Cristián Alejandro Ferretti

3,4‐Dihydropyrimidinones (3,4‐DHPMs) are pharmacologically important heterocycles with antimicrobial, anti‐inflammatory, antihypertensive, and antitumor activities. These compounds are typically synthesized via the Biginelli multicomponent reaction. In this work, Al ₂ O ₃ –SiO ₂ composites with varying Al/Si ratios, as well as pure Al ₂ O ₃ and SiO ₂ , were synthesized, characterized, and evaluated as solid acid catalysts for 3,4‐DHPM production from benzaldehyde, ethyl acetoacetate, and urea. Catalyst characterization encompassed chemical composition, textural properties, crystalline structure, morphology, and acidity, facilitating the correlation of catalyst features with catalytic performance. All Lewis acidic solids exhibited catalytic activity for 3,4‐DHPM synthesis, with the composite containing 80.0% Al ₂ O ₃ demonstrating the highest performance. Under microwave irradiation‐assisted heating at 393 K, this catalyst achieved 80.0% benzaldehyde conversion and 78.6% 3,4‐DHPM yield after 0.5 h. Microwave irradiation‐assisted heating showed an apparent rate enhancement compared to conventional convection heating under the investigated reaction conditions; however, no specific thermal or non‐thermal origin is assigned to this difference. The 80Al–20Si catalyst retained its catalytic activity and selectivity over five consecutive reuse cycles following a simple ethanol washing and low‐temperature drying procedure. Thus, 80% Al ₂ O _3% –20% SiO ₂ composites are identified as reusable, and efficient solid catalyst for the microwave irradiation‐assisted Biginelli reaction for 3,4‐DHPM synthesis.

PEGylation is used to obtain a water‐soluble chrysin derivative. The PEGylated chrysin forms a stable, colored complex with Cu (II) ions in aqueous solution, with a 2:1 ligand‐to‐metal stoichiometry. Based on these findings, a simple and rapid spectrophotometric method for the quantitative determination of Cu (II) in aqueous samples is developed using PEGylated chrysin as a sensing agent. The analytical procedure is performed entirely in aqueous media without the use of toxic organic solvents. This work demonstrates the use of a PEGylated flavonoid as an analytical probe for metal ion detection and highlights PEGylation as a sustainable and technologically attractive strategy for the development of fully water‐based analytical methods employing natural products.

Molecularly imprinted polymer (MIP) sensors were developed to determine d-xylose and d-arabinose in hydrolyzates of lignocellulosic biomass from sugarcane. Sensors were fabricated using molecularly imprinted poly-o-phenylenediamine anchored on composite substrates of functionalized multiwalled carbon nanotubes (FMWCNTs) electrodeposited onto a graphite/paraffin surface. The characterization of the modified electrodes and electrochemical analyses involved the utilization of spectroscopy and electroanalytical techniques such as Fourier-Transform Infrared Spectroscopy (FT-IR), Field Emission Gun Scanning Electron Microscopy (FEG-SEM), Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), and Differential Pulse Voltammetry (DPV). These techniques were employed to gain insight into the modified electrodes’ properties and behavior and perform detailed electrochemical analyses. In addition, the most critical parameters that directly affect the analytical performance of the electrochemical sensor have been optimized. The sensors showed a limit of detection (LOD) of 6.1 × 10^–12 mol L^–1 for d-xylose and 2.5 × 10^–12 mol L^–1 for d-arabinose, in the linear range of concentration from 1.0 × 10^–11 mol L^–1 to 1.0 × 10^–10 mol L^–1. The employed sensor effectively facilitated the quantification of d-xylose and d-arabinose within hydrolyzate samples derived from sugarcane bagasse.

The increasing demand for natural compounds with functional properties in the food, pharmaceutical, and cosmetic industries highlights the importance of sustainable sourcing. Beetroot, rich in betalains, with significant antioxidant potential, is a prime candidate for valorization, especially considering the considerable waste generated during its processing. Recovering these discarded materials not only reduces waste but also provides a valuable source of bioactive substances that can add significant value to various industries. This study focuses on optimizing ultrasound-assisted aqueous extraction (UAE), a versatile and environmentally friendly technology, for recovering these pigments. UAE offers several advantages, including reduced solvent usage, operational simplicity, and the ability to preserve the biological activity of extracted compounds, making it suitable for industrial implementation. Our experimental approach utilized a full factorial design to evaluate the influence of key variables: solvent type (water, ethanol, and mixture of equals parts ethanol and water), extraction time (20, 30, and 40 minutes), and temperature (30, 40 and 50 °C). Following extraction, a sequential process of filtration, evaporation, and oven drying was performed to separate and purify the bioactive compounds. Results consistently showed extraction yields ranging between 7% and 14% across all samples. These findings underscore the potential of UAE as an efficient method for extracting valuable natural pigments from beetroot waste, contributing to a more sustainable agri-food chain and creating new avenues for high-value product development.

