Research progress on chemical composition, pharmacological activity, and quality control methods of kidney tea
Kidney tea, also known as cat whisker grass or cat whisker male, is the dry aboveground part of Clerodendranthus spicatus (Thunb.) C. Y. Wu ex H. W. Li, a plant in the family Lamiaceae. There are five species of this plant, but only one in China. It is distributed in Hainan, Guangdong, southern Yunnan, Fujian and other places, with the most planted in Simao and Xishuangbanna regions of Yunnan. Kidney tea contains various chemical components such as flavonoids, phenylpropanoids, terpenes, etc., which have pharmacological effects such as regulating kidney function, diuresis and stone expulsion, anti-inflammatory, antioxidant, antibacterial, hypoglycemic, and hypotensive effects. According to the Dai medical scripture “Beiye Jing”, kidney tea is used to treat urinary system diseases, including acute and chronic nephritis, urinary tract stones, and rheumatic immune system diseases such as rheumatoid arthritis, gout, etc. This article supplements the relationship between newly discovered compounds and their pharmacological activities in the past five years based on previous reviews, and puts forward its own insights on the pharmacological activity of kidney tea; Due to the fact that the quality of kidney tea determines its medicinal efficacy, this article summarizes the quality control methods for kidney tea in order to provide reference for further research on kidney tea.

In summary, the chemical components in kidney tea are complex and have multiple biological activities. In recent years, scholars at home and abroad have conducted in-depth research on the chemical composition, pharmacological activity, and quality control of kidney tea. The following conclusions have been drawn: (1) terpenoids (including diterpenes, triterpenes, and sesquiterpenes), phenylpropanoids, amides, and other compounds have been newly isolated from kidney tea; (2) Kidney tea and its monomeric compounds exert anti-inflammatory, kidney protective, antibacterial, uric acid lowering, stone expelling, and anti-tumor activities by regulating the ERK-CT1 pathway, downregulating TNF – α, modulating the protein expression of uric acid transporters, inhibiting Notch signaling, and suppressing the TGF – β 1/Smad3 pathway; (3) The establishment of quality standards is closely related to the study of chemical composition and pharmacological activity. Therefore, in recent years, scholars at home and abroad have conducted more research on the quality control of kidney tea, and have created various methods for quality detection of kidney tea using HPLC or UPLC. The quality control methods of kidney tea have been greatly improved. However, there are also the following problems in the research of kidney tea: (1) the chemical composition of kidney tea is relatively abundant, but the pharmacological activity is mostly concentrated in the crude extract, and only a small number of monomeric compounds have been studied for pharmacological activity. The pharmacological activity research of monomeric compounds is relatively weak; (2) There is relatively little research on the mechanism of action of its main pharmacological active monomers, and the mechanism of action has not been fully elucidated, such as the antioxidant activity of phenylpropanoid compounds in kidney tea. Therefore, in the future, it is necessary to strengthen the pharmacological activity and mechanism of action research of the monomers isolated from kidney tea, in order to promote the comprehensive utilization and clinical application of kidney tea.