Nematocidal principles in "oakmoss absolute" and nematocidal activity of 2,4-dihydroxybenzoates

Novel methods to characterise spatial distribution and enantiomeric composition of usnic acids in four Icelandic lichens

Usnic acid is an antibiotic metabolite produced by a wide variety of lichenized fungal lineages. The enantiomers of usnic acid have been shown to display contrasting bioactivities, and hence it is important to determine their spatial distribution, amounts and enantiomeric ratios in lichens to understand their roles in nature and grasp their pharmaceutical potential. The overall aim of the study was to characterise the spatial distribution of the predominant usnic acid enantiomer in lichens by combining spatial imaging and chiral chromatography. Specifically, separation and quantification of usnic acid enantiomers in four common lichens in Iceland was performed using a validated chiral chromatographic method. Molecular dynamics simulation was carried out to rationalize the chiral separation mechanism. Spatial distribution of usnic acid in the lichen thallus cross-sections were analysed using Desorption Electrospray Ionization-Imaging Mass Spectrometry (DESI-IMS) and fluorescence microscopy. DESI-IMS confirmed usnic acid as a cortical compound, and revealed that usnic acid can be more concentrated around the algal vicinity. Fluorescence microscopy complemented DESI-IMS by providing more detailed distribution information. By combining results from spatial imaging and chiral separation, we were able to visualize the distribution of the predominant usnic acid enantiomer in lichen cross-sections: (+)-usnic acid in Cladonia arbuscula and Ramalina siliquosa, and (-)-usnic acid in Alectoria ochroleuca and Flavocetraria nivalis. This study provides an analytical foundation for future environmental and functional studies of usnic acid enantiomers in lichens.

Phytochemical Investigation of New Algerian Lichen Species: Physcia Mediterranea Nimis

The present study provides new data concerning the chemical characterisation of Physcia mediterranea Nimis, a rare Mediterranean species belonging to the family Physciaceae. The phytochemical screening was carried out using GC-MS, HPLC-ESI-MS-MS, and NMR techniques. Hot extraction of n-hexane was carried out, followed by separation of the part insoluble in methanol: wax (WA-hex), from the part soluble in methanol (ME-hex). GC-MS analysis of the ME-hex part revealed the presence of methylbenzoic acids such as sparassol and atraric acid and a diterpene with a kaurene skeleton which has never been detected before in lichen species. Out of all the compounds identified by HPLC-ESI-MS-MS, sixteen compounds are common between WA-hex and ME-hex. Most are aliphatic fatty acids, phenolic compounds and depsides. The wax part is characterised by the presence of atranorin, a depside of high biological value. Proton 1H and carbon 13C NMR have confirmed its identification. Atranol, chloroatranol (depsides compound), Ffukinanolide (sesquiterpene lactones), leprolomin (diphenyl ether), muronic acid (triterpenes), and ursolic acid (triterpenes) have also been identified in ME-hex. The results suggested that Physcia mediterranea Nimis is a valuable source of bioactive compounds that could be useful for several applications as functional foods, cosmetics, and pharmaceuticals.

Atraric Acid Exhibits Anti-Inflammatory Effect in Lipopolysaccharide-Stimulated RAW264.7 Cells and Mouse Models

Lichens, composite organisms resulting from the symbiotic association between the fungi and algae, produce a variety of secondary metabolites that exhibit pharmacological activities. This study aimed to investigate the anti-inflammatory activities of the secondary metabolite atraric acid produced by Heterodermia hypoleuca. The results confirmed that atraric acid could regulate induced pro-inflammatory cytokine, nitric oxide, prostaglandin E2, induced nitric oxide synthase and cyclooxygenase-2 enzyme expression in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. Meanwhile, atraric acid downregulated the expression of phosphorylated IκB, extracellular signal-regulated kinases (ERK) and nuclear factor kappa B (NFκB) signaling pathway to exhibit anti-inflammatory effects in LPS-stimulated RAW264.7 cells. Based on these results, the anti-inflammatory effect of atraric acid during LPS-induced endotoxin shock in a mouse model was confirmed. In the atraric acid treated-group, cytokine production was decreased in the peritoneum and serum, and each organ damaged by LPS-stimulation was recovered. These results indicate that atraric acid has an anti-inflammatory effect, which may be the underlying molecular mechanism involved in the inactivation of the ERK/NFκB signaling pathway, demonstrating its potential therapeutic value for treating inflammatory diseases.

