title: Perinaphthenone phototransformation in a model of leaf epicuticular waxes.
abstract: Perinaphthenone (1H-phenalen-1-one, PN) is a reference photosensitizer producing singlet oxygen with a quantum yield close to one in a large variety of solvents. It is also the basic structure of a class of phototoxic phytoalexins. In this work, the PN photoreactivity was studied for the first time in a paraffinic wax, used as model of leaf epicuticular waxes. The PN photodegradation was monitored by UV-Vis spectroscopy. The triplet excited state, singlet oxygen and the hydroxyperinaphthenyl radical were detected by diffuse reflectance laser flash photolysis, near infrared phosphorescence and by EPR spectroscopy, respectively. The PN phototransformation was found to be fivefold faster in the wax than in n-heptane under steady-state irradiation. The hydroxyperinaphthenyl radical formation was observed in aerated irradiated paraffin wax while in n-heptane solution the radical was observed only in the absence of oxygen. These results show that under continuous irradiation, PN is much more easily phototransformed in a solid environment than in solution. Several photoproducts were identified, in particular phenalanone, PN dimers, and oxidized PN-alkanes adducts. Finally, when pyrethrum extract is added into the wax along with PN, the hydroxyperinaphthenyl radical concentration was increased by a factor of 2.4. Such photochemical reactions may occur when systemic pesticides enter the plant cuticle.
authors.affiliation: Clermont Université, Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand (ICCF), BP 10448, 63000 Clermont-Ferrand, France.
authors.forename: Aurélien S
authors.initials: AS
authors.lastname: Trivella
authors.affiliation: Clermont Université, Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand (ICCF), BP 10448, 63000 Clermont-Ferrand, France.
authors.forename: Shirin
authors.initials: S
authors.lastname: Monadjemi
authors.affiliation: Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
authors.forename: David R
authors.initials: DR
authors.lastname: Worrall
authors.affiliation: Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, UK.
authors.forename: Iain
authors.initials: I
authors.lastname: Kirkpatrick
authors.affiliation: Laboratoire des IMRCP, UMR CNRS 5623, Université Toulouse III (Paul Sabatier, UPS), 31062 Toulouse Cedex 9, France.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Arzoumanian
authors.affiliation: Clermont Université, Université Blaise Pascal, Institut de Chimie de Clermont-Ferrand (ICCF), BP 10448, 63000 Clermont-Ferrand, France; CNRS, UMR 6296, ICCF, 63171 Aubière, France. Electronic address: claire.richard@univ-bpclermont.fr.
authors.forename: Claire
authors.initials: C
authors.lastname: Richard
mesh_terms: D011723:Chrysanthemum cinerariifolium; D006536:Heptanes / Q000737:chemistry; D007834:Lasers; D010232:Paraffin / Q000737:chemistry; D010575:Pesticides / Q000737:chemistry; D043803:Phenalenes / Q000737:chemistry* / Q000528:radiation effects*; D010782:Photolysis; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000528:radiation effects*; D010936:Plant Extracts / Q000737:chemistry; D018515:Plant Leaves / Q000737:chemistry; D026082:Singlet Oxygen / Q000737:chemistry*; D014885:Waxes / Q000737:chemistry
chemical_list: D006536:Heptanes; D010575:Pesticides; D043803:Phenalenes; D017319:Photosensitizing Agents; D010936:Plant Extracts; D014885:Waxes; D026082:Singlet Oxygen; C028618:n-heptane; C038036:phenalen-1-one; D010232:Paraffin
keywords: Epicuticular wax; Hydroxyperinaphthenyl radical; Perinaphthenone; Pesticide; Pyrethrum extract; Singlet oxygen