Lichen-derived compounds show potential for central nervous system therapeutics

Pleiotropic Potential of Evernia prunastri Extracts and Their Main Compounds Evernic Acid and Atranorin: In Vitro and In Silico Studies

Evernia prunastri is a lichen widely distributed in the Northern Hemisphere. Its biological properties still need to be discovered. Therefore, our paper focuses on studies of E. prunastri extracts, including its main metabolites evernic acid (EA) or atranorin (ATR). Phytochemical profiles using chromatographic analysis were confirmed. The antioxidant activity was evaluated using in vitro chemical tests and in vitro enzymatic cells-free tests, namely superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione reductase (GR), and catalase (CAT). The anti-inflammatory potential using cyclooxygenase-2 (COX-2) and hyaluronidase were determined. The neuroprotective potential using acetylcholinesterase, (AChE), butyrylcholinesterase (BChE), and tyrosinase (Tyr) was estimated. The hypoglycemic activity was also confirmed (α-glucosidase). Principal component analysis was performed to determine the relationship between the biological activity of extracts. The inhibitory effect of EA and ATR on COX-2 AChE, BChE, Tyr, and α-glucosidase was evaluated using molecular docking techniques and confirmed for EA and ATR (besides α-glucosidase). The penetration of EA and ATR from extracts through the blood-brain barrier was confirmed using the parallel artificial membrane permeability assay blood-brain barrier test. In conclusion, depending on chemical surroundings and the concentration, the E. prunastri extracts, EA or ATR, showed attractive pleiotropic properties, which should be further investigated.

Bioactive Compounds and Their Influence on Postnatal Neurogenesis

Since postnatal neurogenesis was revealed to have significant implications for cognition and neurological health, researchers have been increasingly exploring the impact of natural compounds on this process, aiming to uncover strategies for enhancing brain plasticity. This review provides an overview of postnatal neurogenesis, neurogenic zones, and disorders characterized by suppressed neurogenesis and neurogenesis-stimulating bioactive compounds. Examining recent studies, this review underscores the multifaceted effects of natural compounds on postnatal neurogenesis. In essence, understanding the interplay between postnatal neurogenesis and natural compounds could bring novel insights into brain health interventions. Exploiting the therapeutic abilities of these compounds may unlock innovative approaches to enhance cognitive function, mitigate neurodegenerative diseases, and promote overall brain well-being.

Iron mediated reductive cyclization/oxidation for the generation of chemically diverse scaffolds: An approach in drug discovery

Chemically diverse scaffolds represent a main source of biologically important starting points in drug discovery. Herein, we report the development of such diverse scaffolds from nitroarene/ nitro(hetero)arenes using a key synthetic strategy. In a pilot-scale study, the synthesis of 10 diverse scaffolds was achieved. The 1,7-phenanthroline, thiazolo[5,4-f]quinoline, 2,3-dihydro-1H-pyrrolo[2,3-g]quinoline, pyrrolo[3,2-f]quinoline, 1H-[1,4]oxazino[3,2-g]quinolin-2(3H)-one, [1,2,5]oxadiazolo[3,4-h]quinoline, 7H-pyrido[2,3-c]carbazole, 3H-pyrazolo[4,3-f]quinoline, pyrido[3,2-f]quinoxaline were obtained from nitro hetero arenes in ethanol using iron-acetic acid treatment followed by reaction under oxygen atmosphere. This diverse library is compliant with the rule of five for drug-likeness. The mapping of chemical space represented by these scaffolds revealed a significant contribution to the underrepresented chemical diversity. Crucial to the development of this approach was the mapping of biological space covered by these scaffolds which revealed neurotropic and prophylactic anti-inflammatory activities. In vitro, neuro-biological assays revealed that compounds 14a and 15a showed excellent neurotropic potential and neurite growth compared to controls. Further, anti-inflammatory assays (in vitro and in vivo models) exhibited that Compound 16 showed significant anti-inflammatory activity by attenuating the LPS-induced TNF-α and CD68 levels by modulating the NFkB pathway. In addition, treatment with compound 16 significantly ameliorated the LPS-induced sepsis conditions, and pathological abnormalities (in lung and liver tissues) and improved the survival of the rats compared to LPS control. Owing to their chemical diversity along with bioactivities, it is envisaged that new quality pre-clinical candidates will be generated in the above therapeutic areas using identified leads.