The potential antifeedant activity of lichen-forming fungal extracts against the invasive Spanish slug (Arion vulgaris)

The protection of horticultural crops from slug feeding can be achieved using slug pellets; however, application of molluscicides is not always safe for the environment. There is a need for alternative methods to reduce the palatability of crop plants. Chemical properties of secondary compounds from lichens influence the feeding behaviour of slugs. Liquid extracts of three lichen species (Cladonia rangiferina (L.) F.H. Wigg., Cladonia stellaris (Opiz) Pouzar & Vězda, and Pseudevernia furfuracea (L.) Zopf) were applied to three different crops and tested for their antifeedant properties against an important agricultural pest, the Spanish slug (Arion vulgaris Moquin-Tandon, 1855). All three extracts had specific activity, showing a decrease in grazing intensity as well as slug mass loss after feeding on treated food. Slugs significantly gained mass after feeding under control condition; however, they did not gain mass when fed on extract-treated food. The most effective extract was from P. furfuracea. We propose to use properties of lichen extracts to develop new environmentally friendly molluscicides.

Anti-inflammatory principles from Heritiera littoralis bark

Compounds from the hexane, dichloromethane and acetone extracts of Heritiera littoralis bark were investigated for their nitric oxide (NO) inhibitory effects using RAW264.7 macrophage cells. The result indicated that ergosterol peroxide (13) exhibited the highest activity against NO release with an IC(50) value of 2.5 microM, followed by 6-alpha-hydroxystigmast-4-en-3-one (11, IC(50)=9.5 microM) and stigmast-4-en-3-one (9, IC(50)=15.9 microM), whereas other compounds showed moderate and mild effects (25.4- > 100 microM). Ergosterol peroxide (13) and 6-alpha-hydroxystigmast-4-en-3-one (11) were also tested against prostaglandin E(2) (PGE(2)) and tumor necrosis factor alpha (TNF-alpha) releases. It was found that ergosterol peroxide (13) possessed marked activity against PGE(2) release with an IC(50) value of 28.7 microM, while 6-alpha-hydroxystigmast-4-en-3-one (11) was 86.7 microM. However, these two compounds were inactive towards TNF-alpha release (IC(50) > 100 microM). The mechanism in transcriptional level of ergosterol peroxide (13) was found to down regulate mRNA expressions of iNOS and COX-2 in dose-dependent manners.

Furanonaphthoquinones, atraric acid and a benzofuran from the stem barks of Newbouldia laevis

The series of naturally occurring furanonaphthoquinones is extended by identification of the derivatives 2-(1'-methylethenyl)-5-hydroxynaphtho[2,3-b]furan-4,9-dione and 2-(1'-methylethenyl)-7-hydroxynaphtho[2,3-b]furan-4,9-dione. They are accompanied in the stem barks of Newbouldia laevis by the known analogues 5-hydroxy-dehydro-iso-alpha-lapachone, 2-acetyl-5-hydroxynaphtho[2,3-b]furan-4,9-dione and 2-(1'-methylethenyl)naphtho[2,3-b]furan-4,9-dione along with the rare atraric acid and the new 2-(1'-methylethenyl)-6-hydroxy-2,3-dihydrobenzofuran. The structures of these compounds were established from spectroscopic studies.

Oxidative stress and usnic acid content in Parmelia caperata and Parmelia soredians (Lichenes)

High light levels together with Paraquat treatment or exposure to pollutants (e.g. SO2) can cause oxidative stress in epiphytic lichens. In some cases, a significant increase in ascorbic acid and other antioxidant metabolites, sometimes occurring in lichens only, was observed. In this study, usnic acid was measured by HPLC in Parmelia caperata and Parmelia soredians thalli treated with Paraquat, a herbicide which transfers electrons from various transport systems to oxygen, producing O2*- superoxide radicals. In light, Paraquat acts by generating active oxygen species within the chloroplast, thus simulating the oxidative component of environmental stress. The significant increase in the usnic acid content measured in P. soredians thalli (+ 36.3%) is in line with the hypothesis that it has an antioxidant action, but it is in contrast to the limited increase measured in P. caperata thalli (+ 13.7%). These apparently contradictory results confirm those found in the literature, which attribute different functions to usnic acid depending on the lichen species considered and on whether they have other detoxifying substances in their thalli. These studies are of potential application-oriented interest in relation to research into new active principles to be used in the pharmaceutical, food and cosmetic fields and/or in environmental biomonitoring.