H-NMR-based metabolic profiling of rat urine to assess the toxicity-attenuating effect of the sweat-soaking method on Radix .

Radix (L.) C.A. Mey. (RWI) is a toxic medicinal species primarily present in the Miao area of China. The toxicity of RWI is effectively reduced whilst maintaining the therapeutic effect when processed using the 'sweat-soaking method', which is a common method of Traditional Chinese Medicine preparation. However, there is a lack of scientific and medical evidence to explain the potential mechanisms by which the toxicity of RWI is reduced after preparation using this method, and the endogenous systemic metabolic effect of RWI remains uncertain. The aim of the present study was to explore the endogetnous metabolic alterations caused by RWI and to examine the possibility of reducing the toxicity of RWI using the sweat-soaking method using proton nuclear magnetic resonance (NMR) metabolomic analysis in rats. Principal Component Analysis, Partial Least Squares-Discriminant Analysis (PLS-DA) and Orthogonal PLS-DA were used to assess individual proton NMR spectra. A total of 34 metabolic products were altered after delivering raw RWI, and 32 endogenous metabolites were induced by processed RWI. The metabolic pathways that lead to a significant impact on energy and carbohydrate, amino acid, organic acids and lipid metabolism following raw and processed RWI use were identified. The mitochondria of hepatic and renal tubules of rats were injured in the raw RWI group, whereas the processed product reduced or interfered with energy substrate, carbohydrate and amino acid metabolism, whilst reducing the levels of metabolic markers of hepatotoxicity and nephrotoxicity, without causing damage to the mitochondria. Our previous study showed that the median lethal dose (LD) value of raw RWI was 4.05 g/kg in rats after oral administration; however, the LD value of the processed RWI could not be measured. The maximum tolerated dose and minimum lethal dose were 20 and 30 g/kg for the processed RWI, respectively, corresponding to 109 and 164 times the clinical daily dose (0.029 g/kg). Thus, the sweat-soaking method reduced the toxicity of RWI. Moreover, after processing, the toxic component YH-10 was converted into a YH-10 + OH compound, reducing the content of the toxic YH-10 by 48%, whilst also reducing the contents of the toxic components YH-12 and YH-15 by 44 and 65%, respectively. In conclusion, the present study showed that the sweat-soaking method reduced the toxicity of RWI, as evidenced by the reduction of the levels of metabolic markers and the activity of metabolic pathways, thus providing a basis for processing of RWI for clinical use.