Developments in taxol production through endophytic fungal biotechnology: a review

Paclitaxel - a Product of Fungal Secondary Metabolism or an Artefact?

Taxol (common name: paclitaxel) is an extremely important component of drugs for the treatment of various cancers. Thirty years after the discovery of its effectiveness, a metabolic precursor of Taxol (10-deacetylbaccatin III) is still primarily extracted from needles of European yew trees. In order to meet the considerable demand, hopes were pinned on the possibilities of biotechnological production from the very beginning. In 1993, as if by chance, Taxol was supposedly discovered in fungi that grow endobiotically in yew trees. This finding aroused hopes of biotechnological use to produce fungal Taxol in large quantities in fermenters. It never came to that. Instead, a confusing flood of publications emerged that claimed to have detected Taxol in more and more eukaryotic and even prokaryotic species. However, researchers never reproduced these rather puzzling results, and they could certainly not be applied on an industrial scale. This paper will show that some of the misguided approaches were apparently based on a seemingly careless handling of sparse evidence and on at least questionable publications. Apparently, the desired gold rush of commercial exploitation was seductive. Scientific skepticism as an indispensable core of good scientific practice was often neglected, and the peer review process has not exerted its corrective effect. Self-critical reflection and more healthy skepticism could help to reduce the risk of such aberrations in drug development. This article uses this case study as a striking example to show what can be learned from the Taxol case in terms of research ethics and the avoidance of questionable research practices.

Alternaria alternata F3, a Novel Taxol-Producing Endophytic Fungus Isolated from the Fruits of Taxus cuspidata: Isolation, Characterization, Taxol Yield Improvement, and Antitumor Activity

In this study, a novel taxol-producing endophytic fungus, strain F3, was isolated from the fruits of Taxus cuspidata and identified as Alternaria alternata according to its macroscopic and microscopic traits and sequence analysis of internal transcribed spacer (ITS). The presence of taxol was detected by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) and confirmed by ultra-high-performance liquid chromatography-electrospray coupled to tandem mass spectrometry (UPLC-ESI-MS/MS) and nuclear magnetic resonance (NMR). The fermentation parameters of strain F3 were then optimized for high taxol production. The maximum taxol yield of 195.4 µg L-1 by A. alternata F3 was observed in 200-mL yeast peptone dextrose (YPD) broth, at an initial pH value of 6.0, supplemented with 0.1 g L-1 sodium acetate, 0.25 g L-1 salicylic acid, and 0.00125 g L-1 silver nitrate and inoculum size 2%, and incubated at 28 °C and 150 rpm for 8 days, which was 2.12-fold compared with the initial yield of taxol. Also, fungal taxol exhibited antitumor activity towards human lung carcinoma (A549) cell line and human cervical carcinoma (Hela) cell line with IC50 values of 3.98 µg mL-1 and 0.35 µg mL-1. Overall, this is the first report on taxol-producing endophytic fungus isolated from the fruits of Taxus. This study offers a novel source for the production of taxol for anticancer treatment.

Endophytic fungi: an overview on biotechnological and agronomic potential

Abstract Endophytic fungi colonize the inter- and/or intracellular regions of healthy plant tissues and have a close symbiotic relationship with their hosts. These microorganisms produce antibiotics, enzymes, and other bioactive compounds that enable them to survive in competitive habitats with other microorganisms. In addition, secondary metabolites confer protection to their host plant against other bacterial and fungal pathogens and/or can promote plant growth. Endophytic fungi are viewed as a promising source of bioactive natural products, which can be optimized through changes in growing conditions. The exploration of novel bioactive molecules produced by these microorganisms has been attracting attention from researchers. The chemical and functional diversity of natural products from endophytic fungi exhibits a broad spectrum of applications in medicine, agriculture, industry and the environment. Fungal endophytes can also enhance the photoprotective effects and photochemical efficiency in the host plants. Modern omic approaches have facilitated research investigating symbiotic plant-endophytic fungi interactions. Therefore, research on endophytic fungi can help discovery novel biomolecules for various biotechnological applications and develop a sustainable agriculture.

