Genome-based proteomic analysis of Lignosus rhinocerotis (Cooke) Ryvarden sclerotium

Tiger Milk Mushroom: A Comprehensive Review of Nutritional Composition, Phytochemicals, Health Benefits, and Scientific Advancements with Emphasis on Chemometrics and Multi-Omics

This article presents a comprehensive overview of tiger milk mushroom (TMM), covering its nutritional composition, phytochemicals, health benefits, and related scientific advancements. It describes various potential positive health benefits of TMM, including anticancer, anti-inflammatory, respiratory function enhancement, antioxidant, anti-aging, neuroprotective, photoprotective, antidiabetic, wound-healing, and anti-HIV, among others. This article also underlines the importance of further research into the phytochemicals present in TMM for additional discoveries. It underscores the importance of further research into phytochemicals content of TMM for additional discoveries and emphasizes the potential applications of TMM in nutrition, health, and well-being. Sophisticated techniques, such as chemometrics and multi-omics technologies revealed latest scientific advancements of TMM. This comprehensive overview provides a foundation for future research and development in harnessing TMM's potential for human health.

Comparative analysis of medicinal attributes between Lignosus cameronensis and its sister species

Lignosus cameronensis holds promise for exploration given its morphological likeness to the renowned Lignosus rhinocerus, or tiger milk mushroom. Investigating its potential medicinal and industrial applications addresses a significant knowledge gap in this field. A comparative analysis with other Lignosus species and cultivars provides insights into biopharmacological potential. L. cameronensis cold water extract (LC-CWE) displayed moderate antioxidant activity, demonstrating promising Trolox equivalent antioxidant -capacity. Variable cytotoxicity was observed in different cell lines, with an IC50 of 215 μg/ml against breast cancer cells (MCF-7) cells. LC-CWE exhibited anti-inflammatory potential with an ED50 of 60 mg/kg in a λ-carrageenan-induced rat paw oedema model. Comparison with other Lignosus species and cultivars emphasised LC-CWE's distinct attributes, including high phenolic content and moderate antioxidant capacity. LC-CWE displayed potential in selectively inhibiting MCF-7 cells and reducing inflammation, highlighting its medicinal promise. This research expands our understanding of L. cameronensis and underscores the need for further mechanistic exploration.

In vivo anti-tumor activity of Lignosus rhinocerus TM02® using a MCF7-xenograft NCr nude mice model

ETHNOPHARMACOLOGICAL RELEVANCE

Lignosus rhinocerus (Cooke) Ryvarden (also known as Tiger Milk mushroom, TMM), is a basidiomycete belonging to the Polyporaceae family. It has been documented to be used by traditional Chinese physicians and indigenous people in Southeast Asia to treat a variety of illnesses, such as gastritis, arthritis, and respiratory conditions, as well as to restore patients' physical well-being. TMM has also been used in folk medicine to treat cancer. For example, people from the indigenous Kensiu tribe of northeast Kedah (Malaysia) apply shredded TMM sclerotium mixed with water directly onto breast skin to treat breast cancer, while Chinese practitioners from Hong Kong, China prescribe TMM sclerotium as a treatment for liver cancer. L. rhinocerus has previously been demonstrated to possess selective anti-proliferative properties in vitro, however pre-clinical in vivo research has not yet been conducted.

AIM OF STUDY

This study aimed to examine the anti-tumor activities of L. rhinocerus TM02®, using two different sample preparations [cold water extract (CWE) and fraction] via various routes of administration (oral and intraperitoneal) on an MCF7-xenograft nude mouse model. This study also investigated the inhibitory effect of TM02® CWE and its fractions against COX-2 in vitro using LPS-induced RAW264.7 macrophages, on the basis of the relationship between COX-2 and metastasis, apoptosis resistance, as well as the proliferation of cancer cells.

