Obtenção de compostos bioativos de folhas de uvaia (Eugenia pyriformis Cambess.) utilizando CO2 supercrítico e extração com solvente assistida por ultrassom

Abstract

Eugenia pyriformis Cambess. (Uvaia), typical of the Atlantic Forest belongs to the Myrtaceae family, the same family of cherry, jabuticaba and other plants, currently studied due to their antioxidant, antimicrobial and medicinal properties. The interest in bioactive compounds obtained from natural sources has led to an increase in researches aiming to find these compounds in plant extracts. The extractions using conventional methods generally have some drawbacks, and an interesting alternative has been the use of non-conventional extraction technologies, such as the supercritical fluid and the ultrasound-assisted extraction. This work aims to study unconventional methods of obtaining uvaia extracts in order to obtain extracts rich in bioactive compounds. Factors such as the influence of type of extraction (supercritical fluid and ultrasound) and the used conditions on the yield and composition were evaluated. The results were compared to those obtained using the extraction by maceration, a conventional extraction method. After drying and milling the uvaia leaves, the plant material was subjected to extraction with the supercritical CO2 solvent under different conditions of temperature (40, 50 and 60 °C) and pressure (100, 150 and 200 bar), with a fixed flow of 2.0 kg min-1. In the ultrasound-assisted extraction, the effects of temperature (40, 50 and 60 °C), power (150, 250 and 350 W) and ratio between the mass of leaves and the volume of solvent (1:10, 1:15 and 1:20) were evaluated. The extracts obtained were chemically characterized by GC-MS giving β-amyrin (53.72 % for SFE and 71.25 % for UAE) and α-amyrin (24.63 % for SFE and 22.69 % for UAE) as main compounds. In the supercritical extraction, the pressure and the interaction between pressure and temperature showed statistically significant effects on the yield, with the best result being achieved at 200 bar and 60 °C, reaching 1.69%. The data obtained from the supercritical fluid extraction were used to adjust the extraction curves simulated by using two empirical models available in the literature. The tested models adjusted well to the experimental data and the analysis of the estimated parameters allowed to define which model best describes the kinetics of each experimental condition. For the ultrasound-assisted extraction, the best yield result found in the determination of the kinetics was 1.81% in 40 minutes, although in the experimental design a 3 minute time extraction was used due to the better characteristics showed by the extracts at this time. The best result obtained in experimental design with ultrasound was 1.79% provided 30% power, 60 °C and mas/solvent ratio 1:20. Statistical analysis of the experimental design of the ultrasound-assisted extraction indicated significant effects from the variables temperature, mass/solvent ratio and the interaction between power and mass/solvent ratio. The best results for amyrin content by extract weight was found for supercritical extraction, with 97.43%. The ultrasound-assisted extraction showed the best amyrin amount per mass of leaves, 12.13 g of the mixture of isomers per kg of dry leaf.