Cardiotoxicity evaluation and comparison of diterpene alkaloids on zebrafish

Diterpene alkaloids (DAs) have a broad spectrum of pharmacological activities, but exhibiting extremely serious cardiotoxicity to induce arrhythmia, heart arrest, even death. This study aimed to evaluate the cardiotoxicity of three diester diterpene alkaloids (DDAs) including aconitine (AC), mesaconitine (MAC), hypaconitine (HAC) and three monoester diterpene alkaloids (MDAs) including 14-α-benzoylaconine (BAC), 14-α-benzoylmesaconine (BMAC), 14-α-benzoylhypaconine (BHAC) on zebrafish. Firstly, the zebrafish embryos after a 72-hour post fertilization were treated with different doses of AC, MAC, HAC, and BAC, BMAC and BHAC for 2, 10 and 24 h, respectively. The heart rates of the treated embryos were calculated and the morphological images of body, together with heart fluorescence were obtained. Results demonstrated that AC, MAC, and HAC at low doses (15.6 and 31.3 μM) decreased the heart rates and increased them at high doses (62.5, 125, and 250 μM), while BAC, BMAC, and BHAC decreased the heart rates in the dose range of 31.3-250 μM, but the highest dose (500 μM) of BAC and BMAC increased the heart rates. In addition, AC, MAC, and HAC exhibited serious organic and functional toxicities, while BAC, BMAC, and BHAC did not. It could be induced that DDAs expressed stronger cardiotoxicities than MDAs, which might be due to that they were known as the Na⁺ channel activators and K⁺ channel inhibitors, respectively. The β-acetate at C-8 position, along with the protonated nitrogen on ring A of their chemical structures contributed more for their different cardiotoxicities. This is the first study on cardiotoxicity comparison of DAs, providing references for the rational and safe application of these compounds and some plant species containing them to reduce side effects while retaining therapeutic efficacy.