Recently, natural photosensitizers, such as berberine, curcumin, riboflavin, and emodin, have received more and more attention in photodynamic therapy. Tanshinone I (TanI) is extracted from a traditional Chinese herb Danshen, and exhibits many physiological functions including antitumor. TanI is a photoactive phytocompounds, but no work was tried to investigate its potential photodynamic effect. This study evaluated the cytotoxicity induced by the photodynamic effect of TanI. The photochemical reactions of TanI were firstly investigated by laser flash photolysis. Then breast cancer cell line MDA-MB-231 was chosen as a model and the photodynamic effect of TanI on cancer cell was evaluated by MTT assay and flow cytometry. The results showed that TanI could be photoexcited by its UV-Vis absorption light to produce 3TanI* which was quickly quenched by O2. MTT assay showed that the photodynamic effect of TanI resulted in more obvious inhibitive effect on cell survival and cell migration. Besides, the photodynamic effect of TanI could induce cell apoptosis and necrosis, lead to cell cycle arrest in G2, increase intracellular ROS, and decrease the cellular Δψm. It can be concluded that the photodynamic effect of TanI can obviously enhance the cytotoxicity of TanI on MDA-MB-231 cells in vitro, which indicated that TanI might serve as a natural photosensitizer.
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