Way to efficient microbial paclitaxel mass production

The microbial synthesis of paclitaxel is attractive for its short-cycle, cost-effectiveness, and sustainability. However, low paclitaxel productivity, depleted capacity during subculture and storage, and unclear biosynthesis mechanisms restrain industrial microbial synthesis. Along with the isolation of various paclitaxel-producing microorganisms and the development of versatile molecular tools, tremendous promises for microbial paclitaxel synthesis have become increasingly prominent. In this review, we summarize the progress of microbial synthesis of paclitaxel in recent years, focusing on paclitaxel-producing endophytes and representative engineering microorganism hosts that were used as chassis for paclitaxel precursor synthesis. Numerous wide-type microbes can manufacture paclitaxel, and fermentation process optimization and strain improvement can greatly enhance the productivity. Engineered microbes can efficiently synthesize precursors of paclitaxel by introducing exogenous synthetic pathway. Mining paclitaxel synthetic pathways and genetic manipulation of endophytes will accelerate the construction of microbial cell factories, indefinitely contributing to paclitaxel mass production by microbes. This review emphasizes the potential and provides solutions for efficient microbial paclitaxel mass production.

Research Advances in Clinical Applications, Anticancer Mechanism, Total Chemical Synthesis, Semi-Synthesis and Biosynthesis of Paclitaxel

Paclitaxel, a natural secondary metabolite isolated and purified from the bark of the Taxus tree, is considered one of the most successful natural anticancer drugs due to its low toxicity, high potency and broad-spectrum anticancer activity. Taxus trees are scarce and slow-growing, and with extremely low paclitaxel content, the contradiction between supply and demand in the market is becoming more and more intense. Therefore, researchers have tried to obtain paclitaxel by various methods such as chemical synthesis, artificial culture, microbial fermentation and tissue cell culture to meet the clinical demand for this drug. This paper provides a comprehensive overview of paclitaxel extraction, combination therapy, total synthesis, semi-synthesis and biosynthesis in recent years and provides an outlook, aiming to provide a theoretical basis and reference for further research on the production and application of paclitaxel in the future.

Insights into Taxol® biosynthesis by endophytic fungi

There have been two hundred reports that endophytic fungi produce Taxol®, but its production yield is often rather low. Although considerable efforts have been made to increase Taxol/taxanes production in fungi by manipulating cocultures, mutagenesis, genome shuffles, and gene overexpression, little is known about the molecular signatures of Taxol biosynthesis and its regulation. It is known that some fungi have orthologs of the Taxol biosynthetic pathway, but the overall architecture of this pathway is unknown. A biosynthetic putative gene homology approach, combined with genomics and transcriptomics analysis, revealed that a few genes for metabolite residues may be located on dispensable chromosomes. This review explores a number of crucial topics (i) finding biosynthetic pathway genes using precursors, elicitors, and inhibitors; (ii) orthologs of the Taxol biosynthetic pathway for rate-limiting genes/enzymes; and (iii) genomics and transcriptomics can be used to accurately predict biosynthetic putative genes and regulators. This provides promising targets for future genetic engineering approaches to produce fungal Taxol and precursors. KEY POINTS: • A recent trend in predicting Taxol biosynthetic pathway from endophytic fungi. • Understanding the Taxol biosynthetic pathway and related enzymes in fungi. • The genetic evidence and formation of taxane from endophytic fungi.

Gut microbiota: A magical multifunctional target regulated by medicine food homology species

BACKGROUND

The relationship between gut microbiota and human health has gradually been recognized. Increasing studies show that the disorder of gut microbiota is related to the occurrence and development of many diseases. Metabolites produced by the gut microbiota are responsible for their extensive regulatory roles. In addition, naturally derived medicine food homology species with low toxicity and high efficiency have been clearly defined owing to their outstanding physiological and pharmacological properties in disease prevention and treatment.

AIM OF REVIEW

Based on supporting evidence, the current review summarizes the representative work of medicine food homology species targeting the gut microbiota to regulate host pathophysiology and discusses the challenges and prospects in this field. It aims to facilitate the understanding of the relationship among medicine food homology species, gut microbiota, and human health and further stimulate the advancement of more relevant research.

KEY SCIENTIFIC CONCEPTS OF REVIEW

As this review reveals, from the initial practical application to more mechanism studies, the relationship among medicine food homology species, gut microbiota, and human health has evolved into an irrefutable interaction. On the one hand, through affecting the population structure, metabolism, and function of gut microbiota, medicine food homology species maintain the homeostasis of the intestinal microenvironment and human health by affecting the population structure, metabolism, and function of gut microbiota. On the other hand, the gut microbiota is also involved in the bioconversion of the active ingredients from medicine food homology species and thus influences their physiological and pharmacological properties.

