ABSTRACT
Introduction: Rhubarb is a traditional Chinese medicine (TCM) used to release heat and has cathartic effects. Official rhubarb in Taiwan Herbal Pharmacopeias 4th edition (THP 4th) and China Pharmacopeia 2020 (CP 2020) are the roots and rhizomes of Rheum palmatum L., Rheum tanguticum Maxim. ex Balf., and Rheum officinale Baill. However, the Rheum genus is a large genus with many different species, and owing to the similarity in appearance and taste with official rhubarb, there needs to be more clarity in the distinction between the species of rhubarb and their applications. Given the time-consuming and complicated extraction and chromatography methods outlined in pharmacopeias, we improved the qualitative analysis and quantitative analysis methods for rhubarb in the market. Hence, we applied our method to identify the species and quality of official and unofficial rhubarb. Method: We analyzed 21 rhubarb samples from the Taiwanese market using a proposed HPLC-based extraction and qualitative analysis employing eight markers: aloe-emodin, rhein, emodin, chrysophanol, physcion, rhapontigenin, rhaponticin, and resveratrol. Additionally, we developed a TLC method for the analysis of rhubarb. KEGG pathway analysis was used to clarify the phytochemical and pharmacological knowledge of official and unofficial rhubarb. Results: Rhein and rhapontigenin emerged as key markers to differentiate official and unofficial rhubarb. Rhapontigenin is abundant in unofficial rhubarb; however, rhein content was low. In contrast, their contents in official rhubarb were opposite to their contents in unofficial rhubarb. The TLC analysis used rhein and rhapontigenin to identify rhubarb in Taiwan's markets, whereas the KEGG pathway analysis revealed that anthraquinones and stilbenes affected different pathways. Discussion: Eight reference standards were used in this study to propose a quality control method for rhubarb in Taiwanese markets. We propose a rapid extraction method and quantitative analysis of rhubarb to differentiate between official and unofficial rhubarb.
ABSTRACT
Quality control of herbal medicines is crucial, especially the role of herbal drug identification. This is essential for preventing the misuse of herbs, which can affect efficacy or cause toxicity. Scleromitrion diffusum is a common herb, yet it is often mistaken for Oldenlandia corymbosa. This study analyzed the morphology, microscopy, thin-layer chromatography (TLC), and high-pressure liquid chromatography (HPLC) using two markers, asperuloside and scandoside methyl ester, to distinguish between S. diffusum and O. corymbosa with the analysis included 10 samples of S. diffusum and 10 samples of O. corymbosa collected from the Taiwan market. By quantifying the total polyphenols and flavonoids, we investigated the antioxidant activity, including the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging effect, 2,2'-azino-bis 3-ethylbenzothiazoline-6-sulfonic acid (ABTSâ¢+) scavenging effect, and reducing power to further elucidate the biological effects of the two herbs. The results of this study revealed notable differences in microscopy and suggested a TLC method for distinguishing between the two herbs in the market. In HPLC, the ratios of asperuloside and scandoside methyl ester differed between the two herbs. S. diffusum contained a higher asperuloside content. In contrast, O. corymbosa contained higher concentrations of scandoside methyl esters. With more total polyphenols and flavonoids in S. diffusum than those in O. corymbosa, the antioxidant activity of S. diffusum was superior to that of O. corymbosa. This study provides a comprehensive understanding for the identification and quality evaluation of S. diffusum in the market. RESEARCH HIGHLIGHTS: The study consolidates and clarifies the morphological and microscopic differences between Scleromitrion diffusum and Oldenlandia corymbosa - a common adulterant species of S. diffusum on the Taiwan markets. Using Asperuloside and Scandoside methyl ester as two chemical markers, the study proposes a TLC method for rapidly testing S. diffusum and O. corymbosa on the market. Through HPLC analysis, our results showed that S. diffusum and O. corymbosa had a clear difference in the ratio of two markers, Asperuloside and Scandoside methyl ester: Asperuloside/Scandoside methyl ester in S. diffusum is higher than that in O. corymbosa. Through phytochemicals contents, including total phenols content, flavonoids content, and antioxidant activity, including DPPH, ABTSâ¢+ scavenging activity, and reducing power, S. diffusum showed slightly higher levels of phenols and flavonoids as well as a better antioxidant activity than O. corymbosa.
