Selenium nanoparticles based on Amphipterygium glaucum extract with antibacterial, antioxidant, and plant biostimulant properties.

BACKGROUND: In recent years, crop production has expanded due to the variety of commercially available species. This increase in production has led to global competition and the search for biostimulant products that improve crop quality and yield. At the same time, agricultural products that protect against diseases caused by phytopathogenic microorganisms are needed. Thus, the green synthesis of selenium nanoparticles (SeNPs) is a proposal for achieving these needs. In this research, SeNPs were synthesized from methanolic extract of Amphipterygium glaucum leaves, and chemically and biologically characterized. RESULTS: The characterization of SeNPs was conducted by ultraviolet-visible spectrophotometry (UV-Vis), scanning electron microscopy (SEM), electron microscopy transmission (TEM), Dynamic Light Scattering (DLS), energy dispersion X-ray spectroscopy (EDX), and infrared spectrophotometry (FTIR) techniques. SeNPs with an average size of 40-60 nm and spherical and needle-shaped morphologies were obtained. The antibacterial activity of SeNPs against Serratia marcescens, Enterobacter cloacae, and Alcaligenes faecalis was evaluated. The results indicate that the methanolic extracts of A. glaucum and SeNPs presented a high antioxidant activity. The biostimulant effect of SeNPs (10, 20, 50, and 100 µM) was evaluated in vinca (Catharanthus roseus), and calendula (Calendula officinalis) plants under greenhouse conditions, and they improved growth parameters such as the height, the fresh and dry weight of roots, stems, and leaves; and the number of flowers of vinca and calendula. CONCLUSIONS: The antibacterial, antioxidant, and biostimulant properties of SeNPs synthesized from A. glaucum extract demonstrated in this study support their use as a promising tool in crop production.

High-Density Chitosan Induces a Biochemical and Molecular Response in Coffea arabica during Infection with Hemileia vastatrix.

The coffee industry faces coffee leaf rust caused by Hemileia vastratix, which is considered the most devastating disease of the crop, as it reduces the photosynthetic rate and limits productivity. The use of plant resistance inducers, such as chitosan, is an alternative for the control of the disease by inducing the synthesis of phytoalexins, as well as the activation of resistance genes. Previously, the effect of chitosan from different sources and physicochemical properties was studied; however, its mechanisms of action have not been fully elucidated. In this work, the ability of food-grade high-density chitosan (0.01% and 0.05%) to control the infection caused by the pathogen was evaluated. Subsequently, the effect of high-density chitosan (0.05%) on the induction of pathogenesis-related gene expression (GLUC, POX, PAL, NPR1, and CAT), the enzymatic activity of pathogenesis-related proteins (GLUC, POX, SOD, PPO, and APX), and phytoalexin production were evaluated. The results showed that 0.05% chitosan increased the activity and gene expression of ß-1,3 glucanases and induced a differentiated response in enzymes related to the antioxidant system of plants. In addition, a correlation was observed between the activities of polyphenol oxidase and the production of phytoalexin, which allowed an effective defense response in coffee plants.

Comparative study of steroidal sapogenins content in leaves of five Agave species.

BACKGROUND: Agaves are mainly used to produce alcoholic beverages such as tequila, mezcal and bacanora. However, the leaves constitute more than 50% of the plant and are not used in the production process, so they are considered waste. This plant material can be used as a source of bioactive compounds such as terpenes, flavonoids and saponins. Therefore, the objective of this study was to characterize the aglycone type of saponins and to quantify three steroidal sapogenins in leaves of five Agave species collected in different regions of Guerrero and Oaxaca, Mexico. RESULTS: Analysis by gas chromatography-flame ionization detection of the hydrolyzed methanolic extracts showed that diosgenin and tigogenin were the most abundant sapogenins identified in the five Agave species. Differences in the content of these sapogenins were found in the same species collected in different localities. The leaves of Agave americana var. oaxacensis L. (Oaxaca) had the highest diosgenin-derived saponin content, while the leaves of A. angustifolia Haw. (Guerrero) had the highest tigogenin-derived saponin content. Only in A. cupreata was sarsasapogenin identified, all three sapogenins occurring in the leaves of this species. For the first time, information is provided on the aglycones of the saponins produced in A. potatorum Zucc. and A. karwinskii Zucc. CONCLUSION: This study made it possible to compare the content of diosgenin and tigogenin-derived saponins in leaves of Agave species from Guerrero and Oaxaca. This information will be useful for better utilization of this plant material and add value to the process of mezcal elaboration. © 2022 Society of Chemical Industry.

