Barbatic Acid Research Articles

Structure analysis of depsides, dibenzofuran and sugar derivatives from Cladia aggregata (SW) Nyl using ultra-performance liquid chromatography-tandem mass spectrometry.

Cladia aggregate (SW) Nyl is a lichenized fungi in the family Cladoniaceae producing characteristic secondary metabolites of interest. There are only limited chemical studies relating to the genus Cladia. A chemical study of the lichen C. aggregata was conducted and their chemical constituents were elucidated by ultra-performance liquid chromatography-electrospray ionization/triple-quadrupole tandem-mass spectrometry analysis. It is the first time report of structure analysis of its metabolite by liquid chromatography-mass spectrometry/mass spectrometry. The molecular masses for 20 compounds were detected from different fractions. Seven compounds were elucidated with mass spectrometry/mass spectrometry fragmentation pattern analysis. Barbatic acid (12) was identified as the major compound being common to all fractions. The identified compounds belong to depsides (2, 11, 12 and 20), dibenzofurans (13, 18) and sugar derivatives (1) which are usually distributed in lichens.

Alpha-glucosidase inhibitory compounds from Vietnamese lichen Usnea baileyi: in vitro and in silico aspects.

Using a bio-guided isolation on the Vietnamese lichen Usnea baileyi based on alpha-glucosidase inhibition, eleven compounds were isolated and structurally elucidated, namely, protocetraric acid (1), 8'-methylstictic acid (2), stictic acid (3), 4,6-diformyl-8-hydroxy-3-methoxy-1,9-dimethyl-11-oxo-11H-dibenzo[b,e][1,4]dioxepine-7-carboxylic acid (4), vicanicin (5), norstictic acid (6), diffractaic acid (7), barbatic acid (8), atranol (9), 5-chlorohaematommic acid (10), and eumitrin A1 (11). Their chemical structures were identified by extensive 1D and 2D NMR analysis and high-resolution mass spectroscopy and compared with those reported in literature. Protocetraric acid (1) and norstictic acid (6) were selected for further modification to derive new compounds, namely, 1a-1e and 6a. Both isolated and synthesized compounds were assessed for their alpha-glucosidase inhibitory activity. Compounds 1-6, 1a-1e, 6a, and 11 showed significant alpha-glucosidase inhibition with IC50 values ranging from 10.4 to 130 μM. Molecular docking was applied to the most active compounds 1-3, 6, 1a-1e, and 6a to clarify the inhibitory mechanism. Compound 1e was determined to be a mixed inhibitor through a kinetic study.

Usnea jezoformosana Y. Ohmura & P. Clerc, sp. nov. (Parmeliaceae, lichenized Ascomycota) from East Asia


 
 
 Usnea jezoformosana is described as a new species from East Asia. The morphology of this taxon is very similar to Usnea fragilescens but differs by the presence of granular soredia (instead of farinose soredia). It differs furthermore chemically by the presence of protocetraric acid (major) and barbatic acid (major to trace). The monophyly and independence of the newly described species from U. fragilescens and related taxa were inferred by a molecular phylogenetic tree based on ITS rDNA sequences. Usnea jezoformosana was collected in subboreal forests of Hokkaido (Japan) and in Taiwan where it grew on tree barks, building wood or cliffs.
 
 

Metabolites from the Andean paramo lichen Cladonia cf. didyma and their effect as photoprotective and antioxidant agents

5α,8α-peroxyergosteryl divaricatinate (1) is isolated for the first time from acetone extract of the thallus of Cladonia cf. didyma together with condidymic (2), isodidymic (3) and barbatic (4) acids. Their UVB/UVA photoprotective and antioxidant activities were determined along with their cyto- and DNA-protecting actions against OH• damage. Compound 1 showed high UVA, cyto- (%cell viability ca. 82 at 15 µM vs 71 for OH•) and DNA (%DNA-integrity ca. 74 at 100 µM vs 22 for OH•) protecting properties. Compounds 2 and 3 exhibited high UVB (SPF ca. 40) and antioxidant activities (free radical scavenging potency EC50 = 0.6694 and 1.700 mol compound/mol DPPH•; ferric reducing power 0.392 and 0.546, at 500 ppm and inhibited lipid peroxidation); protecting cells (%cell viability ca. 76 at 15 µM) and DNA (%DNA-integrity ca. 57 at 100 µM). Compounds 1 to 3 fulfilled some physicochemical properties to act topically on the skin.

In vitro anthelminthic activity and ultrastructural analysis of barbatic acid against schistosomulae and juvenile worms of Schistosoma mansoni.

