Comparative study of Scleromitrion diffusum and Oldenlandia corymbosa: Microscopy, TLC, HPLC, and antioxidant activity

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 (ABTS^•+) 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

1. 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.
2. 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.
3. Through phytochemicals contents, including total phenols content, flavonoids content, and antioxidant activity, including DPPH, ABTS^•+ 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.