Usnic Research Articles

Evaluation of Antimicrobial Properties of Lichen Substances against Plant Pathogens

Plant pathogens pose major threats on agriculture and horticulture, causing significant economic loss worldwide. Due to the continuous and excessive use of synthetic pesticides, emergence of pesticide resistant pathogens has become more frequent. Thus, there is a growing needs for environmentally-friendly and selective antimicrobial agents with a novel mode of action, which may be used in combination with conventional pesticides to delay development of pesticide resistance. In this study, we evaluated the potentials of lichen substances as novel biopesticides against eight bacterial and twelve fungal plant pathogens that have historically caused significant phytopathological problems in South Korea. Eight lichen substances of diverse chemical origins were extracted from axenic culture or dried specimen, and further purified for comparative analysis of their antimicrobial properties. Usnic acid and vulpinic acid exhibited strong antibacterial activities against Clavibacter michiganensis subsp. michiganensis. In addition, usnic acid and vulpinic acid were highly effective in the growth inhibition of fungal pathogens, such as Diaporthe eres, D. actinidiae, and Sclerotinia sclerotiorum. Intriguingly, the growth of Rhizoctonia solani was specifically inhibited by lecanoric acid, indicating that lichen substances exhibit some degrees of selectivity to plant pathogens. These results suggested that lichen substance can be used as a selective biopesticide for controlling plant disease of agricultural and horticultural significance, minimizing possible emergence of pesticide resistant pathogens in fields.

Evaluation of the utility of the Beta Human Liver Emulation System (BHLES) for CFSAN's regulatory toxicology program

Microphysiological systems (MPS), such as organ-on-a-chip platforms, are an emerging alternative model that may be useful for predicting human physiology and/or toxicity. Due to the interest in these platforms, the Center for Food Safety and Applied Nutrition partnered with Emulate to evaluate the utility of the Beta Human Liver Emulation System (BHLES) for its regulatory science program. Using known hepatotoxic compounds (usnic acid, benzbromarone, tamoxifen, and acetaminophen) and compounds that have no reported human cases of liver toxicity (dimethyl sulfoxide, theophylline, and aminohippurate) the platform's performance was evaluated. Chemical toxicity was assessed by albumin secretion, urea and LDH release, nuclei number, mitochondrial membrane potential, and apoptosis. System/platform performance was evaluated in terms of sensitivity and specificity, power, and variability and repeatability. Chemical interactions with the Chip material were also assessed. Preliminary findings suggested that for the model test compounds selected, the BHLES accurately predicted toxicity, demonstrated high sensitivity and specificity, high power, and low variability. However, some compounds interacted with the Chip material indicating variable exposure levels that should be accounted for when planning experimentation. The details of the evaluation are presented herein.

Usnic acid-induced programmed cell death in ovarian cancer cells

Usnic acid (UA) is a secondary metabolite obtained by lichen species and exerts a significant anti-proliferative effect on different cancer cells. The current study aimed to determine the efficiency of UA on ovarian cancer and reveal the underlying molecular mechanisms of UA mediated anti-cancer activity. In this study, the cytotoxic effect of UA was evaluated by xCELLigence real-time online cell analysis in OVCAR-3, A2780 ovarian cancer cells and L929 non-cancerous cell compared with Carboplatin. After treatment with IC50 concentration of UA, apoptosis, cell cycle analysis, mRNA expression levels, invasion, wound healing and metastasis assays were performed to evaluate of the molecular mechanism of the apoptosis pathway. UA showed more anti-proliferative effect than carboplatin on OVCAR-3 which is the most aggressive cell among ovarian cancer cells. UA significantly decreased the cell proliferation of OVCAR-3 cells through apoptosis and G0/G1 arrest. Additionally, UA inhibited the invasion and particularly the migration of OVCAR-3 cells compared with control. Moreover, the expression level of 63 target genes from 87 apoptosis associated genes in the primary panel was determined after IC50 concentration of UA in OVCAR-3 cells. UA caused apoptotic cell death through the extrinsic pathway and over-expression of p53. Our findings demonstrated that UA-induced early and late apoptosis through G0/G1 arrest and extrinsic apoptosis signaling pathways and inhibited the migration and invasion of OVCAR-3 cells. Therefore, UA as a novel candidate molecule may be used for the treatment of ovarian cancer.Graphical abstractUsnic acid (UA) exerts anti-cancer effects and induces apoptosis through the extrinsic pathway and over-expression of p53. Additionally, UA potentially inhibits the migration ability of OVCAR-3 ovarian cancer cells. (Created with BioRender.com)

