The growing concern about the emergence of increasingly antibiotic-r4esistant bacteria imposes the need to search and develop drugs to combat these microorganisms. This, combined with the search for low-cost synthesis methods, was the motivation for the elaboration of this work. Abietic acid present in the resin of Pinus elliotti var. elliotti was used to generate a sodium salt by salification. The synthesis route was low-cost, consisting of only two reaction steps at mild temperatures without toxic organic solvents, and eco-friendly and easy to conduct on an industrial scale. Sodium abietate (Na-C20H29O2) was characterized by mass spectrometry, infrared spectroscopy, elemental analysis, X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. To perform the antimicrobial tests, the determination of minimum inhibitory concentration and the disk diffusion assay was performed. The results obtained showed that the salt Na abietate performed an antimicrobial action against the bacterial strains S. aureus, E. coli, L.monocytogenes, and S. enterica Typhimurium and the yeast C. albicans. The disk diffusion test showed a high inhibition potential against S. enterica compared to the standard antimicrobial tetracycline, as an inhibition index of 1.17 was found. For the other bacterial strains, the inhibition values were above 40%. The MIC test showed promising results in the inhibition of E. coli, L. monocytogenes, and C. albicans, indicating bacteriostatic activity against the first microorganism and bactericidal and fungicidal activities against the others. Therefore, the results showed the action of Na abietate as a possible effective antimicrobial drug, highlighting its sustainability within a circular economy.

The search for less expensive and viable products is always one of the challenges for research development. Commonly, the synthesis of coordination compounds involves expensive ligands, through expensive and low-yield routes, in addition to generating toxic and unusable residues. In this work, the organic ligand used is derived from the resin of a reforestation tree, Pinus elliottii var. elliottii. The synthesis method used Pinus resin and an aqueous solution of vanadium(III) chloride at a temperature of 80 °C. The procedure does not involve organic solvents and does not generate toxic residues, thus imparting the complex formation reaction a green chemistry character. The synthesis resulted in an unprecedented oxovanadium(IV)-bis(abietate) complex, which was characterized by mass spectrometry (MS), chemical analysis (CHN), vibrational (FTIR) and electronic spectra (VISIBLE), X-ray diffraction (XRD), and thermal analysis (TG/DTA). Colorimetric studies were performed according to the CIELAB color space. The structural formula found, consisted of a complex containing two abietate ligands, [VO(C₂₀H₂₉O₂)₂]. The VO(IV)-bis(abietate) complex was applied against microorganisms and showed promising results in antibacterial and antifungal activity. The best result of inhibitory action was against the strains of Gram-positive bacteria S. aureus and L. monocytogenes, with minimum inhibitory concentration (MIC) values of 62.5 and 125 μmol L⁻¹, respectively. For Gram-negative strains the results were 500 μmol L⁻¹ for E. coli; and 1000 μmol L⁻¹ for Salmonella enterica Typhimurium. Antifungal activity was performed against Candida albicans, where the MIC was 15.62 μmol L⁻¹, and for C. tropicalis it was 62.5 μmol L⁻¹. According to the MFC analysis, the complex presented, in addition to the fungistatic action, a fungicidal action, as there was no growth of fungi on the plates tested. The results found for the tests demonstrate that the VO(IV)-bis(abietate) complex has great potential as an antimicrobial and mainly antifungal agent. In this way, the pigmented ink with antimicrobial activity could be used in environments with a potential risk of contamination, preventing the spread of microorganisms harmful to health.

Magnesium oxide is typically white and can be colorized with transition metal insertion by doping. We present the preparation of a green-colored hydroxide by the exchange of Mg²⁺ on the crystalline lattice with Ni²⁺ in MgO, using three nickel salts. MgO_st was prepared by the colloidal starch suspension method, using cassava starch. The oxides and hydroxides, before and after, were characterized by X-ray diffraction (XRD), and show that a phase change occurs: a transition from periclase (MgO) to brucite (Mg(OH)₂) due to the incorporation of nickel ions from different salts (acetate, chloride, and nitrate), resulting in the solid solution [Ni_xMg_1−x(OH)₂]. The FTIR spectrum corroborates the crystallographic structure identified through XRD patterns, confirming the formation of a crystal structure resembling brucite. The new samples present a green color, indicative of the incorporation of the Ni²⁺ ions. The antimicrobial activity of products resulting from the doping of magnesium oxide with nickel and the precursor MgO_st was assessed through the minimum inhibitory concentration (MIC) test. The evaluation included three bacterial strains: Staphylococcus aureus (ATCC 25923), Escherichia coli (ATCC 25922), Salmonella gallinarum (ATCC 9184), and a yeast strain, Candida albicans (ATCC 10231). The obtained results were promising; the tested samples exhibited antimicrobial activity, with a MIC ranging from 0.312 to 0.625 μg.μL⁻¹. The nickel compound, derived from the precursor chloride salt, demonstrated superior MIC activity. Notably, all tested samples displayed bactericidal activity against the S. aureus strain and exhibited a broad spectrum of inhibition, encompassing both Gram-positive and Gram-negative strains. Only the nickel compounds derived from precursors with acetate and nitrate anions demonstrated antimicrobial activity against C. albicans, exhibiting a fungistatic behavior. Based on the conducted studies, [Ni_xMg_1−x(OH)₂] has emerged as a promising antimicrobial agent, suitable for applications requiring the delay or inhibition of bacterial growth.