Bioactive Lichen Secondary Metabolites and Their Presence in Species from Chile

Lichens are symbiotic organisms composed of at least one fungal and one algal species. They are found in different environments around the world, even in the poles and deserts. Some species can withstand extreme abiotic conditions, including radiation and the vacuum of space. Their chemistry is mainly due to the fungal metabolism and the production of several secondary metabolites with biological activity, which have been isolated due to an increasing interest from the pharmaceutical community. However, beyond the experimental data, little is known about their mechanisms of action and the potential pharmaceutical use of these kinds of molecules, especially the ones isolated from lesser-known species and/or lesser-studied countries. The main objective of this review is to analyze the bibliographical data of the biological activity of secondary metabolites from lichens, identifying the possible mechanisms of action and lichen species from Chile. We carried out a bibliographic revision of different scientific articles in order to collect all necessary information on the biological activity of the metabolites of these lichen species. For this, validated databases were used. We found the most recent reports where in vitro and in vivo studies have demonstrated the biological properties of these metabolites. The biological activity, namely anticancer, antioxidant, and anti-inflammatory activity, of 26 secondary metabolites are described, as well as their reported molecular mechanisms. The most notable metabolites found in this review were usnic acid, atranorin, protolichesterinic acid, and lobaric acid. Usnic acid was the most investigated metabolite, in addition to undergoing toxicological and pharmacological studies, where a hepatotoxicity effect was reported due to uncoupling oxidative phosphorylation. Additionally, no major studies have been made to validate the pharmacological application of these metabolites, and few advancements have been made in their artificial growth in bioreactors. Despite the described biological activities, there is little support to consider these metabolites in pharmaceutical formulations or to evaluate them in clinical trials. Nevertheless, it is important to carry out further studies regarding their possible human health effects. These lichen secondary metabolites present a promising research opportunity to find new pharmaceutical molecules due to their bioactive properties.

Unravelling Novel Phytochemicals and Anticholinesterase Activity in Irish Cladonia portentosa

Acetylcholinesterase inhibitors remain the mainstay of symptomatic treatment for Alzheimer's disease. The natural world is rich in acetylcholinesterase inhibitory molecules, and research efforts to identify novel leads is ongoing. Cladonia portentosa, commonly known as reindeer lichen, is an abundant lichen species found in Irish Boglands. The methanol extract of Irish C. portentosa was identified as an acetylcholinesterase inhibitory lead using qualitative TLC-bioautography in a screening program. To identify the active components, the extract was deconvoluted using a successive extraction process with hexane, ethyl acetate and methanol to isolate the active fraction. The hexane extract demonstrated the highest inhibitory activity and was selected for further phytochemical investigations. Olivetolic acid, 4-O-methylolivetolcarboxylic acid, perlatolic acid and usnic acid were isolated and characterized using ESI-MS and two-dimensional NMR techniques. LC-MS analysis also determined the presence of the additional usnic acid derivatives, placodiolic and pseudoplacodiolic acids. Assays of the isolated components confirmed that the observed anticholinesterase activity of C. portentosa can be attributed to usnic acid (25% inhibition at 125 µM) and perlatolic acid (20% inhibition at 250 µM), which were both reported inhibitors. This is the first report of isolation of olivetolic and 4-O-methylolivetolcarboxylic acids and the identification of placodiolic and pseudoplacodiolic acids from C. portentosa.

Antioxidant and antimicrobial activities and GC/MS-based phytochemical analysis of two traditional Lichen species Trypethellium virens and Phaeographis dendritica

BACKGROUND

Lichens are complex plants living in symbiotic relationship between fungi and algae. They are used for human and animal nutrition and are used in folk medicine in many countries over a considerable period of time. In the present study, various solvent extracts of Trypethelslium virens and Phaeographis dendritica were tested for their antioxidant and antimicrobial activity.

RESULTS

The phytochemical analysis by GC/MS revealed phenolics (1.273%), terpene (0.963%), hydrocarbons (2.081%), benzofurans (2.081%), quinone (1.273%), alkanes (0.963%), and aliphatic aldehydes (0.963%) as the predominant compounds in Trypethellium virens SPTV02, whereas secondary alcohol (1.184%), alkaloids (1.184%), and fatty acids (4.466) were the major constituents in Phaeographis dendritica. The antioxidant property of methanolic extract of T. virens and P. dendritica revealed the presence of total phenolic and terpenoids. The methanolic extracts of both the lichens exhibited encouraging DPPH antiradical activity, with the IC50 of 62.4 ± 0.76 µg/ml for T. virens and 68.48 ± 0.45 µg/ml for P. dendritica. Similarly, ferric reducing power assay result exhibited higher reducing activity. Further, the lichen extracts (methanolic) indicated promising antimicrobial activities against pathogens showing MIC from 62.5 to 500 µg/ml.

