Lichen Metabolites Research Articles

A shift in substrate requirement might cause speciation of the lichenized fungi, Varicellaria hemisphaerica and V. lactea (Pertusariales, Ascomycota)

Proper species recognition is required to correctly estimate species preferences and their vulnerability or for eco-evolutionary inference. Varicellaria hemisphaerica and Varicellaria lactea are almost completely morphologically homogeneous species with unclear identification features. To evaluate the importance of morphological, chemical, and ecological characteristics used in recognition of these species, we tested 670 specimens, of which 42 were analyzed phylogenetically using nucITS rDNA, SSU rDNA, and LSU rDNA markers. This integrated taxonomical approach showed that V. hemisphaerica is distinct from V. lactea, and that substrate requirements, together with phylogenetic differences and the size of soredia, differentiate these species. The chemical composition of secondary lichen metabolites in both analyzed species showed similar variation and, therefore, this feature is not diagnostic in species recognition, although suggested by previous studies. The potential speciation of the two species seems to be caused by the shift in the substrate requirements.

Secondary Metabolites from Australian Lichens Ramalina celastri and Stereocaulon ramulosum Affect Growth and Metabolism of Photobiont Asterochloris erici through Allelopathy.

In the present work, the phytotoxic effects of secondary metabolites extracted from lichen Ramalina celastri (usnic acid) and lichen Stereocaulon ramulosum (a naturally occurring mixture of atranorin and perlatolic acid, approx. 3:1) on cultures of the aposymbiotically grown lichen photobiont Asterochloris erici were evaluated. Algae were cultivated on the surface of glass microfiber disks with applied crystals of lichen extracts for 14 days. The toxicity of each extract was tested at the two selected doses in quantities of 0.01 mg/disk and 0.1 mg/disk. Cytotoxicity of lichen extracts was assessed using selected physiological parameters, such as growth (biomass production) of photobiont cultures, content of soluble proteins, chlorophyll a fluorescence, chlorophyll a integrity, contents of chlorophylls and total carotenoids, hydrogen peroxide, superoxide anion, TBARS, ascorbic acid (AsA), reduced (GSH) and oxidized (GSSG) glutathione, and composition of selected organic acids of the Krebs cycle. The application of both tested metabolic extracts decreased the growth of photobiont cells in a dose-dependent manner; however, a mixture of atranorin and perlatolic acid was more effective when compared to usnic acid at the same dose tested. A higher degree of cytotoxicity of extracts from lichen S. ramulosum when compared to identical doses of extracts from lichen R. celastri was also confirmed by a more pronounced decrease in chlorophyll a fluorescence and chlorophyll a integrity, decreased content of chlorophylls and total carotenoids, increased production of hydrogen peroxide and superoxide anion, peroxidation of membrane lipids (assessed as TBARS), and a strong decrease in non-enzymatic antioxidants such as AsA, GSH, and GSSG. The cytotoxicity of lichen compounds was confirmed by a strong alteration in the composition of selected organic acids included in the Krebs cycle. The increased ratio between pyruvic acid and citric acid was a very sensitive parameter of phytotoxicity of lichen secondary metabolites to the algal partner of symbiosis. Secondary metabolites of lichens are potent allelochemicals and play significant roles in maintaining the balance between mycobionts and photobionts, forming lichen thallus.

Interplay of heavy metal accumulation, physiological responses, and microbiome dynamics in lichens: insights and future directions.

Lichens are increasingly recognised as valuable bioindicators for environmental heavy metal pollution due to their sensitivity to spatial and temporal variations in pollution levels and their ability to adapt to diverse and often harsh habitats. This review initially examines the mechanisms of metal absorption in lichens, including particulate entrapment, ion exchange, and intracellular absorption, as well as their physiological responses to abiotic stressors such as heavy metal exposure and desiccation. In the latter part, we compile and synthesise evidence showing that secondary metabolites in lichens are significantly influenced by metal concentrations, with varying impacts across different species. Although extensive research has addressed the broader physiological effects of heavy metal hyperaccumulation in lichens, there remains a significant gap in understanding the direct or indirect influences of heavy metals on the lichen microbiome, possibly mediated by changes in secondary metabolite production. Our review integrates these aspects to propose new research directions aimed at elucidating the mechanisms underlying physiological responses such as resilience and adaptability in lichens. Overall, this review highlights the dynamic interplay between microbiome composition, secondary metabolite variation, and metal accumulation, suggesting that these factors collectively contribute to the physiological responses of lichens in polluted environments.

