Lichen Secondary Metabolites Research Articles

Anti-cancer Evaluation of Depsides Isolated from Indonesian Folious Lichens: Physcia millegrana, Parmelia dilatata and Parmelia aurulenta.

Cancer is a serious health burden on global societies. The discovery and development of new anti-cancer therapies remains a challenging objective. Although it has been shown that lichen secondary metabolites may be potent sources for new anti-cancer agents, the Indonesian- grown folious lichens, Physcia millegrana, Parmelia dilatata and Parmeila aurulenta, have not yet been explored. In this study exhaustive preparative high-performance liquid chromatography was employed to isolate the lichen constituents with spectroscopic and spectrometric protocols identifying nine depsides 9–17, including the new methyl 4-formyl-2,3-dihydroxy-6-methylbenzoate 13. The cytotoxicity of the depsides towards cancer cells was assessed using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The results indicated lowest toxicity of the depsides towards human A549 lung cancer cells. Importantly, the di-depsides (11, 12 and 17) showed greatest toxicity, indicating that these structures are biologically more active than the mono-depsides against the HepG2 liver cancer, A549 lung cancer and HL-60 leukemia cell lines.

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 Aβ1−42 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.

Unraveling the Pharmacological Potential of Lichen Extracts in the Context of Cancer and Inflammation With a Broad Screening Approach.

Lichen-forming fungi are symbiotic organisms that synthesize unique natural products with potential for new drug leads. Here, we explored the pharmacological activity of six lichen extracts (Evernia prunastri, Pseudevernia furfuracea, Umbilicaria pustulata, Umbilicaria crustulosa, Flavoparmelia caperata, Platismatia glauca) in the context of cancer and inflammation using a comprehensive set of 11 functional and biochemical in vitro screening assays. We assayed intracellular Ca2+ levels and cell migration. For cancer, we measured tumor cell proliferation, cell cycle distribution and apoptosis, as well as the angiogenesis-associated proliferation of endothelial cells (ECs). Targeting inflammation, we assayed leukocyte adhesion onto ECs, EC adhesion molecule expression, as well as nitric oxide production and prostaglandin (PG)E2 synthesis in leukocytes. Remarkably, none of the lichen extracts showed any detrimental influence on the viability of ECs. We showed for the first time that extracts of F. caperata induce Ca2+ signaling. Furthermore, extracts from E. prunastri, P. furfuracea, F. caperata, and P. glauca reduced cell migration. Interestingly, F. caperata extracts strongly decreased tumor cell survival. The proliferation of ECs was significantly reduced by E. prunastri, P. furfuracea, and F. caperata extracts. The extracts did not inhibit the activity of inflammatory processes in ECs. However, the pro-inflammatory activation of leukocytes was inhibited by extracts from E. prunastri, P. furfuracea, F. caperata, and P. glauca. After revealing the potential biological activities of lichen extracts by an array of screening tests, a correlation analysis was performed to evaluate particular roles of abundant lichen secondary metabolites, such as atranorin, physodic acid, and protocetraric acid as well as usnic acid in various combinations. Overall, some of the lichen extracts tested in this study exhibit significant pharmacological activity in the context of inflammation and/or cancer, indicating that the group lichen-forming fungi includes promising members for further testing.

Usnic acid improves memory impairment after cerebral ischemia/reperfusion injuries by anti-neuroinflammatory, anti-oxidant, and anti-apoptotic properties.

Objective(s):Cerebral ischemia/reperfusion causes complex pathological mechanisms that lead to brain tissue damage. Usnic acid is a lichen secondary metabolite that has many different biological properties including anti-inflammatory and anti-oxidant activities. Therefore, the objective of the current study was to investigate the neuroprotective effects of usnic acid on apoptotic cell death, neuroinflammation, anti-oxidant enzyme activities, and oxidative stress levels after transient cerebral ischemia/reperfusion. Materials and Methods:Forty-two male Wistar rats were randomly assigned to three groups (sham, ischemia/reperfusion, and ischemia/reperfusion+usnic acid). Ischemia was induced by 20 min occlusion of common carotid arteries. Injection of usnic acid (25 mg/kg, intraperitoneally) and saline was done at the beginning of reperfusion time. Morris water maze was applied to assess spatial memory. The protein expression amount was measured using immunohistochemical and immunofluorescence staining. Spectrophotometric assay was performed to determine the levels of anti-oxidant enzymes. Results:Usnic acid significantly reduced caspase-3, glial fibrillary acidic protein- positive and ionized calcium-binding adaptor molecule 1-positive cells (P<0.001) and enhanced spatial memory disorders (P<0.05) due to brain ischemia. In addition, treatment with usnic acid improves effects in the antioxidant system following cerebral ischemia (P<0.05).Conclusion:Our findings indicate that usnic acid has neuroprotective properties, which possibly is applicable as a promising candidate for cerebral injuries caused by ischemia.