Potential of Usnic Acid Compound from Lichen Genus Usnea sp. as Antidiabetic Agents.

Lichen Usnea sp. is potential as a new natural medicine. This study report isolation of secondary metabolites from lichen Usnea sp. and α-glucosidase inhibitory, which is potential as an antidiabetic agent. Lichen powder was macerated using methanol, separated using column chromatography gravity and thin-layer chromatography. The crystalline was isolated and purified by the recrystallization process for obtaining pure compound. The isolated compound was determined using FTIR and NMR spectroscopy (1H and 13C). The results showed that the isolated compound was yellow needle crystals. Based on the spectra data interpretation, it was obtained usnic acid compound with the molecular formula of C18H16O7. The α-glucosidase inhibitory activity test showed that the usnic acid had activity in inhibiting the α-glucosidase enzyme with an IC50 value of 106.78 µg/mL. The usnic acid from Usnea sp. has a very good impact on the source of natural compounds as an antidiabetic drug in the future.

Anti-ageing and Anti-lung Carcinoma Effects of Vulpinic Acid and Usnic Acid Compounds and Biological Investigations with Molecular Modeling Study.

Disorganization and breakdown of extracellular matrix proteins like fibronectin, collagen, and elastin are key characteristics of skin aging due to the increased activation of important proteolytic enzymes like elastases and collagenase enzymes. Also, inhibition of their enzymatic activities by natural molecules might be a promising factor to prevent extrinsic skin aging. All chemicals were obtained from Sigma-Aldrich unless otherwise stated. The assay employed was based on spectrophotometric methods reported in the literature. The collagenase and elastase inhibition assays of some phenolic compounds were performed according to the previous studies. These compounds showed excellent to good inhibitory activities of vulpinic acid against studied these enzymes with IC50 values of 195.36 µM for collagenase and 25.24 µM for elastase. The molecular docking calculations were conducted to investigate the chemical and biological activity of vulpinic acid and usnic acid against collagenase and elastase. The results indicated that these two compounds can interact with the essential residues of the enzymes and affect their activities. The calculations of binding free energies were also performed to obtain more details about the characteristics and free energies of the ligand-enzyme complexes. Additionally, both compounds exhibited the most potent inhibition in the three lung cancer cells, with an IC50 value of 21-68 µM, indicating that vulpinic acid is more potent than Doxorubicin, which exhibited an IC50 value of 21-29 µM.

Usnic acid: A promising bioactive agent for wound healing

Usnic acid: A promising bioactive agent for wound healing

Synthesis of the New Derivatives of Usnic Acid and Investigation of Their Hypoglycemic Properties

Synthesis of the New Derivatives of Usnic Acid and Investigation of Their Hypoglycemic Properties

The RP-HPLC method for analysis of usnic acid as potential marker of herbal drugs-based formulations containing Usnea barbata

The aim of this study was to develop and validate a sensitive RP-HPLC method for the determination of usnic acid, as a potential marker substance of the herbal product for oromucosal use being a complex mixture of plant extracts and an essential oil, including the extract of Usnea barbata. Analysis of usnic acid in the tested formulation was performed through an extraction with methanol, prior to injection onto the HPLC column (Zorbax Eclipse XDB-C18 600 Bar (4.6 mm?100 mm, 1.8 ?m)). The employed gradient procedure of the solvents (phosphoric acid (pH 2.5) and acetonitrile), at flow rate of 0.1 mL min-1 allowed for the efficient and reproducible separation of usnic acid from the other compounds present in the investigated complex mixture. The established suitability, linearity, precision, accuracy and selectivity/specificity of this assay implied its applicability for the reliable examination in the stability study of the investigated multi-ingredient herbal preparation.

