Nanopartículas metálicas mediadas por extrato vegetal como possíveis agentes alelopáticos

Abstract

Currently, Brazil is one of the world leaders in the production and export of agricultural commodities, an activity with a direct impact on its GDP and trade agreements. In this context, the use of agrochemicals is a well-established practice, but one that has generated intense debate. In this context, environmental agencies and the scientific community warn of the risks of its excessive use, which include soil and water contamination, wildlife poisoning, and damage to human health. As an alternative, Green Chemistry emerges as a scientific approach to revise conventional practices from a sustainability perspective. In parallel, nanotechnology has made significant progress, especially in the synthesis of nanoparticles with studies exploring biological applications. Para tal, sintetizar nanopártículas de cobre (CuNPs) a partir de sulfato de cobre (II) mediadas por extrato de murici (Byrsonima crassiifolia) e avaliar seu potencial alelopático é o objetivo do estudo. Para isso, realizou-se a coleta do vegetal, a obtenção do extrato aquoso bruto e a análise do seu perfil fitoquímico. A síntese das CuNPs foi bem- sucedida, conforme indicado pela caracterização por UV-Vis, mostrondo bandas de absorção entre 240-260 nm e 270-340 nm, compatíveis com a formação de nanopartículas. Furthermore, qualitative tests of the extract confirmed the presence of active metabolic classes, such as saponins, hydrolyzable tannins, quinones, alkaloids, terpenes, and flavonoids. On the other hand, the analysis of variance demonstrated that 71.9% of the total variability in the data, that is, the extract concentration factor, emerged significantly (p < 0.001), being responsible for 54.2% of the variance explained in the study. Regarding the standardized effects, the vertical dashed line indicates the significance limit (α=0.05), the extract concentration factor presents the most significant absolute effect. In addition, validation techniques using ANOVA explain 71.9% of the variance (R² = 0.719), with the positive coefficient for concentration (0.3637) confirming the beneficial impact. However, the negative interaction (-0.1417) reveals that the positive effect of high concentration is attenuated at 40°C. Thus, the optimal condition identified – pH 7, 1.0% extract, 30°C – represents an equilibrium, maximum concentration of reducing agent, at a temperature that moderates the kinetics for controlled growth, in an alkaline pH that favors the deprotonation of phenolic groups, increasing their reducing power. In this regard, temperature proved to be the most sensitive parameter, with total cost variations exceeding 0.15 units for a 20% fluctuation; extract concentration showed moderate sensitivity, whereas pH was the least impactful parameter. Furthermore, both analyzed scenarios (Low_Cost and Optimal_Technical) exhibit steep decay curves, with cost reductions exceeding 70% when moving from the smallest to the largest scale. Finally, the allelopathic studies indicate that the main effects for both factors were significant (Treatment: p<0.0001; Crop/Species: p=0.0211), demonstrating that both nanomaterial concentration and plant species were decisive and essential factors in the germination outcome, yielding concrete results for the study.