Discovery and Heterologous Expression of Functional 4-O-Dimethylallyl-l-tyrosine Synthases from Lichen-Forming Fungi.

Fungal aromatic prenyltransferases are a family of biosynthetic enzymes that catalyze the prenylation of a range of aromatic substrates during the biosynthesis of bioactive indole alkaloids, diketopiperazines, and meroterpenoids. Their broad substrate scope and soluble nature make these enzymes particularly adept for applications in biocatalysis; for example, the enzymatic derivatization of aromatic drugs improves their bioactivity. Here, we investigated four putative aromatic prenyltransferases from lichen-forming fungi, an underexplored group of organisms that produce more than 1,000 unique metabolites. We successfully expressed two enzymes, annotated as dimethylallyltryptophan synthases, from two lichen species in the heterologous host A. oryzae. Based on their in vivo activity, we hypothesize that these enzymes are in fact 4-O-dimethylallyl-l-tyrosine synthases. Our extensive bioinformatic analysis further confirmed that these and related lichen aromatic prenyltransferases are likely not active on indoles but rather on aromatic polyketides and phenylpropanoids, major metabolites in lichens. Overall, our work provides new insights into fungal aromatic prenyltransferases at the family level and enables future efforts aimed at identifying new candidates for biocatalytic transformations of aromatic compounds.

An investigation on the cardioprotective potential of lichen compound protocetraric acid by H2O2-induced toxicity in H9c2 rat heart cells through in vitro and in silico analysis.

Worldwide, cardiovascular diseases (CVDs) are the leading cause of death and require treatment and prevention. Lichens are symbiotic organisms that are known to produce unique secondary metabolites and have been used as folk medicines. The aim of the study is to emphasize the importance of lichens in improving heart health, with the objective of investigating protocetraric acid, a lichen metabolite, for its antioxidant and cardioprotective potential by using in vitro and in silico techniques. Protocetraric acid (PRC) was isolated, characterized, and tested for antioxidant properties using six assays. In cardiovascular investigations, hydroxymethylglutaryl-coenzymeA reductase (HMGCR), angiotensin-converting enzyme inhibitory, and fibrinolytic capacities, along with enzyme inhibitory kinetics studies, were carried out. In silico toxicology and molecular docking analysis were done to determine the binding sites on target proteins. The cytoprotective ability of PRC was evaluated by H2O2-induced toxicity in H9c2 rat heart cells. Out of six lichens, the extract of F. caperata showed comparatively stronger antioxidant activity in terms of 1,1-diphenyl-2-picryl hydrazil (DPPH), scavenging of nitric oxide (SNO), and ferric reducing potential (FRAP) equivalent values. PRC showed significant antioxidant properties, and with respect to cardiovascular studies, PRC exhibited 86% HMGCR and 82% ACE inhibition, while 57% fibrinolysis at 320µM concentration. Inhibitory kinetic tests of PRC showed competitive and uncompetitive HMGCR and ACE inhibition types respectively. PRC showed minimum binding energies of - 7.9, - 8.9, and - 9.0kcal/mol with 1HWK, 1O8A, and 4BZS. The H9c2 cell line pre-treated with PRC was found to reduce H2O2 toxicity as well as increase cell viability. Protocetraric acid is a potent compound that has been experimentally shown to have hypocholesterolemic, hypotensive, and cardioprotective properties for treating cardiovascular diseases.