Evaluation of the Cytotoxic Activity of the Usnea barbata (L.) F. H. Wigg Dry Extract.

The secondary metabolites of lichens have proven to be promising sources of anticancer drugs; one of the most important of these is usnic acid, which is a phenolic compound with dibenzofuran structure that is responsible for the numerous biological actions of lichens of genus Usnea. As a result, in this study, we related to this phenolic secondary metabolite. The aim of the present study is the evaluation of the cytotoxic activity of Usnea barbata (L.) F. H. Wigg dry acetone extract (UBE). In advance, the usnic acid content was determined in various extracts of Usnea barbata (L.) F. H. Wigg: the liquid extracts were found in water, ethanol, acetone, and the dry acetone extract; the highest usnic acid quantity was found in the dry acetone extract. First, the cytotoxic action of UBE was assessed using Brine Shrimp Lethality (BSL) test; a significant lethal effect was obtained after 24 h of treatment at high used concentrations of UBE, and it was quantified by the high mortality rate of the Artemia salina (L.) larvae. Secondly, in vitro cytotoxicity of UBE was evaluated on human tongue squamous cells carcinoma, using CAL 27 (ATCC® CRL-2095™) cell line. The most intense cytotoxic effect of UBE on CAL 27 cells was registered after 24 h; this response is directly proportional with the tested UBE concentrations. The obtained results have been reported regarding usnic acid content of UBE, and the data show that CAL 27 cells death was induced by apoptosis and high oxidative stress.

Usnic acid as calcium ionophore and mast cells stimulator

Usnic acid (UA), a secondary lichen metabolite, has long been popular as one of natural fat-burning dietary supplements. Similar to 2,4-dinitrophenol, the weight-loss effect of UA is assumed to be associated with its protonophoric uncoupling activity. Recently, we have shown that the ability of UA to shuttle protons across both mitochondrial and artificial membranes is strongly modulated by the presence of calcium ions in the medium. Here, by using fluorescent probes, we studied the calcium-transporting capacity of usnic acid in a variety of membrane systems comprising liposomes, isolated rat liver mitochondria, erythrocytes and rat basophilic leukemia cell culture (RBL-2H3). At concentrations of tens of micromoles, UA appeared to be able to carry calcium ions across membranes in all the systems studied. Similar to the calcium ionophore A23187, UA caused degranulation of RBL-2H3 cells. Therefore, UA, being a protonophoric uncoupler of oxidative phosphorylation, at higher concentrations manifests itself as a calcium ionophore, which could be relevant to its overdose toxicity in humans and also its phytotoxicity.

Theoretical Study on the Antioxidant Activity of Natural Depsidones.

Depsidones are secondary metabolites in lichens with a range of potential health benefits. Among others, these compounds are believed to exhibit high hydroxyl radical and superoxide scavenging abilities, warranting a detailed investigation of their antioxidant properties. In this study, the radical scavenging activity of natural depsidones from Ramalina lichenized fungi was investigated in silico. Calculations of the thermodynamic parameters suggested that the main radical scavenging pathway follows the formal hydrogen transfer (FHT) mechanism; however, unexpectedly low rate constants were found in the CH3OO• scavenging reaction. Establishing that the depsidones are mostly ionized in an aqueous environment suggested that the single-electron transfer (SET) mechanism should not be ruled out. Consistently, depsidones were revealed to be excellent HO• and O2•– scavengers in aqueous solutions (k = 4.60 × 105 – 8.60 × 109 M–1 s–1 and k = 2.60 × 108 – 8.30 × 109 M–1 s–1, respectively) following the sequential proton loss electron transfer (SPLET) mechanism. These results suggest that natural fungal depsidones are potent hydroxyl and superoxide radical scavengers in aqueous solutions.

