So far, several studies have focused on the synthesis of metallic nanoparticles making use of extracts from the fruit of the plants from the genus Capsicum. However, as the fruit is the edible, and highly commercial, part of the plant, in this work we focused on the leaves, a part of the plant that is considered agro-industrial waste. The biological synthesis of gold (AuNPs) and silver (AgNPs) nanoparticles using aqueous extracts of root, stem and leaf of Capsicum chinense was evaluated, obtaining the best results with the leaf extract. Gold and silver nanoparticles synthesized using leaf extract (AuNPs-leaf and AgNPs-leaf, respectively) were characterized by UV-visible spectrophotometry (UV-Vis), Fourier Transform Infrared Spectroscopy with Attenuated Total Reflection (FTIR-ATR), X-ray Photoelectron Spectroscopy (XPS), Ultra Hight Resolution Scanning Electron Microscopy coupled to Energy-Dispersive X-ray spectroscopy (UHR-SEM-EDX) and Transmission Electron Microscopy (TEM), and tested for their antioxidant and antimicrobial activities. In addition, different metabolites involved in the synthesis of nanoparticles were analyzed. We found that by the use of extracts derived from the leaf, we could generate stable and easy to synthesize AuNPs and AgNPs. The AuNPs-leaf were synthesized using microwave radiation, while the AgNPs-leaf were synthesized using UV light radiation. The antioxidant activity of the extract, determined by ABTS, showed a decrease of 44.7% and 60.7% after the synthesis of the AuNPs-leaf and AgNPs-leaf, respectively. After the AgNPs-leaf synthesis, the concentration of polyphenols, reducing sugars and amino acids decreased by 15.4%, 38.7% and 46.8% in the leaf extract, respectively, while after the AuNPs-leaf synthesis only reducing sugars decreased by 67.7%. These results suggest that these groups of molecules are implicated in the reduction/stabilization of the nanoparticles. Although the contribution of these compounds in the synthesis of the AuNPs-leaf and the AgNPs-leaf was different. Finally, the AgNPs-leaf inhibited the growth of S. aureus, E. coli, S. marcescens and E. faecalis. All of them are bacterial strains of clinical importance due to their fast antibiotic resistance development.

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. Graphical

In recent years, the increase in antibiotic resistance demands searching for new compounds with antimicrobial activity. Phytochemicals found in plants offer an alternative to this problem. The genus Pelargonium contains several species; some have commercial use in traditional medicine such as P. sinoides, and others such as P. peltatum are little studied but have promising potential for various applications such as phytopharmaceuticals. In this work, we characterized the freeze-dried extracts (FDEs) of five tissues (root, stem, leaf, and two types of flowers) and the ethyl acetate fractions from leaf (Lf-EtOAc) and flower (Fwr-EtOAc) of P. peltatum through the analysis by thin-layer chromatography (T.L.C.), gas chromatography coupled to mass spectrometry (GC-MS), phytochemicals quantification, antioxidant capacity, and antimicrobial activity. After the first round of analysis, it was observed that the FDE-Leaf and FDE-Flower showed higher antioxidant and antimicrobial activities compared to the other FDEs, for which FDE-Leaf and FDE-Flower were fractionated and analyzed in a second round. The antioxidant activity determined by ABTS showed that Lf-EtOAc and Fwr-EtOAc had the lowest IC₅₀ values with 27.15 ± 1.04 and 28.11 ± 1.3 µg/mL, respectively. The content of total polyphenols was 264.57 ± 7.73 for Lf-EtOAc and 105.39 ± 4.04 mg G.A./g FDE for Fwr-EtOAc. Regarding the content of flavonoid, Lf-EtOAc and Fw-EtOAc had the highest concentration with 34.4 ± 1.06 and 29.45 ± 1.09 mg Q.E./g FDE. In addition, the minimum inhibitory concentration (M.I.C.) of antimicrobial activity was evaluated: Lf-EtOAc and Fwr-EtOAc were effective at 31.2 µg/mL for Staphylococcus aureus and 62.5 µg/mL for Salmonella enterica, while for the Enterococcus feacalis strain, Fwr-EtOAc presented 31.2 µg/mL of M.I.C. According to the GC-MS analysis, the main compounds were 1,2,3-Benzenetriol (Pyrogallol), with 77.38% of relative abundance in the Lf-EtOAc and 71.24% in the Fwr-EtOAc, followed by ethyl gallate (13.10%) in the Fwr-EtOAc and (Z)-9-Octadecenamide (13.63% and 6.75%) in both Lf-EtOAc and Fwr-EtOAc, respectively.