MATERIALS AND METHODS

The first preparation, L. rhinocerus TM02® sclerotium powder (TSP) was dissolved in cold water to obtain the cold water extract (CWE). It was further fractionated based on its molecular weight to obtain the high (HMW), medium (MMW) and low (LMW) molecular weight fractions. The second preparation, known as the TM02® rhinoprolycan fraction (TRF), was obtained by combining the HMW and MMW fractions. TSP was given orally to mimic the daily consumption of a supplement; TRF was administered intraperitoneally to mimic typical tumorous cancer treatment with a rapid and more thorough absorption through the peritoneal cavity. Another experiment was conducted to examine changes in COX-2 activity in LPS-induced RAW264.7 macrophages after a 1-h pre-treatment with CWE, HMW, and MMW.

RESULTS

Our results revealed that intraperitoneal TRF-injection (90 μg/g BW) for 20 days reduced initial tumor volume by ∼64.3% (n = 5). The percentage of apoptotic cells was marginally higher in TRF-treated mice vs. control, suggesting that induction of apoptosis as one of the factors that led to tumor shrinkage. TSP (500 μg/g BW) oral treatment (n = 5) for 63 days (inclusive of pre-treatment prior to tumor inoculation) effectively inhibited tumor growth. Four of the five tumors totally regressed, demonstrating the effectiveness of TSP ingestion in suppressing tumor growth. Although no significant changes were found in mouse serum cytokines (TNF-α, IL-5, IL-6 and CCL2), some increasing and decreasing trends were observed. This may suggest the immunomodulatory potential of these treatments that can directly or indirectly affect tumor growth. Pre-treatment with CWE, HMW and MMW significantly reduced COX-2 activity in RAW264.7 macrophages upon 24 h LPS-stimulation, suggesting the potential of L. rhinocerus TM02® extract and fractions in regulating M1/M2 polarization.

CONCLUSION

Based on the findings of our investigation, both the rhinoprolycan fraction and crude sclerotial powder from L. rhinocerus TM02® demonstrated tumor suppressive effects, indicating that they contain substances with strong anticancer potential. The antitumor effects of L. rhinocerus TM02® in our study highlights the potential for further explorations into its mechanism of action and future development as a prophylactic or adjunct therapeutic against tumorous cancer.

Increasing the production of the bioactive compounds in medicinal mushrooms: an omics perspective

Macroscopic fungi, mainly higher basidiomycetes and some ascomycetes, are considered medicinal mushrooms and have long been used in different areas due to their pharmaceutically/nutritionally valuable bioactive compounds. However, the low production of these bioactive metabolites considerably limits the utilization of medicinal mushrooms both in commerce and clinical trials. As a result, many attempts, ranging from conventional methods to novel approaches, have been made to improve their production. The novel strategies include conducting omics investigations, constructing genome-scale metabolic models, and metabolic engineering. So far, genomics and the combined use of different omics studies are the most utilized omics analyses in medicinal mushroom research (both with 31% contribution), while metabolomics (with 4% contribution) is the least. This article is the first attempt for reviewing omics investigations in medicinal mushrooms with the ultimate aim of bioactive compound overproduction. In this regard, the role of these studies and systems biology in elucidating biosynthetic pathways of bioactive compounds and their contribution to metabolic engineering will be highlighted. Also, limitations of omics investigations and strategies for overcoming them will be provided in order to facilitate the overproduction of valuable bioactive metabolites in these valuable organisms.

Towards Understanding the Function of Aegerolysins

Aegerolysins are remarkable proteins. They are distributed over the tree of life, being relatively widespread in bacteria and fungi, but also present in some insects, plants, protozoa, and viruses. Despite their abundance in cells of certain developmental stages and their presence in secretomes, only a few aegerolysins have been studied in detail. Their function, in particular, is intriguing. Here, we summarize previously published findings on the distribution, molecular interactions, and function of these versatile aegerolysins. They have very diverse protein sequences but a common fold. The machine learning approach of the AlphaFold2 algorithm, which incorporates physical and biological knowledge of protein structures and multisequence alignments, provides us new insights into the aegerolysins and their pore-forming partners, complemented by additional genomic support. We hypothesize that aegerolysins are involved in the mechanisms of competitive exclusion in the niche.

