Searching Clue of the Relationship between the Alteration of Bioactive Ingredients and the Herbal “Property” Transformation from Raw Rehmanniae Radix (<i>Sheng-Di-Huang</i>) to Steam-Heating-Processed Rehmanniae Radix (<i>Shu-Di-Huang</i>) by Chromatographic Fingerprint Analysis

Abstract

“ Di-Huang ” (Rehmanniae Radix) is a peculiar Chinese herbal drug, the fresh root named “ Xian-Di-Huang ” (“ Xian ” means fresh; the commerce is now rarely available), mild-baking-dried raw roots “ Sheng-Di-Huang ” (“ Sheng ” means raw) and steam-processed “ Shu-Di-Huang ” (“ Shu ” implies steam-processed). The both kinds of herbal drug exert different efficiencies with different property according to the traditional clinical theory. It would be of interest that searching the clue of why the therapeutic functions of the same drug differ between the pre- and post-processing. To disclose the comprehensive alteration of the iridoids, saccharides and phenylethanoids occurred between the raw and steam-processed “ Di-Huang ”, the HPTLC and HPLC chromatographic fingerprint analysis has been carried out. The results showed that in the raw crude drug, the iridoids like catalpol is the major bioactive components, and the oligosaccharides composition kept rather consistent; however, in the steam-processed Di-Huang , iridoids was almost disappeared and the oligosaccharides were hydrolyzed gradually through the repeated steam-heating process. The worst case showed only fructose was detected with other minor residual components in the root tuber. It is due to presumably the uncontrollable steaming process in folk workshops. Defining reasonably the boundary between the “ Sheng-Di-Huang ” (mild-baking-dried Rehmanniae radix) and “ Shu-Di-Huang ” (steaming processed Rehmanniae radix) set up by chromatographic fingerprint pattern and standardizing the process would be necessary for assuring the consistent quality of the commercial herbal drugs.