Comini Laura R, Morán Vieyra F Eduardo, Mignone Ricardo A, Páez Paulina L, Laura Mugas M, Konigheim Brenda S, Cabrera José L, Núñez Montoya Susana C, Borsarelli Claudio D
IMBIV, CONICET and Facultad de Ciencias Químicas, Universidad Nacional Córdoba, Haya de la Torre y Medina Allende, X5000HUA Córdoba, Argentina.
Instituto de Bionanotecnología del NOA (INBIONATEC), Universidad Nacional de Santiago del Estero - CONICET, RN9, Km 1125, G4206XCP Santiago del Estero, Argentina.
Photochem Photobiol Sci. 2017 Feb 15;16(2):201-210. doi: 10.1039/c6pp00334f.
The photophysical, photoinduced pro-oxidant and antibacterial properties in vitro of the natural occurring parietin (PTN; 1,8-dihydroxy-3-methoxy-6-methyl-9,10-anthraquinone) were evaluated. PTN was extracted from the lichen identified as Teloschistes flavicans (Sw.) Norm. (Telochistaceae). Results indicate that in chloroform solution, PTN presents spectroscopic features corresponding to an excited-state intramolecular proton-transfer (ESIPT) state with partial keto-enol tautomerization. In argon-saturated solutions, the singlet excited state is poorly fluorescent (Φ = 0.03), decaying by efficient intersystem crossing to an excited triplet state PTN*, as detected by laser-flash photolysis experiments. In the presence of triplet molecular oxygen, the PTN* was fully quenched producing singlet molecular oxygen (O) with a quantum yield of 0.69. In addition, in buffer solutions, PTN has the ability to also generate a superoxide radical anion (O˙) in a human leukocyte model and its production was enhanced under UVA-Vis irradiation. Finally, the in vitro antibacterial capability of PTN in the dark and under UVA-Vis illumination was compared in microbial cultures of both Gram positive and negative bacteria. As a result, PTN showed promising photo-induced antibacterial activity through the efficient photosensitized generation of both O and O˙ species. Thus, we have demonstrated that PTN, an efficient photo-screening pigment in lichens, is also a good photosensitizer in solution with promising applications in antibacterial photodynamic therapy.
对天然存在的苔红素（PTN；1,8 - 二羟基 - 3 - 甲氧基 - 6 - 甲基 - 9,10 - 蒽醌）的光物理、光诱导促氧化剂和体外抗菌性能进行了评估。PTN是从被鉴定为黄橙衣（Teloschistes flavicans (Sw.) Norm. (Telochistaceae)）的地衣中提取的。结果表明，在氯仿溶液中，PTN呈现出与具有部分酮 - 烯醇互变异构的激发态分子内质子转移（ESIPT）态相对应的光谱特征。在氩气饱和溶液中，单重激发态荧光较弱（Φ = 0.03），通过激光闪光光解实验检测到，它通过有效的系间窜越衰减为激发三重态PTN*。在三重态分子氧存在下，PTN*被完全猝灭，产生单重态分子氧（O），量子产率为0.69。此外，在缓冲溶液中，PTN在人白细胞模型中也有能力产生超氧阴离子自由基（O˙），并且在紫外 - 可见光照射下其产生会增强。最后，在革兰氏阳性和阴性细菌的微生物培养物中比较了PTN在黑暗和紫外 - 可见光照射下的体外抗菌能力。结果表明，PTN通过有效光致敏产生O和O˙物种显示出有前景的光诱导抗菌活性。因此，我们证明了PTN作为地衣中一种有效的光屏蔽色素，在溶液中也是一种良好的光敏剂，在抗菌光动力疗法中有广阔的应用前景。