Towards a Fungal Science That Is Independent of Researchers’ Gender

The main drivers of gender mainstreaming in basic and clinical research appear to be funding agencies and scientific journals. Some funding agencies have already recognized the importance of their actions for the global development of ideas in science, but further targeted efforts are needed. The challenges for women scientists in fungal research appear to be similar to those in other science, technology, engineering, and mathematics disciplines, although the gender gap in mycology publishing appears to be less pronounced; however, women are underrepresented as last (corresponding) authors. Two examples of best practices to bridge the gap have been promoted in the fungal community: “power hour” and a central resource database for women researchers of fungi and oomycetes. A more balanced ratio of women researchers among (plenary) session speakers, (plenary) session chairs, and committee members at the recent fungal genetics conference is an encouraging sign that the gender gap can be closed. The editorial policy of some journals follows the guidance “Sex and Gender Equality in Research,” and other journals should follow, and indicate the gender ratio among authors and reviewers.

In silico analysis and characterization of medicinal mushroom cystathionine beta-synthase as an angiotensin converting enzyme (ACE) inhibitory protein

Angiotensin-converting enzyme (ACE) regulates blood pressure and has been implicated in several conditions including lung injury, fibrosis and Alzheimer's disease. Medicinal mushroom Ganordema lucidum (Reishi) cystathionine beta-synthase (GlCBS) was previously reported to possess ACE inhibitory activities. However, the inhibitory mechanism of CBS protein remains unreported. Therefore, this study integrates in silico sequencing, structural and functional based-analysis, protein modelling, molecular docking and binding affinity calculation to elucidate the inhibitory mechanism of GlCBS and Lignosus rhinocerus (Tiger milk mushroom) CBS protein (LrCBS) towards ACE. In silico analysis indicates that CBSs from both mushrooms share high similarities in terms of physical properties, structural properties and domain distribution. Protein-protein docking analysis revealed that both GlCBS and LrCBS potentially modulate the C-terminal domain of ACE (C-ACE) activity via regulation of chloride activation and/or prevention of substrate entry. GICBS and LrCBS were also shown to interact with ACE at the same region that presumably inhibits the function of ACE.

Antioxidant and Cytotoxic Effects and Identification of Ophiocordyceps sinensis Bioactive Proteins Using Shotgun Proteomic Analysis

RESEARCH BACKGROUND

Ophiocordyceps sinensis, a highly valued medicinal fungus, is close to extinction due to overexploitation. Successful cultivation of O. sinensis fruiting body (OCS02®) shows that the cultivar has a promising nutritional value and numerous bioactive compounds. Antioxidant and antiproliferative properties and biologically active proteins of the OCS02® are investigated for possible development into nutraceuticals.

EXPERIMENTAL APPROACH

The chemical composition of the OCS02® cold water extract was determined, and the antioxidant activities were examined using ferric reducing, DPPH• and O2 •- scavenging assays. Tetrazolium dye (MTT) cytotoxic assay was performed to assess the antiproliferative activity of the extract. Bioactive proteins in the active fraction of the extract were identified using liquid chromatography (LC) and tandem-mass spectrometry (MS/MS).

RESULTS AND CONCLUSIONS

The OCS02® extract exhibited strong O2 •- scavenging (expressed as Trolox equivalents (18.4±1.1) mol/g) and potent cytotoxic activities against adenocarcinomic human alveolar basal epithelial (A549) cells (IC50=(58.2±6.8) µg/mL). High molecular mass polysaccharides, proteins and protein-polysaccharide complexes could have contributed to the antioxidant and cytotoxic selectivity of the OCS02®. LC-MS/MS analysis identified several potential cytotoxic proteases and an oxalate decarboxylase protein which may exhibit protection effects on kidneys.

NOVELTY AND SCIENTIFIC CONTRIBUTIONS

The findings demonstrate the potential of OCS02® to be developed into functional food due to its promising superoxide anion radical scavenging capacity, cytotoxic effect and presence of biopharmaceutically active proteins.