Chronic wound healing by controlled release of chitosan hydrogels loaded with silver nanoparticles and calendula extract.

As the skin is the main protective organ of the body, it is exposed to wounds or injuries which carry out a healing process during a period of approximately 15 days depending on the severity of the injury. In the present research, the development of chitosan-based hydrogels loaded with silver nanoparticles and calendula extract (Ch-AgNPs-Ce) was proposed. This can be used to fulfill the hemostatic, anti-infective, antibacterial, healing and anti-inflammatory functions through controlled release of the nanoparticles and calendula extract in substitution of commonly used drugs. The physical properties of the silver nanoparticles were analyzed by UV-visible spectroscopy, scanning and transmission electron microscopy, showing a size between 50 and 100 nm. The antibacterial properties were evaluated by the agar well diffusion method. Antimicrobial testing of the hydrogels showed that the inclusion of silver nanoparticles provides concentration-dependent antibacterial behavior against E. coli and S. aureus. The healing properties of the system were tested in two diabetic patients to whom said hydrogels were placed, obtaining a positive curative result after a few weeks. Therefore, it can be concluded that Ch-AgNPs-Ce hydrogels can achieve healing in chronic or exposed wounds after a period of time which can be used in alternative treatments in patients with poor healing capacity.

Antibacterial Activity of Biosynthesized Selenium Nanoparticles Using Extracts of Calendula officinalis against Potentially Clinical Bacterial Strains.

The use of selenium nanoparticles (SeNPs) in the biomedical area has been increasing as an alternative to the growing bacterial resistance to antibiotics. In this research, SeNPs were synthesized by green synthesis using ascorbic acid (AsAc) as a reducing agent and methanolic extract of Calendula officinalis L. flowers as a stabilizer. Characterization of SeNPs was performed by UV-vis spectrophotometry, infrared spectrophotometry (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM) techniques. SeNPs of 40-60 nm and spherical morphologies were obtained. The antibacterial activity of marigold extracts and fractions was evaluated by disk diffusion methodology. The evaluation of SeNPs at different incubation times was performed through the colony-forming unit (CFU) count, in both cases against Serratia marcescens, Enterobacter cloacae, and Alcaligenes faecalis bacteria. Partial antibacterial activity was observed with methanolic extracts of marigold leaves and flowers and total inhibition with SeNPs from 2 h for S. marcescens, 1 h for E. cloacae, and 30 min for A. faecalis. In addition, SeNPs were found to exhibit antioxidant activity. The results indicate that SeNPs present a potentiated effect of both antimicrobial and antioxidant activity compared to the individual use of marigold extracts or sodium selenite (Na2SeO3). Their application emerges as an alternative for the control of clinical pathogens.

Plant-mediated synthesis of nanoparticles and their antimicrobial activity against phytopathogens.

