Hypocrellin B (HB), a lipid‐soluble natural pigment of perylenequinone derivative, is considered as potential photosensitizer for photodynamic therapy. Liposomes loaded with HB can constitute a simple model system, appropriate for better understanding the photodynamic action of HB in vivo. The steady‐state absorption and emission spectra, quantum yield and lifetime of fluorescence of HB incorporated into egg l‐a‐phosphatidyl‐choline (EPC) liposome were examined. The photochemical properties (Type I and/or Type II) of HB have also been studied in aqueous dispersions of small unilamellar liposomes of EPC using electron paramagnetic resonance and spectrophotometric methods, respectively. The quantum yield of 1O2 generated by HB is ca 0.76 in chloroform solution and it did not change upon the incorporation of HB into liposomes of EPC. The superoxide anion radical was generated by the electron transfer from the anion radical of HB (HB·−) to oxygen. The disproportionation of O2·− can generate H2O2 and ultimately the highly reactive ·OH via the Fenton reaction. It could be that the disproportionation proceeded too fast, so we could not detect O2·− directly in aqueous dispersions of liposome EPC. Moreover, the self‐sensitized photooxygenation of HB embedded in liposomes was studied, and almost fully (87%) inhibiting this reaction of HB by p‐benzoquinone (as the quencher of O2·−) in aqueous dispersion of liposome EPC indicated that the radical mechanism (Type I) might be mainly involved in this oxygenation. All these findings suggested that the photodynamic action of HB proceeded via both Type‐I and ‐II mechanisms, but Type‐I mechanism might play a more important role in the aqueous dispersion.

中文翻译：

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Hypocrellin B 在脂质体中的光谱研究和光动力作用¶

Hypocrellin B (HB) 是一种苝醌衍生物的脂溶性天然色素，被认为是光动力疗法的潜在光敏剂。载有 HB 的脂质体可以构成一个简单的模型系统，适用于更好地了解 HB 在体内的光动力作用。研究了掺入鸡蛋 l-a-磷脂酰胆碱 (EPC) 脂质体的 HB 的稳态吸收和发射光谱、量子产率和荧光寿命。HB 的光化学性质（I 型和/或 II 型）也在 EPC 的小单层脂质体的水分散体中分别使用电子顺磁共振和分光光度法进行了研究。HB 产生的 1O2 的量子产率在氯仿溶液中约为 0.76，并且在将 HB 掺入 EPC 脂质体时没有变化。超氧阴离子自由基是通过电子从 HB (HB·-) 的阴离子自由基转移到氧而产生的。O2·-的歧化可通过芬顿反应生成H2O2，最终生成高反应性·OH。可能是歧化进行得太快，所以我们无法直接检测到脂质体 EPC 的水分散体中的 O2·-。此外，研究了嵌入脂质体中的 HB 的自敏光氧化作用，并且几乎完全（87%）抑制了对苯醌（作为 O2·− 的淬灭剂）在脂质体 EPC 的水分散体中的这种反应表明自由基机制（I 型）可能主要参与这种氧化。所有这些发现表明 HB 的光动力作用通过 I 型和 II 型机制进行，