Proteins from Lignosus tigris with selective apoptotic cytotoxicity towards MCF7 cell line and suppresses MCF7-xenograft tumor growth

Background

Lignosus tigris, a recently discovered species of the unique Lignosus family, has been traditionally used by the indigenous communities in Peninsular Malaysia to treat various ailments and as an alternative medicine for cancer treatment. The L. tigris cultivar sclerotia (Ligno TG-K) was found to contain numerous bioactive compounds with beneficial biomedicinal properties and the sclerotial extract exhibited potent antioxidant activity. However, the anticancer property of the Ligno TG-K including in vitro and in vivo antitumor effects as well as its anticancer active compounds and the mechanisms has yet to be investigated.

Methods

The cytotoxicity of the Ligno TG-K against human breast (MCF7), prostate (PC3) and lung (A549) adenocarcinoma cell lines was evaluated using MTT cytotoxicity assay. The cytotoxic mechanisms of the active high molecular weight proteins (HMWp) fraction were investigated through detection of caspases activity and apoptotic-related proteins expression by Western blotting. The in vivo antitumor activity of the isolated HMWp was examined using MCF7 mouse xenograft model. Shotgun LC-MS/MS analysis was performed to identify the proteins in the HMWp.

Results and Discussion

Cold water extract of the sclerotia inhibited proliferation of MCF7, A549 and PC3 cells with IC₅₀ ranged from 28.9 to 95.0 µg/mL. Bioassay guided fractionation of the extract revealed that HMWp exhibited selective cytotoxicity against MCF7 cells via induction of cellular apoptosis by the activation of extrinsic and intrinsic signaling pathways. HMWp activated expression of caspase-8 and -9 enzymes, and pro-apoptotic Bax protein whilst inhibiting expression of tumor survivor protein, Bcl-2. HMWp induced tumor-cell apoptosis and suppressed growth of tumor in MCF-7 xenograft mice. Lectins, serine proteases, RNase Gf29 and a 230NA deoxyribonuclease are the major cytotoxic proteins that accounted for 55.93% of the HMWp.

Conclusion

The findings from this study provided scientific evidences to support the traditional use of the L. tigris sclerotia for treatment of breast cancer. Several cytotoxic proteins with high abundance have been identified in the HMWp of the sclerotial extract and these proteins have potential to be developed into new anticancer agents or as adjunct cancer therapy.

Protein components of water extracts from fruiting bodies of the reishi mushroom Ganoderma lucidum contribute to the production of functional molecules

BACKGROUND

Mushrooms have been widely considered as health foods as their extracts have anti-hypertensive and anti-tumor activities. After a thorough literature survey, we hypothesized that enzymes in mushroom extracts play an important role in synthesizing functional molecules. Therefore, in this study, proteins extracted from reishi mushroom (Ganoderma lucidum), which is used in oriental medicine, were identified by the proteomic approach, and appropriate extraction methods for improving angiotensin-converting enzyme (ACE) inhibitory activities were investigated.

RESULTS

Various glycoside hydrolases (GHs), such as β-N-acetylhexosaminidase (GH family 20), α-1,2-mannosidase (GH family 47), endo-β-1,3-glucanase (GH family 128), and β-1,3-glucanase (GH152), that degrade glycans in the fruiting body were identified. The residual glucanase activities generated β-oligosaccharides. Additionally, the glutamic acid protease of the peptidase G1 family was determined as the major protein in the extract, and the residual peptidase activity of the extracts was found to improve ACE inhibitory activities. Finally, it was observed that extraction at 50 °C is suitable for yielding functional molecules with high ACE inhibitory activities.

CONCLUSION

Water extraction is generally believed to extract only functional macromolecules that exist in mushroom fruiting bodies. This study proposed a new concept that describes how functional molecules are produced by enzymes, including proteases and GHs, during extraction. © 2018 Society of Chemical Industry.