A spectrophotometric analysis of extracted water-soluble phenolic metabolites of lichens

Main conclusionRainwater most probably constitutes a relatively effective solvent for lichen substances in nature which have the potential to provide for human and environmental needs in the future.The aims were (i) to test the hypothesis on the potential solubility of lichen phenolic compounds using rainwater under conditions that partly reflect the natural environment and (ii) to propose new and effective methods for the water extraction of lichen substances. The results of spectrophotometric analyses of total phenolic metabolites in rainwater-based extracts from epigeic and epiphytic lichens, employing the Folin–Ciocalteu (F.–C.) method, are presented. The water solvent was tested at three pH levels: natural, 3, and 9. Extraction methods were undertaken from two perspectives: the partial imitation of natural environmental conditions and the potential use of extraction for economic purposes. From an ecological perspective, room-temperature water extraction (‘cold’ method) was used for 10-, 60-, and 120-min extraction periods. A variant of water extraction at analogous time intervals was an ‘insolation’ with a 100W light bulb to simulate the heat energy of the sun. For economic purposes, the water extraction method used the Soxhlet apparatus and its modified version, the ‘tea-extraction’ method (‘hot’ ones). The results showed that those extractions without an external heat source were almost ineffective, but insolation over 60- and 120-min periods proved to be more effective. Both tested ‘hot’ methods also proved to be effective, especially the ‘tea-extraction’ one. Generally, an increase in the concentration of phenolic compounds in water extracts resulted from an increasing solvent pH. The results show the probable involvement of lichen substances in biogeochemical processes in nature and their promising use for a variety of human necessities.

Green Extraction of Depsidones and Depsides from Hypogymnia physodes (L.) Nyl. Using Natural Deep Eutectic Solvents.

Various studies have shown that Hypogymnia physodes are a source of many biologically active compounds, including lichen acids. These lichen-specific compounds are characterized by antioxidant, antiproliferative, and antimicrobial properties, and they can be used in the cosmetic and pharmaceutical industries. The main aim of this study was to optimize the composition of natural deep eutectic solvents based on proline or betaine and lactic acid for the extraction of metabolites from H. physodes. The design of the experimental method and the response surface approach allowed the optimization of the extraction process of specific lichen metabolites. Based on preliminary research, a multivariate model of the experiment was developed. For optimization, the following parameters were employed in the experiment to confirm the model: a proline/lactic acid/water molar ratio of 1:2:2. Such a mixture allowed the efficient extraction of three depsidones (i.e., physodic acid, physodalic acid, 3-hydroyphysodic acid) and one depside (i.e., atranorin). The developed composition of the solvent mixtures ensured good efficiency when extracting the metabolites from the thallus of H. physodes with high antioxidant properties.

The algal partnership is associated with quantitative variation of lichen specific metabolites in Cladonia foliacea from Central and Southern Europe

AbstractLichen specific metabolites (LSMs) have interesting biological activities and quantitative variations may be present intraspecifically. For example, variations in medullary fumarprotocetraric acid (FA) and cortical usnic acid (UA) were observed in the lichen Cladonia foliacea, but the mechanism of variation is not well understood. The current study aimed to characterise the quantitative variation of FA and UA and to investigate the association between lichen metabolite content and ecological / biological variables. Fungal and algal trees were constructed using fungal (nrITS, RPB2) and algal (nrITS) loci, respectively. Using a chiral chromatographic method, the contents of (-)-UA were determined in 29 C. foliacea specimens and range from 6.88 to 34.27 mg/g dry wt. The FA contents were lower and varied from 1.44 to 9.87 mg/g dry wt. Although the fungal tree showed two well resolved clades, no significant differences of UA or FA contents were found between the two fungal clades. However, a significantly higher UA/FA ratio as well as a unique habitat were found to be associated with specimens which contained the alga Asterochloris lobophora than those specimens associated other Asterochloris algae. Taking all predictive variables into account (i.e. substrate type, elevation, collection season, photobiont identity), the multivariate data analysis indicated that photobiont identity explained most of the variance of LSM contents in C. foliacea. Thus future LSM biosynthetic studies should take the photobiont into consideration when dealing with intraspecific quantitative variation.

