Journal
ENVIRONMENTAL POLLUTION
Volume 157, Issue 10, Pages 2776-2780Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.envpol.2009.04.022
Keywords
Acidic precipitation; Depsides; Depsidones; Dissociation constant; pH
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Funding
- Deutsche Forschungsgemeinschaft (DFG) [Ha 3152/8-1]
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The depsidone fumarprotocetraric acid as well as the depsides perlatolic and thamnolic acids are lichen secondary metabolites. Their first dissociation constants (pK(a1)) in methanol were determined to be 2.7 for perlatolic acid and 2.8 for fumarprotocetraric and thamnolic acids by UV spectroscopy. Lower pK(a1) values are. so far, not known from lichen substances. Several lichens producing at least one of these compounds are known for their outstanding tolerance to acidic air pollution. This is demonstrated by evaluating published pH preferences for central European lichens. The low pK(a1) values suggest that strong dissociation of the studied lichen substances is a prerequisite for the occurrence of lichens with these compounds on very acidic substrata, as protonated lichen substances of different chemical groups, but not their conjugated bases, are known to shuttle protons into the cytoplasm and thereby apparently damage lichens. (C) 2009 Elsevier Ltd. All rights reserved.
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