Antibacterial activity of biosynthesized gold nanoparticles using biomolecules from Lignosus rhinocerotis and chitosan

A simple, cost-effective, and environmentally friendly method is needed for synthesizing metal nanoparticles, including gold nanoparticles (AuNPs). In this study, AuNPs were synthesized with Lignosus rhinocerotis sclerotial extract (LRE) and chitosan (CS) as reducing and stabilizing agents, respectively. Different LRE concentrations from cold and hot water extraction (CWE and HWE, respectively) were used to reduce chloroauric acid (HAuCl₄) to form AuNPs. Positively charged chitosan stabilized AuNPs (CS-AuNPs) mediated by LRE exhibited a surface plasmon resonance (SPR) band at 533 nm. The CS-AuNPs synthesized using CWE had a smaller particle size (49.5 ± 6.7-82.4 ± 28.0 nm) compared to that of the HWE samples (80.3 ± 23.4-125.3 ± 41.5 nm), depending on LRE concentration. FTIR results suggested protein and polysaccharides in LRE were the sources of reducing power, reducing gold ions to AuNPs. CS-AuNPs were mostly spherical with higher LRE concentrations, whereas some triangular, pentagonal, irregular, and rod shaped AuNPs were observed at lower LRE concentrations. CS-AuNPs mediated by LRE displayed effective antibacterial activity against gram-negative (Pseudomonas aeruginosa and Escherichia coli) and gram-positive bacteria (Staphylococcus aureus and Bacillus sp.). Thus, the biosynthesized AuNPs using LRE and chitosan provide opportunities for developing stable and eco-friendly nanoparticles with effective antibacterial properties.

Molecular attributes and apoptosis-inducing activities of a putative serine protease isolated from Tiger Milk mushroom (Lignosus rhinocerus) sclerotium against breast cancer cells in vitro

Background

The highly valued medicinal tiger milk mushroom (also known as Lignosus rhinocerus) has the ability to cure numerous ailments. Its anticancer activities are well explored, and recently a partially purified cytotoxic protein fraction termed F5 from the mushroom’s sclerotial cold water extract consisting mainly of fungal serine proteases was found to exhibit potent selective cytotoxicity against a human breast adenocarcinoma cell line (MCF7) with IC₅₀ value of 3.00 μg/ml. However, characterization of its cell death-inducing activity has yet to be established.

Methods

The mechanism involved in the cytotoxic activities of F5 against MCF7 cells was elucidated by flow cytometry-based apoptosis detection, caspases activity measurement, and expression profiling of apoptosis markers by western blotting. Molecular attributes of F5 were further mined from L. rhinocerus’s published genome and transcriptome for future exploration.

Results and Discussion

Apoptosis induction in MCF7 cells by F5 may involve a cross-talk between the extrinsic and intrinsic apoptotic pathways with upregulation of caspase-8 and -9 activities and a marked decrease of Bcl-2. On the other hand, the levels of pro-apoptotic Bax, BID, and cleaved BID were increased accompanied by observable actin cleavage. At gene level, F5 composed of three predicted non-synonymous single nucleotide polymorphisms (T > C) and an alternative 5′ splice site.

Conclusions

Findings from this study provide an advanced framework for further investigations on cancer therapeutics development from L. rhinocerus.

Inhibition of Protein Glycation by Tiger Milk Mushroom [Lignosus rhinocerus (Cooke) Ryvarden] and Search for Potential Anti-diabetic Activity-Related Metabolic Pathways by Genomic and Transcriptomic Data Mining

