A combination of light, oxygen and a photosensitizer is used to induce death of cancer cells by photodynamic therapy. In this study, we have synthesized several new methyl helianthrone derivatives and compared their phototoxicity with that of hypericin. In contrast to hypericin, methyl helianthrones are soluble in aqueous solutions and have a broad range of light absorbance, which allows the use of polychromatic light. Structural modifications of methyl helianthrone demonstrated that substitution of hydrogen atoms of methyl helianthrone at Positions 2 and 5 with Br atoms or methylation of its phenolic hydroxyls, significantly increases the corresponding singlet oxygen quantum yield and their phototoxicity toward αT3‐1, M2R and LNCaP cells. The phototoxicity of some of these compounds was similar to that of hypericin. Methyl helianthrones, like hypericin, accumulated mainly in the perinuclear region as evident by confocal microscopy. Irradiation of cells pretreated with methyl helianthrone derivatives generates intracellular reactive oxygen species and lipid free radicals, as shown by a fluorescentic probe and electron paramagnetic resonance methods, respectively. The phototoxicity of these methyl helianthrones as well as their ability to oxidize membrane lipids were significantly decreased on addition of specific Type‐II inhibitors, suggesting the involvement of singlet oxygen as the main oxidant.

中文翻译：

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作为光敏剂的新型甲基向日葵酮：合成和生物学评价¶

光、氧气和光敏剂的组合用于通过光动力疗法诱导癌细胞死亡。在这项研究中，我们合成了几种新的甲基向日葵酮衍生物，并将它们的光毒性与金丝桃素的光毒性进行了比较。与金丝桃素相反，甲基向日葵酮可溶于水溶液并具有广泛的吸光度，允许使用多色光。甲基莨菪酮的结构修饰表明，甲基莨菪酮第 2 和 5 位的氢原子被 Br 原子取代或酚羟基的甲基化，显着增加了相应的单线态氧量子产率及其对 αT3-1、M2R 和 LNCaP 细胞的光毒性。其中一些化合物的光毒性与金丝桃素相似。甲基向日葵酮，像金丝桃素一样，主要在核周区域积累，共聚焦显微镜很明显。如荧光探针和电子顺磁共振方法所示，对用甲基向日葵酮衍生物预处理的细胞进行辐照会产生细胞内活性氧和脂质自由基。添加特定的 II 型抑制剂后，这些甲基向日葵酮的光毒性及其氧化膜脂的能力显着降低，表明单线态氧作为主要氧化剂的参与。如荧光探针和电子顺磁共振方法所示，分别。添加特定的 II 型抑制剂后，这些甲基向日葵酮的光毒性及其氧化膜脂的能力显着降低，表明单线态氧作为主要氧化剂的参与。如荧光探针和电子顺磁共振方法所示，分别。添加特定的 II 型抑制剂后，这些甲基向日葵酮的光毒性及其氧化膜脂的能力显着降低，表明单线态氧作为主要氧化剂的参与。