Chemical Compounds
L. pulmonaria is known to contain a variety of acids common to lichens, such as stictic acid, desmethyl stictic acid, gyrophoric acid, tenuiorin, constictic acid, norstictic acid, peristictic acid, and methylnorstictic acid. These compounds, collectively known as depsidones, are known to be involved in defense against grazing herbivores like lichen-feeding molluscs. It also contains the sugar alcohols -arabitol, volemitol, in addition to several carotenoids (total content > 10 mg/kg), such as alpha carotene, beta carotene, and beta cryptoxanthin. The upper cortex of the lichen contains melanins that screen UV and PAR radiation from the photobiont. The synthesis of melanin pigments in the lichen increases in response to greater solar irradiation, and shade-adapted thalli are greenish-grey in the air-dry state, while sun-exposed thalli can be dark brown in color. This adaptation helps protect the photosymbiont D. reticulata, known to be relatively intolerant to high light levels.
Also known to be present are various steroids, namely ergosterol, episterol, fecosterol and lichesterol.
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