Diffractaic acid, a novel proapoptotic agent, induces with olive oil both apoptosis and antioxidative systems in Ti-implanted rabbits

Effect of Usnea longissima ethyl acetate extract on acute oxidative and inflammatory lung damage from Staphylococcus aureus infection in rats

The role of oxidants and proinflammatory cytokines in the pathogenesis of pneumonia caused by Staphylococcus aureus (S. aureus) has been demonstrated. The present study aims to investigate the protective effect of ethyl acetate extract (EtOAc) obtained from Usnea longissima (UL) against acute oxidative and inflammatory lung damage due to S. aureus infection in rats. Albino Wistar-type male rats were divided into three groups: Healthy (HG), S. aureus inoculated (SaG), and S. aureus inoculated + ULEtOAc administered (SUL). SaG (n = 6) and SUL (n = 6) group rats' left nostrils (excluding HG) were inoculated with 0.1 ml bacterial mixture. After 24 hours, ULEtOAc (50 mg/kg) was administered orally to the SUL group, and the same volume of normal saline was administered orally to the HG (n = 6) and SaG groups. This procedure was performed once a day for seven days. Levels of oxidant and antioxidant parameters such as malondialdehyde (MDA) and total glutathione (tGSH), as well as pro-inflammatory cytokine levels such as nuclear factor-kappa B (NF-κB), tumor necrosis factor-alpha (TNF-α), interleukin-one beta (IL-1β), were measured in removed lung tissues. Tissues were also examined histopathologically. Biochemical results showed that ULEtOAc significantly suppressed the increase of MDA, NF-κB, TNF-α, and IL-1β levels and the decrease of tGSH caused by S. aureus in lung tissue. S. aureus inoculation caused severe mononuclear cell infiltration in interstitial areas, severe lymphoid hyperplasia in bronchial-associated lymphoid tissue and severe alveolar edema, histopathologically. Treatment with ULEtOAc had an attenuating effect on these histopathological findings. Experimental results from this study suggest that ULEtOAc may be beneficial in treating S. aureus-induced oxidative and inflammatory lung damage.

Diffractaic acid exhibits thioredoxin reductase 1 inhibition in lung cancer A549 cells

Lung cancer is the leading cause of cancer-related deaths all over the world. Therefore, it has gained importance in the development of new chemotherapeutic strategies to identify anticancer agents with low side effects, reliable, high anticancer potential, and specific to lung cancer cells. Thioredoxin reductase 1 (TrxR1) is an important therapeutic target for lung cancer treatment because of its overexpression in tumor cells. Here, we aimed to examine the anticancer effect of diffractaic acid, a lichen secondary metabolite, in A549 cells by comparing it with the commercial chemotherapeutic drug carboplatin and also to investigate whether the anticancer effect of diffractaic acid occurs via TrxR1-targeting. The IC50 value of diffractaic acid on A549 cells was determined as 46.37 μg/mL at 48 h, and diffractaic acid had stronger cytotoxicity than carboplatin in A549 cells. qPCR results revealed that diffractaic acid promoted the intrinsic apoptotic pathway through the upregulation of the BAX/BCL2 ratio and P53 gene in A549 cells, which is consistent with the flow cytometry results. Furthermore, migration analysis results indicated that diffractaic acid impressively suppressed the migration of A549 cells. While the enzymatic activity of TrxR1 was inhibited by diffractaic acid in A549 cells, no changes were seen in the quantitative expression levels of gene and protein. These findings provide fundamental data on the anticancer effect of diffractaic acid on A549 cells targeting TrxR1 activity, suggesting that it could be considered a chemotherapeutic agent for lung cancer therapy.