Potential effects of parietin on apoptosis and cell cycle related genes in SH-SY5Y neuroblastoma cells

Background: Ingredients obtained from natural products have been used in cancer treatments for years. High diversity and non-toxicity compared to chemotherapeutic agents are the main reasons for their preference. Lichens having potential for treatment of cancer consist of fungus and 1-2 species of algae. Under the name of lichen substances, many of them have also been synthesized as specific substances. The secondary metabolites in lichens are generally insoluble in water, and have many biological activities such as antiviral, antitumor, antibacterial, and antioxidant; they store in the fungal cell or on the surface of the hyphae and can only be extracted with organic solvents.
 Parietin extracted from lichen species such as xanthoria parietina is an anthraquinone pigment and a secondary metabolite. 
 In our study, the effects of parietin on cytotoxicity, gene expression, migration, invasion, and colony formation in neuroblastoma cells treated with parietin were investigated. The SH-SY5Y neuroblastoma (NB), which is not treated with parietin, was administered as a control group.
 Methods: The IC50 value of the parietin was determined using XTT assay. The total RNA extractions were performed from the cells using the Tri-Reagent kit. The expressions of BCL-XL, BCL-2, MMP2, MMP9, P21, CYCLIN D1, CASAPASE-3, CASAPASE-9, BAX, P53, PUMA, and NOXA genes were investigated by Lightcycler 480 (Roche) using SYBR Green dye. Migration analysis of the control and the dose group cells were performed in accordance with the Wound-healing assay protocol. Invasion activities were determined using the “Invasion Chamber” (BD Biosciences) protocol. The colony assay was treated with crystal violet and the cells were observed under the light microscope.
 Results: The IC50 value of the parietin used for 48-hour treatment on the cells was determined as 35 µM. It was found that the expression levels of BCL-XL, BCL-2, MMP2, MMP9, P21, and CYCLIN D1 mRNA were downregulated, and it was also shown the expression levels of CASAPASE-3, CASAPASE-9, BAX, P53, PUMA, and NOXA to be upregulated. It was determined that parietin suppressed both cell invasion and migration, and colony formation in the neuroblastoma cells. 
 Conclusions: Thus, it can be possible parietin to be used as an alternative, complementary, and supportive agent together with the other drugs in the treatment of neuroblastoma. However, more comprehensive studies supporting these significant effects of parietin will increase its potential in the application.

Allelopathic effects of three lichen secondary metabolites on cultures of aposymbiotically grown lichen photobionts and free-living alga Scenedesmus quadricauda

In the present work, we studied the influence of lichen secondary metabolites (evernic acid, orcinol, usnic acid) on selected species of algae: Trebouxia erici, photobiont of lichen Cladonia cristatella producing typical lichen secondary metabolites, Coccomyxa solorinae-saccatae, photobiont of lichen Solorina saccata which does not produce typical secondary metabolites of lichens, and free-living alga Scenedesmus quadricauda.For the determination of the cytotoxic effects of these compounds, algae were cultivated on the surface of disks composed of glass microfibers, in quantities of 0.1 mg/disk for each metabolite. After 14-days prolonged cultivation, we analysed selected physiological parameters: growth of algae, chlorophyll a fluorescence, the content of ascorbic acid, content of reduced and oxidized glutathione and contents of selected organic acids. The presence of secondary compounds typically inhibited the growth of tested algae and chlorophyll a fluorescence. In the presence of evernic acid and usnic acid, we observed a decrease of ascorbic acid, glutathione, and significant changes in the composition of organic acids.Lichen metabolites, except for their other biological and ecological roles, may act as phytotoxic substances, causing oxidative stress in photobiont cells. These metabolites may play an important role in the “controlled parasitism” of fungal partner on algal/cyanobacterial partner of symbiosis. Differences in the sensitivity of algal cells from different habitats to lichen compounds are, however, not understood sufficiently.

Antiproliferative, antimigratory, and apoptotic effects of diffractaic and vulpinic acids as thioredoxin reductase 1 inhibitors on cervical cancer.

