OBJECTIVE To optimize the extraction and purification process of indican in Isatidis Folium and evaluate the nephrotoxic effect of indican on rats.

METHODS Taking the extraction rate of indican as the evaluation index, the ultrasonic alcohol extraction process of indican from Isatidis Folium was optimized successively through single-factor experiments and the Box-Behnken response surface method, namely ethanol concentration, liquid-solid ratio, extraction time and extraction power. The X-5 macroporous adsorption resin was used to further enrich and purify indican. The levels of kidney injury molecule-1(Kim-1), cystatin C(Cys-C), interleukin 6(IL-6) in the serum of rats administered indican were determined, and the pathological changes of renal tissues in rats were observed.

RESULTS The optimal extraction process was as follows: Ethanol concentration was 30%, liquid-solid ratio was 12.7∶1, extraction time was 35 min, extraction power was 300 W. The purification process was selected X-5 macroporous adsorption resin, eluting with 30% ethanol. The purity of indican obtained after enrichment and purification was 77.45%, and the recovery rate was 86.06%. The levels of Kim-1, Cys-C and IL-6 in the serum of rats in the low-dose and high-dose indican administration groups were significantly higher than those in the normal group. The results of pathological sections showed that renal tubular dilation and inflammatory cell infiltration occurred to varying degrees in the renal tissues of rats in the low-dose and high-dose indican administration groups.

CONCLUSION This method is stable and reliable, and can be used to extract and purify indican from Isatidis Folium. Indican has certain nephrotoxicity in rats.