Monocyclic aromatics, methyl-[beta]-orcinolcarboxylate, and methylorsellinate exhibited 4-5-fold higher activity than acarbose , whereas depsidone
salazinic acid, depside sekikaic acid, and dibenzofuran usnic acid showed compatible [IC.sub.50] value as compared to the standard acarbose .
Flavoparmelia euplecta has been reported to contain the dibenzofuran usnic acid and the depsidone
protocetraric acid ; on the other hand, Myelochroa irrugans present as bioactive compounds the depside atranorin, the triterpenes zeorin and leucotylic acid, and the xanthone secalonic acid A ; and the main secondary metabolites in Parmelia omphalodes have been described to be the depsides atranorin, the depsidones
salazinic and lobaric acids, and the acyclic fatty acid protolichesterinic acid .
Except for usnic acid, no cytotoxic effects were observed for the two depsides (atranorin and perlatolic acid) and the alkyl depsidone
Variolaric acid (orcinol depsidone
) is a compound generally known in crustose lichens and frequent in Ochrolechia and Pertusaria (Zedda 1999).
The antimicrobial activity of olivetoric acid 16 (MIC [greater than or equal to] 1.3 mM) against various bacterial and fungal pathogens is rather weak compared with both (+)- and (-)-usnic acids, but stronger than its depsidone
analogue physodic acid (Tay et al.
Characterization of the product of depsidone
In addition to one singlet at 3.92 ppm, that suggests the loxodin depsidone
, chromatographically shown to be present at low concentration in the extract (Figure 2), the doublets at 5.97 (J, 2.7 Hz) and 6.26 ppm (J, 2.7 Hz) suggest hydrogens in an olefinic system.
Comparing the retention times ([t.sub.R]) and UV spectra (190-400 nm) of the main peaks with those of reference substances previously isolated from lichens confirmed that the methanol extract of Cetraria islandica contains the depsidone
fumarprotocetraric acid ([t.sub.R] = 26.397 min) as its main constituent (> 90% of total integrated area); it also contains traces of the related depsidone
protocetraric acid ([t.sub.R] = 21.769 min).
A novel depsidone
and some new xanthones from Garcinia species.
caperata) and depsidone
salazinic acid (other two species).
The in vitro antimicrobial activities of pannarin, a depsidone
isolated from lichens, collected in several Southern regions of Chile (including Antarctica), was evaluated alone and in combination with five therapeutically available antibiotics, using checkerboard microdilution assay against methicillin-resistant clinical isolates strains of Staphylococcus aureus.