Solventes eutéticos naturais como materiais alternativos aplicados à extração de bioativos de matrizes amazônicas

Abstract

The extraction of bioactive compounds from Amazonian plant matrices is constrained by the environmental liabilities, toxicity, and increasingly stringent regulatory requirements associated with conventional organic solvents, making the development of safer and more sustainable alternatives necessary. Natural deep eutectic solvents (NADES), formed by combining biologically derived components at specific molar ratios, represent a green chemistry-based alternative with tunable physicochemical properties suited to different target compound classes. This dissertation developed, optimized, and applied NADES systems for the extraction of bioactive compounds from Bixa orellana L. (annatto) and Genipa americana L. (genipap), two species of biological and socioeconomic relevance to the Amazon region, evaluating extractive performance, chemical characterization, and the technological potential of the obtained extracts. The methodological approach was structured in sequentially dependent stages: in the selection phase, eight extractive systems — six NADES and two hydroalcoholic controls — were compared for total carotenoid content, total phenolic compounds, and antioxidant activity (DPPH and FRAP), with thymol:lactic acid (Thy:Lac, 1:2) and choline chloride:lactic acid (ChCl:Lac, 1:2) identified as the most promising systems for B. orellana and G. americana, respectively, with statistically confirmed superiority over conventional solvents; both systems were characterized by attenuated total reflectance Fourier-transform infrared spectroscopy (FTIR-ATR), with band shifts confirming the formation of hydrogen bond networks consistent with the hydrophobic character of Thy:Lac and the polar, ionic profile of ChCl:Lac. In the optimization phase, extraction conditions were determined using a Box-Behnken design combined with response surface methodology (RSM), with molar ratio, temperature, and extraction time as independent variables: for Thy:Lac, molar ratio and temperature were co-determinant factors for carotenoid yield, with an experimentally validated optimal point and a gain of approximately 28% over preliminary screening; for ChCl:Lac, only molar ratio was statistically significant, with a gain exceeding 100% over screening and DPPH antioxidant activity becoming measurable only after optimization. Evaluation of the optimized extracts revealed distinct functional profiles between the two matrices — higher ABTS reactivity in the annatto extract, consistent with the lipophilic nature of carotenoids, and superior DPPH and FRAP performance in the genipap extract, reflecting the diversity of antioxidant mechanisms in hydrophilic phenolic compounds —, with chromatic and pH stability of the systems monitored over 150 days. In the application phase, the optimized extracts were encapsulated by freeze-drying with maltodextrin and arabic gum at two extract-to-carrier ratios (1:3 and 1:5), yielding approximately 79% retention for G. americana phenolics, reflecting compatibility between hydrophilic compounds and the polar carrier matrix, and between 43% and 46% for B. orellana carotenoids, determined by the intrinsic incompatibility between nonpolar compounds and a carrier system lacking a lipid phase; in vitro digestibility, assessed using the INFOGEST protocol with sampling across oral, gastric, and intestinal phases, demonstrated effective gastric protection and partial intestinal recovery for the G. americana formulation, while B. orellana encapsulates exhibited pronounced losses across all phases, with antioxidant activity expressed functionally only in the intestinal phase and captured exclusively by the ABTS method. The results establish that the superiority of NADES over conventional organic solvents is demonstrable when there is a deliberate match between solvent composition and target compound structure, and confirm the feasibility of a complete green processing chain for Amazonian bioactives — from extraction through evaluation of post-digestion functional behavior — without solvent removal steps, constituting the first study to systematically evaluate NADES for both Amazonian matrices investigated.