Comparison of content-toxicity-activity of six ingenane-type diterpenoids between Euphorbia kansui before and after stir-fried with vinegar by using UFLC-MS/MS, zebrafish embryos and HT-29 cells

The dried roots of Euphorbia kansui (EK) are especially beneficial for the treatment of edema, but the severe toxicity limits their clinical applications. Euphorbia kansui stir-fried with vinegar (VEK) is traditionally employed to reduce the toxicity of EK. However, the material basis for the toxicity reduction with effectivity conservation is still unclear. Therefore, in this study, a rapid, sensitive, and reliable ultra-fast liquid chromatography tandem mass spectrometry (UFLC-MS/MS) method was firstly established to simultaneously determine six ingenane-type diterpenoids, i.e. kansuiphorin C (1), 5-O-benzoyl-20-deoxyingenol (2), 20-deoxyingenol (3), 3-O-(2'E,4'E-decadienoyl)-20-O-acetylingenol (4), 20-O-(2'E,4'Z-decadienoyl)ingenol (5), and ingenol (6), in EK and VEK based on the processing conversion. Then, the toxicity evaluation on zebrafish embryos and modulation of the expression of aquaporin-3 (AQP3) proteins in HT-29 cells were employed to investigate the toxicity-activity of six compounds. Chromatographic separation was obtained on Waters BEH RP18 column (2.1 mm × 100 mm, 2.5 μm) with the mobile phase composed of 0.1 % formic acid in acetonitrile and water, respectively. The column temperature was 35 ℃ at a flow rate of 0.4 mL min-1. Multiple reaction monitoring was conducted in both positive and negative modes for quantitative analysis. The method was then successfully used for the determination of six compounds in EK and VEK. In addition, 1, 2, 4, and 5 had evident cardiotoxicity, intestinal irritation and nutrient absorption disorders on zebrafish larvae, while no in-vivo toxicity was seen for groups given 3 and 6 (LC50 > 200 μM). Meanwhile, 1, 2, 4, 5, and 6 significantly increased the expression of AQP3 protein (p < 0.05) to promote the excretion of water in the colon. This study demonstrated that toxic ingenane-type diterpenoids converted into the less toxic compounds with the same core structure through the breakage of multiple ester bonds in the side chain. At the same time, the laxative effect was retained, providing useful information for the optimization of the process of EK and quality evaluation of other similar toxic Chinese herbal medicines.