Secondary metabolites from endophytic fungi: Production, methods of analysis, and diverse pharmaceutical potential

The synthesis of secondary metabolites is a constantly functioning metabolic pathway in all living systems. Secondary metabolites can be broken down into numerous classes, including alkaloids, coumarins, flavonoids, lignans, saponins, terpenes, quinones, xanthones, and others. However, animals lack the routes of synthesis of these compounds, while plants, fungi, and bacteria all synthesize them. The primary function of bioactive metabolites (BM) synthesized from endophytic fungi (EF) is to make the host plants resistant to pathogens. EF is a group of fungal communities that colonize host tissues' intracellular or intercellular spaces. EF serves as a storehouse of the above-mentioned bioactive metabolites, providing beneficial effects to their hosts. BM of EF could be promising candidates for anti-cancer, anti-malarial, anti-tuberculosis, antiviral, anti-inflammatory, etc. because EF is regarded as an unexploited and untapped source of novel BM for effective drug candidates. Due to the emergence of drug resistance, there is an urgent need to search for new bioactive compounds that combat resistance. This article summarizes the production of BM from EF, high throughput methods for analysis, and their pharmaceutical application. The emphasis is on the diversity of metabolic products from EF, yield, method of purification/characterization, and various functions/activities of EF. Discussed information led to the development of new drugs and food additives that were more effective in the treatment of disease. This review shed light on the pharmacological potential of the fungal bioactive metabolites and emphasizes to exploit them in the future for therapeutic purposes.

Genetic approaches in improving biotechnological production of taxanes: An update

Paclitaxel (PTX) and its derivatives are diterpene alkaloids widely used as chemotherapeutic agents in the treatment of various types of cancer. Due to the scarcity of PTX in nature, its production in cell cultures and plant organs is a major challenge for plant biotechnology. Although significant advances have been made in this field through the development of metabolic engineering and synthetic biology techniques, production levels remain insufficient to meet the current market demand for these powerful anticancer drugs. A key stumbling block is the difficulty of genetically transforming the gymnosperm Taxus spp. This review focuses on the progress made in improving taxane production through genetic engineering techniques. These include the overexpression of limiting genes in the taxane biosynthetic pathway and transcription factors involved in its regulation in Taxus spp. cell cultures and transformed roots, as well as the development and optimization of transformation techniques. Attempts to produce taxanes in heterologous organisms such as bacteria and yeasts are also described. Although promising results have been reported, the transfer of the entire PTX metabolic route has not been possible to date, and taxane biosynthesis is still restricted to Taxus cells and some endophytic fungi. The development of a synthetic organism other than Taxus cells capable of biotechnologically producing PTX will probably have to wait until the complete elucidation of its metabolic pathway.

Studies on biotransformation mechanism of Fusarium sp. C39 to enhance saponin content of Paridis Rhizoma

Paridis Rhizoma is a natural medicine with strong anti-tumor and anti-inflammatory activities. Our previous research have found that Fusarium sp. C39, an endophytic fungus isolated from Dioscorea nipponica which contains the similar chemical components, significantly increased the steroidal saponins content of Paridis Rhizoma by fermentation. In this study, the inhibitory effects of fermentated Paridis Rhizoma extract (PRE) on liver cancer cells (Hepal-6), cervical cancer cells (Hela), and lung cancer cells (A549) were determined to be stronger than that of the unfermented extract. For discovering the fermentation mechanism of PRE with Fusarium sp. C39, 36 components with obviously quantitative variations were screened out by UPLC-Q/TOF-MS and 53 key genes involved in the metabolic pathways of steroidal saponins were identified by transcriptome. On the basis of comprehensively analyzing information from the metabonomics and transcriptome, it can be speculated that the increase of spirostanol saponins and nuatigenin-type saponins enhanced the inhibitory effect of fermented PRE on cancer cell proliferation. Under the action of glycosidase, glycosyltransferase, oxidoreductases, and genes involved in sterol synthesis, strain C39 achieved the synthesis of diosgenin and the alteration of configurations, sugar chain and substituent of steroidal saponins. The research suggested a microbial transformation approach to increase the resource utilization and activity of Paris polyphylla.

