The Effects of Salt-Water Processing of Phellodendri Chinensis Cortex on the Enhancement of Kidney Absorption of the Main Alkaloids

Abstract

Phellodendri chinensis cortex (PC) is a commonly used traditional Chinese medicine for clearing heat. It is often applied in the clinical practice by using the salt-water processing method. According to the theory of Chinese meteria medica processing, after being processed with salt-water, traditional Chinese medicine can increase absorption of the kidney and enhance the effects of kidney disease treatments, which can be abbreviated as “entering into kidney by processing with salt-water”. PC is a typical traditional Chinese medicine using the salt-water processing method. The resulting salt-water processed PC（SPC）can specifically enter the kidney meridian, as compared to raw PC (RPC), which enhances the kidney yin nourishing and purges away kidney fire. However, the effect of “entering into kidney by processing with salt-water” of PC has not been proven and its mechanism is unknown. Therefore, it is of great significance to compare the renal absorption effect of PC before and after salt-water processing and elucidate its mechanism. In this article, using the PC alkaloid content as an indicator, a human proximal tubular epithelial cell (HK-2 cell) experiment and the binding rate of alkaloids to lysozyme-kidney target enzyme was was conducted to simulate kidney absorption in vitro. These results were combined with an investigation of the alkaloid content in rat kidneys after a gavage of PC solution, comprehensively evaluating the difference in kidney absorption after salt-water processing. Compared with RPC, the efflux of SPC alkaloids in the HK-2 cell permeability experiment was significantly reduced, and affinity of the lysozyme-kidney target enzyme was higher. In addition, those who were given SPC had a higher alkaloid concentration in the kidneys than the RPC group. Finally, we verified enhanced kidney absorption effect of PC by salt-water processing, and to a certain extent revealed the mechanism of enhanced kidney absorption of SPC.