Effect of drying method on transformation of bioactive constituents in Polygoni Multiflori Radix / 中草药

ABSTRACT

Objective: To explore the effects of different drying methods on the transformation of bioactive constituents, such as stilbene glycosides and anthraquinones, in Polygoni Multiflori Radix (PMR), and to provide a scientific evidence for the suitable drying method for PMR. Methods: Using crude PMR as materials, six drying methods including shade-drying, sun-drying, oven-drying, freeze-drying, microwave-drying, and far-infrared-drying were used to process the samples of PMR. HPLC was used to simultaneously determine the contents of stilbene glycosides, free and conjugated anthraquinones with different drying methods and drying time. Results: The contents of stilbene glycosides in the samples processed with the above methods were as follows in descending order sun-drying > far-infrared-drying > freeze-drying > shade-drying > oven-drying > microwave-drying; The shade-drying and sun-drying methods were more suitable for the conjugated anthraquinones transforming into the free ones and the contents of conjugated anthraquinones in the sample processed with far-infrared-drying method were the highest. The comprehensive evaluation index obtained with principal component analysis showed that the far-infrared-drying method is significantly higher than those with other drying methods for PMR. Conclusion: Far-infrared-drying method is the suitable approach for the primary drying processing of PMR.