title: Parietin: an efficient photo-screening pigment in vivo with good photosensitizing and photodynamic antibacterial effects in vitro.
abstract: 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 (ΦF= 0.03), decaying by efficient intersystem crossing to an excited triplet state3PTN*, as detected by laser-flash photolysis experiments. In the presence of triplet molecular oxygen, the3PTN* was fully quenched producing singlet molecular oxygen (1O2) with a quantum yield of 0.69. In addition, in buffer solutions, PTN has the ability to also generate a superoxide radical anion (O2˙-) 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 both1O2and O2˙-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.
authors.affiliation: IMBIV, CONICET and Facultad de Ciencias Químicas, Universidad Nacional Córdoba, Haya de la Torre y Medina Allende, X5000HUA Córdoba, Argentina. sununez@fcq.unc.edu.ar.
authors.forename: Laura R
authors.initials: LR
authors.lastname: Comini
authors.affiliation: Instituto de Bionanotecnología del NOA (INBIONATEC), Universidad Nacional de Santiago del Estero - CONICET, RN9, Km 1125, G4206XCP Santiago del Estero, Argentina. cdborsarelli@gmail.com.
authors.forename: F Eduardo
authors.initials: FE
authors.lastname: Morán Vieyra
authors.affiliation: Instituto de Bionanotecnología del NOA (INBIONATEC), Universidad Nacional de Santiago del Estero - CONICET, RN9, Km 1125, G4206XCP Santiago del Estero, Argentina. cdborsarelli@gmail.com.
authors.forename: Ricardo A
authors.initials: RA
authors.lastname: Mignone
authors.affiliation: Dto. Farmacia, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Unidad de Tecnología Farmacéutica (UNITEFA) - CONICET, Haya de la Torre y Medina Allende, X5000HUA Córdoba, Argentina.
authors.forename: Paulina L
authors.initials: PL
authors.lastname: Páez
authors.affiliation: IMBIV, CONICET and Facultad de Ciencias Químicas, Universidad Nacional Córdoba, Haya de la Torre y Medina Allende, X5000HUA Córdoba, Argentina. sununez@fcq.unc.edu.ar.
authors.forename: M
authors.initials: M
authors.lastname: Laura Mugas
authors.affiliation: Instituto de Virología "Dr. J.M. Vanella", Facultad de Ciencias Médicas, Universidad Nacional de Córdoba, Ciudad Universitaria, X5000HUA Córdoba, Argentina.
authors.forename: Brenda S
authors.initials: BS
authors.lastname: Konigheim
authors.affiliation: IMBIV, CONICET and Facultad de Ciencias Químicas, Universidad Nacional Córdoba, Haya de la Torre y Medina Allende, X5000HUA Córdoba, Argentina. sununez@fcq.unc.edu.ar.
authors.forename: José L
authors.initials: JL
authors.lastname: Cabrera
authors.affiliation: IMBIV, CONICET and Facultad de Ciencias Químicas, Universidad Nacional Córdoba, Haya de la Torre y Medina Allende, X5000HUA Córdoba, Argentina. sununez@fcq.unc.edu.ar.
authors.forename: Susana C
authors.identifier: 0000-0002-2030-0890
authors.initials: SC
authors.lastname: Núñez Montoya
authors.affiliation: Instituto de Bionanotecnología del NOA (INBIONATEC), Universidad Nacional de Santiago del Estero - CONICET, RN9, Km 1125, G4206XCP Santiago del Estero, Argentina. cdborsarelli@gmail.com.
authors.forename: Claudio D
authors.initials: CD
authors.lastname: Borsarelli
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects; D002522:Chlorocebus aethiops; D004642:Emodin / Q000031:analogs & derivatives* / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000528:radiation effects; D006094:Gram-Positive Bacteria / Q000187:drug effects / Q000528:radiation effects; D006801:Humans; D007962:Leukocytes / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D008011:Lichens / Q000737:chemistry / Q000378:metabolism; D008027:Light; D008826:Microbial Sensitivity Tests; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D026082:Singlet Oxygen / Q000737:chemistry / Q000378:metabolism; D013056:Spectrophotometry, Ultraviolet; D013481:Superoxides / Q000737:chemistry / Q000378:metabolism; D014466:Ultraviolet Rays; D014709:Vero Cells
chemical_list: D000900:Anti-Bacterial Agents; D017319:Photosensitizing Agents; D013481:Superoxides; D026082:Singlet Oxygen; C008905:physcione; D004642:Emodin