Schistosomiasis affects about 260 million people worldwide and the search for new schistosomicidal compounds is urgent. In this study we evaluated the in vitro effect of barbatic acidagainst schistosomulae and young worms of Schistosoma mansoni. The barbatic acid was evaluated through the bioassay of motility and mortality, cellular viability and ultrastructural analysis of juvenile stages through Scanning Electron Microscopy. Barbatic acid showed a schistosomicidal effect against schistosomulae and young worms of S. mansoni after 3 h of exposure. At the end of 24 h, barbatic acid showed 100%, 89.5%, 52% and 28.5% of lethality for schistosomulae at the concentrations of 200, 100, 50 and 25 µM, respectively. For young worms, barbatic acid showed 100% and 31.7% of lethality at the concentrations of 200 and 100 µM, respectively. Motility changes were observed at all sublethal concentrations. There was a significant reduction in the viability of young worms after exposure to barbatic acid at 50, 100 and 200 µM. Extensive damage to the schistosomulae and young worm's tegument, was observed from 50 μM. This report provides data showing the schistosomicidal effect of barbatic acid on schistosomulae and young worms of S. mansoni, causing death, motility changes and ultrastructural damage to worms.

Metabolism and toxicity of usnic acid and barbatic acid based on microsomes, S9 fraction, and 3T3 fibroblasts in vitro combined with a UPLC-Q-TOF-MS method.

Introduction: Usnic acid (UA) and barbatic acid (BA), two typical dibenzofurans and depsides in lichen, have a wide range of pharmacological activities and hepatotoxicity concerns. This study aimed to clarify the metabolic pathway of UA and BA and illuminate the relationship between metabolism and toxicity. Methods: An UPLC-Q-TOF-MS method was developed for metabolite identification of UA and BA in human liver microsomes (HLMs), rat liver microsomes (RLMs), and S9 fraction (RS9). The key metabolic enzymes responsible for UA and BA were identified by enzyme inhibitors combined with recombinant human cytochrome P450 (CYP450) enzymes. The cytotoxicity and metabolic toxicity mechanism of UA and BA were determined by the combination model of human primary hepatocytes and mouse 3T3 fibroblasts. Results: The hydroxylation, methylation, and glucuronidation reactions were involved in the metabolic profiles of UA and BA in RLMs, HLMs, and RS9. CYP2C9, CYP3A4, CYP2C8, and UGT1A1 are key metabolic enzymes responsible for metabolites of UA and CYP2C8, CYP2C9, CYP2C19, CYP1A1, UGT1A1, UGT1A3, UGT1A7, UGT1A8, UGT1A9, and UGT1A10 for metabolites of BA. UA and BA did not display evident cytotoxicity in human primary hepatocytes at concentrations of 0.01-25 and 0.01-100 µM, respectively, but showed potential cytotoxicity to mouse 3T3 fibroblasts with 50% inhibitory concentration values of 7.40 and 60.2 µM. Discussion: In conclusion, the attenuated cytotoxicity of BA is associated with metabolism, and UGTs may be the key metabolic detoxification enzymes. The cytotoxicity of UA may be associated with chronic toxicity. The present results provide important insights into the understanding of the biotransformation behavior and metabolic detoxification of UA and BA.

Hydroxide-Mediated SNAr Rearrangement for Synthesis of Novel Depside Derivatives Containing Diaryl Ether Skeleton as Antitumor Agents.

A simple and efficient hydroxide-mediated SNAr rearrangement was reported to synthesize new depside derivatives containing the diaryl ether skeleton from the natural product barbatic acid. The prepared compounds were determined using 1H NMR, 13C NMR, HRMS, and X-ray crystallographic analysis and were also screened in vitro for cytotoxicity against three cancer cell lines and one normal cell line. The evaluation results showed that compound 3b possessed the best antiproliferative activity against liver cancer HepG2 cell line and low toxicity, which made it worth further study.

Semisynthesis, Biological Evaluation and Molecular Docking Studies of Barbatic Acid Derivatives as Novel Diuretic Candidates.

Barbatic acid, a compound isolated from lichen, has demonstrated a variety of biological activities. In this study, a series of esters based on barbatic acid (6a-q') were designed, synthesized, and evaluated for their diuretic and litholytic activity at a concentration of 100 μmol/L in vitro. All target compounds were characterized using 1H NMR, 13C NMR, and HRMS, and the spatial structure of compound 6w was confirmed using X-ray crystallography. The biological results showed that some derivatives, including 6c, 6b', and 6f', exhibited potent diuretic activity, and 6j and 6m displayed promising litholytic activity. Molecular docking studies further suggested that 6b' had an optimal binding affinity to WNK1 kinases related to diuresis, while 6j could bind to the bicarbonate transporter CaSR through a variety of forces. These findings indicate that some barbatic acid derivatives could be further developed into novel diuretic agents.

Inhibition of Autophagy Increases Cell Death in HeLa Cells through Usnic Acid Isolated from Lichens.