Cervical cancer is among the most frequently observed cancer types in females. New therapeutic targets are needed because of the side impacts of existing cancer drugs and the inadequacy of treatment methods. Thioredoxin reductase 1 (TrxR1) is often overexpressed in many cancer cells, and targeting TrxR1 has become an attractive target for cancer therapy. This study investigated the anticancer impacts of diffractaic and vulpinic acids, lichen secondary metabolites, on the cervical cancer HeLa cell line. XTT findings demonstrated showed that diffractaic and vulpinic acids suppressed the proliferation of HeLa cells in a dose- and time-dependent manner and IC50 values were 22.52μg/ml and 66.53μg/ml at 48h, respectively. Each of these lichen metabolites significantly suppressed migration. Diffractaic acid showed an increase in both the BAX/BCL2 ratio by qPCR analysis and the apoptotic cell population via flow cytometry analysis on HeLa cells. Concerning vulpinic acid, although it decreased the BAX/BCL2 ratio in this cells, it increased apoptotic cells according to the flow cytometry analysis results. Diffractaic and vulpinic acids significantly suppressed TrxR1 enzyme activity rather than the gene and protein expression levels in HeLa cells. This research demonstrated for the first time, that targeting TrxR1 with diffractaic and vulpinic acids was an effective therapeutic strategy for treating cervical cancer.

Dimeric (Poly)Hydroxynaphthazarins, Metabolites of Echinoderms and Lichens: The History of the Synthesis and Structure Elucidation.

This review provides information on the synthesis and revision of the structures of natural dimeric (poly)hydroxynaphthazarins, metabolites of echinoderms and lichens, and on the refinement of the direction and mechanism of reactions in the synthesis of some of these compounds.

Virtual screening of the natural antifoulants: In silico approach to screen lichen metabolites against marine biofoulers

AbstractThe present study aims to explore the inhibitory action of lichen metabolites against important protein targets of marine fouling organisms using computational methods. Lichens with their unique ability to produce various secondary metabolites find versatile applications in Biotechnology and allied fields. The 3D structure of target proteins associated with fouling activity of marine organism were collected from the protein data bank (PDB) and the computational docking analysis was performed using the PyRx software with 40 lichen compounds that are collected from PubChem. The lichen compounds were docked against the following protein targets—mannose‐specific lectin CGL1 of Crassostrea gigas, Proximal thread matrix protein 1 PTMP 1 of Mytilus galloprovincialis, and G protein‐coupled receptor (GPCR) of Balanus amphitrite. As there was no experimentally determined structure available for GPCR of B. amphitrite, homology modeling was performed to predict the protein structure. The docking study showed effective binding of lichen compounds to various fouling targets with the binding energies in the range of −10.1 to −5 kcal/mol. Among the lichen compounds studied, roccanin showed the least binding energy for CGL1, PTMP1 and GPCR. The correlation assessments predict a positive relationship between binding energy, molecular weight and retention time. MD Simulation studies were performed using LARMD online tool and the RMSD and radius of gyration (Rg) values was recorded. This study proves that the compounds produced by lichens have high antifouling effect against marine foulers under in silico conditions.

Anti-Inflammatory Activity of Mycobiont Extract of Parmotrema austrosinense (Zahlbr.) Hale in a Zebrafish Model

Thousands of different kinds of lichen metabolites are being examined for their biological activities, including anticancer properties. In this context, the present study aims to assess the anti-inflammatory activity of the acetone extract of Parmotrema austrosinense mycobiont. A lipid peroxidation assay was performed with the acetone extracts of P. austrosinense mycobiont, which was further used to evaluate its anti-inflammatory efficacy using a zebrafish model. Furthermore, the histopathological study was also carried out with muscle tissues and amplification of its inflammation marker. The results revealed that the lichen compound (i.e., lecanoric acid) in the acetone extract of P. austrosinense possesses anti-inflammatory activity. Histopathology studies confirmed the decreased numbers of neutrophil cells in the 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced zebrafishes, as confirmed by changes in the fishes’ weight before and after the sample treatment, prompted by TNBS inflammation. The present results also demonstrated a dose-dependent decrease in the lipid peroxidation (LPO) levels in the muscle tissues of zebrafishes. Gene amplification studies suggested that the lichen compound might perform dose-dependent downregulation of the inflammatory gene marker of the tumor necrosis factor (TNF)-α gene; this further confirms that the extract should possess anti-inflammatory activity. As per the literature, this study is one of the most complete, comprehensive in vivo anti-inflammatory analyses in which inflammation was induced in zebrafish by using 2,4,6-trinitrobenzene sulfonic acid (TNBS). Particularly, this study successfully identified a bioactive compound isolated from the lichen P. austrosinense, and which exhibited decent anti-inflammatory activity.