Taxoid profile in endophytic fungi isolated from Corylus avellana, introduces potential source for the production of Taxol in semi-synthetic approaches

Taxol (Paclitaxel) and its derivative taxanes are widely used in chemotherapy and treatment of different types of cancer. Although the extracted taxanes from Taxus sp. are currently used in semi-synthetic production of Taxol, providing alternative always available sources is still a main concern. Due to availability and fast growth rate, microorganisms are much potent alternative sources for taxanes. In the present study, 249 endophytic fungi were isolated from Corylus avellana at six different locations of Iran, among which 18 species were capable to produce taxanes. Genotyping analysis indicated that 17 genera were ascomycetes but only one basidiomycete. Seven taxanes were detected and quantified in solid and suspension cultures by HPLC and their structures were confirmed by LC-Mass analysis. Among endophytes, CA7 had all 7 taxoids and CA1 had the highest Taxol yield. In 78% of endophytes transferring to liquid media was accompanied by increase of taxanes yield and increased taxan production and its release to media up to 90%. Evaluation of cytotoxicity indicated that extracts of all isolated fungi were lethal to MCF7 cells. Since endophytes produced remarkable amounts of taxanes, they can be suggested as alternative inexpensive and easily available resources for Taxol production in semi-synthesis plans.

Impact of novel microbial secondary metabolites on the pharma industry

Abstract

Microorganisms are remarkable producers of a wide diversity of natural products that significantly improve human health and well-being. Currently, these natural products comprise half of all the pharmaceuticals on the market. After the discovery of penicillin by Alexander Fleming 85 years ago, the search for and study of antibiotics began to gain relevance as drugs. Since then, antibiotics have played a valuable role in treating infectious diseases and have saved many human lives. New molecules with anticancer, hypocholesterolemic, and immunosuppressive activity have now been introduced to treat other relevant diseases. Smaller biotechnology companies and academic laboratories generate novel antibiotics and other secondary metabolites that big pharmaceutical companies no longer develop. The purpose of this review is to illustrate some of the recent developments and to show the potential that some modern technologies like metagenomics and genome mining offer for the discovery and development of new molecules, with different functions like therapeutic alternatives needed to overcome current severe problems, such as the SARS-CoV-2 pandemic, antibiotic resistance, and other emerging diseases.

Key points

• Novel alternatives for the treatment of infections caused by bacteria, fungi, and viruses.

• Second wave of efforts of microbial origin against SARS-CoV-2 and related variants.

• Microbial drugs used in clinical practice as hypocholesterolemic agents, immunosuppressants, and anticancer therapy.

Endophytic Fungal Terpenoids: Natural Role and Bioactivities

Endophytic fungi are a highly diverse group of fungi that intermittently colonize all plants without causing symptoms of the disease. They sense and respond to physiological and environmental changes of their host plant and microbiome. The inter-organism interactions are largely driven by chemical networks mediated by specialized metabolites. The balance of these complex interactions leads to healthy and strong host plants. Endophytic strains have particular machinery to produce a plethora of secondary metabolites with a variety of bioactivities and unknown functions in an ecological niche. Terpenoids play a key role in endophytism and represent an important source of bioactive molecules for human health and agriculture. In this review, we describe the role of endophytic fungi in plant health, fungal terpenoids in multiple interactions, and bioactive fungal terpenoids recently reported from endophytes, mainly from plants used in traditional medicine, as well as from algae and mangroves. Additionally, we highlight endophytic fungi as producers of important chemotherapeutic terpenoids, initially discovered in plants. Despite advances in understanding endophytism, we still have much to learn in this field. The study of the role, the evolution of interactions of endophytic fungi and their terpenoids provide an opportunity for better applications in human health and agriculture.

A review of alpha-glucosidase inhibitors from plants as potential candidates for the treatment of type-2 diabetes

Diabetes mellitus is a multifactorial global health disorder that is rising at an alarming rate. Cardiovascular diseases, kidney damage and neuropathy are the main cause of high mortality rates among individuals with diabetes. One effective therapeutic approach for controlling hyperglycemia associated with type-2 diabetes is to target alpha-amylase and alpha-glucosidase, enzymes that catalyzes starch hydrolysis in the intestine. At present, approved inhibitors for these enzymes are restricted to acarbose, miglitol and voglibose. Although these inhibitors retard glucose absorption, undesirable gastrointestinal side effects impede their application. Therefore, research efforts continue to seek novel inhibitors with improved efficacy and minimal side effects. Natural products of plant origin have been a valuable source of therapeutic agents with lesser toxicity and side effects. The anti-diabetic potential through alpha-glucosidase inhibition of plant-derived molecules are summarized in this review. Eight molecules (Taxumariene F, Akebonoic acid, Morusin, Rhaponticin, Procyanidin A2, Alaternin, Mulberrofuran K and Psoralidin) were selected as promising drug candidates and their pharmacokinetic properties and toxicity were discussed where available.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s11101-021-09773-1.

