Polyphenols are predominantly present as glycosides in Chinese herbs, and many of them are hydrolyzed to less polar aglycones by enzymes or bacteria in the intestines and then became absorbable. Therefore, it is more appropriate to use the amount of total glycosides as the standard for the quality control of Chinese herbs since most glycosides are assimilated with the aglycone form after oral administration. Currently there are limited requirements for the quality control of crude drugs in pharmacopoeias in many countries, and assays for only one glycoside or aglycone are required. However, these requirements cannot ensure the efficacy of Chinese herbs. This study attempted to determine aglycones in Rhei rhizome (RR), crude Polygoni multiflori radix (cPM), processed Polygoni multiflori radix (pPM), and Cassiae torae semen (CS) after acid hydrolysis in order to investigate the total amount of absorbable components. The decoctions of these four Chinese herbs were hydrolyzed by hydrochloric acid in water bath. Before and after hydrolysis, the contents of aloe-emodin, rhein, emodin, chrysophanol and physcion from RR, emodin and physcion from cPM and pPM, and chrysophanol and physcion from CS were determined by HPLC. The total glycoside contents were calculated by subtracting the amounts of aglycones in decoction from those in hydrolysate. The results showed that the contents of aloe-emodin, emodin, chrysophanol and physcion in RR after acid hydrolysis increased by 154%, 145%, 127% and 95%, respectively. Emodin and physcion in cPM increased by 1174% and 800%, respectively. Chrysophanol and physcion in CS existed solely as glycoside forms. However, emodin and physcion in pPM displayed no significant difference between decoction and hydrolysate. The methods developed in this study are suitable for the determination of total glycosides in RR, cPM, and CS, whereas pPM was suggested to determine the contents of aglycones directly.
Chiang, H.-M.; Tsao, H.-T.; Chao, P.-D.L.; Hou, Y.-C.; and Wen, K.-C.
"Determination of anthraquinone glycosides in Rhei rhizome, Polygoni multiflori radix, and Cassia torae semen,"
Journal of Food and Drug Analysis: Vol. 15
, Article 5.
Available at: https://doi.org/10.38212/2224-6614.2390