Discovery and excavation of lichen bioactive natural products.

Lichen natural products are a tremendous source of new bioactive chemical entities for drug discovery. The ability to survive in harsh conditions can be directly correlated with the production of some unique lichen metabolites. Despite the potential applications, these unique metabolites have been underutilized by pharmaceutical and agrochemical industries due to their slow growth, low biomass availability, and technical challenges involved in their artificial cultivation. At the same time, DNA sequence data have revealed that the number of encoded biosynthetic gene clusters in a lichen is much higher than in natural products, and the majority of them are silent or poorly expressed. To meet these challenges, the one strain many compounds (OSMAC) strategy, as a comprehensive and powerful tool, has been developed to stimulate the activation of silent or cryptic biosynthetic gene clusters and exploit interesting lichen compounds for industrial applications. Furthermore, the development of molecular network techniques, modern bioinformatics, and genetic tools is opening up a new opportunity for the mining, modification, and production of lichen metabolites, rather than merely using traditional separation and purification techniques to obtain small amounts of chemical compounds. Heterologous expressed lichen-derived biosynthetic gene clusters in a cultivatable host offer a promising means for a sustainable supply of specialized metabolites. In this review, we summarized the known lichen bioactive metabolites and highlighted the application of OSMAC, molecular network, and genome mining-based strategies in lichen-forming fungi for the discovery of new cryptic lichen compounds.

Regioselectivity Amination of Usnic Acid by Ammonia in Water

Usnic acid is a well-known secondary lichen metabolite exhibiting a broad spectrum of biological activity. Previously it was shown that the reaction of usnic acid with various amines resulted in enamine-bond formation instead of the C(11)=O carbonyl group. Enamines obtained have a pronounced biological activity. In this work, we have shown that the reaction of usnic acid with ammonia can be regioselective if the solvent is replaced by water. The regioselectivity of that reaction depends on temperature and ammonia quantity. The C-1 enamine as only product formation has been obtained by the usnic acid reaction with an excess of ammonia (20 eq.) in water with cooling (+9 °C).

How to build a lichen: from metabolite release to symbiotic interplay.

Exposing their vegetative bodies to the light, lichens are outstanding amongst other fungal symbioses. Not requiring a pre-established host, 'lichenized fungi' build an entirely new structure together with microbial photosynthetic partners that neither can form alone. The signals involved in the transition of a fungus and a compatible photosynthetic partner from a free-living to a symbiotic state culminating in thallus formation, termed 'lichenization', and in the maintenance of the symbiosis, are poorly understood. Here, we synthesise the puzzle pieces of the scarce knowledge available into an updated concept of signalling involved in lichenization, comprising five main stages: (1) the 'pre-contact stage', (2) the 'contact stage', (3) 'envelopment' of algal cells by the fungus, (4) their 'incorporation' into a pre-thallus and (5) 'differentiation' into a complex thallus. Considering the involvement of extracellularly released metabolites in each phase, we propose that compounds such as fungal lectins and algal cyclic peptides elicit early contact between the symbionts-to-be, whereas phytohormone signalling, antioxidant protection and carbon exchange through sugars and sugar alcohols are of continued importance throughout all stages. In the fully formed lichen thallus, secondary lichen metabolites and mineral nutrition are suggested to stabilize the functionalities of the thallus, including the associated microbiota.