Recent Developments in Metabolomics Studies of Endophytic Fungi

Endophytic fungi are microorganisms that colonize living plants' tissues without causing any harm. They are known as a natural source of bioactive metabolites with diverse pharmacological functions. Many structurally different chemical metabolites were isolated from endophytic fungi. Recently, the increasing trends in human health problems and diseases have escalated the search for bioactive metabolites from endophytic fungi. The conventional bioassay-guided study is known as laborious due to chemical complexity. Thus, metabolomics studies have attracted extensive research interest owing to their potential in dealing with a vast number of metabolites. Metabolomics coupled with advanced analytical tools provides a comprehensive insight into systems biology. Despite its wide scientific attention, endophytic fungi metabolomics are relatively unexploited. This review highlights the recent developments in metabolomics studies of endophytic fungi in obtaining the global metabolites picture.

The plant endosphere-hidden treasures: a review of fungal endophytes

The endosphere represents intracellular regions within plant tissues colonize by microbial endophytes without causing disease symptoms to host plants. Plants harbor one or two endophytic microbes capable of synthesizing metabolite compounds. Environmental factors determine the plant growth and survival as well as the kind of microorganisms associated with them. Some fungal endophytes that symbiotically colonize the endosphere of medicinal plants with the potential of producing biological products have been employed in traditional and modern medicine. The bioactive resources from endophytic fungi are promising; biotechnologically to produce cheap and affordable commercial bioactive products as alternatives to chemical drugs and other compounds. The exploration of bioactive metabolites from fungal endophytes has been found applicable in agriculture, pharmaceutical, and industries. Thus, fungal endophytes can be engineered to produce a substantive quantity of pharmacological drugs through the biotransformation process. Hence, this review shall provide an overview of fungal endophytes, ecology, their bioactive compounds, and exploration with the biosystematics approach.

Classifying natural products from plants, fungi or bacteria using the COCONUT database and machine learning

Natural products (NPs) represent one of the most important resources for discovering new drugs. Here we asked whether NP origin can be assigned from their molecular structure in a subset of 60,171 NPs in the recently reported Collection of Open Natural Products (COCONUT) database assigned to plants, fungi, or bacteria. Visualizing this subset in an interactive tree-map (TMAP) calculated using MAP4 (MinHashed atom pair fingerprint) clustered NPs according to their assigned origin ( https://tm.gdb.tools/map4/coconut_tmap/ ), and a support vector machine (SVM) trained with MAP4 correctly assigned the origin for 94% of plant, 89% of fungal, and 89% of bacterial NPs in this subset. An online tool based on an SVM trained with the entire subset correctly assigned the origin of further NPs with similar performance ( https://np-svm-map4.gdb.tools/ ). Origin information might be useful when searching for biosynthetic genes of NPs isolated from plants but produced by endophytic microorganisms.

Acetylcholinesterase and butyrylcholinesterase inhibition by nectriapyrone and tryptophol isolated from endophytic fungus Phomopsis sp

Cholinesterase (ChE) inhibitors are currently the main drugs used to treat the cognitive symptoms of Alzheimer's disease (AD). Dual cholinesterase inhibitors, that is, compounds capable of inhibiting both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), are considered a new potential approach for the long-term treatment of patients with AD. We evaluated the ethyl acetate extract of Phomopsis sp., grown in liquid medium malt extract and potato dextrose (PDB), an endophyte isolated from the Brazilian medicinal plant Hancornia speciosa. The anticholinesterase (AChE) and butyrylcholinesterase (BuChE) activities were evaluated. The extracts exhibited dual action against AChE and BuChE. The compounds isolated from these extracts, nectriapyrone (1) and tryptophol (2), showed inhibitory action on BuChE (IC50 = 29.05 and 34.15 μM respectively), being selective towards BuChE. The discovery of selective BuChE inhibitors is extremely important for the development of drugs that can be used in the treatment of patients diagnosed with AD.