Synthesis of the New Derivatives of Usnic Acid and Investigation of Their Hypoglycemic Properties

Synthesis of the New Derivatives of Usnic Acid and Investigation of Their Hypoglycemic Properties

Antibacterial Activity and Stability of Methanol Extract from Thamnolia subuliformis in Vitro

The objective of the study was preliminarily explore the antibacterial activity and stability of Thamnolia subuliformis in vitro, the plate drilling method was used to determine the antibacterial activity of methanol extract of Thamnolia subuliformis against common pathogenic bacteria in vitro. The indicator bacteria of Staphylococcus aureus was used to determine the effects of factors such as different temperature, pH and UV irradiation time on antibacterial stability. Petroleum ether, ethyl acetate and n-butanol were used to extract the methanol extract, determine the polarity of its antibacterial active substances, and determine the content of usnic acid. The results showed that the methanol extract of Thamnolia subuliformis had good antibacterial effect on Gram-positive bacteria such as Staphylococcus aureus, Bacillus subtilis, Listeria stephensi, Staphylococcus surface, Listeria evansi, paratyphoid A, paratyphoid B of Gram-negative bacteria and Candida albicans. The minimum inhibitory concentration and minimum bactericidal concentration against Staphylococcus aureus were 0.625 and 10 mg/mL respectively; The results of antibacterial stability test showed that temperature had no significant effect on the antibacterial activity of methanol extract of Thamnolia subuliformis（P>0.05）, and it still had high antibacterial activity after treatment at 100 ℃ for 30 min; The antibacterial activity of UV irradiation for 40 min and 50 min decreased significantly (P 0.05）, showing high antibacterial activity. When the pH was high (8.0, 10.0) or low (2.0, 4.0), the antibacterial activity of the treatment group decreased significantly (P<0.05), and decreased with the increase or decrease of pH, The content of usnic acid in methanol extract and ethyl acetate extract of Thamnolia subuliformis was 0.8613% and 0.9379%, respectively. The results show that the methanol extract of Thamnolia subuliformis has a certain broad-spectrum antibacterial effect, low concentration and good stability. It can be used for the development and utilization of natural food preservatives and plant-derived antibacterial drugs.

Divergent Reactivity of Usnic Acid and Evaluation of its Derivatives for Antiproliferative Activity Against Cancer Cells

Divergent Reactivity of Usnic Acid and Evaluation of its Derivatives for Antiproliferative Activity Against Cancer Cells

Usnic Acid Reduces Colon Cancer Cell Viability and Colony Formation by Aff ecting Cancer Cell Metabolism

Usnic Acid Reduces Colon Cancer Cell Viability and Colony Formation by Aff ecting Cancer Cell Metabolism

Elemental Analysis and In Vitro Evaluation of Antibacterial and Antifungal Activities of Usnea barbata (L.) Weber ex F.H. Wigg from Călimani Mountains, Romania.

