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Special Issue "Lichens: Chemistry, Ecological and Biological Activities"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Natural Products".

Deadline for manuscript submissions: closed (15 January 2017)

Special Issue Editors

Guest Editor
Prof. Dr. Sophie Tomasi

UMR CNRS ISCR 6226, Equipe PNSCM, Université de Rennes 1, 2 avenue du Pr Léon Bernard, 35043 Rennes cedex, France
Website | E-Mail
Phone: +33 2 23 23 48 17
Fax: +33 2 23 23 47 04
Interests: lichens; lichen-associated bacteria; actinobacteria; natural products isolation and identification; symbiosis; chemical ecology; fermentation; drug discovery
Guest Editor
Prof. Dr. Joel Boustie

UMR CNRS ISCR 6226, Equipe PNSCM, Université de Rennes 1, 2 avenue du Pr Léon Bernard, 35043 Rennes cedex, France
Website | E-Mail
Phone: +33 2 23 23 47 11
Fax: +33 2 23 23 47 04
Interests: lichens; symbiosis; phytochemistry; bioactivity; chemical profiling; dereplication; herbarium

Special Issue Information

Dear Colleagues,

Lichens are of increasing concern in research looking for new bioactive compounds, and are challenging in a variety of domains. The long-living lichen symbioses are responsible for the production of original secondary metabolites, and also provide an ecological niche for a high diversity of additional microorganisms. Lichens are, thus, a compelling model to study the exchange of small molecules involved in cell-to-cell communications, but also serve as precursors or regulators of silent biosynthetic pathways. Approaches to activate these silent pathways represent an additional opportunity for the discovery of novel bioactive agents. In this context, lichens and their symbiotic partners appear to be an untapped source of highly effective new secondary metabolites. Accurate, new, analytical techniques also facilitate the recognition of additional compounds of interest.

This Special Issue aims to give an overview of recent advances in the field of lichen studies, describing metabolites and their applications, ranging from ecological to future therapeutic relevance. Studies investigating production, structural elucidation, bioactivities, biosynthesis, metabolomic analysis, ecological chemistry relevance of metabolites produced by lichens or symbiotic partners should be encouraged. Biotechnological aspects will be also taken into consideration.

Prof. Dr. Sophie Tomasi
Prof. Dr. Joel Boustie
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Lichen
  • Symbiosis
  • Secondary metabolites
  • Phytochemistry
  • Chemical ecology
  • Bioactive compounds
  • Biotechnology
  • Thallus-associated microflora

Published Papers (7 papers)