Current Perspectives on Taxanes: Focus on Their Bioactivity, Delivery and Combination Therapy

Taxanes, mainly paclitaxel and docetaxel, the microtubule stabilizers, have been well known for being the first-line therapy for breast cancer for more than the last thirty years. Moreover, they have been also used for the treatment of ovarian, hormone-refractory prostate, head and neck, and non-small cell lung carcinomas. Even though paclitaxel and docetaxel significantly enhance the overall survival rate of cancer patients, there are some limitations of their use, such as very poor water solubility and the occurrence of severe side effects. However, this is what pushes the research on these microtubule-stabilizing agents further and yields novel taxane derivatives with significantly improved properties. Therefore, this review article brings recent advances reported in taxane research mainly in the last two years. We focused especially on recent methods of taxane isolation, their mechanism of action, development of their novel derivatives, formulations, and improved tumor-targeted drug delivery. Since cancer cell chemoresistance can be an unsurpassable hurdle in taxane administration, a significant part of this review article has been also devoted to combination therapy of taxanes in cancer treatment. Last but not least, we summarize ongoing clinical trials on these compounds and bring a perspective of advancements in this field.

Pharmacological Potential of Fungal Endophytes Associated with Medicinal Plants: A Review

Endophytic microbes are microorganisms that colonize the intracellular spaces within the plant tissues without exerting any adverse or pathological effects. Currently, the world population is facing devastating chronic diseases that affect humans. The resistance of pathogens to commercial antibiotics is increasing, thus limiting the therapeutic potential and effectiveness of antibiotics. Consequently, the need to search for novel, affordable and nontoxic natural bioactive compounds from endophytic fungi in developing new drugs with multifunction mechanisms to meet human needs is essential. Fungal endophytes produce invaluable bioactive metabolic compounds beneficial to humans with antimicrobial, anticancer, antidiabetic, anti-inflammatory, antitumor properties, etc. Some of these bioactive compounds include pestacin, taxol, camptothecin, ergoflavin, podophyllotoxin, benzopyran, isopestacin, phloroglucinol, tetrahydroxy-1-methylxanthone, salidroside, borneol, dibenzofurane, methyl peniphenone, lipopeptide, peniphenone etc. Despite the aforementioned importance of endophytic fungal metabolites, less information is available on their exploration and pharmacological importance. Therefore, in this review, we shall elucidate the fungal bioactive metabolites from medicinal plants and their pharmacological potential.

Endophytic microbes from Nigerian ethnomedicinal plants: a potential source for bioactive secondary metabolites-a review

BACKGROUND

Endophytes are highly beneficial species of microbes that live in symbiosis with plant tissues in the setting. Endophytes are difficult to isolate in their natural environment, and they are understudied despite being a rich source of bioactive molecules. There are varieties of new infectious diseases emerging across the world, necessitating a constant and expanded search for newer and more efficient bioactive molecules. Nigeria is known for its biodiversity in ethnomedicinal plants, yet these plants are understudied for endophytic microbes harbouring novel bioactive molecules.

MAIN BODY

Endophytes are a source of novel organic natural molecules and are thought to be drug discovery frontiers. Endophyte research has contributed to the discovery of possible anticancer agents following the discovery of taxol. Endophyte research has contributed to the discovery of possible drug compounds with antimicrobial, antioxidant, antiviral, antidiabetic, anti-Alzheimers disease and immunosuppressive properties among others. These breakthroughs provide hope for combating incurable diseases, drug resistance, the emergence of new infectious diseases, and other human health issues. Finding new medicines that may be effective candidates for treating newly emerging diseases in humans has a lot of promise. Most studies have been on fungi endophytes, with just a few reports on bacterial endophytes. The biology of endophytic bacteria and fungi, as well as endophytic microbes isolated from Nigerian medicinal plants, their isolation methods, identification by morphological and molecular methods, fermentation, purification, identification of bioactive compounds and biosynthetic gene clusters are all covered in this study.

CONCLUSION

In Nigeria, the sourcing and isolation of endophytes harboring biosynthetic gene clusters are still understudied, necessitating a rigorous quest for bioactive molecules in endophytes inhabiting various ethnomedicinal plants.

A Compressive Review about Taxol®: History and Future Challenges

Taxol^®, which is also known as paclitaxel, is a chemotherapeutic agent widely used to treat different cancers. Since the discovery of its antitumoral activity, Taxol^® has been used to treat over one million patients, making it one of the most widely employed antitumoral drugs. Taxol^® was the first microtubule targeting agent described in the literature, with its main mechanism of action consisting of the disruption of microtubule dynamics, thus inducing mitotic arrest and cell death. However, secondary mechanisms for achieving apoptosis have also been demonstrated. Despite its wide use, Taxol^® has certain disadvantages. The main challenges facing Taxol^® are the need to find an environmentally sustainable production method based on the use of microorganisms, increase its bioavailability without exerting adverse effects on the health of patients and minimize the resistance presented by a high percentage of cells treated with paclitaxel. This review details, in a succinct manner, the main aspects of this important drug, from its discovery to the present day. We highlight the main challenges that must be faced in the coming years, in order to increase the effectiveness of Taxol^® as an anticancer agent.