This study aims to complete our research on Usnea barbata (L.) Weber ex F.H. Wigg (U. barbata) from the Călimani Mountains, Romania, with an elemental analysis and to explore its antibacterial and antifungal potential. Thus, we analyzed twenty-three metals (Ca, Fe, Mg, Mn, Zn, Al, Ag, Ba, Co, Cr, Cu, Li, Ni, Tl, V, Mo, Pd, Pt, Sb, As, Pb, Cd, and Hg) in dried U. barbata lichen (dUB) by inductively coupled plasma mass spectrometry (ICP-MS). For the second study, we performed dried lichen extraction with five different solvents (ethyl acetate, acetone, ethanol, methanol, and water), obtaining five U. barbata dry extracts (UBDE). Then, using an adapted disc diffusion method (DDM), we examined their antimicrobial activity against seven bacterial species—four Gram-positive (Staphylococcus aureus, Enterococcus casseliflavus, Streptococcus pyogenes, and Streptococcus pneumoniae) and three Gram-negative (Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa)—and two fungi species (Candida albicans and Candida parapsilosis). Usnic acid (UA) was used as a positive control. The ICP-MS data showed a considerable Ca content (979.766 µg/g), followed by, in decreasing order, Mg, Mn, Al, Fe, and Zn. Other elements had low levels: Ba, Cu, Pb, and Cr (3.782–1.002 µg/g); insignificant amounts (<1 µg/g) of Hg and V were also found in dUB. The trace elements Ag, As, Cd, Co, Li, Tl, Mo, Pd, Pt, and Sb were below detection limits (<0.1 µg/g). The DDM results—expressed as the size (mm) of the inhibition zone diameter (IZs)—proved that the water extract did not have any inhibitory activity on any pathogens (IZs = 0 mm). Gram-positive bacteria displayed the most significant susceptibility to all other UBDE, with Enterococcus casseliflavus showing the highest level (IZs = 20–22 mm). The most susceptible Gram-negative bacterium was Pseudomonas aeruginosa (IZs = 16–20 mm); the others were insensitive to all U. barbata dry extracts (IZs = 0 mm). The inhibitory activity of UBDE and UA on Candida albicans was slightly higher than on Candida parapsilosis.

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.

Dibenzofurans from Lichens - A Pharmacological Overview.

Lichens are a symbiotic association between a fungus (mycobiont) and a green algae/- cyanobacterium (photobiont). Lichens are a source of secondary metabolites, most of them being exclusively for these species, among which dibenzofurans are found. Dibenzofurans are a small group (over 35 different identified compounds), being usnic acid the most studied. In the last 10 years, there has been a growing interest in the pharmacological activity of dibenzofurans. In this work, dibenzofurans isolated from lichens (alectosarmentin, condidymic acid, didymic acid, isousnic acid, isostrepsilic acid, usimines A-C and usnic acid) were reviewed, most of which showed antibacterial, antifungal, and cytotoxic activities. These findings provide future guidance for research on pharmacological activity of dibenzofurans.

Virtual Screening-Based Identification of Potent DENV-3 RdRp Protease Inhibitors via In-House Usnic Acid Derivative Database

Dengue virus (DENV) is the causative agent of dengue fever, dengue hemorrhagic disease and dengue shock syndrome (DSS), transmitted predominantly in tropical and subtropical regions by Aedes aegypti. It infects millions of people and causes thousands of deaths each year, but there is no antiviral drug against DENV. Usnic acid lately piqued the interest of researchers for extraordinary biological characteristics, including antiviral activity. Based on high larvicidal activities against Aedes aegypti, this study aims to search usnic acid derivatives as novel anti-DENV agents through a combination of ligand-based and pharmacophore-based virtual screening. One hundred and sixteen (116) usnic acid derivatives were obtained from a database of 428 in-house usnic acid derivatives through pharmacophore filtering steps. Subsequent docking simulation on DENV-3 NS-5 RdRp afforded 41 compounds with a strong binding affinity towards the enzyme. The pharmacokinetics and drug likeness prediction resulted in seven hit compounds, which eventually undergo cytochrome P450 enzyme screening to obtain the lead compound, labelled as 362. In addition, molecular dynamic (MD) simulation of lead compound 362 was performed to verify the stability of the docked complex and the binding posture acquired in docking experiments. Overall, the lead compounds have shown a high fit value of pharmacophore, strong binding affinity towards RdRp enzyme, good pharmacokinetics, and drug likeness properties. The discovery of a new usnic acid derivative as a novel anti-DENV agent targeting RdRp could lead to further drug development and optimization to treat dengue.

Structural Studies of β-Diketones and Their Implications on Biological Effects.