Naturally occurring anti-glycation compounds have drawn much interest in recent years as they show potential in reducing or preventing the risk of chronic complications for diabetic patients. In this study, annotation of the genome–transcriptome data from tiger milk mushroom (Lignosus rhinocerus, syn. Lignosus rhinocerotis) to PlantCyc enzymes database identified transcripts that are related to anti-diabetic properties, and these include genes that are involved in carotenoid and abscisic acid biosynthesis as well as genes that code for glyoxalase I, catalase-peroxidases, and superoxide dismutases. The existence of these genes suggests that L. rhinocerus may contain bioactive compound(s) with anti-glycation properties that can be exploited for management of diabetic complications. A medium-molecular-weight (MMW) fraction which was obtained from a combination of cold water extraction and Sephadex^® G-50 (fine) gel filtration chromatography of L. rhinocerus sclerotia powder was demonstrated to exhibit potent anti-glycation activity. The fraction specifically inhibited the formation of N𝜀-(carboxymethyl)lysine, pentosidine, and other advanced glycation end-product (AGE) structures in a human serum albumin-glucose system, with an IC₅₀ value of 0.001 mg/ml, almost 520 times lower than that of the positive control, aminoguanidine hydrochloride (IC₅₀ = 0.52 mg/ml). Its ability to suppress protein glycation may be partly associated with its strong superoxide anion radical scavenging activity (10.16 ± 0.12 mmol TE/g). Our results suggest that the MMW fraction of L. rhinocerus shows potential to be developed into a potent glycation inhibitor for preventing AGE-mediated diabetic complications.

A Status Review of the Bioactive Activities of Tiger Milk Mushroom Lignosus rhinocerotis (Cooke) Ryvarden

Edible and medicinal mushrooms are regularly used in natural medicines and home remedies since antiquity for ailments like fever, inflammation, and respiratory disorders. Lignosus rhinocerotis (Cooke) Ryvarden is a polypore found in Malaysia and other regions in South East Asia. It can be located on a spot where a tigress drips milk while feeding, hence the name “tiger's milk mushroom.” The sclerotium of L. rhinocerotis is highly sought after by the native communities in Malaysia to stave off hunger, relieve cough and asthma, and provide stamina. The genomic features of L. rhinocerotis have been described. The pharmacological and toxicity effects, if any, of L. rhinocerotis sclerotium have been scientifically verified in recent years. In this review, the validated investigations including the cognitive function, neuroprotection, immune modulation, anti-asthmatic, anti-coagulation, anti-inflammatory, anti-microbial/ anti-viral, anti-obesity, anti-cancer/ anti-tumor, and antioxidant properties are highlighted. These findings suggest that L. rhinocerotis can be considered as an alternative and natural medicine in the management of non-communicable diseases. However, there is a paucity of validation studies including human clinical trials of the mycochemicals of L. rhinocerotis.

Heterologous expression of cytotoxic sesquiterpenoids from the medicinal mushroom Lignosus rhinocerotis in yeast

Background

Genome mining facilitated by heterologous systems is an emerging approach to access the chemical diversity encoded in basidiomycete genomes. In this study, three sesquiterpene synthase genes, GME3634, GME3638, and GME9210, which were highly expressed in the sclerotium of the medicinal mushroom Lignosus rhinocerotis, were cloned and heterologously expressed in a yeast system.

Results

Metabolite profile analysis of the yeast culture extracts by GC–MS showed the production of several sesquiterpene alcohols (C₁₅H₂₆O), including cadinols and germacrene D-4-ol as major products. Other detected sesquiterpenes include selina-6-en-4-ol, β-elemene, β-cubebene, and cedrene. Two purified major compounds namely (+)-torreyol and α-cadinol synthesised by GME3638 and GME3634 respectively, are stereoisomers and their chemical structures were confirmed by ¹H and ¹³C NMR. Phylogenetic analysis revealed that GME3638 and GME3634 are a pair of orthologues, and are grouped together with terpene synthases that synthesise cadinenes and related sesquiterpenes. (+)-Torreyol and α-cadinol were tested against a panel of human cancer cell lines and the latter was found to exhibit selective potent cytotoxicity in breast adenocarcinoma cells (MCF7) with IC₅₀ value of 3.5 ± 0.58 μg/ml while α-cadinol is less active (IC₅₀ = 18.0 ± 3.27 μg/ml).

Conclusions

This demonstrates that yeast-based genome mining, guided by transcriptomics, is a promising approach for uncovering bioactive compounds from medicinal mushrooms.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-017-0713-x) contains supplementary material, which is available to authorized users.