Secondary Metabolites of Lasiodiplodia theobromae: Distribution, Chemical Diversity, Bioactivity, and Implications of Their Occurrence

Lasiodiplodia theobromae is a plant pathogenic fungus from the family Botryosphaeriaceae that is commonly found in tropical and subtropical regions. It has been associated with many hosts, causing diverse diseases and being responsible for serious damages on economically important crops. A diverse array of bioactive low molecular weight compounds has been described as being produced by L. theobromae cultures. In this review, the existing literature on secondary metabolites of L. theobromae, their bioactivity, and the implications of their occurrence are compiled. Moreover, the effects of abiotic factors (e.g., temperature, nutrient availability) on secondary metabolites production are highlighted, and possible avenues for future research are presented. Currently, a total of 134 chemically defined compounds belonging to the classes of secondary metabolites and fatty acids have been reported from over 30 L. theobromae isolates. Compounds reported include cyclohexenes and cyclohexenones, indoles, jasmonates, lactones, melleins, phenols, and others. Most of the existing bioactivity studies of L. theobromae metabolites have assessed their potential phytotoxic, cytotoxic, and antimicrobial activities. In fact, its host adaptability and its ability to cause diseases in plants as well as in humans may be related to the capacity to produce bioactive compounds directly involved in host–fungus interactions.

A Potent and Safer Anticancer and Antibacterial Taxus-Based Green Synthesized Silver Nanoparticle

Purpose

Paclitaxel is a generic drug produced based on Taxol which is an extract of Taxus tree, well known for its anticancer and antibacterial effects. This study was aimed at building up an agent with the antibacterial and anticancer benefits of both the silver ions and Taxol, together with less cytotoxic effects.

Materials and Methods

Colloidal silver nanoparticles (AgNPs) were synthesized by reducing aqueous AgNO₃ with aqueous Taxus leaf extract at nonphotomediated conditions, without any catalyst, template or surfactant. The AgNP production was confirmed by ultraviolet-visible (UV-VIS) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier-transform infrared (FTI) spectroscopy. The MTT assay for human breast cancer cells as well as the DAPI fluorescent staining microscopy tested the biocompatibility and anticancer effects of AgNPs, silver nitrate, and Taxol. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) techniques were performed to determine the shape and size of the nanoparticles. MTT assay showed the best inhibitory concentration of AgNPs on cancer cells. The antibacterial activity of the three case study materials was tested for gram-positive (Staphylococcus aureus) and gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) using well diffusion test.

Results

This work proposes more anticancer effects for AgNP made by Taxus brevifolia extract, comparing Taxol solution. IC50 was observed as 3.1 mM for Taxol while 1.5 mM for new AgNP. Moreover, Taxus showed no antibacterial effects while the new AgNP showed a dose-dependent biocompatibility along with slightly more antibacterial effects (MIC: 1.6 and 6.6mM for gram-positive and -negative bacteria, respectively) comparing with silver nitrate solution (MIC: 1.5 and 6.2 mM for gram-positive and -negative bacteria, respectively).

Conclusion

The production of herbal-mediated silver nanoparticles may be an efficient substitution for the silver nitrate–based medicines with less side effects.

Alternative sources and metabolic engineering of Taxol: Advances and future perspectives

Paclitaxel is one of the strong plant-derived anti-cancer drugs that was first isolated from the Pacific yew. Despite many paclitaxel's clinical successes, the limited accessibility of paclitaxel for clinical trials is recognized as the most important challenge. Thus, researchers are continuously trying to find the innovative ways to meet the community's need for this medicine. In the first step, the alternative sources for Taxol supply were recognized, such as Taxus genus, other plant genera, and endophytic fungi. In the next step, the biosynthetic pathways of Taxol or related metabolites were manipulated in the original organisms, or introduced to heterologous systems and then were manipulated in them. Here, a range of metabolic manipulating approaches have been successfully developed to redirect the metabolic flux toward Taxol, including promoter engineering, enzyme engineering, overexpressing the bottleneck enzymes, over- or down-regulation of transcription factors, activation of the cryptic genes, removing/minimizing the flux for competing pathways, tunable regulation of the metabolic pathway, and increasing the supplies of precursors. In this review, we discuss research progress on the alternative Taxol sources and its metabolic manipulating, and we suggest recent challenges and future perspectives.

