Aplicação de técnicas não convencionais de extração para obtenção de bioativos em torta prensada de sementes de pracaxi [(Pentaclethra macroloba (Willd.) Kuntze)]

Abstract

This doctoral research aimed to enhance the value of pracaxi press cake, a byproduct of oil extraction, by applying innovative and sustainable techniques aligned with the principles of green chemistry. The study focused on extracting bioactive compounds with antioxidant activity to enrich this industrial residue and strengthen the pracaxi production chain in the Amazon, thereby benefiting local communities. The methodology involved comprehensively characterizing the press cake and residual oil, including compositional, elemental, and mineral analyses. The microscopic structure of the press cake was examined using scanning electron microscopy (SEM), while Fourier-transform infrared spectroscopy (FTIR) was employed to identify functional groups. The physicochemical properties of pracaxi oil, such as density, viscosity, refractive index, and fatty acid composition, were investigated. Pressurized liquid extraction (PLE) techniques were applied using five solvents of different polarities (propane, ethyl acetate, ethanol, 75% aqueous ethanol solution, and water) with two distinct procedures: single-solvent extraction (SSE) and sequential two-solvent extraction (STSE). Mathematical modeling of pressurized liquid extraction kinetics was performed using models such as the two-line spline and the two-site desorption model. Additionally, enzyme-assisted extraction (EAE) was conducted using three commercial enzymatic complexes (Celluclast® 1.5L, Pectinex® Ultra SP-L, and Viscozyme® L), with water as the solvent. The obtained extracts were evaluated for their total phenolic and flavonoid content as well as their antioxidant activity (DPPH and FRAP assays). Furthermore, their antimicrobial activity against Staphylococcus aureus and Escherichia coli was investigated. The results demonstrated that pracaxi press cake is a rich source of bioactive compounds, with high crude protein (28.66%) and crude fiber (16.79%), while exhibiting low levels of potentially toxic elements. Elemental analysis indicated a predominance of carbon (50.50%) and nitrogen (4.18%), with molar ratios typical of lignocellulosic biomass. PLE proved to be effective in extracting phenolic compounds and flavonoids, with polar solvents such as ethanol-water (EtOH75) yielding the best results. The sequential two-solvent extraction (STSE) procedure, which used propane as a pretreatment, enhanced the efficiency of phenolic compound extraction. EAE, employing enzymes such as Pectinex® Ultra SP-L and Celluclast® 1.5L, improved the recovery of bioactive compounds, achieving high antioxidant activity—in some cases surpassing the results obtained with PLE. Mathematical modeling of extraction kinetics provided valuable insights for process optimization, enabling the identification of mass transfer mechanisms and optimal extraction times. The obtained extracts exhibited significant antioxidant activity, correlating with their total phenolic and flavonoid content, although no antimicrobial activity was observed under the tested conditions. This research highlights the potential of pracaxi press cake as a sustainable source of bioactive compounds, emphasizing the effectiveness of PLE and EAE techniques in their recovery. PLE offers flexibility in solvent and procedure selection, whereas EAE stands out for its use of an environmentally friendly solvent, water. These findings contribute to the full valorization of this agro-industrial residue, aligning with circular economy principles and promoting the sustainable development of the Amazon region