have one or more nuclear chlorine substituents. The fundamental structure of the
known lichen xanthones could be derived directly by linear condensation of seven
acetate and malonate units with one orsellinic acid-type cyclization. The two rings
are joined by a ketonic carbon and by an ether-oxygen arising from
cyclodehydration.
Norlichexanthone
Norlichexanthone (Fig. 19) is lichen compound that fully inhibits p56
1ck tyrosine
kinase at 200 μg/mL [72] and inhibits the activity of the protein kinases aurora-B,
PIM1, and VEGF-R2, where IC 50 values from 0.3 to 12 μM [73].
Thiophanic Acid
Allelopathic effect of thiophanic acid (Fig. 20) on wide number of higher plants was
demonstrated [74]. Fungicidal activity of thiophanic acid and thiophaninic acid was
recorded as well [75].
Anthraquinones
Anthraquinones is a class of phenolic compounds based on the 9,10-anthraquinone
skeleton and is probably formed by internal cyclization of a single polyacetyl chain.
Fig. 19 Norlichexanthone structure (Lecanora symmicta)
Fig. 20 Thiophanic acid structure (Lecidella elaeochroma)
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M. Goga et al.