Pithecellobium dulce as a Sustainable Source of Macromolecules and High-Value Biocompounds: Sequential Extraction and Selective Separation Using Aqueous Two-Phase Systems

Abstract

Pithecellobium dulce is an American native plant that presents edible arils rich in white to red and is composed of macromolecules (reducing sugars, RS, and total sugars, TS) and high-value-added compounds (total phenolic compounds, TPC, flavonoids, FLA, and anthocyanins, ANT). This study optimized solid–liquid extraction parameters (solvent type and concentration, solid–liquid ratio, and temperature), adjusted models for the process kinetics, and selectivity separates the biomolecules using aqueous two-phase systems (ATPS). The optimal extraction of bioactive compounds was achieved using 10% choline chloride ([Ch]Cl) at a 1:10 solid/liquid ratio and 35 °C, yielding FLA (8.59 ± 0.23 mg·g^–1), TPC (37.94 ± 1.38 mg·g^–1), and ANT (0.396 ± 0.006 mg·g^–1). In contrast, water proved most effective for RS (520.75 ± 9.66 mg·g^–1) and TS (865.07 ± 58.66 mg·g^–1) extraction. Kinetic modeling showed an excellent fit with R² values from 0.9721 to 0.9982 using first-order (RS and TS), second-order (TPC), Simeonov (FLA), and power law (ANT) models. Extracts with [Ch]Cl were further processed via ATPS using acetonitrile, tetrahydrofuran, or K₂HPO₄. The system [Ch]Cl (25 wt %) + K₂HPO₄ (30 wt %) + water (45 wt %) enabled efficient separation: RS and TS concentrated in the bottom phase, while FLA, TPC, and ANT migrated to the top phase with selectivities ranging from 10.6 to 2725.0.