Abstract: Aiming to establish the HPLC-RID characteristic chromatogram and various sugar content determination methods of different processing products of Rehmanniae radix, and analyze the change trend of sugar composition in the processing process combining pattern recognition, Agilent ZORBAX NH₂ column （250.0 mm×4.6 mm, 5 μm） was used with acetonitrile-pure water （70∶30） mixed solution as mobile phase, the flow rate was 1.0 mL/min, column temperature was 40 ℃, flow cell temperature was 50 ℃, and a HPLC-RID characteristic chromatographic analysis method for different processed products of Rehmanniae radix was established. The contents of fructose, glucose, sucrose, raffinose and stachyose in different processed products of Rehmanniae radix were determined by the external standard method. Principal component analysis （PCA） and hierarchical cluster analysis （HCA） pattern recognition methods were used to analyze the differences and associations of sugar components in different processed products of fresh Rehmanniae radix （including Rehmanniae radix slice）, Rehmanniae radix and Rehmanniae radix praeparata. The results showed that, 12 batches of Rehmanniae radix samples were analyzed, 6 common peaks in the HPLC-RID characteristic chromatogram were matched, and 5 chromatographic peaks were identified. There was no significant difference between Rehmanniae radix slice and fresh Rehmanniae radix. The content of stachyose in fresh Rehmanniae radix was the highest. In the processing from fresh to dried to prepared Rehmanniae radix, the content of stachyose decreased sharply and the content of fructose increased continuously. PCA and HCA could distinguish different processed products, and the results were consistent. It was concluded that, HPLC-RID characteristic map could reflect the changes in the processing of Rehmanniae radix. Simultaneous determination of five sugars in Rehmanniae radix by HPLC-RID method was simple and reliable, which provided research foundation for the extraction technology screening of sugar components and product development of Rehmanniae radix.

Key words: Rehmanniae radix, fingerprint chromatogram, sugars, pattern recognition, content determination