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Research

Open AccessFeature PaperArticle Specialized Metabolites of the Lichen Vulpicida pinastri Act as Photoprotective Agents
Molecules 2017, 22(7), 1162; doi:10.3390/molecules22071162
Received: 6 June 2017 / Accepted: 7 July 2017 / Published: 12 July 2017
PDF Full-text (2192 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The extreme resiliency of lichens to UV radiations makes them an interesting model to find new photoprotective agents acting as UV-blockers and antioxidant. In this research, using a new in vitro method designed to overcome the shortage of material associated to many studies
[...] Read more.
The extreme resiliency of lichens to UV radiations makes them an interesting model to find new photoprotective agents acting as UV-blockers and antioxidant. In this research, using a new in vitro method designed to overcome the shortage of material associated to many studies dealing with natural products, we show that the three major compounds isolated from the lichen Vulpicida pinastri, vulpinic acid, pinastric acid and usnic acid, were UV blocker agents. Antioxidant assays evidenced superoxide anion scavenging activity. Combination of the most promising compounds against UVB and UVB radiations, usnic acid, vulpinic acid and pinastric acid, increased the photoprotective activity. At the same time, they were found not cytotoxic on keratinocyte cell lines and photostable in the UVA and UVB ranges. Thus, lichens represent an attractive source to find good candidate ingredients as photoprotective agents. Additionally, the uncommon scalemic usnic acid mixture in this Vulpicida species was proven through electronic circular dichroism calculation. Full article
(This article belongs to the Special Issue Lichens: Chemistry, Ecological and Biological Activities)
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Open AccessArticle Effects of Growth Media on the Diversity of Culturable Fungi from Lichens
Molecules 2017, 22(5), 824; doi:10.3390/molecules22050824
Received: 1 March 2017 / Revised: 10 May 2017 / Accepted: 11 May 2017 / Published: 17 May 2017
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Abstract
Microscopic and molecular studies suggest that lichen symbioses contain a plethora of associated fungi. These are potential producers of novel bioactive compounds, but strains isolated on standard media usually represent only a minor subset of these fungi. By using various in vitro growth
[...] Read more.
Microscopic and molecular studies suggest that lichen symbioses contain a plethora of associated fungi. These are potential producers of novel bioactive compounds, but strains isolated on standard media usually represent only a minor subset of these fungi. By using various in vitro growth conditions we are able to modulate and extend the fraction of culturable lichen-associated fungi. We observed that the presence of iron, glucose, magnesium and potassium in growth media is essential for the successful isolation of members from different taxonomic groups. According to sequence data, most isolates besides the lichen mycobionts belong to the classes Dothideomycetes and Eurotiomycetes. With our approach we can further explore the hidden fungal diversity in lichens to assist in the search of novel compounds. Full article
(This article belongs to the Special Issue Lichens: Chemistry, Ecological and Biological Activities)
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Open AccessArticle Antifungal and Anti-Biofilm Activities of Acetone Lichen Extracts against Candida albicans
Molecules 2017, 22(4), 651; doi:10.3390/molecules22040651
Received: 20 February 2017 / Revised: 6 April 2017 / Accepted: 14 April 2017 / Published: 19 April 2017
PDF Full-text (251 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Candida albicans is a commensal coloniser of the human gastrointestinal tract and an opportunistic pathogen, especially thanks to its capacity to form biofilms. This lifestyle is frequently involved in infections and increases the yeast resistance to antimicrobials and immune defenses. In this context,
[...] Read more.
Candida albicans is a commensal coloniser of the human gastrointestinal tract and an opportunistic pathogen, especially thanks to its capacity to form biofilms. This lifestyle is frequently involved in infections and increases the yeast resistance to antimicrobials and immune defenses. In this context, 38 lichen acetone extracts have been prepared and evaluated for their activity against C. albicans planktonic and sessile cells. Minimum inhibitory concentrations of extracts (MICs) were determined using the broth microdilution method. Anti-biofilm activity was evaluated using tetrazolium salt (XTT) assay as the ability to inhibit the maturation phase (anti-maturation) or to eradicate a preformed 24 h old biofilm (anti-biofilm). While none of the extracts were active against planktonic cells, biofilm maturation was limited by 11 of the tested extracts. Seven extracts displayed both anti-maturation and anti-biofilm activities (half maximal inhibitory concentrations IC50_mat and IC50_biof ≤ 100 µg/mL); Evernia prunastri and Ramalina fastigiata were the most promising lichens (IC50_mat < 4 µg/mL and IC50_biof < 10 µg/mL). Chemical profiles of the active extracts performed by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC) have been analyzed. Depsides, which were present in large amounts in the most active extracts, could be involved in anti-biofilm activities. This work confirmed that lichens represent a reservoir of compounds with anti-biofilm potential. Full article
(This article belongs to the Special Issue Lichens: Chemistry, Ecological and Biological Activities)
Open AccessArticle Barbatic Acid Offers a New Possibility for Control of Biomphalaria Glabrata and Schistosomiasis
Molecules 2017, 22(4), 568; doi:10.3390/molecules22040568
Received: 16 January 2017 / Revised: 24 March 2017 / Accepted: 27 March 2017 / Published: 31 March 2017
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Abstract
This study evaluated the biological activity of an ether extract and barbatic acid (BAR) from Cladia aggregata on embryos and adult mollusks of Biomphalaria glabrata, cercariae of Schistosoma mansoni and the microcrustacean Artemia salina. The ether extract and BAR were obtained
[...] Read more.
This study evaluated the biological activity of an ether extract and barbatic acid (BAR) from Cladia aggregata on embryos and adult mollusks of Biomphalaria glabrata, cercariae of Schistosoma mansoni and the microcrustacean Artemia salina. The ether extract and BAR were obtained by successive extractions with diethyl ether. The obtained extracts were analyzed using thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC), proton nuclear magnetic resonance (1H-NMR) and infrared (IR) spectroscopy. The results demonstrated that the ether extract exerted embryotoxic effects at 50 and 100 µg/mL and molluscicidal effects at 20 and 25 µg/mL. BAR exhibited no embryotoxicity, and its molluscicidal concentration was equal to that of the ether extract. However, after 60 min of exposure, 1 µg/mL BAR presented cercaricidal activity against the parasite S. mansoni at the second larval stage. Neither substance induced toxicity against A. salina. These results indicate the potential molluscicidal activities of the ether extract and BAR against B. glabrata and S. mansoni cercariae. In addition to these effects, there was a lack of toxicity against the aquatic environment and no damage to the biota, indicating the potential of these products for large-scale control and/or eradication of schistosomiasis. Full article
