Abstract
Distillate was obtained in different processing cycles of processed Rehmanniae Radix (PRR). In this study, we investigated the chemical compositions of distillates 1 (Dis1) to 9 (Dis9) via GC-MS and LC-MS. Differences between Dis1–Dis9 were noticeable. A total of 13 and 21 compounds were detected via GC-MS and LC-MS, respectively, including organic acids, furans, alcohols, iridoid glycosides, phenylpropanoid glycosides, and saccharides. The relative contents of compound 2,5-hydroxymethylfurfural and furans all gradually increased with steaming time. Other compounds, however, exhibited a negative trend or fluctuated. Of these compounds, iridoid glycosides and phenylpropanoid glycosides were unstable and easily degraded, which led to a gradually decreasing concentration with increased steaming times. In addition, the degradation products were mainly derived from catalpol and acteoside, among which catalpol mainly existed as aglycone and its rearranged products. However, acteoside was converted into verbasoside through the removal of caffeoyl. Some volatile alcohols, such as phenylethyl alcohol, hydroxyphenyl ethanol, and 3-hydroxy-4-methoxybenzoic acid, were also likely from the degradation of acteoside and its homologs. These results provide an important reference basis for the processing methods, quality evaluation, and rational clinical application of PRR and its distillate.
Highlights
Rehmanniae Radix (RR), the root of Rehmannia glutinosa Libosch., is one of the four major “huaiyao” in the Henan Province and has been widely used for the treatment of various diseases in East Asia for thousands of years [1]. ree types of Rehmanniae Radix are widely used as a common Chinese Medicine owing to different processing methods, namely, fresh Rehmanniae Radix (FRR), raw Rehmanniae Radix (RRR), and processed Rehmanniae Radix (PRR)
Water-soluble compounds could be distilled with steam, and the distillate appeared to be black and thick and gave off a sweet and sour smell. e distillate was a byproduct of PRR and generally used as supplementary material mixed with PRR of different processing times. ere were different compositions in different processing times
distillates 1 (Dis1) to Dis9 were collected during the nine processing cycles of PRR, respectively. e liquid formed when water vapour cooled in nine cycles. ree samples were collected during each processing cycle, among which, the volume of each samples was about 1000 mL, and a total of 27 samples were collected during February–May 2020 and stored at 4°C prior to analysis
Summary
Rehmanniae Radix (RR), the root of Rehmannia glutinosa Libosch., is one of the four major “huaiyao” in the Henan Province and has been widely used for the treatment of various diseases in East Asia for thousands of years [1]. ree types of Rehmanniae Radix are widely used as a common Chinese Medicine owing to different processing methods, namely, fresh Rehmanniae Radix (FRR), raw Rehmanniae Radix (RRR), and processed Rehmanniae Radix (PRR). It is believed to be efficient in enriching yin and reinforcing the kidney in Traditional Chinese Medicine (TCM), prevent osteoporosis [3, 4], possess renoprotective activity [5, 6], and prevent cardiovascular diseases [7]. It has become one of the most popular dietary supplements for healthcare [8]. E distillate was a byproduct of PRR and generally used as supplementary material mixed with PRR of different processing times.
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