The paper briefly summarizes methods to determine the structure of β-diketones with emphasis on NMR methods. Density functional calculations are also briefly treated. Emphasis is on the tautomeric equilibria of β-diketones in relation to biological effects. Relevant physical parameters such as acidity and solubility are treated. A series of biologically active molecules are treated with respect to structure (tautomerism). Characteristic molecules or groups of molecules are usnic acids, tetramic and tetronic acids, o-hydroxydibenzoylmethanes, curcumines, lupulones, and hyperforines.

State and prospects of modern research in biotechnology of licens as a medicinal raw material

Based on the content analysis of the sources of patent and scientific literature on the biotechnology of lichens as a medicinal raw material, systematized modern information is provided, as well as original experimental data regarding the cultivation of botanical species of lichens of various ecological and geographical groups under controlled conditions. Since ancient times, lichens havebeen used as medicines and are included in the pharmacopoeias of various countries. At present, methodological approaches have been developed for the cultivation of lichens (genera Usnea, Rhinocarpon, Umbilicara ) and their components: phycobiont (genera Nostoc, Chlorella ), mycobiont ( Petrusaria pertiza, Leydea parasema, Alternaria sp.). The main biologically active compounds (usnic acid, lichenin, cetrarin, water-soluble vitamins, calcium oxalate) and the pharmacological effects caused by them (antimicrobial, stimulating appetite, enveloping, anti-inflammatory, anti-burn, regenerating). Biotechnological approaches can be implemented for species cloning, reproduction, creation of a bank of cell cultures of lichens and their components in order to preserve economically valuable producers in an active state and develop technologies for obtaining biomass and pharmacologically valuable biologically active compounds.

Antibacterial Activity of (+) Usnic Acid against Multi Drug Resistant Acinetobacter baumannii from Clinical Isolates

Acinetobacter baumannii (Ab) is developing resistance to a variety of common antibiotics. and becomemultidrug resistant, extreme drug resistant, and pan drug resistant pathogens, requiring the identificationof new antibiotics as well as the identification of new plant compounds capable of acting against Ab.Recent research has revealed MDR Ab co-infections with COVID-19,, raising alarm bells. Sinceits isolation, Usnic acid has been investigated for a variety of pharmacological activities, includingantioxidant, antitumor, antibacterial, antifungal, antiviral, antiprotozoal, and insecticidal. ManyPlant-derived drugs show promising activity as new antimicrobial agents against multidrug resistant(MDR) strains. There is insufficient data to support the antibacterial activity of (+)-UA against MDRAcinetobacter baumannii..

Evaluation of the Antimicrobial Efficacy of N-Acetyl-l-Cysteine, Rhamnolipids, and Usnic Acid-Novel Approaches to Fight Food-Borne Pathogens.

In the food industry, the increasing antimicrobial resistance of food-borne pathogens to conventional sanitizers poses the risk of food contamination and a decrease in product quality and safety. Therefore, we explored alternative antimicrobials N-Acetyl-l-cysteine (NAC), rhamnolipids (RLs), and usnic acid (UA) as a novel approach to prevent biofilm formation and reduce existing biofilms formed by important food-borne pathogens (three strains of Salmonella enterica and two strains of Escherichia coli, Listeria monocytogenes, Staphylococcus aureus). Their effectiveness was evaluated by determining minimum inhibitory concentrations needed for inhibition of bacterial growth, biofilm formation, metabolic activity, and biofilm reduction. Transmission electron microscopy and confocal scanning laser microscopy followed by image analysis were used to visualize and quantify the impact of tested substances on both planktonic and biofilm-associated cells. The in vitro cytotoxicity of the substances was determined as a half-maximal inhibitory concentration in five different cell lines. The results indicate relatively low cytotoxic effects of NAC in comparison to RLs and UA. In addition, NAC inhibited bacterial growth for all strains, while RLs showed overall lower inhibition and UA inhibited only the growth of Gram-positive bacteria. Even though tested substances did not remove the biofilms, NAC represents a promising tool in biofilm prevention.