The amount of lichen secondary metabolites in Cladonia foliacea (Cladoniaceae, lichenised Ascomycota)

The terricolous species Cladonia foliacea (Cladoniaceae, lichenised Ascomycota) widely distributed in open, dry lowland steppe and rocky mountain grassland vegetation in Europe was chosen as a potential test organism for ecological experiments, since their thalli are producing cortical solar radiation-protective and UV screening pigment dibenzofuran usnic acid and medullary secondary substance depsidone fumarprotocetraric acid. Significant seasonal differences were found in the amounts of lichen secondary metabolites analysed by HPTLC and HPLC-PDA between summer and winter collected thalli in sandy grassland area in Hungary. The concentrations of usnic acid varied between 7.34 and 15.52 mg/g in summer collected samples and 13.90 and 21.61 mg/g in winter collected ones. A comparable amount (11.61±0.29 mg/g) was measured in pulverised samples. The concentrations of fumarprotocetraric acid varied between 0.60 and 3.01 mg/g in summer collected samples and 2.26 and 5.81 mg/g in winter collected thalli. A comparable amount (2.45±0.21 mg/g) was found in pulverised samples. The range of concentration values is comparable with data known from lichens. A higher amount of usnic acid is produced in winter probably to ensure sufficient protection also for summer. The fumarprotocetraric acid content of the medulla might contribute to the solar irradiation reflecting role of the pale lower surface lobes turning upwards in dry condition.

Lichen Allelopathy: An Agricultural Prospect

Allelopathy is a common biological miracle by which one organism produces biochemicals that affect the growth, existence, development, and reproduction of other organisms. These biochemicals are known as allelochemicals and have advantageous, as well as, harmful effects on target organisms. Lichens produce over a thousand different extracellular biochemical terms as secondary metabolites. The lichen secondary metabolites may show either positive effects, such as, in weed control, crop protection, or crop re-establishment or negative effects, e.g., autotoxicity, biological invasion, competition, deterioration, and eutrophic soil sickness. However, several lichen secondary metabolites can potentially be used as growth regulators, insecticidal, and antimicrobial since dated back. Here, we discuss the application of lichen allelopathy in various agricultural prospects in the near future.

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.

Two new Micarea species (Pilocarpaceae) from Western Europe

Two new Micarea species, M. minuta and M. pseudotsugae, are described from the Netherlands based on morphological, chemical and molecular data. Micarea minuta belongs to the M. denigrata group and can be distinguished from other similar species of this group by its small apothecia, Sedifolia-grey pigment in the epihymenium, mostly 1-septate and small ascospores, 40–80 μm wide mesopycnidia, and the lack of secondary lichen metabolites detectable by thin-layer chromatography. Micarea pseudotsugae is a member of the M. prasina group and is characterized by an areolate, granular to subsquamulose thallus, the presence of methoxymicareic acid, the lack of Sedifolia-grey pigment, the presence of crystals (visible in polarized light) in the apothecia only, and one type of conidia (mesoconidia). The phylogenetic position of the newly described species was studied based on mtSSU rDNA marker analysis; M. minuta was found to be closely related to M. denigrata, M. nitschkeana and M. subnigrata, while M. pseudotsugae was found to be closely related to M. byssacea and M. laeta. Notes on secondary chemistry, ecology, distribution and phylogeny are given.

Morphology and secondary chemistry in species recognition of Parmelia omphalodes group - evidence from molecular data with notes on the ecological niche modelling and genetic variability of photobionts.

