ABSTRACT
This study was designed to investigate the correlations of the spatial structure properties of Chinese medicinal extracts with hygroscopicity and the anti-hygroscopic techniques. With Poria extract used as the model drug, pregelatinised starch and microcrystalline cellulose at different ratios were added into Poria fluid extract for preparing powder particles with diverse spatial structures using different drying processes. Then, their hygroscopic behaviours were characterized by equilibrium hygroscopicity(F~∞) and semi-hygroscopic time(t_(1/2)). The correlations of the hygroscopicity of each powder with the spatial structure properties such as particle size(D_(90)), porosity(ε), true density(ρ_t), and surface element distribution were analyzed using partial least-squares method. The F~∞ and t_(1/2) values of Poria extract prepared by three drying methods were sorted in a descending order as follows: F~∞(spray drying>drying at ordinary pressure>drying at reduced pressure); t_(1/2)(drying at reduced pressure>drying at ordinary pressure>spray drying). The powder obtained by spray drying showed a spherical structure with the smallest particle size and intra-particle ε but relatively stronger hygroscopicity. The large-scale surface element enrichment of the powders dried by reduced pressure effectively reduced their hygroscopicity. F~∞ and t_(1/2) were negatively correlated with ε but positively with D_(90), and the interactive influence of each spatial structural properties was not significant. There existed a correlation between the spatial structure of the powder particles of Chinese medicine extracts and their hygroscopicity, and the hygroscopicity could be improved by designing the spatial structure. This study has provided some practical basis for developing the moisture-proof technology of Chinese medicinal preparations.