(This article belongs to the Special Issue Lichens: Chemistry, Ecological and Biological Activities)
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Open AccessArticle Which Specialized Metabolites Does the Native Subantarctic Gastropod Notodiscus hookeri Extract from the Consumption of the Lichens Usnea taylorii and Pseudocyphellaria crocata?
Molecules 2017, 22(3), 425; doi:10.3390/molecules22030425
Received: 26 January 2017 / Revised: 23 February 2017 / Accepted: 1 March 2017 / Published: 8 March 2017
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Abstract
Notodiscus hookeri is the only representative of terrestrial gastropods on Possession Island and exclusively feeds on lichens. The known toxicity of various lichen metabolites to plant-eating invertebrates led us to propose that N. hookeri evolved means to protect itself from their adverse effects.
[...] Read more.
Notodiscus hookeri is the only representative of terrestrial gastropods on Possession Island and exclusively feeds on lichens. The known toxicity of various lichen metabolites to plant-eating invertebrates led us to propose that N. hookeri evolved means to protect itself from their adverse effects. To validate this assumption, the current study focused on the consumption of two lichen species: Usnea taylorii and Pseudocyphellaria crocata. A controlled feeding experiment was designed to understand how the snail copes with the unpalatable and/or toxic compounds produced by these lichen species. The occurrence of two snail ecophenotypes, represented by a mineral shell and an organic shell, led to address the question of a metabolic response specific to the phenotype. Snails were fed for two months with one of these lichens and the chemical profiles of biological samples of N. hookeri (i.e., crop, digestive gland, intestine, and feces) were established by HPLC-DAD-MS and compared to that of the lichens. N. hookeri appears as a generalist lichen feeder able to consume toxic metabolite-containing lichens, independently of the ecophenotype. The digestive gland did not sequester lichen metabolites. The snail metabolism might be based on four non-exclusive processes according to the concerned metabolites (avoidance, passive transport, hydrolysis, and excretion). Full article
(This article belongs to the Special Issue Lichens: Chemistry, Ecological and Biological Activities)
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Open AccessArticle Isolation and Structure Identification of Novel Brominated Diketopiperazines from Nocardia ignorata—A Lichen-Associated Actinobacterium
Molecules 2017, 22(3), 371; doi:10.3390/molecules22030371
Received: 25 January 2017 / Revised: 22 February 2017 / Accepted: 23 February 2017 / Published: 28 February 2017
Cited by 2 | PDF Full-text (1213 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Actinobacteria are well known for their potential in biotechnology and their production of metabolites of interest. Lichens are a promising source of new bacterial strains, especially Actinobacteria, which afford a broad chemical diversity. In this context, the culture medium of the actinobacterium Nocardia
[...] Read more.
Actinobacteria are well known for their potential in biotechnology and their production of metabolites of interest. Lichens are a promising source of new bacterial strains, especially Actinobacteria, which afford a broad chemical diversity. In this context, the culture medium of the actinobacterium Nocardia ignorata, isolated from the terrestrial lichen Collema auriforme, was studied. The strain was cultivated in a BioFlo 115 bioreactor, and the culture medium was extracted using an XAD7HP resin. Five known diketopiperazines: cyclo (l-Pro-l-OMet) (1), cyclo (l-Pro-l-Tyr) (2), cyclo (d-Pro-l-Tyr) (3), cyclo (l-Pro-l-Val) (4), cyclo (l-Pro-l-Leu) (5), and one auxin derivative: indole-carboxaldehyde (8) were isolated, along with two new brominated diketopiperazines: cyclo (d-Pro-l-Br-Tyr) (6) and cyclo (l-Pro-l-Br-Tyr) (7). Structure elucidation was performed using HRMS and 1D and 2D NMR analysis, and the synthesis of compounds 6 and 7 was carried out in order to confirm their structure. Full article
(This article belongs to the Special Issue Lichens: Chemistry, Ecological and Biological Activities)
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Open AccessArticle A Multifunctional and Possible Skin UV Protectant, (3R)-5-Hydroxymellein, Produced by an Endolichenic Fungus Isolated from Parmotrema austrosinense
Molecules 2017, 22(1), 26; doi:10.3390/molecules22010026
Received: 7 September 2016 / Revised: 14 December 2016 / Accepted: 22 December 2016 / Published: 26 December 2016
Cited by 1 | PDF Full-text (3178 KB) | HTML Full-text | XML Full-text
Abstract
Lichens are considered a great bio-resource because they produce large numbers of secondary metabolites with many biological activities; however, they have not been cultivated under artificial conditions to date. As a result, lichen substances from natural sources are limited and have not been
[...] Read more.
Lichens are considered a great bio-resource because they produce large numbers of secondary metabolites with many biological activities; however, they have not been cultivated under artificial conditions to date. As a result, lichen substances from natural sources are limited and have not been widely utilized in commercial applications. Accordingly, interest in lichen-associated fungi, especially endogenic fungi, has increased. Ultraviolet (UV) radiation in sunlight is harmful to human health, resulting in demand for effective UV filtering agents for use in sunscreen. In this study, we purified (3R)-5-hydroxymellein, which has UVA absorption activity, from the secondary metabolites of an endolichenic fungus (ELF000039). The antioxidant properties were then assessed by in vitro tests. The antioxidant activity of (3R)-5-hydroxymellein was high when compared to the recognized antioxidants ascorbic acid (ASA) and butyl hydroxyl anisole (BHA). Moreover, the compound exhibited no cytotoxicity toward mouse melanoma cell lines, B16F1 and B16F10, or the normal cell line, HaCaT. Furthermore, (3R)-5-hydroxymellein recovered the damage caused by UVB irradiation and inhibited melanin synthesis. Taken together, these results suggest that (3R)-5-hydroxymellein could have an interesting and vital profile to go further development as a multifunctional skin UV protectant. Full article
(This article belongs to the Special Issue Lichens: Chemistry, Ecological and Biological Activities)
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