To evaluate the importance of morphological and chemical characters used in the recognition of species within the Parmelia omphalodes group, we performed phylogenetic, morphological and chemical analyses of 335 specimens, of which 34 were used for molecular analyses. Phylogenetic analyses, based on ITS rDNA sequences, show that P. pinnatifida is distinct from P. omphalodes and the most important difference between those species is the development of pseudocyphellae. In P. pinnatifida, they are mostly marginal and form white rims along lobes margins, but laminal pseudocyphellae can develop in older parts of thalli and are predominantly connected with marginal pseudocyphellae. In contrast, in P. omphalodes laminal pseudocyphellae are common and are predominantly not connected to marginal pseudocyphellae. Chemical composition of secondary lichen metabolites in both analysed species is identical and therefore this feature is not diagnostic in species recognition. Few samples of P. discordans, species morphologically similar to P. omphalodes and P. pinnatifida, were also included in the analyses and they are nested within the clade of P. omphalodes, despite the different chemistry (protocetraric acid present versus salazinic acid in P. omphalodes). All taxa of the P. omphalodes group occupy similar niches, but their potential distributions are wider than those currently known. The absence of specimens in some localities may be limited by the photobiont availability. Parmelia omphalodes and P. pinnatifida are moderately selective in photobiont choice as they form associations with at least two or three lineages of Trebouxia clade S. Parmelia pinnatifida, as well as P. discordans are associated with Trebouxia OTU S02 which seems to have a broad ecological amplitude. Other lineages of Trebouxia seem to be rarer, especially Trebouxia sp. OTU S04, which is sometimes present in P. pinnatifida. This study indicates the importance of extensive research including morphology, chemistry and analysis of molecular markers of both bionts in taxonomical studies of lichens.

Lichen Secondary Metabolite Physciosporin Decreases the Stemness Potential of Colorectal Cancer Cells.

Secondary metabolites of lichens are promising bioresources for candidate anti-cancer drugs. Accordingly, several approaches have been proposed for screening these molecules for novel anti-cancer lead compounds. In this study, we found that a non-toxic concentration of physciosporin, a compound isolated from Pseudocyphellaria granulata, significantly decreased colony formation on soft agar and spheroid formation by CSC221 cancer stem-like cells. Physciosporin also decreased spheroid formation in other colorectal cancer cell lines, including DLD1, Caco2, and HT29. Aldehyde dehydrogenase-1 (ALDH1), the most important cancer stem marker, was sharply downregulated at both the protein and mRNA level following treatment with physciosporin. Physciosporin also decreased the transcriptional activity of the glioma-associated oncogene homolog zinc finger protein (Gli), as well as the Hes1 and CSL promoters, in reporter assays. Moreover, the drug significantly suppressed spheroid formation in CSC221 cells overexpressing Gli1/2 or ΔEN1 (an S2-cleaved but membrane-tethered form of human Notch1) but did not suppress spheroid formation in cells overexpressing both Gli1/2 and ∆EN1, suggesting that physciosporin suppresses colon cancer cell stemness through the Sonic hedgehog and Notch signaling pathways. Together, these results demonstrate for the first time that physciosporin is a potent inhibitor of colorectal cancer cell stemness.

Effect of Cu on the fluorescence of the Cu-hyperaccumulator lichen Stereocaulon sorediiferum.

Stereocaulon sorediiferum is expected to be a Cu-hyperaccumulator lichen and has fluorescent substances. To clarify the relationship between the fluorescence (FL) of the lichen and its Cu concentration, we collected S. sorediiferum samples at Cu-contaminated and uncontaminated sites in Japan, determined the concentration of Cu, K, Mg, Al, Ca, Mn, Fe, Zn, chlorophyll a,b, and total carotenoids in them, analyzed lichen secondary metabolites and fluorescent substances extracted from them, and measured the FL of them and their extracts. We found that the FL intensity of S. sorediiferum samples is significantly negatively correlated with their Cu concentration. The application of its FL for Cu monitoring may allow a new nondestructive quantitative method for assessing Cu contamination. The spectroscopic and chromatographic analysis shows that the fluorescent substances negatively correlated with Cu concentration are not major lichen secondary metabolites (lobaric acid and atranorin) and remain after immersion in acetone. The correlation analysis and the comparison with the causal relationship between Cu concentration and the chlorophyll a/b ratio suggest that the reason for the decrease in FL intensity with increasing Cu concentration is a structural change of the fluorescent substances by accumulated Cu. These findings lead to a better understanding of the relationship between the FL of S. sorediiferum and its Cu concentration and provide new insights into fluorescent lichen substances.