Larvicidal activity and docking study of Ramalina complanata and Cladonia verticillaris extracts and secondary metabolites against Aedes aegypti

The Aedes aegypti mosquito is the main vector of the arboviruses that cause Zika, Yellow Fever, Dengue, and Chikungunya, incapacitating diseases that may even be fatal. There are still no vaccines for any of these viruses. Therefore, the only way to contain outbreaks is to control the vector that transmits them. In the present study, we investigated the larvicidal activity of lichen extracts (Ramalina complanata (Sw.) Ach., 1810 and Cladonia verticillaris (Raddi) Fr.), isolating components that were used against larvae of the mosquito A. aegypti. The ether extract from R. complanata exhibited an LC50 = 5.9 µg.ml−1, while a compound isolated from this species, divaricatic acid, had an LC50 = 27.1 µg.ml−1. The acetone extract of C. verticilaris exhibited an LC50 = 17.4 µg.ml−1 and the isolated compound fumarprotocetraric acid (FUM) had an LC50 = 13.6 µg.ml−1. These results demonstrate that extracts and isolated compounds from the two lichen species have strong larvicidal activities. FUM is the most active compound in our investigation. The molecular docking studies of divaricatic acid and FUM demonstrated that they bind to the active site of AaAChE1 in an energetically favorable manner. The TRP286 residue may have contributed to the more pronounced activity of fumarprotocetraric acid compared to divaricatic acid. Other aspects related to the more pronounced activity of fumarprotocetraric acid are its molecular weight and higher solubility. Our results provide evidence of the importance of studying lichen secondary metabolites as natural sources of insecticides and investigating possible interactions with AaAChE1.

Molecular docking and dynamics supported investigation of antiviral activity of Lichen metabolites of Roccella montagnei: an in silico and in vitro study

Lichens are symbiotic organisms that have been traditionally used for treating different kinds of ailments. As there are only a few reports on the antiviral activity of lichens, we thought of evaluating the anti-Herpes simplex virus-1 (HSV-1) activity of methanolic extract of Roccella montagnei and their isolated compounds. Fractionation of crude methanolic extract of Roccella montagnei by column chromatography isolated two pure compounds. Antiviral activity was assessed using a CPE inhibition assay at non-cytotoxic concentrations on Vero cells. Molecular docking and dynamics studies were carried out against Herpes simplex type-1 thymidine kinase to understand the binding interactions of the isolated compounds with reference to acyclovir. Isolated compounds were characterized as methyl orsellinate and montagnetol by spectral methods. Methanolic extract of Roccella montagnei exhibited an EC50 value of 56.51 µg/ml, while the compounds methyl orsellinate and montagnetol offered EC50 values of 13.50 µg/ml and 37.52 µg/ml, respectively, against HSV-1 viral infection on Vero cell lines. The selectively index (SI) of montagnetol (10.93) was found to be higher when compared to that of methyl orsellinate (5.55), indicating its better anti-HSV-1 activity. The docking and dynamics studies showed montagnetol was stable throughout the 100 ns, having better interactions and docking scores with HSV-1 thymidine kinase than methyl orsellinate, as well as the standard. To understand the mechanism of montagnetol’s anti-HSV-1 activity, more research is required, and this could lead to the discovery of new and effective antiviral agents. Communicated by Ramaswamy H. Sarma

Screening Evaluation of Antiproliferative, Antimicrobial and Antioxidant Activity of Lichen Extracts and Secondary Metabolites In Vitro.

Lichen metabolites represent a wide range of substances with a variety of biological effects. The present study was designed to analyze the potential antiproliferative, antimicrobial and antioxidative effects of several extracts from lichens (Pseudevernia furfuracea, Lobaria pulmonaria, Cetraria islandica, Evernia prunastri, Stereocaulon tomentosum, Xanthoria elegans and Umbilicaria hirsuta) and their secondary metabolites (atranorin, physodic acid, evernic acid and gyrophoric acid). The crude extract, as well as the isolated metabolites, showed potent antiproliferative, cytotoxic activity on a broad range of cancer cell lines in 2D (monolayer) and 3D (spheroid) models. Furthermore, antioxidant (2,2-diphenyl-1-picryl-hydrazylhydrate (DPPH) and in vitro antimicrobial activities were assessed. Data showed that the lichen extracts, as well as the compounds present, possessed biological potential in the studied assays. It was also observed that the extracts were more efficient and their major compounds showed strong effects as antiproliferative, antioxidant and antibacterial agents. Moreover, we demonstrated the 2D and 3D models' importance to drug discovery for further in vivo studies. Despite the fact that lichen compounds have been neglected by the scientific community for long periods, nowadays they are objects of investigation based on their promising effects.