In a previous publication, we have shown that two depsides (Glomelliferic acid and Glomellic acid) extracted from Xanthoparmelia delisei or X. loxodes, exhibited a blue fluorescence at 365 nm when aqueous solutions of KOH (reagent K) were added. These two secondary metabolites are substituted on the C-6 by an alkyl chain with a keto function in beta-position (2-oxo chain). This fluorescence was confirmed with other depsides such as Confluentic, 2’-O-Methylmicrophyllinic, 2’-O-Methylsuperphyllinic, Olivetoric or Arthoniac acids whereas adding KOH to 2-oxo alkyl C-6 substituded depsidones (a-Collatolic acid, a-Alectoronic acid, Physodic acid) results in suppressing fluorescence. A physico-chemical study, including additional depsidones with the same 2-oxo chain in C-6, was performed in order to explain this particular behaviour. The chemical mechanism of this reaction allows us to explain the different behavior of depsides and depsidones. Therefore, we propose a new probe, called KUV, which has been efficiently applied to the determination of morphologically close lichens species such as Xanthoparmelia pulla and X. delisei, Xanthoparmelia verruculifera and X. loxodes, Porpidia macrocarpa and P. cinereoatra. Another important application of this KUV probe, concerning the metabolites revelation on TLC plates is also illustrated.
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