CONCLUSION

The study results concludes that both the lichens could be used as new natural source of antioxidants and antimicrobial agents which can be exploited for pharmaceutical applications.

Lichen Depsides and Tridepsides: Progress in Pharmacological Approaches

Depsides and tridepsides are secondary metabolites found in lichens. In the last 10 years, there has been a growing interest in the pharmacological activity of these compounds. This review aims to discuss the research findings related to the biological effects and mechanisms of action of lichen depsides and tridepsides. The most studied compound is atranorin, followed by gyrophoric acid, diffractaic acid, and lecanoric acid. Antioxidant, cytotoxic, and antimicrobial activities are among the most investigated activities, mainly in in vitro studies, with occasional in silico and in vivo studies. Clinical trials have not been conducted using depsides and tridepsides. Therefore, future research should focus on conducting more in vivo work and clinical trials, as well as on evaluating the other activities. Moreover, despite the significant increase in research work on the pharmacology of depsides and tridepsides, there are many of these compounds which have yet to be investigated (e.g., hiascic acid, lassalic acid, ovoic acid, crustinic acid, and hypothamnolic acid).

Atranorin, a Secondary Metabolite of Lichens, Exhibited Anxiolytic/Antidepressant Activity in Wistar Rats

Atranorin (ATR) is one of lichens' many known secondary metabolites. Most current studies have investigated the various effects of ATR in vitro and only sporadically in vivo. The latest data indicate that ATR may have anxiolytic/antidepressive effects. This study aimed to analyze the potential of ATR in a depression-like state in male Wistar rats. Pregnant females were stressed by restricting their mobility in the final week of pregnancy three times a day for 45 min each, for three following days. After birth, progeny aged 60 days was stressed repeatedly. The male progeny was divided into three groups as follows: CTR group as a healthy control (n = 10), DEP group as a progeny of restricted mothers (n = 10), and ATR group as a progeny of restricted mothers, treated daily for one month with ATR (n = 10; 10 mg/kg of body weight, p.o.). Our results show that ATR acts as an antioxidant and markedly changes animal behavior. Concomitantly, hippocampal neurogenesis increases in the hilus and subgranular zone, together with the number of NeuN mature neurons in the hilus and CA1 regions. Our results indicate a potential antidepressant/anxiolytic effect of ATR. However, further studies in this area are needed.

Is Caperatic Acid the Only Compound Responsible for Activity of Lichen Platismatia glauca within the Nervous System?

Lichens are a source of various biologically active compounds. However, the knowledge about them is still scarce, and their use in medicine is limited. This study aimed to investigate the therapeutic potential of the lichen Platismatia glauca and its major metabolite caperatic acid in regard to their potential application in the treatment of central nervous system diseases, especially neurodegenerative diseases and brain tumours, such as glioblastoma. First, we performed the phytochemical analysis of the tested P. glauca extracts based on FT-IR derivative spectroscopic and gas chromatographic results. Next the antioxidant properties were determined, and moderate anti-radical activity, strong chelating properties of Cu²⁺ and Fe²⁺ ions, and a mild effect on the antioxidant enzymes of the tested extracts and caperatic acid were proved. Subsequently, the influence of the tested extracts and caperatic acid on cholinergic transmission was determined by in vitro and in silico studies confirming that inhibitory effect on butyrylcholinesterase is stronger than against acetylcholinesterase. We also confirmed the anti-inflammatory properties of P. glauca extracts and caperatic acid using a COX-2 and hyaluronidase inhibition models. Moreover, our studies show the cytotoxic and pro-apoptotic activity of the P. glauca extracts against T98G and U-138 MG glioblastoma multiforme cell lines. In conclusion, it is possible to assume that P. glauca extracts and especially caperatic acid can be regarded as the source of the valuable substances to finding new therapies of central nervous system diseases.