Lichen-Derived Diffractaic Acid Inhibited Dengue Virus Replication in a Cell-Based System

Dengue is a mosquito-borne flavivirus that causes 21,000 deaths annually. Depsides and depsidones of lichens have previously been reported to be antimicrobials. In this study, our objective was to identify lichen-derived depsides and depsidones as dengue virus inhibitors. The 18 depsides and depsidones of Usnea baileyi, Usnea aciculifera, Parmotrema dilatatum, and Parmotrema tsavoense were tested against dengue virus serotype 2. Two depsides and one depsidone inhibited dengue virus serotype 2 without any apparent cytotoxicity. Diffractaic acid, barbatic acid, and Parmosidone C were three active compounds further characterized for their efficacies (EC₅₀), cytotoxicities (CC₅₀), and selectivity index (SI; CC₅₀/EC₅₀). Their EC₅₀ (SI) values were 2.43 ± 0.19 (20.59), 0.91 ± 0.15 (13.33), and 17.42 ± 3.21 (8.95) μM, respectively. Diffractaic acid showed the highest selectivity index, and similar efficacies were also found in dengue serotypes 1-4, Zika, and chikungunya viruses. Cell-based studies revealed that the target was mainly in the late stage with replication and the formation of infectious particles. This report highlights that a lichen-derived diffractaic acid could become a mosquito-borne antiviral lead as its selectivity indices ranged from 8.07 to 20.59 with a proposed target at viral replication.

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).

Lichens: An update on their ethnopharmacological uses and potential as sources of drug leads

ETHNOPHARMACOLOGICAL RELEVANCE

Lichens, a unique symbiotic association between an alga/cyanobacterium and a fungus, produce secondary metabolites that are a promising source of novel drug leads. The beauty and importance of lichens have not been adequately explored despite their manifold biological activities such as anticancer, antimicrobial, antioxidant, anti-inflammatory, analgesic, antipyretic and antiparasitic.

AIM OF THE STUDY

The present review collates and discusses the available knowledge on secondary metabolites and biological activities of lichens (in vitro and in vivo).

MATERIALS AND METHODS

Using relevant keywords (lichens, secondary metabolites, bioactivity, pharmacological activities), five electronic databases, namely ScienceDirect, PubMed, Google Scholar, Scopus and Recent Literature on Lichens, were searched for past and current scientific contributions up until May 2022. Literature focusing broadly on the bioactivity of lichens including their secondary metabolites were identified and summarized.

RESULTS

A total of 50 review articles and 189 research articles were searched. Information related to antioxidant, antimicrobial, anti-inflammatory, anticancer and insecticidal activities of 90 lichen species (from 13 families) and 12 isolated metabolites are reported. Over 90% of the studies comprised in vitro investigations, such as bioassays evaluating radical scavenging properties, lipid peroxidation inhibition and reducing power, cytotoxicity and antimicrobial bioassays of lichen species and constituents. In vivo studies were scarce and available only in fish and rats. Most of the studies were done by research groups in Brazil, France, Serbia, India and Turkey. There were relatively few reports from Asia and Africa despite the ubiquitous nature of lichens and the high occurrence in these continents.

CONCLUSION

Secondary metabolites from lichens are worthy of further investigation in terms of their potential therapeutic applicability, including better understanding of their mechanism(s) of action. This would be of great importance in the search for novel drugs.

Inhibition of growth of U87MG human glioblastoma cells by Usnea longissima Ach

Herbal medicines are efficient to reduce side effects in the fight against glioblastoma, which plays a critical role within brain cancer species. The recent studies designated for testing the effects of lichens that have shown numerous anticancer activities on glioblastoma so far. In the present study, different concentrations of water extract obtained from Usnea longissima Ach. were used in order to determine cytotoxic (via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and lactate dehydrogenase tests), antioxidant (via total antioxidant capacity test), pro-oxidant (via total oxidant status test) and genotoxic (via 8-hydroxy-2'-deoxyguanosine test) effects of them on human U87MG-glioblastoma cancer cell lines. Primary mixed glial-neuronal non-cancerous cells from Sprague-Dawley rats were also utilized to measure the effects of treatments on non-cancerous cells. Based on median inhibitory concentration values, the data belonged to non-cancerous cells (2486.71 mg/L) showed distinct towering compared to U87MG (80.93 mg/L) cells. The viability of non-cancerous and U87MG cells exposed to extract is decreased in a dose dependent manner. It was also showed that low concentrations of extract notably increased total antioxidant capacity on non-cancerous cells. In addition, various phenolic compounds in extract were detected through high-performance liquid chromatography. The recent results encourage that extract will be able to have therapeutic potential against glioblastoma.

