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A rapid expansion from supercritical solution into aqueous solution (RESSAS) technology was presented for the micronization of Chinese medicinal material. Magnolia bark extract (MBE) obtained by supercritical carbon dioxide (scCO2) extraction technology was chosen as the experimental material. RESSAS process produced 303.0 nm nanoparticles (size distribution, 243.6--320.5 nm), which was significantly smaller than the 55.3 µµm particles (size distribution, 8.3--102.4 µµm) prepared by conventional mechanical milling. The effect of process parameters, including extraction temperature (30°°C, 40°°C, 50°°C), extraction pressure (200, 250, 300 bar) and nozzle size (50, 100, 200 µµm), on the size distribution of nanoparticles was investigated. The characteristics of nanoparticles and materials were also studied by scanning electron microscopy (SEM) and laser light scattering (LLS). This study demonstrates that RESSAS is applicable for preparing nanoparticles of MBE at low operating temperature; the process is simple without any residual solvent. [ABSTRACT FROM AUTHOR]

Objective: To prepare nano-particles of SCF-CO2 extraction of Magnolia officinalis with rapid expansion of supercritical solution (RESS) and optimize the preparation procedure with orthogonal experiment., Method: The preparation procedures were optimized by orthogonal test L9(3(4)) with the mean particle size and the amounts of total-phenol as indexes. Factors of the extraction pressure and temperature, diameter of nozzle, pre-expansion temperature were evaluated for their effects on preparation process., Result: The optimal preparation technology was as follows: the pressure was at 25 MPa and temperature was at 50 degrees C, the diameter of nozzle was 200 microm, the pre-expansion temperature was at 30 degrees C. The nano-particles solution was settled, of which the average particle size was 303.50 nm and the total-phenol contents was 0.091 g x L(-1), and the stability of the particle size kept well after 1 month of storage at low temperature and obturation the mean particle size., Conclusion: The RESS method is applicable for preparing nanoparticles solution of SCF-CO2 extraction of M. officinalis at low operating temperature. It is simple processing, and no environmental pollution, and no residual solvent.