Epanorin, a lichen secondary metabolite, inhibits proliferation of MCF-7 breast cancer cells

BackgroundEpanorin (EP) is a secondary metabolite of the Acarospora lichenic species. EP has been found in lichenic extracts with antimicrobial activity, and UV-absorption properties have been described for closely related molecules; however, its antiproliferative activity in cancer cells has not yet been explored. It has been hypothesized that EP inhibits cancer cell growth. MCF-7 breast cancer cells, normal fibroblasts, and the non-transformed HEK-293 cell line were exposed to increasing concentrations of EP, and proliferation was assessed by the sulforhodamine-B assay.ResultsMCF-7 cells exposed to EP were examined for cell cycle progression using flow cytometry, and DNA fragmentation was examined using the TUNEL assay. In addition, EP’s mutagenic activity was assessed using the Salmonella typhimurium reverse mutation assay. The data showed that EP inhibits proliferation of MCF-7 cells, and it induces cell cycle arrest in G0/G1 through a DNA fragmentation-independent mechanism. Furthermore, EP’s lack of overt cytotoxicity in the normal cell line HEK-293 and human fibroblasts in cell culture is supported by the absence of mutagenic activity of EP.ConclusionEP emerges as a suitable molecule for further studies as a potential antineoplastic agent.

A facile in vivo procedure to analyze metabolic pathways in intact lichens.

Lichen secondary metabolites show important biological activities as well as pharmaceutical and chemotaxonomic potential. In order to utilize such substances of interest, detailed knowledge of their biosynthetic pathways is essential. 13 CO2 -pulse/chase experiments using intact thalli of the lichen Usnea dasopoga resulted in multiple 13 C-labeled isotopologs in amino acids, but not in the dibenzofuran derivative usnic acid - one of the best-studied lichen metabolites, with considerable and renewed interest for pharmaceutical and lifestyle applications. Spraying an aqueous solution of [U-13 C6 ]glucose onto the thalli of U.dasopoga afforded a specific mixture of multiple 13 C-labeled isotopologs in usnic acid. One- and two-dimensional NMR analysis of the crude lichen extract corroborated the polyketide biosynthetic pathway via methylphloroacetophenone but not via phloroacetophenone. With usnic acid as an exemplar, we provide proof-of-principle experiments that can be used in general to study metabolic pathways and fluxes in intact lichens.

Insights into physiological responses of mosses Physcomitrella patens and Pohlia drummondii to lichen secondary metabolites.

It is widely accepted that allelopathy among mosses and lichens do exist due to its similar ecological needs, though it is rarely documented. With an aim to test whether there is an effect of allelochemicals to mosses, we grow axenically two moss species (namely Physcomitrella patens and Pohlia drummondii) in controlled conditions and use them to test the effect of lichen Pseudevernia furfuracea acetone extracts containing active compounds: atranorin, chloratranorin, and physodic acid. The photosynthesis value and the biochemical parameters were measured to detect changes in moss organisms upon application of different concentration of lichen extract. The results obtained clearly showed that both moss species reacted to allelochemicals applied in test but to different extent. This suggests that tested moss species have various patterns on reaction to allelochemicals, and that the process of allelopathy is rather a recently coevolving one, than pre-defined. The lichen secondary metabolites are allelochemicals effective also to moss species that are not selected lichen cohabitants.

The Effects of Edaphic and Climatic Factors on Secondary Lichen Chemistry: A Case Study Using Saxicolous Lichens

