In vitro nephrotoxicity and quantitative UPLC-MS analysis of three aristololactams in Houttuynia cordata

Three analogues of aristololactam Ⅰ (AL Ⅰ), AL AⅡ, AL FⅠ and AL BⅡ, had been isolated from Houttuynia cordata, a commonly used medicinal and edible plant with heat-removing and toxin-removing functions. Considering the significant nephrotoxicity of AL Ⅰ, this study evaluated the toxicity of these three aristololactams (ALs) on human proximal tubular epithelial cells (HK-2) by MTT assay, ROS assay, ELISA tests and cytologic morphology observation. Furthermore, the distribution of the three ALs in H. cordata were investigated by UPLC-MSⁿ recognition and quantitation in SIM mode, so as to estimate primarily the safety of the plant. The results showed that all the three ALs in H. cordata had comparative cytotoxicity as AL I with the IC₅₀ values from 3.88 μM to 20.63 μM, caused high levels of cellular levels of reactive oxygen species (ROS) in HK-2 cells, exhibited the potential to cause renal fibrosis by remarkably increasing the levels of transforming growth factor-β (TGF-β1) and fibronectin (FN), and induced fibrous changes in morphology of HK-2 cells. The contents of the three ALs varied significantly in 30 batches of H. cordata from different regions and parts. Overall, the aerial part contained much more ALs (3.20 - 108.19 μg/g) than the underground part (0.95 - 11.66 μg/g), and flowers had the highest contents. Besides, no ALs were detected in the water extract of any part of H. cordata. This work revealed that the aristololactams in H. cordata had similar in vitro nephrotoxicity as AL Ⅰ and were mainly distributed in the aerial part of the plant.