The use of zinc oxide nanoparticles (ZnONPs) in agriculture has increased due to their biostimulant potential; however, their effects on plant chemical communication and associated microbial communities are still poorly understood. This study presents a multi-perspective analysis contrasting the effects of ZnONPs with those of conventional ZnO (Bulk) on Capsicum annuum seedlings grown in a substrate with concentrations of 50 and 500 mg kg⁻¹. The results reveal that, at high doses, the bulk material (B500) generated a higher foliar accumulation of zinc (128.7 mg kg⁻¹) than ZnONPs (NP500, 119.7 mg kg⁻¹), a phenomenon attributed to the agglomeration of nanoparticles in the soil matrix, which limits their root absorption. At the physiological level, a critical divergence was observed: while bulk ZnO stimulated the activity of the enzyme superoxide dismutase (SOD), ZnONPs caused severe inhibition of the same (93% reduction), compromising the enzymatic antioxidant machinery and forcing the plant to rely on non-enzymatic mechanisms, such as an increase in total phenols. The volatilomic profile revealed a specific metabolic disturbance induced by ZnONPs in the green leaf volatiles (GLV) pathway. A significant accumulation of hexanal and suppression of hexanol and hexyl acetate were detected, suggesting that the nanomaterial inhibited alcohol dehydrogenase (ADH). In addition, ZnONPs suppressed the emission of methyl salicylate (MeSA)—a key messenger in acquired systemic resistance—whereas the Bulk treatment increased its abundance to 41.7%. Finally, metagenomic analysis indicated that zinc stress restructured the phyllosphere microbiota, promoting the proliferation of Actinobacteria and eliminating sensitive taxa such as Spirochaetes. Taken together, these findings demonstrate that ZnONPs act as multifactorial stressors that not only alter internal metabolism but also silence chemical communication and remodel plant ecology.

The application of zinc oxide nanoparticles (ZnONPs) in agriculture is expanding due to their biostimulant potential; however, their influence on plant chemical communication and associated microbial communities remains not fully characterized. This study presents a multi-perspective analysis contrasting the effects of ZnONPs with those of conventional microparticulate ZnO (Bulk) on Capsicum annuum seedlings grown in substrate at 50 and 500 mg kg⁻¹. Results indicate that, at high doses, the bulk material (B500) led to higher foliar zinc accumulation (128.7 mg kg⁻¹) compared to ZnONPs (NP500, 119.7 mg kg⁻¹), a difference potentially linked to nanoparticle aggregation in the soil matrix limiting root uptake. At the physiological level, a distinct response was observed: while Bulk ZnO stimulated superoxide dismutase (SOD) activity, ZnONPs resulted in a marked reduction (93%), suggesting a shift in the antioxidant strategy toward non-enzymatic mechanisms, such as increased total phenol content. Regarding the volatilomic profile, ZnONPs induced specific metabolic alterations in the green leaf volatile (GLV) pathway, characterized by hexanal accumulation and reduced levels of hexanol and hexyl acetate. Additionally, ZnONPs were associated with lower methyl salicylate (MeSA) emissions, whereas the Bulk treatment increased its relative abundance to 41.7%. Finally, metagenomic analysis revealed that zinc treatments modulated the phyllosphere microbiota, favoring the proliferation of Actinobacteria while decreasing the abundance of sensitive taxa, such as Spirochaetes. Taken together, these findings suggest that ZnONPs act as a distinct metabolic modulator, altering internal physiology and chemical signaling.