Diversity of secondary lichen metabolites and their relationship to substrate and environmental parameters were studied in saxicolous lichens in the Middle and South Urals of Russia. Atranorin, usnic acid, gyrophoric acid, zeorin, norstictic acid, antraquinones and stictic acid were found in 73, 42, 41, 37, 36, 35 and 32 species, respectively, of 543 taxa collected. One hundred and ninety six species (i.e., 36% of total species documented) contained no secondary metabolites. Spectra of secondary metabolites of crustose lichens varied on different rock types, while in fruticose and foliose groups only those species without lichen acids were dependent on the substrate type. In Canonical Correspondence Analysis, secondary lichen metabolites were subdivided into groups depending on the concentration of Ca and metals in the substrate. Gyrophoric, lobaric, psoromic, rhizocarpic and stictic acids were common in crustose lichens in metal-poor habitats; species with antraquinones and lichens without any secondary metabolites were most abundant on limestone (alkalic and metal-poor), while other common lichen metabolites had no to minimal dependence on the chemistry of the substrate. The two additional abiotic factors affecting the composition of secondary metabolites were the maximum temperature of the warmest month and elevation. Our results suggest a range of possible relationships exist among lichen acids, rocks and climatic parameters. Furthermore, the same metabolite may affect both accumulation of metals and stress tolerance under unfavorable conditions.

Inhibitory Effects of Usnic and Carnosic Acid on Some Metabolic Enzymes: An In vitro Study.

Natural products are produced via primary and secondary metabolism in different organisms. The compounds obtained via secondary metabolism are not essential for the survival of the organism, but they can have a different value for humans. The objective of this study was to examine inhibitory effects of Usnic Acid (UA), a well-known lichen secondary metabolite, and Carnosic Acid (CA), the primary antioxidant compound of Rosmarinus officinalis L., on purified Human Paraoxonase, (PON1), Glutathione Reductase (GR) and Glutathione S-Transferase (GST). These enzymes have antioxidant properties and a protective effect on the oxidation of free radicals. Hence, deficiencies of such enzymes inside cells can result in a buildup of toxic substances and cause some metabolic disorders. UA and CA were tested in various concentrations against human GST, PON1, and GR activity in vitro and they reduced human GST, PON1, and GR activity. UA Ki constants were calculated as 0.012±0.0019, 0.107±0.06 and 0.21±0.1 mM for GST, PON1, and GR enzymes. CA Ki constants were determined as 0.028±0.009, 0.094±0.03 and 0.79±0.33 mM, for GST, PON1, and GR enzymes. UA and CA showed competitive inhibition for GR and GST enzymes, while they exhibited non-competitive inhibition for PON1. These findings indicate that UA and CA could be useful in drug development studies.

Antiproliferative Properties of Lichens Parmelia vagans and Parmelia sulcata

The purpose of this project was to analyze antiproliferative properties of the secondary metabolites extracted from lichens Parmelia vagans and Parmelia sulcata collected from the semi‐deserts of Russia. An isolation and characterization of novel natural compounds that can selectively slow down or stop proliferation of cancer cells can enhance development of anticancer therapeutics.Various lichen extracts were prepared using either water or organic solvents. We assessed the antiproliferative activity against several human cancer cell lines; human hepatocellular carcinoma (Hep G2), human non‐small cell lung cancer (NCI‐H1299), and human mammary gland ductal carcinoma (T‐47D). The same number of cells of different cell lines were plated into a 96‐well plate and allowed to adhere overnight. Next day, different dilutions of the lichen extracts were added to the adhered cells and the plate was placed in CO2 incubator for 6–72 hours. By the end of the incubation time a picture of each well was taken to assess cell confluency and the cells were subjected to Resazurin assay to analyze the effect of the lichen extracts on cell growth and proliferation. After Resazurin assay, the cells in each well were treated with trypsin, suspended in growth medium and counted using Bio‐Rad cell counter to evaluate a percent of live cells.Our experimental data from cell viability assay and live cells count indicate that bottled water and ethyl acetate extracts of P. vagans and P. sulcata significantly suppress (30%–60%) the growth of human hepatocellular carcinoma and human non‐small cell lung carcinoma. We also found that cancer cells treated by the lichen extracts results in their morphological changes that resemble an activation of apoptosis.Our findings indicate that these lichen species produce secondary metabolites that slow cancer cells growth and proliferation. Future experiments will be focused on isolation and characterization of the compounds from P. vagans and P. sulcata crude extracts that are responsible for the inhibition of cancer cells growth. Another important direction of the future research is to identify the cellular target(s) of the antiproliferative compound(s) and its molecular mechanism of action. I summary, the lichen's secondary metabolites may hold a vast medicinal potential and could be a viable source of a novel of anticancer drugs.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.