A single, quick, and effective film kit for the quantification of cyanide ions in water and soil samples was developed. The film kit consists of a polymeric membrane of sodium carboxymethyl cellulose and hydroxypropyl methyl cellulose that contains matrix dispersed SBA‐15 particles impregnated with the molecular sensor. The molecular sensor is highly selective for the chromogenic and fluorometric detection of CN⁻, whose recognition mechanism is based on the nucleophilic addition to the dicyanovinyl group linked to an anthracenyl moiety. The analytical evaluation was carried out for quantification of CN⁻ with the film kit and with the free sensor using UV–vis spectroscopy and fluorescence spectroscopy. The detection limit for the film kit by fluorescence spectroscopy was 0.6 μM CN⁻, which is lower than the WHO guideline for cyanide in drinking water. This method was successfully validated, and the application in real water and soil samples gave excellent results, suggesting that the film kit is versatile for determining CN⁻ in these media.

Protein-based hydrogels have attracted considerable interest due to their biocompatibility, nontoxic properties, biodegradability, and renewable nature, as well as their being inexpensive and easy to obtain. Hydrogel properties depend on the temperature, polymer concentration, pH, crosslinking levels, salt concentrations, and aging. Casein is a natural protein present in bovine milk (about 80%), which exists in the form of various micelles. It is composed of α-s1, α-s2, β-, and κ-casein and tends toward self-assembly. Casein-based hydrogels are suitable for use in biomedical applications. Considering their potential applications in the field of medicine, in this work, our objective is to find the best conditions for the development of a casein hydrogel with tetracaine hydrochloride as the active compound. The tetracaine hydrochloride has anesthetic properties; therefore, it would allow for a painless and comfortable treatment to be offered to the patient. Accordingly, different hydrogel formulations were proposed. The selected components were casein, glycerol, tetracaine hydrochloride, potassium carbonate, and sodium alginate. Stability and swelling tests was carried out, and apparent density, pH, and moisture content were investigated. The formulation that allowed us to obtain hydrogel with the desired properties was composed of tetracaine hydrochloride 1%, casein 2%, glycerol 50%, sodium alginate 4%, and potassium carbonate solution 18% (the percentages use the casein as the basis).

The aim of this study was to investigate the in vitro and in silico antioxidant properties of four hydrazones and semicarbazones derived from vanillin and cinnamaldehyde, aromatic aldehydes found in essential oils. They were synthesized by condensation of these aldehydes with the corresponding phenylhydrazine and semicarbazide in good yields. The antioxidant properties of the target molecules were determined using the Reducing Power assay (RP) and the hydrogen peroxide scavenging method (HP), and the results were compared with thermodynamic descriptors obtained from theoretical calculations using the DFT method. The target molecules were shown to be highly active for the total antioxidant assay and the results of theoretical calculations were consistent with the antioxidant activity observed experimentally, making them a useful tool to understand the mechanism of action. This would also allow theoretical tests of new antioxidant compounds to be carried out in a predictive manner.

The upgrading of fatty alcohols synthesis from natural fatty acid methyl esters’ reduction using alumina-supported NaBH₄ without H₂ supply was investigated. It was possible to synthesize fatty alcohols efficiently with high yields. By using pure NaBH₄ or alumina-supported NaBH₄ and methanol as co-reactants, 100% selectivity towards fatty alcohols was achieved. The purpose of supporting the metal hydride is to increase its stability and ensure the recovery of the product at the end of the reaction. A high final fatty alcohol yield was obtained when alumina-supported NaBH₄ was used. The use of more than stoichiometric amounts of methanol and NaBH₄ is important to produce alkoxyborohydride anions that act as better reducing species than NaBH₄. The reaction conditions effect was investigated and the role of short carbon chain alcohol structure was explained. The effect of fatty acid methyl ester structure was also examined. Saturated fatty acid methyl esters (methyl laurate, methyl myristate) with short carbon chains can be easily reduced using NaBH₄/Al₂O₃ and methanol, thus obtaining high conversion and selectable fuel alcohol. Unsaturated fatty acid methyl ester (methyl oleate) with longer carbon shows steric hindrance, which is not suitable for the interaction of esters and reduces the surface area, meaning that the conversion of fatty acid methyl ester is lower.