Chemopreventive role of olive oil in colon carcinogenesis by targeting noncoding RNAs and methylation machinery

Epigenetic therapy induced by dietary components has become a strong interest in the field of cancer prevention. Olive oil, a potent dietary chemopreventive agent, control colon cancer, however, its role in epigenetic therapy remains unclear. Thus, we aimed to investigate the effect of olive oil in a preclinical model of colon cancer by targeting genetic and epigenetic mechanisms. DMH was used to induce colon cancer in rats; while olive oil was given to separate group of rats along with DMH treatment. Tumor burden and incidence in DMH and DMH + olive oil-treated rats was observed by macroscopic examination and histoarchitectural studies. Potent anti-inflammatory, anti-angiogenic and pro-apoptotic activity of olive oil was explored by gene expression and immunohistochemical studies. The effect of olive oil on epigenetic alterations was examined by detecting promoter methylation with MS-HRM and dysregulation of miRNA by TaqMan MicroRNA Assay. We observed that olive oil administration lowered tumor incidence and inhibited the development of tumors in DMH-treated rats. Olive oil markedly decreased the expression of inflammatory and angiogenic markers and restored the expression of pro-apoptotic markers in DMH-treated rats. Furthermore, the inverse relationship between gene expression and DNA methylation, deviant miRNA pattern and miRNA silencing mediated by aberrant DNA methylation was also seen in DMH-treated rats, which was potentially reversible upon olive oil treatment. Our study concludes that olive oil may play a role in the epigenetic therapy by altering NF-κB and apoptotic pathways via targeting noncoding RNAs and methylation machinery that affecting epigenome to prevent colon carcinogenesis.

Usnic Acid Derivatives with Cytotoxic and Antifungal Activities from the Lichen Usnea longissima

Eight usnic acid derivatives, that is, usenamines A-F (1-6), usone (7), and isousone (8), together with the known (+)-usnic acid (9), were isolated from the lichen Usnea longissima. Their structures were elucidated using 1D and 2D NMR and MS data, and the absolute configurations of compounds 1 and 2 were defined by single-crystal X-ray diffraction analyses. Compounds 1, 2, and 8 showed inhibitory effects on the growth of human hepatoma HepG2 cells with IC50 values of 6.0-53.3 μM compared with methotrexate as the positive control, which had an IC50 value of 15.8 μM. Furthermore, 1 induced apoptosis of HepG2 cells in a dose-dependent manner at concentrations of 0-15.0 μM. The isolated compounds were also evaluated for their antifungal and antibacterial activities, with 7 and 8 exhibiting weak inhibitory effects on fungal Trichophyton rubrum spp. with an MIC value of 41.0 μM.

The genus Usnea: a potent phytomedicine with multifarious ethnobotany, phytochemistry and pharmacology

The genusUsneaAdans. (Parmeliaceae; lichenized Ascomycetes) is a typical group of mostly pale grayish-green fruticoselichens that grow as leafless mini-shrubs.

Antioxidant activity and mechanisms of action of natural compounds isolated from lichens: a systematic review

Chronic diseases such as cancer, diabetes, neurodegenerative and cardiovascular diseases are characterized by an enhanced state of oxidative stress, which may result from the overproduction of reactive species and/or a decrease in antioxidant defenses. The search for new chemical entities with antioxidant profile is still thus an emerging field on ongoing interest. Due to the lack of reviews concerning the antioxidant activity of lichen-derived natural compounds, we performed a review of the antioxidant potential and mechanisms of action of natural compounds isolated from lichens. The search terms “lichens”, “antioxidants” and “antioxidant response elements” were used to retrieve articles in LILACS, PubMed and Web of Science published until February 2014. From a total of 319 articles surveyed, 32 met the established inclusion and exclusion criteria. It was observed that the most common isolated compound studied was usnic acid, cited in 14 out of the 32 articles. The most often described antioxidant assays for the study of in vitro antioxidant activity were mainly DPPH, LPO and SOD. The most suggested mechanisms of action were scavenging of reactive species, enzymatic activation and inhibition of iNOS. Thus, compounds isolated from lichens are possible candidates for the management of oxidative stress, and may be useful in the treatment of chronic diseases.