Nanotechnology is an emerging science with a wide array of applications involving the synthesis and manipulation of materials with dimensions in the range of 1-100 nm. Nanotechnological applications include diverse fields such as pharmaceuticals, medicine, the environment, food processing and agriculture. Regarding the latter, applications are mainly focused on plant growth and crop protection against plagues and diseases. In recent years, the biogenic reduction of elements such as Ag, Au, Cu, Cd, Al, Se, Zn, Ce, Ti and Fe with plant extracts has become one of the most accepted techniques for obtaining nanoparticles (NPs), as it is considered an ecological and cost-effective process without the use of chemical contaminants. The objective of this work was to review NPs synthesized by green chemistry using vegetable extracts, as well as their use as antimicrobial agents against phytopathogenic fungi and bacteria. Given the need for alternatives to control and integrate management of phytopathogens, this review is relevant to agriculture, although this technology is barely exploited in this field. © 2020 Society of Chemical Industry.

Bioactive Compounds, Antioxidant Activity, and Antinutritional Content of Legumes: A Comparison between Four Phaseolus Species.

Beans (Phaseolus spp.) are one of the most important legumes for their nutritional value and health benefits in many world regions. In addition to Phaseolus vulgaris, there are four additional species that are cultivated in many regions of the world and are a source of food for human consumption: P. lunatus, P. coccineus, P. polyanthus, and P. acutifolius. In this work, phenolic compounds, antioxidant activity, and anti-nutritional compounds of 18 bean accessions, corresponding to four different species of the genus Phaseolus, were analyzed. In addition, their physical characteristics, proximate composition, and amino acid content were determined in order to compare their phytochemical composition and nutritional value. The species closest to each other in terms of essential amino acid content were P. polyanthus with P. vulgaris and P. lunatus with P. coccineus. Furthermore, there was a strong positive correlation between antioxidant activity and flavonoids, anthocyanins, and lectins with all the accessions collected. Significant differences in the content of phenolic compounds were found among the bean species studied. Therefore, in addition to P. vulgaris, other species such as P. coccineus and P. lunatus have high biological and antioxidant potential that could be beneficial to human health when consumed as nutraceutical foods.

Antifungal Activity of Selenium Nanoparticles Obtained by Plant-Mediated Synthesis.

The continuous need to satisfy world food demand has led to the search for new alternatives to combat economic losses in agriculture caused by phytopathogenic fungi. These organisms cause plant diseases, reducing their productivity and decreasing fruit quality. Among the new tools being explored is nanotechnology. Nanoparticles with antimicrobial properties could be an excellent alternative to address this problem. In this work, selenium nanoparticles (SeNPs) were obtained using plant extracts of Amphipterygium glaucum leaves (SeNPs-AGL) and Calendula officinalis flowers (SeNPs-COF). Characterization of the SeNPs was performed and their ability as antifungal agents against two commercially relevant plant pathogenic fungi, Fusarium oxysporum and Colletotrichum gloeosporioides, was evaluated. Assays were performed with different concentrations of SeNPs (0, 0.25, 0.5, 1.0, and 1.7 mg/mL). It was observed that both SeNPs had antifungal activity against both plant pathogens at concentrations of 0.25 mg/mL and above. SeNPs-AGL demonstrated better antifungal activity and smaller size (around 8.0 nm) than SeNPs-COF (134.0 nm). FTIR analysis evidenced the existence of different functional groups that constitute both types of SeNPs. There are factors that have to be considered in the antimicrobial activity of SeNPs such as nanoparticle size and phytochemical composition of the plant extracts used, as these may affect their bioavailability.

The Role of Selenium Nanoparticles in Agriculture and Food Technology.

Selenium (Se) is an essential micronutrient for diverse organisms such as mammals, bacteria, some insects and nematodes, archaea, and algae, as it is involved in a large number of physiological and metabolic processes and is part of approximately 25 selenoproteins in mammals. In plants, Se has no essential metabolic role, high concentrations of inorganic Se can lead to the formation of Se-amino acids, and its incorporation into selenoproteins can generate toxicity. Conversely, low doses of Se can trigger a variety of beneficial effects as an antioxidant, antimicrobial, or stress-modulating agent without being an essential element. Therefore, Se can generate toxicity depending on the dose and the chemical form in which it is supplied. Selenium nanoparticles (SeNPs) have emerged as an approach to reduce this negative effect and improve its biological properties. In turn, SeNPs have a wide range of potential advantages, making them an alternative for areas such as agriculture and food technology. This review focuses on the use of SeNPs and their different applications as antimicrobial agents, growth promoters, crop biofortification, and nutraceuticals in agriculture. In addition, the utilization of SeNPs in the generation of packaging with antioxidant and antimicrobial traits and Se enrichment of animal source foods for human consumption as part of food technology is addressed. Additionally, possible action mechanisms and potential adverse effects are discussed. The concentration, size, and synthesis method of SeNPs are determining factors of their biological properties.