Materiais híbridos formados entre polianilina e hidróxidos duplos lamelares de Zn e Al (Pani/ZnAl_HDL) foram obtidos adicionando a Polianilina (Pani) previamente preparada ao meio reacional da síntese dos HDLs e também HDLs modificado com os surfactantes aniônicos dodecilsulfato de sódio e dodecilbenzenosulfato de sódio. Os compósitos apresentaram cor azul que é característica da fase base esmeraldina da Pani. Os difratogramas de raios X destes compostos apresentaram deslocamento dos picos (003) e (006) do ZnAl_HDL para menores valores de 2θ, indicando a presença das duas fases nos compósitos. Além disso, foi constatado também que os surfactantes aniônicos também exercem influência nas características estruturais dos compósitos. Os espectros de FTIR corroboram os resultados do DRX. Os compósitos obtidos com os surfactantes foram submetidos à testes de sensor colorimétrico para HCl. Após 5 minutos apenas de exposição aos vapores do HCl, os materiais apresentaram mudança na sua coloração de azul para verde, indicando a formação da fase da Pani, sal esmeraldina. Esse indício foi confirmado por espectroscopia na região do UV-Vis, uma vez que os espectros após interação com ácido, apresentaram novas bandas, nas regiões de 400 nm e 820 nm, que são características do sal esmeraldina, forma estrutural da Pani de coloração verde. Esses resultados mostram a viabilidade da utilização destes materiais no sensoriamento de ambientes ácidos, apresentando resposta rápida e eficaz.

Magnesium oxide is typically white and can be colorized with transition metal insertion by doping or by adsorption. We present the preparation of green colored hydroxide by the adsorption of nickel ions by porous MgO. MgO was prepared by the colloidal starch suspension method and used to remove nickel ions from the aqueous solution. The oxides and hydroxides, before and after adsorption, were characterized by X-ray diffraction technical, and show that a phase change occurs, a transition from periclase (MgO) to brucite (Mg(OH)2) due to the interaction with nickel salts (acetate, chloride, and nitrate). The FTIR spectrum corroborates with the DRX data on the formation of brucite like crystal lattices. The new samples present a green color, indicative of the incor-po-ration of the Ni2+ ions. Mixed oxides in the form of brucite were used in microbiological tests and showed action against fungi and bacteria, with bactericidal, bacteriostatic, or fungistatic function. Green brucite (NixMg1-x(OH)2) can be used as an inorganic pigment in white or colorless paints with a special biocidal property.

Antimicrobial resistance is a major global public health challenge, motivating the search for new antimicrobial agents for biomedical and agricultural applications. This study reports the synthesis of a silver coordination assembly using a natural ligand derived from Pinus elliottii resin under mild temperature and pH conditions. The resulting brown solid was characterized by mass spectrometry, infrared spectroscopy, and complementary techniques. The characterization data suggest the formation of a silver(I)-abietate compound with bridging coordination through the carboxylate oxygen atoms. Antimicrobial activity was evaluated by minimum inhibitory concentration (MIC) and disk diffusion assays. MIC values were 3.9 µmol L-1 for Candida albicans, 15.6 µmol L-1 for Escherichia coli and Salmonella gallinarum, and 31.2 µmol L-1 for Staphylococcus aureus. For the phytopathogenic bacteria, MIC values were 31.2 µmol L-1 for Pectobacterium carotovorum and Xanthomonas citri, and 62.5 µmol L-1 for Ralstonia solanacearum. The disk diffusion assay yielded inhibition halos ranging from 14 to 20 mm against three pathogenic bacteria, one pathogenic fungus, and three phytopathogenic bacteria, indicating strong inhibitory activity. In toxicity assays using Drosophila melanogaster, Ag-abietate did not significantly affect survival, and an median lethal dose (LD₅₀) could not be determined within the tested concentration range. The results demonstrate that Ag-abietate is a promising candidate for both biomedical and agricultural applications, underscoring the potential of metal-based compounds in addressing antimicrobial resistance.