Thermal degradation, kinetic analysis and evaluation of biological activity on human melanoma for artemisinin

Abstract

In this paper, the bioactive compound artemisinin (ART) was evaluated by instrumental techniques, regarding its thermal stability and mechanism of decomposition, but for the biological activity as well, using in vitro techniques, namely the cytotoxic activity evaluation on two cell types (HaCaT and A375) employing the MTT proliferation method, and the antioxidant activity (AOA) using the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging assay. The results of the isoconversional kinetic study first lead to an indication of complex decomposition mechanism, which was later confirmed by the modified nonparametric kinetics (NPK) method. According to the NPK method, it was shown that ART is mainly degraded by the involvement of two parallel processes, with different energetic contributions that are due to chemical and physical transformations. However, the estimated mean apparent activation energy yields similar results with all four kinetic methods, ranging between 61.3 and 68.7 kJ mol−1, confirming the low thermal stability of the compound, which can be explained by the presence of reactive functional groups, such as the peroxide one. Regarding the biological activity of ART, it was shown that it can be used to induce cell growth arrest on human melanoma cell line A375, but affecting in a smaller measure the viability of HaCaT cell line, while the AOA is negligible, in comparison with standard antioxidants.