Evaluation of the Physicochemical Properties of Chitosans in Inducing the Defense Response of Coffea arabica against the Fungus Hemileia vastatrix.

Chitosan is a natural polymer, and its biological properties depend on factors such as the degree of deacetylation and polymerization, viscosity, molecular mass, and dissociation constant. Chitosan has multiple advantages: it is biodegradable, biocompatible, safe, inexpensive, and non-toxic. Due to these characteristics, it has a wide range of applications. In agriculture, one of the most promising properties of chitosan is as an elicitor in plant defense against pathogenic microorganisms. In this work, four kinds of chitosan (practical grade, low molecular weight, medium molecular weight, and high-density commercial food grade) were used in concentrations of 0.01 and 0.05% to evaluate its protective effect against coffee rust. The best treatment was chosen to evaluate the defense response in coffee plants. The results showed a protective effect using practical-grade and commercial food-grade chitosan. In addition, the activity of enzymes with ß-1,3 glucanase and peroxidase was induced, and an increase in the amount of phenolic compounds was observed in plants treated with high-molecular-weight chitosan at 0.05%; therefore, chitosan can be considered an effective molecule for controlling coffee rust.

Cerium enhances germination and shoot growth, and alters mineral nutrient concentration in rice.

Cerium (Ce) belongs to the rare earth elements (REEs), and although it is not essential for plants, it can stimulate growth and other physiological processes. The objective of this research was to evaluate the effect of Ce on seed germination, initial seedling growth, and vegetative growth in rice (Oryza sativa L.) cv. Morelos A-98. During the germination process, the seeds were treated with Ce concentrations of 0, 4, 8, and 12 µM; after 5 d, germination percentage was recorded and after 10 d seedling growth was measured. For vegetative growth, a hydroponic system was established where 14-d-old plants without previous Ce treatment were transferred into nutrient solution. After two weeks of acclimatizing, 0, 25, 50, and 100 µM Ce were added to the nutrient solution for 28 d. Ce significantly increased germination and the initial growth variables of the seedlings. During vegetative growth, Ce increased plant height, number of tillers, root volume, and shoot fresh and dry biomass, without affecting root biomass weight. With low Ce concentrations (25 and 50 µM), the concentrations of chlorophylls and amino acids in the shoots were similar to those in the control, like amino acid concentration in the roots at a concentration of 25 µM Ce. Conversely, the concentration of total sugars increased in the shoot with the application of 25, 50, and 100 µM Ce, and in the roots with the application of 50 µM Ce. Also, Ce did not affect the concentration of macro or micronutrients in the shoots. However, in the roots, the high Ce concentration decreased the concentrations of Ca, Fe, Mn, and Zn, while the Mg concentration increased. Our results indicate that Ce, at the right concentrations, can function as a biostimulant in rice germination and growth.

Fertigation: Nutrition, Stimulation and Bioprotection of the Root in High Performance.

Temperature changes, drought, frost, and the presence of pest and diseases place enormous stress on crops, which implies that the potential performance of these crops may be affected. One of the main goals for agronomists, horticulturists, growers, physiologists, soil scientists, geneticists, plant breeders, phytopathologists, and microbiologists is to increase the food production on the same cultivable area and to ensure that they are safe and of high quality. Understanding the biophysical changes in soil will help to manage the crop's ability to cope with biotic and abiotic stress. Optimization is needed in the nutrition of crops, which involves the use of biostimulants to counter oxidative stress and the management of strain bioformulations (bacteria and fungi) that protect and stimulate roots for the acquisition of nutrients. The implementation of these strategies in fertigation programs improves crop yields. This article addresses the importance of the stimulation and the bioprotection of the root as a fundamental pillar in ensuring the high performance of a crop.