Proteomics of edible mushrooms: A mini-review

Mushrooms are considered an important food for their traditionally famous nutritional and medicinal values, although much information about their potential at the molecular level is unfortunately unknown. Edible mushrooms include fungi that are either collected wild or cultivated. Many important species are difficult to cultivate but attempts have been made with varying degrees of success, with the results showing unsatisfactory economical cultivation methods. Recently, proteomic analysis has been developed as a powerful tool to study the protein content of fungi, particularly basidiomycetes. This mini-review article highlights the contribution of proteomics platforms to the study of edible mushrooms, focusing on the molecular mechanisms involved in developmental stages. This includes extracellular and cytoplasmic effector proteins that have potential or are involved in the synthesis of anticancer, antidiabetic, antioxidant, and antibiotic, in blood pressure control, in the supply of vitamins and minerals, and in other responses to environmental changes. The contribution of different proteomics techniques including classical and more advanced techniques is also highlighted.

Transcriptome Analysis Revealed Highly Expressed Genes Encoding Secondary Metabolite Pathways and Small Cysteine-Rich Proteins in the Sclerotium of Lignosus rhinocerotis

Lignosus rhinocerotis (Cooke) Ryvarden (tiger milk mushroom) has long been known for its nutritional and medicinal benefits among the local communities in Southeast Asia. However, the molecular and genetic basis of its medicinal and nutraceutical properties at transcriptional level have not been investigated. In this study, the transcriptome of L. rhinocerotis sclerotium, the part with medicinal value, was analyzed using high-throughput Illumina HiSeq^TM platform with good sequencing quality and alignment results. A total of 3,673, 117, and 59,649 events of alternative splicing, novel transcripts, and SNP variation were found to enrich its current genome database. A large number of transcripts were expressed and involved in the processing of gene information and carbohydrate metabolism. A few highly expressed genes encoding the cysteine-rich cerato-platanin, hydrophobins, and sugar-binding lectins were identified and their possible roles in L. rhinocerotis were discussed. Genes encoding enzymes involved in the biosynthesis of glucans, six gene clusters encoding four terpene synthases and one each of non-ribosomal peptide synthetase and polyketide synthase, and 109 transcribed cytochrome P450 sequences were also identified in the transcriptome. The data from this study forms a valuable foundation for future research in the exploitation of this mushroom in pharmacological and industrial applications.

Shotgun proteomic analysis of tiger milk mushroom (Lignosus rhinocerotis) and the isolation of a cytotoxic fungal serine protease from its sclerotium

ETHNOPHARMACOLOGICAL RELEVANCE

The sclerotium of Lignosus rhinocerotis (Cooke) Ryvarden (tiger milk mushroom) has been traditionally used as a complementary and alternative medicine for cancer treatment by the local communities of Southeast Asia. Despite the continuous research interest in its antiproliferative activity, the identity of the bioactive compound(s) responsible has yet to be determined. This study aims to bridge the gap in existing research literature by using proteomics approach for investigation of the nature of the anticancer substance of L. rhinocerotis.

AIM OF THE STUDY

To elucidate the proteome of L. rhinocerotis TM02 sclerotium by protein mass spectrometry and to further isolate and identify the cytotoxic component(s) bearing anticancer potential.

MATERIALS AND METHODS

The proteome of L. rhinocerotis sclerotium was analyzed by label-free quantitative shotgun proteomics, using 1D-SDS-PAGE coupled with nano-ESI-LC-MS/MS based on the availability of its genome-sequence database. The cytotoxicity of L. rhinocerotis sclerotial extracts against human breast adenocarcinoma cells (MCF7) were assessed by MTT cytotoxicity assay prior to successive purification steps by a combination of gel filtration chromatography, ammonium sulfate precipitation, and anion exchange chromatography. Bioactive compound(s) in the extracts was identified by shotgun proteomics and N-terminal protein sequencing.

