The Response Surface Optimization of Supercritical CO2 Modified with Ethanol Extraction of p-Anisic Acid from Acacia mearnsii Flowers and Mathematical Modeling of the Mass Transfer

Abstract

A widely disseminated native species from Australia, Acacia mearnsii, which is mainly cultivated in Brazil and South Africa, represents a rich source of natural tannins used in the tanning process. Many flowers of the Acacia species are used as sources of compounds of interest for the cosmetic industry, such as phenolic compounds. In this study, supercritical fluid extraction was used to obtain non-volatile compounds from A. mearnsii flowers for the first time. The extract showed antimicrobial activity and the presence of p-anisic acid, a substance with industrial and pharmaceutical applications. The fractionation of the extract was performed using a chromatographic column and the fraction containing p-anisic acid presented better minimum inhibitory concentration (MIC) results than the crude extract. Thus, the extraction process was optimized to maximize the p-anisic acid extraction. The response surface methodology and the Box-Behnken design was used to evaluate the pressure, temperature, the cosolvent, and the influence of the particle size on the extraction process. After the optimization process, the p-anisic acid yield was 2.51% w/w and the extraction curve was plotted as a function of time. The simulation of the extraction process was performed using the three models available in the literature.

Keywords: Acacia mearnsii; mathematical modeling; p-anisic acid; response surface methodology; supercritical fluid extraction.

Figure 1

Contour plot for global extraction yield as a function of CO₂ pressure and modifier.

Figure 2

Response surfaces and contour plots for effects of two independent variables on the yield of p-anisic acid in the extract obtained by supercritical extraction: (a) CO₂ pressure (P) and CO₂ temperature (T); (b) CO₂ temperature (T) and medium particle size of milled flowers (G); (c) CO₂ pressure (P) and medium particle size of milled flowers (G).

Figure 3

Process parameters optimized to maximum yield of p-anisic acid.

Figure 4

The yield curve for supercritical fluid extraction at 40 °C, 279 bar, and milled flower (42 mesh): mathematical models and experimental data.