Lichen Depsidones with Biological Interest

Depsidones are some of the most abundant secondary metabolites produced by lichens. These compounds have aroused great pharmacological interest due to their activities as antioxidants, antimicrobial, and cytotoxic agents. Hence, this paper aims to provide up-to-date knowledge including an overview of the potential biological interest of lichen depsidones. So far, the most studied depsidones are fumarprotocetraric acid, lobaric acid, norstictic acid, physodic acid, salazinic acid, and stictic acid. Their pharmacological activities have been mainly investigated in in vitro studies and, to a lesser extent, in in vivo studies. No clinical trials have been performed yet. Depsidones are promising cytotoxic agents that act against different cell lines of animal and human origin. Moreover, these compounds have shown antimicrobial activity against both Gram-positive and Gram-negative bacteria and fungi, mainly Candida spp. Furthermore, depsidones have antioxidant properties as revealed in oxidative stress in vitro and in vivo models. Future research should be focused on further investigating the mechanism of action of depsidones and in evaluating new potential actions as well as other depsidones that have not been studied yet from a pharmacological perspective. Likewise, more in vivo studies are prerequisite, and clinical trials for the most promising depsidones are encouraged.

Phytochemical Analysis, Antioxidant, Antimicrobial, and Cytotoxic Activity of Different Extracts of Xanthoparmelia stenophylla Lichen from Stara Planina, Serbia

The aim of this study was to identify some of the secondary metabolites present in acetonic, methanolic, and hexanic extracts of lichen Xanthoparmelia stenophylla and to examine their antioxidant, antimicrobial, and cytotoxic activity. Compounds of the depsid structure of lecanoric acid, obtusic acid, and atranorin as well as usnic acid with a dibenzofuran structure were identified in the extracts by HPLC. The acetone extract was shown to have the highest total phenolic (167.03 ± 1.12 mg GAE/g) and total flavonoid content (178.84 ± 0.93 mg QE/g) as well as the best antioxidant activity (DPPH IC50 = 81.22 ± 0.54). However, the antimicrobial and antibiofilm tests showed the best activity of hexanic extract, especially against strains of B. cereus, B. subtilis, and S. aureus (MIC < 0.08, and 0.3125 mg/mL, respectively). Additionally, by using the MTT method, the acetonic extract was reported to exhibit a strong cytotoxic effect on the HeLa and HCT-116 cell lines, especially after 72 h (IC50 = 21.17 ± 1.85 and IC50 = 21.48 ± 3.55, respectively). The promising antioxidant, antimicrobial, and cytotoxic effects of Xanthoparmelia stenophylla extracts shown in the current study should be further investigated in vivo and under clinical conditions.

Lichen Secondary Metabolites Inhibit the Wnt/β-Catenin Pathway in Glioblastoma Cells and Improve the Anticancer Effects of Temozolomide

Lichens are a source of secondary metabolites with significant pharmacological potential. Data regarding their possible application in glioblastoma (GBM) treatment are, however, scarce. The study aimed at analyzing the mechanism of action of six lichen secondary metabolites: atranorin, caperatic acid, physodic acid, squamatic acid, salazinic acid, and lecanoric acid using two- and three-dimensional GBM cell line models. The parallel artificial membrane permeation assay was used to predict the blood-brain barrier penetration ability of the tested compounds. Their cytotoxicity was analyzed using the MTT test on A-172, T98G, and U-138 MG cells. Flow cytometry was applied to the analysis of oxidative stress, cell cycle distribution, and apoptosis, whereas qPCR and microarrays detected the induced transcriptomic changes. Our data confirm the ability of lichen secondary metabolites to cross the blood-brain barrier and exert cytotoxicity against GBM cells. Moreover, the compounds generated oxidative stress, interfered with the cell cycle, and induced apoptosis in T98G cells. They also inhibited the Wnt/β-catenin pathway, and this effect was even stronger in case of a co-treatment with temozolomide. Transcriptomic changes in cancer related genes induced by caperatic acid and temozolomide were the most pronounced. Lichen secondary metabolites, caperatic acid in particular, should be further analyzed as potential anti-GBM agents.

Lichen-Derived Compounds and Extracts as Biologically Active Substances with Anticancer and Neuroprotective Properties

Lichens are a source of chemical compounds with valuable biological properties, structurally predisposed to penetration into the central nervous system (CNS). Hence, our research aimed to examine the biological potential of lipophilic extracts of Parmelia sulcata, Evernia prunastri, Cladonia uncialis, and their major secondary metabolites, in the context of searching for new therapies for CNS diseases, mainly glioblastoma multiforme (GBM). The extracts selected for the study were standardized for their content of salazinic acid, evernic acid, and (−)-usnic acid, respectively. The extracts and lichen metabolites were evaluated in terms of their anti-tumor activity, i.e., cytotoxicity against A-172 and T98G cell lines and anti-IDO1, IDO2, TDO activity, their anti-inflammatory properties exerted by anti-COX-2 and anti-hyaluronidase activity, antioxidant activity, and anti-acetylcholinesterase and anti-butyrylcholinesterase activity. The results of this study indicate that lichen-derived compounds and extracts exert significant cytotoxicity against GBM cells, inhibit the kynurenine pathway enzymes, and have anti-inflammatory properties and weak antioxidant and anti-cholinesterase properties. Moreover, evernic acid and (−)-usnic acid were shown to be able to cross the blood-brain barrier. These results demonstrate that lichen-derived extracts and compounds, especially (−)-usnic acid, can be regarded as prototypes of pharmacologically active compounds within the CNS, especially suitable for the treatment of GBM.