RESULTS

Several proteins with interesting biological activities including lectins, fungal immunomodulatory proteins, and several antioxidant proteins were identified from the proteome of L. rhinocerotis. A cytotoxic protein fraction (termed F5) which was partially purified from its sclerotial cold water extract F5 shows two distinct bands of 31 and 36 kDa in reducing SDS-PAGE and exhibited potent selective cytotoxicity against MCF7 cells with IC50 value of 3.00 ± 1.01 μg/ml. Both bands were identified to be serine protease by LC-MS/MS analysis. Phenylmethylsulfonyl fluoride, a specific serine protease inhibitor, inhibited both the proteolytic activity and cytotoxicity of F5, suggesting that the cytotoxicity of F5 is related to its protease activity.

CONCLUSIONS

This study provides the first comprehensive and semi-quantitative profiling of the proteome of L. rhinocerotis sclerotium. Further investigation into its selective cytotoxicity shows that a serine protease-like protein, termed F5, may be targeted for new anticancer agent development.

Ethnomedicinal uses, pharmacological activities, and cultivation of Lignosus spp. (tiger׳s milk mushrooms) in Malaysia - A review

ETHNOPHARMACOLOGICAL RELEVANCE

Several members of the genus Lignosus, which are collectively known as cendawan susu rimau (in Malay) or tiger׳s milk mushrooms (TMM), are regarded as important local medicine particularly by the indigenous communities in Malaysia. The mushroom sclerotia are purportedly effective in treating cancer, coughs, asthma, fever, and other ailments. The most commonly encountered Lignosus spp. in Malaysia was authenticated as Lignosus rhinocerotis (Cooke) Ryvarden (synonym: Polyporus rhinocerus), which is also known as hurulingzhi in China and has been used by Chinese physicians to treat liver cancer, gastric ulcers, and chronic hepatitis. In spite of growing interest in the therapeutic potential of TMM, there is no compilation of scientific evidence that supports the ethnomedicinal uses of these mushrooms. Therefore, the present review is intended (i) to provide a comprehensive, up-to-date overview of the ethnomedicinal uses, pharmacological activities, and cultivation of TMM in general and L. rhinocerotis in particular, (ii) to demonstrate how recent scientific findings have validated some of their traditional uses, and (iii) to identify opportunities for future research and areas to prioritize for TMM bioprospecting.

MATERIALS AND METHODS

A detailed literature search was conducted via library search (books, theses, reports, newspapers, magazines, and conference proceedings) and electronic search (Web of Science, PubMed, and Google Scholar) for articles published in peer-reviewed journals. These sources were scrutinized for information on TMM and specifically for L. rhinocerotis.

RESULTS

Ethnomycological knowledge about TMM, with an emphasis on cultural associations and use as local medicine, has been comprehensively and systematically compiled for the first time. Some of the reported medicinal properties of TMM have been validated by scientific studies. The anti-tumor, immuno-modulatory, anti-inflammatory, anti-oxidative, anti-microbial, neurite outgrowth stimulation, and other pharmacological activities of L. rhinocerotis sclerotial extracts have been explored. The nature of sclerotial bioactive components, such as proteins, polysaccharides, and/or polysaccharide-protein complexes, has been identified, whereas the low-molecular-weight constituents remain poorly studied. The artificial cultivation of L. rhinocerotis via solid substrate and liquid fermentations successfully yielded fruiting bodies, sclerotium, mycelium, and culture broth that could be exploited as substitutes for the wild resources. The cultivated sclerotium and mycelium were shown to be safe from a toxicological point of view. Other research areas, e.g., chemical studies, genomics, and proteomics, have been employed to gain insights into the medicinal properties of TMM.

CONCLUSIONS

This review clarified the medicinal properties of TMM as recorded in various ethnomycological records, and it simultaneously highlighted the current efforts to provide scientific evidence by using various in vitro and in vivo models. Thus far, only the anti-tumor and immuno-modulatory effects of L. rhinocerotis sclerotial aqueous extracts have been extensively investigated, and other medicinal properties relevant to their traditional uses, e.g., anti-tussive and anti-pyretic properties, have yet to be validated. Further studies focusing on (i) the isolation and characterization of active components, (ii) the elucidation of their modes of action, and (iii) an evaluation of their safety and efficacy, when compared with the crude aqueous preparations, are warranted to accelerate potential drug discovery from TMM.