Aluminum Enhances Growth and Sugar Concentration, Alters Macronutrient Status and Regulates the Expression of NAC Transcription Factors in Rice.

Aluminum (Al) is a beneficial element for some plant species, especially when used at low concentrations. Though some transcription factors are induced by exposure to this element, no data indicate that Al regulates the expression of NAC genes in rice. In this study we tested the effect of applying 200 µM Al on growth, chlorophyll, amino acids, sugars, macronutrient concentration and regulation of NAC transcription factors gene expression in 24-day-old plants of four rice (Oryza sativa ssp. indica) cultivars: Cotaxtla, Tres Ríos, Huimanguillo and Temporalero, grown hydroponically under greenhouse conditions. Twenty days after treatment, we observed that Al enhanced growth in the four cultivars studied. On average, plants grown in the presence of Al produced 140% more root dry biomass and were 30% taller than control plants. Cotaxtla and Temporalero showed double the root length, while Huimanguillo and Cotaxtla had three times more root fresh biomass and 2.5 times more root dry biomass. Huimanguillo plants showed 1.5 times more shoot height, while Cotaxtla had almost double the root dry biomass. With the exception of Tres Ríos, the rest of the cultivars had almost double the chlorophyll concentration when treated with Al, whereas amino acid and proline concentrations were not affected by Al. Sugar concentration was also increased in plants treated with Al, almost 11-fold in comparison to the control. Furthermore, we observed a synergic response of Al application on P and K concentration in roots, and on Mg concentration in shoots. Twenty-four hours after Al treatment, NAC transcription factors gene expression was measured in roots by quantitative RT-PCR. Of the 57 NAC transcription factors genes primer-pairs tested, we could distinguish that 44% (25 genes) showed different expression patterns among rice cultivars, with most of the genes induced in Cotaxtla and Temporalero plants. Of the 25 transcription factors up-regulated, those showing differential expression mostly belonged to the NAM subfamily (56%). We conclude that Al improves growth, increases sugar concentration, P and K concentrations in roots, and Mg concentration in shoots, and report, for the first time, that Al differentially regulates the expression of NAC transcription factors in rice.

Expression patterns and promoter analyses of aluminum-responsive NAC genes suggest a possible growth regulation of rice mediated by aluminum, hormones and NAC transcription factors.

In acid soils, the solubilized form of aluminum, Al+3, decreases root growth and affects the development of most crops. However, like other toxic elements, Al can have hormetic effects on plant metabolism. Rice (Oryza sativa) is one of the most tolerant species to Al toxicity, and when this element is supplied at low doses, growth stimulation has been observed, which could be due to combined mechanisms that are partly triggered by NAC transcription factors. This protein family can regulate vital processes in plants, including growth, development, and response to environmental stimuli, whether biotic or abiotic. Under our experimental conditions, 200 µM Al stimulated root growth and the formation of tillers; it also caused differential expression of a set of NAC genes. The promoter regions of the genes regulated by Al were analyzed and the cis-acting elements that are potentially involved in the responses to different stimuli, including environmental stress, were identified. Through the Genevestigator platform, data on the expression of NAC genes were obtained by experimental condition, tissue, and vegetative stage. This is the first study on NAC genes where in vivo and in silico data are complementarily analyzed, relating the hormetic effect of Al on plant growth and gene expression with a possible interaction in the response to phytohormones in rice. These findings could help to elucidate the possible convergence between the signaling pathways mediated by phytohormones and the role of the NAC transcription factors in the regulation of growth mediated by low Al doses.