Green Roccella phycopsis Ach. mediated silver nanoparticles: synthesis, characterization, phenolic content, antioxidant, antibacterial and anti-acetylcholinesterase capacities

In this study, we develop here for the first time an easy, eco-friendly method for synthesizing silver nanoparticles (AgNPs) using the lichen Roccella phycopsis. AgNPs formation was first determined by a color change of the lichen filtrate to brown, subsequent to addition of AgNO₃ solution, and confirmed by a maximum absorbance peak at 425 nm in UV-vis spectrum. Scanning electron microscope images showed a spherical shape with a size distribution between 11 and 18 nm, while the elemental composition was elucidated by the energy dispersive X-ray spectroscopy. The chemical compounds responsible for reduction and stabilization of silver nanoparticles were detected by Frourier transform infrared spectroscopy analysis. The synthesized R. phycopsis silver nanoparticles displayed a strong antioxidant activity. Further, the antibacterial activity was more effective against Gram-negative than Gram-positive bacteria. Besides, the R. phycopsis-AgNPs were potent in inhibiting acetylcholinesterase enzyme with IC₅₀ value of 1.65 ± 0.07 mg/mL.

Permeability of Hypogymnia physodes Extract Component-Physodic Acid through the Blood-Brain Barrier as an Important Argument for Its Anticancer and Neuroprotective Activity within the Central Nervous System

Simple Summary

Central nervous system (CNS) diseases, including tumors such as glioblastomas and neurodegenerative diseases, such as Alzheimer’s disease, are some of the greatest challenges of modern medicine. Therefore, our study aimed to evaluate the anticancer and neuroprotective activity of the extract from a common European lichen Hypogymnia physodes and of its compound-physodic acid. The examined substances were cytotoxic against the glioblastoma cell lines A-172, T98G, and U-138 MG. Both substances strongly inhibited hyaluronidase, and diminished cyclooxygenase-2 activity (H. physodes extract), enzymes expressed in patients with malignant glioma. Furthermore, H. physodes extract inhibited tyrosinase activity, the enzyme linked to neurodegenerative diseases. The tested substances exhibited antioxidant activity, however, acetylcholinesterase and butyrylcholinesterase inhibitory activity were not high. We proved that physodic acid can cross the blood–brain barrier. We conclude that physodic acid and H. physodes extract should be regarded as promising agents with anticancer, chemopreventive, and neuroprotective activities, especially concerning CNS.

Abstract

Lichen secondary metabolites are characterized by huge pharmacological potential. Our research focused on assessing the anticancer and neuroprotective activity of Hypogymnia physodes acetone extract (HP extract) and physodic acid, its major component. The antitumor properties were evaluated by cytotoxicity analysis using A-172, T98G, and U-138 MG glioblastoma cell lines and by hyaluronidase and cyclooxygenase-2 (COX-2) inhibition. The neuroprotective potential was examined using COX-2, tyrosinase, acetylcholinesterase (AChE), and butyrylcholinesterase (BChE) activity tests. Moreover, the antioxidant potential of the tested substances was examined, and the chemical composition of the extract was analyzed. For physodic acid, the permeability through the blood–brain barrier using Parallel Artificial Membrane Permeability Assay for the Blood–Brain Barrier assay (PAMPA-BBB) was assessed. Our study shows that the tested substances strongly inhibited glioblastoma cell proliferation and hyaluronidase activity. Besides, HP extract diminished COX-2 and tyrosinase activity. However, the AChE and BChE inhibitory activity of HP extract and physodic acid were mild. The examined substances exhibited strong antioxidant activity. Importantly, we proved that physodic acid crosses the blood–brain barrier. We conclude that physodic acid and H. physodes should be regarded as promising agents with anticancer, chemopreventive, and neuroprotective activities, especially regarding the central nervous system diseases.

Natural Compounds for the Prevention and Treatment of Cardiovascular and Neurodegenerative Diseases

Secondary metabolites from plants and fungi are stimulating growing interest in consumers and, consequently, in the food and supplement industries. The beneficial effects of these natural compounds are being thoroughly studied and there are frequent updates about the biological activities of old and new molecules isolated from plants and fungi. In this article, we present a review of the most recent literature regarding the recent discovery of secondary metabolites through isolation and structural elucidation, as well as the in vitro and/or in vivo evaluation of their biological effects. In particular, the possibility of using these bioactive molecules in the prevention and/or treatment of widely spread pathologies such as cardiovascular and neurodegenerative diseases is discussed.

Usnic acid enantiomers restore cognitive deficits and neurochemical alterations induced by Aβ1-42 in mice

Alzheimer's disease (AD) is the most prevalent form of dementia with a complex pathophysiology not fully elucidated but with limited pharmacological treatment. The Usnic acid (UA) is a lichen secondary metabolite found in two enantiomeric forms: (R)-(+)-UA or (S)-(-)-UA, with antioxidant and anti-inflammatory potential. Thus, given the role of neuroinflammation and oxidative injury in the AD, this study aimed to investigate experimentally the cognitive enhancing and anti-neuroinflammatory effects of UA enantiomers. First, the interactions of UA on acetylcholinesterase (AChE) was assessed by molecular docking and its inhibitory capability on AChE was assessed in vitro. In vivo trials investigated the effects of UA enantiomers in mice exposed to Aβ_1-42 peptide (400 pmol/mice) intracerebroventricularly (i.c.v.). For this, mice were treated orally during 24 days with (R)-(+)-UA or (S)-(-)-UA at 25, 50, or 100 mg/kg, vehicle, or donepezil (2 mg/kg). Animals were submitted to the novel object recognized, Morris water maze, and inhibitory-avoidance task to assess the cognitive deficits. Additionally, UA antioxidant capacity and neuroinflammatory biomarkers were measured at the cortex and hippocampus from mice. Our results indicated that UA enantiomers evoked complex-receptor interaction with AChE like galantamine in silico. Also, UA enantiomers improved the learning and memory of the animals and in parallel decreased the myeloperoxidase activity and the lipid hydroperoxides (LOOH) on the cortex and hippocampus and reduced the IL-1β levels on the hippocampus. In summary, UA restored the cognitive deficits, as well as the signs of LOOH and neuroinflammation induced by Aβ1-42 administration in mice.

Anti-inflammatory effects of usnic acid in an MPTP-induced mouse model of Parkinson's disease

Neuroinflammation is often associated with astrocyte and microglial activations particularly in Parkinson's disease (PD) and other brain damage such as Alzheimer's disease. Therefore, the modulation of glial activation offers a possible target for treating PD-associated pathologies. Here, we evaluated the neuroprotective effects of usnic acid, a naturally occurring dibenzofuran derivative found in several lichen species in an acute mouse model of PD. Male mice were administered with vehicle or usnic acid (5 or 25 mg/kg) for 10 consecutive days, and then on day 11, MPTP (20 mg/kg, i.p.) was administered four times (with 2hrs intervals between injections) to induce PD pathologies. It was found that MPTP-induced motor dysfunction and neuronal loss were ameliorated in the usnic acid-treated mice versus vehicle-treated controls. Further study revealed that usnic acid effectively inhibited MPP⁺-induced glial activation in primary astrocytes by blocking NF-κB activation. Taken together, these findings suggest that usnic acid could be considered potentially useful therapeutic candidates for PD and other neurodegenerative diseases associated with neuroinflammation.

Anticancer Potential of Lichens' Secondary Metabolites

Lichens produce different classes of phenolic compounds, including anthraquinones, xanthones, dibenzofuranes, depsides and depsidones. Many of them have revealed effective biological activities such as antioxidant, antiviral, antibiotics, antifungal, and anticancer. Although no clinical study has been conducted yet, there are number of in vitro and in vivo studies demonstrating anticancer effects of lichen metabolites. The main goal of our work was to review most recent published papers dealing with anticancer activities of secondary metabolites of lichens and point out to their perspective clinical use in cancer management.

