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Perinaphthenone phototransformation in a model of leaf epicuticular waxes

Paper ID Volume ID Publish Year Pages File Format Full-Text
30425 44478 2014 9 PDF Available
Title
Perinaphthenone phototransformation in a model of leaf epicuticular waxes
Abstract

•Perinaphthenone is photodegraded faster in paraffinic wax than in n-heptane.•In air-equilibrated wax the hydroxyperinaphthenyl radical is formed in high amounts.•On prolonged use the production of singlet oxygen from perinaphthenone drastically decreases.•Pyrethrum extract in the wax promotes the hydroxyperinaphthenyl radical formation.

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.

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Keywords
Perinaphthenone; Singlet oxygen; Epicuticular wax; Hydroxyperinaphthenyl radical; Pesticide; Pyrethrum extract
First Page Preview
Perinaphthenone phototransformation in a model of leaf epicuticular waxes
Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Photochemistry and Photobiology B: Biology - Volume 130, 5 January 2014, Pages 93–101
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering