinical isolate, respectively. Interestingly, the exposure to the Scaffold@CNPs significantly decreased the expression of the genes shv, kpc, and imp.
Conclusions
A concentration of CNPs and scaffold@CNPs higher than 50 μg/mL can be used to inhibit the growth of P. aeruginosa. The fact that the scaffold@CNPs significantly reduced the expression of resistance genes, it has the potential to be used for medical applications such as wound dressings.
Stevia rebaudiana B. extract as a low-calorie sweetener has gained worldwide approval. Synthesized nanoparticles by plant have been used in different programs such as medical, pharmaceutical and agricultural fields. Here, we report the increase of the main glycosides of stevia plant with silver nanoparticles (AgNPs) treatment. This fact has stimulated research on the analysis and comparison of different concentrations of commercial and synthesized AgNPs on the glycosides of stevia plant by highperformance liquid chromatography (HPLC). After AgNPs synthesis, spectrum absorption of extracts was analyzed in different ranges from 300 to 700 nm and the maximum peak was observed at 420 nm. Transmission electron microscopy (TEM) micrograph of synthesized AgNPs from Stevia rebaudiana extract showed spherical shape with the size of 25 nm. A comparison between quantities of glycoside by HPLC under both treatments of AgNP exhibited that synthesized AgNPs were more effective than commercial AgNPs on stevioside and then rebaudioside. On the other hand, results showed that increasing AgNP concentration in both treatments will lead to glycoside content enhancement. Overall, significant changes were observed in the glycosides in plants under synthesized and commercial AgNP treatment that could be used to create plants with higher quality of glycosides for pharmaceutical approaches.
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