The Western Ghats, India, is a hotspot for lichen diversity. However, the pharmacological importance of lichen-associated metabolites remains untapped. This study aimed to evaluate the cytotoxic potential of lichens of this region. For this, sixteen macrolichens were collected and identified from two locations in the Western Ghats. The acetone extract of Usnea cornuta (UC2A) showed significant cytotoxicity towards multiple human cancer cell lines. Interestingly, co-treatment with chloroquine (CQ), an autophagy inhibitor, increased the cytotoxic potential of the UC2A extract. A gas chromatography mass spectrometry (GCMS) study revealed usnic acid (UA), atraric acid and barbatic acid as the dominant cytotoxic compounds in the UC2A extract. Further, UA was purified and identified from the UC2A extract and evaluated for cytotoxicity in HeLa cells. The monodansyl cadaverine and mitotracker red double staining revealed the autophagy-inducing activities of UA, and the inhibition of autophagy was confirmed via CQ treatment. Autophagy inhibition increased the cytotoxicity of UA by 12-16% in a concentration-dependent manner. It also increased lipid peroxidation, ROS levels and mitochondrial depolarization and decreased glutathione availability. A decrease in zeta potential and a 40% increase in caspase 3/7 activity were also noted after CQ treatment of UA-treated cells. Thus, cytotoxicity of UA can be increased by inhibiting autophagy.

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.

Lepra yunlingensis and L. taiwanensis spp. nov. from China

Two new species of Lepra are described from China: L. yunlingensis is characterized by its 2-spored asci and the presence of norstictic and cryptostictic acids; L. taiwanensis is characterized by its 1-spored asci and the presence of barbatic acid.

Synthesis of barbacic acid

A new approach for the synthesis of the active barbatic acid has been achieved in eight steps with 22.3% total yield by using commercially available methyl atratate as starting material. This synthesis provides access to multi-gram quantities of barbatic acid with good purity for reference supplies and further analytical and toxicology investigations.

Naming and describing the diversity in the Usnea cornuta aggregate (lichenized Ascomycota, Parmeliaceae) focusing on Brazilian specimens

This study is a reassessment of the Usnea cornuta aggregate diversity mainly in Brazil. Based on previous multi-locus species delimitation analyses using the multispecies coalescent model (MSC), we carried out a posteriori morphological and anatomical studies. The following corticolous new species are described: Usnea arianae with norstictic or fatty or lobaric acids, convex and efflorescent soralia and a lax medulla; U. flabelliformis with protocetraric acid, fan-shaped main branches and a high medulla/cortex ratio; U. rubropallens with protocetraric acid and a faint orange cortical/subcortical pigment; U. stipitata with constictic acid, stipitate soralia and a high medulla/cortex ratio; and U. tenuicorticata with protocetraric acid, a thin cortex and a high medulla/cortex ratio. The newly described species were found to occur so far only in the Americas, except U. arianae which shows an amphi-atlantic distribution in Europe and on the American continent. Seven species already described belonging to the U. cornuta aggr. in Brazil are further treated here: Usnea boomiana with caperatic acid and large, concave soralia, new to South America; U. brasiliensis with protocetraric acid, minute and irregular soralia; U. cornuta with mainly salazinic acid and minute soralia fusing into consoralia; U. macaronesica (syn. nov.: U. subglabrata) with barbatic acid, large excavate soralia and a lax medulla; Usnea subpectinata, a so far european species resurrected from the U. cornuta synonymy, with stictic acid and numerous isidiofibrils, new to South America; and U. trachyclada with thamnolic acid and K+ bright yellow stipitate soralia. Full descriptions with morphological, anatomical and chemical features, geographical distributions, and illustrations are provided for each species along with an identification key.

Parmosidone K, a new meta-depsidone from the lichen Parmotrema tsavoense

Further phytochemical investigation on P. tsavoense led to one new meta-depsidone, parmosidone K together with one known compound, barbatic acid. Their structures were determined by 1D and 2D NMR analysis, high resolution mass spectroscopy, and comparison their NMR data with those reported in literatures. Parmosidone K was evaluated for α-glucosidase inhibition and revealed the powerful activity with IC50 value of 3.12 µM.

Characterization of chemical components with diuretic potential from Pyrrosia petiolosa

Three compounds with diuretic potential were identified from the 95% ethanol extract of Pyrrosia petiolosa (Christ) Ching. Among them, one was a new benzanilide named petiolide A (1), and the other two were phenolic derivatives barbatic acid (2) and kaempferol (3). Their structures were elucidated based on extensive spectral analyses and comparison with the literature data. The docking experiments of all compounds into the active site of the With-No-Lysine kinase 1 (WNK1) domain demonstrated that kaempferol (3) was the most effective component with diuretic potential for its comparative diuretic effect to that of an orally bioavailable WNK inhibitor WNK463 (docking score −10.99 vs −11.09).

