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.
Highlights
Rehmanniae radix is the fresh or dried tuberous roots of Rehmannia glutinosa Libosch, belonging to the family Scrophulariaceae
As a typical Sheng-Di-Huang, among saccharides, strachyose is the strongest fluorescence band, raffinose and sucrose gave stronger or weaker fluorescence bands, fructose is the weakest in different samples; As iridoids, catalpol were obviously detected as grey-blue fluorescence bands, but the content fluctuated widely
Recent studies claimed that 5-HMF is likely an important bioactive component which exists in many herbal drugs with the function of antioxidant and nourishing kidney Yin deficiency [15]
Summary
Rehmanniae radix is the fresh or dried tuberous roots of Rehmannia glutinosa Libosch, belonging to the family Scrophulariaceae. The drug is usually collected in autumn, removed from root stock, rootlet and soil, and used either in fresh state or mild-baked to dryness. For the patients of “Kidney-Yin”-deficiency, Di-Huang should be transformed to have a “warm” property by repeated steaming process until the crude drug turned black and was called as “Shu-Di-Huang” (steamprocessed Rehmnania radix or prepared Rehmannia radix). This drug is used to nourish “yin” and replenish blood, reinforce the essence of life and marrow and tonify the “Yin-deficient Kidney” [1] [2]
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