Crafting Carbazole-Based Vorinostat and Tubastatin-A-like Histone Deacetylase (HDAC) Inhibitors with Potent in Vitro and in Vivo Neuroactive Functions

Small-molecule inhibitors of HDACs (HDACi) induce hyperacetylation of histone and nonhistone proteins and have emerged as potential therapeutic agents in most animal models tested. The established HDACi vorinostat and tubastatin-A alleviate neurodegenerative and behavioral conditions in animal models of neuropsychiatric disorders restoring the neurotrophic milieu. In spite of the neuroactive pharmacological role of HDACi (vorinostat and tubastatin-A), they are limited by efficacy and toxicity. Considering these limitations and concern, we have designed novel compounds 3-11 as potential HDACi based on the strategic crafting of the key pharmacophoric elements of vorinostat and tubastatin-A into architecting a single molecule. The molecules 3-11 were synthesized through a multistep reaction sequence starting from carbazole and were fully characterized by NMR and mass spectral analysis. The novel molecules 3-11 showed remarkable pan HDAC inhibition and the potential to increase the levels of acetyl H3 and acetyl tubulin. In addition, few novel HDAC inhibitors 4-8, 10, and 11 exhibited significant neurite outgrowth-promoting activity with no observable cytotoxic effects, and interestingly, compound 5 has shown comparably more neurite growth than the parent compounds vorinostat and tubastatin-A. Also, compound 5 was evaluated for possible mood-elevating effects in a chronic unpredictable stress model of Zebrafish. It showed potent anxiolytic and antidepressant-like effects in the novel tank test and social interaction test, respectively. Furthermore, the potent in vitro and in vivo neuroactive compound 5 has shown selectivity for class II over class I HDACs. Our results suggest that the novel carbazole-based HDAC inhibitors, crafted with vorinostat and tubastatin-A pharmacophoric moieties, have potent neurite outgrowth activity and potential to be developed as therapeutics to treat depression and related psychiatric disorders.

Fellutamide B Synthetic Path Intermediates with in Vitro Neuroactive Function Shows Mood-Elevating Effect in Stress-Induced Zebrafish Model

Fellutamide B is reported to have cytotoxic and proteasome inhibitory activity. Interestingly, fellutamide B and its simplified analogues have also been observed for the neurotrophic activity by stimulating the synthesis and secretion of neurotrophins. Owing to the interesting structural and potent neurotrophic role of fellutamide B (a lipopeptide aldehyde), we have assessed the synthetic path intermediates (compounds A-D) of fellutamide B for their neuroactive potential (in vitro and in vivo). We have observed few compounds (comp #A-D) to have potential neurite outgrowth activity in Neuro2a cells with no observable negative effect on the cell viability. In addition, most compounds (comp #A, C, and D) have shown neurogenic activity ex vivo in hippocampal neurosphere culture, with increased acetyl H3 and acetyl H4 induction ability (comp #C). Furthermore, the intermediate product comp #C has shown anxiolytic and antidepressant-like activity in novel tank test and social interaction test, in the chronic unpredictable stress model of zebrafish mood disorder, inducing BDNF gene expression in the telencephalon region of the fish brain. Our results thus demonstrate that the fellutamide B synthetic path intermediates have potential neurotrophic, neurogenic, and mood-elevating effects and thus good prospect to be developed as potential therapeutics to treat psychiatric disorders.

Depsidone Derivatives and a Cyclopeptide Produced by Marine Fungus Aspergillus unguis under Chemical Induction and by Its Plasma Induced Mutant

A new depsidone derivative (1), aspergillusidone G, was isolated from a marine fungus Aspergillus unguis, together with eight known depsidones (2‒9) and a cyclic peptide (10): agonodepside A (2), nornidulin (3), nidulin (4), aspergillusidone F (5), unguinol (6), aspergillusidone C (7), 2-chlorounguinol (8), aspergillusidone A (9), and unguisin A (10). Compounds 1‒4 and 7‒9 were obtained from the plasma induced mutant of this fungus, while 5, 6, and 10 were isolated from the original strain under chemical induction. Their structures were identified using spectroscopic analysis, as well as by comparison with literature data. The HPLC fingerprint analysis indicates that chemical induction and plasma mutagenesis effectively influenced the secondary metabolism, which may be due to their regulation in the key steps in depsidone biosynthesis. In bioassays, compound 9 inhibited acetylcholinesterase (AChE) with IC₅₀ in 56.75 μM. Compounds 1, 5, 7, 8, and 9 showed moderate to strong activity towards different microbes. Compounds 3, 4, and 5 exhibited potent larvicidality against brine shrimp. In docking studies, higher negative CDOCKER interaction energy and richer strong interactions between AChE and 9 explained the greater activity of 9 compared to 1. Chemical induction and plasma mutagenesis can be used as tools to expand the chemodiversity of fungi and obtain useful natural products.