Natural Bioactive Compounds from Fungi as Potential Candidates for Protease Inhibitors and Immunomodulators to Apply for Coronaviruses

The inhibition of viral protease is an important target in antiviral drug discovery and development. To date, protease inhibitor drugs, especially HIV-1 protease inhibitors, have been available for human clinical use in the treatment of coronaviruses. However, these drugs can have adverse side effects and they can become ineffective due to eventual drug resistance. Thus, the search for natural bioactive compounds that were obtained from bio-resources that exert inhibitory capabilities against HIV-1 protease activity is of great interest. Fungi are a source of natural bioactive compounds that offer therapeutic potential in the prevention of viral diseases and for the improvement of human immunomodulation. Here, we made a brief review of the current findings on fungi as producers of protease inhibitors and studies on the relevant candidate fungal bioactive compounds that can offer immunomodulatory activities as potential therapeutic agents of coronaviruses in the future.

Anti-HIV, antitumor and immunomodulatory activities of paclitaxel from fermentation broth using molecular imprinting technique

In this study, a single component paclitaxel was obtained from fermentation broth by molecular imprinting technique, and its antiviral, antitumor and immunomodulatory activities were studied. The results showed that paclitaxel had a good inhibitory activity on human breast cancer MCF-7 cells and showed a concentration- dependent relationship with an IC50 of about 15 μg/mL in the sulforhodamine B assay. At the same time, paclitaxel exerted a weak inhibitory activity on cervical cancer Hela cells. In addition, paclitaxel not only inhibited the invasion of HIV-1 pseudovirus into cells, but also exhibited inhibitory activity to a certain extent after viral invasion of the cells. At a paclitaxel concentration of 20 μg/mL, the inhibition of HIV-1 pseudovirus reached about 66%. The inhibition of HIV-1 protease activity was concentration-dependent. At a concentration of 20 μg/mL, the inhibitory effect of paclitaxel on HIV-1 protease was similar to that of the positive control pepstatin A, being 15.8%. The HIV-1 integrase inhibiting activity of paclitaxel was relatively weak. Paclitaxel significantly up-regulated the expression of interleukin-6.

Factors Affecting the Metabolite Productions in Endophytes: Biotechnological Approaches for Production of Metabolites

Since 1980, many species and different strains from endophytic genera of Phomopsis, Fusarium, Pestaliopsis and Aspergillus have been studied because of their ability to produce medicinal compounds found in their host plants. Some of these medicinal agents such as Taxol, Brefeldine A, Camptothecin and Podophyllotoxin are being produced in large-scale after an optimization process. However, the potential of fungal endophytes to produce host-like medicinal compounds remains largely unexplored.

Identification of Lysine Histidine Transporter 2 as an 1-Aminocyclopropane Carboxylic Acid Transporter in Arabidopsis thaliana by Transgenic Complementation Approach

1-Aminocyclopropane-1-carboxylic acid (ACC), a biosynthetic precursor of ethylene, has long been proposed to act as a mobile messenger in higher plants. However, little is known about the transport system of ACC. Recently, our genetic characterization of an ACC-resistant mutant with normal ethylene sensitivity revealed that lysine histidine transporter 1 (LHT1) functions as a transporter of ACC. As amino acid transporters might have broad substrate specificity, we hypothesized that other amino acid transporters including LHT1 paralogs might have the ACC-transporter activity. Here, we took a gain-of-function approach by transgenic complementation of lht1 mutant with a selected set of amino acid transporters. When we introduced transgene into the lht1 mutant, the transgenic expression of LHT2, but not of LHT3 or amino acid permease 5 (AAP5), restored the ACC resistance phenotype of the lht1 mutant. The result provides genetic evidence that some, if not all, amino acid transporters in Arabidopsis can function as ACC transporters. In support, when expressed in Xenopus laevis oocytes, both LHT1 and LHT2 exhibited ACC-transporting activity, inducing inward current upon addition of ACC. Interestingly, the transgenic expression of LHT2, but not of LHT3 or AAP5, could also suppress the early senescence phenotypes of the lht1 mutant. Taking together, we propose that plants have evolved a multitude of ACC transporters based on amino acid transporters, which would contribute to the differential distribution of ACC under various spatiotemporal contexts.