Monoamine oxidase A (MAO-A) is a promising diagnostic marker for cancer, depression, Parkinson’s disease, and liver disease. The fluorescence detection of MAO-A in living animals is of extreme importance for the early diagnosis of related diseases. However, the development of specific and mitochondrial-targeted and near-infrared (NIR) fluorescence MAO-A probes is still inadequate. Here, we designed and synthesized four NIR fluorescence probes containing a dihydroxanthene (DH) skeleton to detect MAO-A in complex biological systems. The specificity of our representative probe DHMP2 displays a 31-fold fluorescence turn-on in vitro, and it can effectively accumulate in the mitochondria and specifically detect the endogenous MAO-A concentrations in PC-3 and SH-SY5Y cell lines. Furthermore, the probe DHMP2 can be used to visualize the endogenous MAO-A activity in zebrafish and tumor-bearing mice. More importantly, it is the first time that the MAO-A activity of hepatic fibrosis tissues is detected through the probe DHMP2. The present study shows that the synthesized DHMP2 might serve as a potential tool for monitoring MAO-A activity in vivo and diagnosing related diseases.

Two new isoquinolines (1 and 3), along with 4 known isoquinolines were obtained from the ethanol extract of Corydalis saxicola Bunting. Their structures were elucidated based on detailed spectroscopic data (NMR, HR-ESIMS) and comparison with literature data. The absolute configurations of the new compounds were assigned by comparing computed electronic circular dichroism (ECD). The anti-inflammatory effects of the isolates were assessed by inhibiting NO production in LPS-induced RAW264.7 macrophage cells, and the results showed that compounds 1-6 exhibited anti-inflammatory activities, with IC50 values ranged from 44.24 ± 1.16 to 69.00 ± 5.41µM.