Effects of two lichen acids isolated from Pseudevernia furfuracea (L.) Zopf in cultured human lymphocytes

The present study aims at assessing the efficacies of olivetoric acid (OA) and physodic acid (PA) isolated from Pseudevernia furfuracea (L.) Zopf (Parmeliaceae) in human lymphocytes (HLs) in vitro. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and lactate dehydrogenase assays were performed to establish cytotoxicity in HLs. Besides, oxidative stress and genotoxicity were monitored by estimating the changes of total oxidative stress (TOS) and 8-hydroxy-2′-deoxyguanosine (8-OH-dG) levels, respectively, in HLs. At the same time, OA- and PA-induced total antioxidant capacity (TAC) levels in HLs were determined. Although especially low concentrations of OA (IC50=109.94 mg/L) and PA (IC50=665.49 mg/L) did not show cytotoxic effect at high levels in HLs, it was revealed that cytotoxicity was significantly (p<0.05) associated with oxidative stress and genotoxicity via correlation analysis. While TOS level in HLs did not statistically (p>0.05) increase in the presence of all treatments (0.5–100 mg/L) of PA, TAC level was increased by PA applications in certain concentrations (0.5–10 mg/L). Overall, the obtained data indicate that OA and especially PA as lichen compounds that do not cause oxidative stress can be a new resource of therapeutics as recognized in the present study with their high antioxidant features.

Isolation, Synthesis and AChE Inhibitory Potential of Some Novel Cinnamyl Esters of Taraxerol, the Major Metabolite of the Mangrove Bruguiera cylindrica

Systematic chemical screening of the leaves of Bruguiera cylindrica, the tree mangrove of Rhizophoraceae family, afforded five single and pure compounds. The structures of the isolated compounds were established by their spectroscopic data as taraxerol (1), 3β-(E)-coumaroyltaraxerol (2), 3β-(Z)-coumaroyltaraxerol (3), β-sitosterol (4), and eicosanol (5). In view of significant accumulation and interesting biological activities, taraxerol (1) was chemically transformed to synthesize a series of ten cinnamyl esters in very good to excellent yields. The synthesized analogues along with the parent compound were evaluated for their AChE inhibitory potential, BBB permeability and cytotoxicity against Neuro 2A cell line. Among the tested samples, compound 9 showed promising AChE inhibition with significantly low IC₅₀ values, low cytotoxicity and high BBB permeability. Hence, compound 9 can be considered as a lead molecule for further development as potent AChE inhibitor.

In vitro neuroprotective potential of lichen metabolite fumarprotocetraric acid via intracellular redox modulation

The lichen-forming fungi Cetraria islandica has been largely used in folk medicines, and it has recently showed promising in vitro antioxidant effects in glial-like cells. Current work aimed at investigating the neuroprotective potential of its major isolated secondary metabolite: the depsidone fumarprotocetraric acid (FUM). H₂O₂ was used herein to induce oxidative stress (OS)-mediated cytotoxicity in two models of neurons and astrocytes cells (SH-SY5Y and U373-MG cell lines). We found that a pre-treatment with FUM significantly enhanced cell viability compared to H₂O₂-treated cells, and we selected the optimal concentrations in each model (1 and 25μg/ml, respectively) for assessing its cytoprotective mechanisms. FUM, which exerted effective peroxyl radical scavenging effect in the chemical oxygen radical antioxidant capacity (ORAC) assay, alleviated the alterations in OS markers provoked by H₂O₂. It attenuated intracellular ROS formation, lipid peroxidation and GSH depletion. At mitochondrial level, FUM prevented from the dissipation of mitochondrial membrane potential and the increase in mitochondrial calcium, implying a protective role against oxidative damage in mitochondrial membrane. Similarly, FUM pre-treatment diminished H₂O₂-induced apoptosis, as evidenced by the reduction in caspase-3 activity and expression; inmunoblot analysis also revealed a decrease in Bax and an increase in Bcl-2 proteins levels. Furthermore, FUM up-regulated the expression of the antioxidant enzymes catalase, superoxide dismutase-1, and hemeoxigenase-1. These findings and the activation of Nrf2 binding activity in nuclear extracts suggest a plausible involvement of Nrf2 signaling pathway in the cytoprotection by FUM. In conclusion, FUM emerges as a potential drug candidate in the therapy of OS-related diseases, such as the neurodegenerative disorders.