Barbatic acid from Cladia aggregata (lichen): Cytotoxicity and in vitro schistosomicidal evaluation and ultrastructural analysis against adult worms of Schistosoma mansoni

Schistosomiasis is one of the most significant neglected tropical diseases, affecting around 260 million people worldwide, and Praziquantel is currently the only available drug for the treatment of infected persons. Thus, the search for new schistosomicidal compounds is urgent. The objective of this study was to investigate of the schistosomicidal effect of barbatic acid, a lichen metabolite, on adult worms of Schistosoma mansoni. The in vitro schistosomicidal effect was evaluated through the assessment of motility and mortality, cellular viability of the worms and ultrastructural analysis through scanning electron microscopy. To evaluate the cytotoxicity of barbatic acid, a cell viability assay was performed with human peripheral blood mononuclear cells. Barbatic acid showed a schistosomicidal effect after 3 h of exposure. At the end of 24 h the concentrations of 50–200 μM presented lethality on the worms. Motility changes were observed at sublethal concentrations. The IC50 obtained by the cell viability assay for S. mansoni was 99.43 μM. Extensive damage to the worm's tegument was observed from 25 μM. No cytotoxicity was observed on human peripheral blood mononuclear cells. This report provides data showing the schistosomicidal effect of barbatic acid on S. mansoni, causing death, motility changes and ultrastructural damage to worms. In addition, barbatic acid was shown to be non-toxic to human peripheral blood mononuclear cells at concentrations that are effective against S. mansoni.

Phenolic compounds from Usnea baileyi (Stirt.) Zahlbr growing in Lam Dong province

This study entails a continuation of the phytochemical study regarding the lichen Usnea baileyi collected in Lam Dong province. Eight compounds, 8'-O-methylprotocetraric acid (1), protocetraric acid (2), virensic acid (3), subvirensic acid (4), barbatic acid (5), diffractaic acid (6), 4-O-demethylbabartic acid (7), and atranorin (8), were isolated using various chromatographic methods. Their chemical structures were elucidated through spectroscopic analysis as well as through a comparison of their data with that in the literature.

A new species of Cryptothecia (Arthoniales, Arthoniaceae) from the Western Ghats biodiversity hotspot, India

Cryptothecia panchganiensis, a new lichen species is described from the Western Ghats, India. It is characterized by verrucose heteromerous thallus, distinctly raised whitish ascigerous areas, small muriform ascospores and produces barbatic acid and zeorin.

Nuevos registros de líquenes terrícolas en los páramos ecuatorianos

Se presentan 49 nuevas citas para los páramos de El Cajas y El Ángel, en las provincias de Azuay y Carchi, respectivamente. Se encontraron los nuevos registros para Ecuador Cladonia scabriuscula, Cora accipiter, C. caucensis, C. dalehana, C. hafecesweorthensis, C. inversa, Dictyonema caespitosum y Diploschistes hypoleucus. Para Ecuador continental se reporta Cladonia corymbosula, y el nuevo quimiotipo Cladonia squamosa QIII, con ácidos estíctico y barbático. Se documentan 39 nuevos registros para las provincias de Azuay y Carchi.

Comprehensive Analysis of Secondary Metabolites in Usnea longissima (Lichenized Ascomycetes, Parmeliaceae) Using UPLC-ESI-QTOF-MS/MS and Pro-Apoptotic Activity of Barbatic Acid

Considering the importance of ultra-performance liquid chromatography-electrospray ionization-quadrupole time of flight-tandem mass spectrometry (UPLC-ESI-QTOF-MS/MS) hyphenated techniques for analysis of secondary metabolites from crude extracts, the present study was aimed at identification of secondary metabolites in acetone extract of the lichen Usnea longissima. From our study, 19 compounds were tentatively identified through comparison of exact molecular masses from their MS/MS spectra, mass fragmentation studies and comparison with literature data. In addition, potent cytotoxic activity of U. longissima extract prompted us to isolate four compounds, 18R-hydroxy-dihydroalloprotolichesterinic acid (19), neuropogolic acid (20), barbatic acid (21), and usnic acid (22) from this extract which were adequately identified through mass spectrometry and NMR spectroscopy. All four compounds displayed cytotoxic activity. Barbatic acid (21) manifested doxorubicin equivalent activity against A549 lung cancer cell line with IC50 of 1.78 µM and strong G0/G1 accumulation of cells. Poly ADP-ribose polymerase (PARP) cleavage confirmed that it induced cytotoxic activity via apoptosis. Finally, our work has discerned the depside, barbatic acid (21) from crude extract as a candidate anti-cancer molecule, which induces cell death by stepping up apoptosis.