Synthetic dyes are persistent organic environmental pollutants that can cause extensive damage to living beings and to the ecosystem as a whole. Cost-effective, sustainable, and efficient strategies to deal with this type of pollution are necessary as it commonly resists conventional water treatment methods. Silver nanoparticles (AgNPs) synthesized using the aqueous extract from the leaves, stem, and fruits of Leucaena leucocephala (Leucena) were produced and characterized through UV–vis, TEM, EDS, SDL, XPS, XRD, and zeta potential, and they proved to be able to promote adsorption to remediate methylene blue and tartrazine pollution in water. The nanoremediation was performed and did not require direct exposure to sunlight or any special lamp or a specific reduction agent. The AgNPs produced using the extract from the leaves exhibited the best performance in nanoremediation and also presented antioxidant activity that surpassed the one from butylated hydroxytoluene (BHT). Consequently, it is an interesting nanotool to use in dye nanoremediation and/or as an antioxidant nanostructure.

Tecoma stans (L.) Juss. Ex Kunth is a species belonging to the Bignoniaceae family, popularly known as yellowing, yellow bell, and garden little ipe. Studies with T. stans seeds are scarce and it have potential in the search for natural compounds with biological activities. This study aimed to evaluate the toxicity and antioxidant activity of the ether extract (EE) and fractions from T. stans seeds. The EE was obtained in Soxhlet apparatus with petroleum ether and fractions were obtained by hydrolysis and esterification reactions. Phytochemical screening evaluated the presence of steroids, triterpenoids, alkaloids, coumarins and anthraquinones in EE. The toxicity was evaluated by the A. salina lethality test and antioxidant activity by DPPH method. It was observed the presence of steroids, triterpenoids and alkaloids in EE, which had no toxicity to A. salina (LC50 > 1000 µg/mL). The fractions of seeds exhibited toxicity on A. salina. All samples showed antioxidant activity with EC50 between 0.9 and 1.1 µg/mL. These results indicated potential applications for T. stans seeds.

Synthetic dyes are commonly present in industrial wastewater and when discharged in water bodies without receiving a treatment capable of removing or destroying them, they turn into concerning water pollutants. These organic contaminants threaten living beings due to their toxicity, and some of them can even damage DNA. Consequently, in order to achieve sustainable development, it is necessary to develop eco-friendly tools that can efficiently manage this kind of pollution. In the present study the aqueous extract from the leaves of Leucaena leucocephala (an invasive plant species native to Mexico) was used to produce green nano zero-valent iron (nZVI). The nanomaterial was characterized (TEM, UV–vis, FTIR, SEM, EDS, XRD) and assayed regarding its antioxidant potential (DPPH test) and capacity to remediate the pollution caused by two dyes. It proved to be able to adsorb nigrosine (288.30 mg/g of nanomaterial) and tartrazine (342.50 mg/g of nanomaterial), and also displayed antioxidant activity (effective concentration to discolor 50% of the DPPH solution = 286.02 μg/mL). Therefore, the biogenic antioxidant nanoparticle proved also to be a possible nanotool to be applied to remediate water contamination caused by these synthetic dyes.

The extract and fractions from flowers of Tecoma stans (Bignoniaceae), an invasive plant in Brazil, were evaluated for their larvicidal potential against Culex quinquesfasciatus larvae and for the toxicity to Artemia salina. The hexane (HEX) fraction caused 100% mortality at 1000 µg mL^-1 in the first 24 h of exposure (LC₅₀ = 118.73 µg mL^-1 and LC₉₀ = 306.06 µg mL^-1). The LC₅₀ and LC₉₀ values for the dichloromethane (DCM) fraction were 399.40 µg mL^-1 and 853.36 µg mL^-1. Only the ethyl acetate (EA) fraction was toxic to A. salina. The results suggest selectivity from the HEX and DCM fractions of T. stans against C. quinquefasciatus and may serve as eco-friendly alternatives to synthetic larvicides.

Staphylococcus spp. are the primary pathogens responsible for caprine mastitis. These bacteria can form biofilms, hindering treatment and compromising milk production. In this context, plant-based natural products derived from Lippia grata Schauer have emerged as a potential alternative for treatment. This study aimed to evaluate the antibacterial and antibiofilm properties of the essential oil (EO) of L. grata against Staphylococcus spp. isolated from caprine mastitis. The EO was obtained by hydrodistillation, and its chemical constituents were identified by gas chromatography coupled with mass spectrometry. Fourteen clinical isolates of Staphylococcus spp. and two standard strains were tested. Antibacterial activity was assessed using broth microdilution. Biofilm production and the interference capacity of the EO were evaluated using a microplate adherence assay. The EO of L. grata yielded 5.47%, with carvacrol (78%), thymol (7.1%), and p-cymene (3.16%) as the main constituents. It exhibited inhibitory and bactericidal effects at concentrations ranging from 256 to 512 μg mL^-1. All isolates formed biofilms, and the EO reduced biofilm formation in two isolates classified as moderate and strong producers. Additionally, it disrupted pre-established biofilms in all isolates. Therefore, the EO of L. grata exhibits antimicrobial and antibiofilm activities and represents a promising alternative for treating caprine mastitis, particularly in infections involving biofilm formation.