Endophytic fungi isolated from medicinal plants: future prospects of bioactive natural products from Tabebuia/Handroanthus endophytes

Medicinal plants are a rich source of natural products used to treat many diseases; therefore, they are the basis for a new drug discovery. Plants are capable of generating different bioactive secondary metabolites, but a large amount of botanical material is often necessary to obtain small amounts of the target substance. Nowadays, many medicinal plants are becoming rather scarce. For this reason, it is important to point out the interactions between endophytic microorganisms and the host plant, because endophytes are able to produce highly diverse compounds, including those from host plants that have important biological activities. Thence, this review aims at presenting the richness in bioactive compounds of the medicinal plants from Tabebuia and Handroanthus genera, as well as important aspects about endophyte-plant interactions, with emphasis on the production of bioactive compounds by endophytic fungi, which has been isolated from various medicinal plants for such a purpose. Furthermore, bio-prospection of natural products synthesized by endophytes isolated from the aforementioned genera used in traditional medicine could be used to treat illnesses.

     

A potential antioxidant resource: Endophytic fungi from medicinal plants

Medicinal plants and their endophytes are important resources for discovery of natural products. Several previous studies have found a positive correlation between total antioxidant capacity (TAC) and total phenolic content (TPC) of many medicinal plant extracts. However, no information is available on whether such a relationship also exists in their endophytic fungal metabolites. We investigated the relationship between TAC and TPC for 292 morphologically distinct endophytic fungi isolated from 29 traditional Chinese medicinal plants. The antioxidant capacities of the endophytic fungal cultures were significantly correlated with their total phenolic contents, suggesting that phenolics were also the major antioxidant constituents of the endophytes. Some of the endophytes were found to produce metabolites possessing strong antioxidant activities. Several bioactive constituents from the fungal cultures and host plant extracts were identified. This investigation reveals that the metabolites produced by a wide diversity of endophytic fungi in culture can be a potential source of novel natural antioxidants.     

Bioactive secondary metabolites produced by microorganisms associated with plants

In the past few decades groups of scientists have focused their study on relatively new microorganisms called endophytes. By definition these microorganisms, mostly fungi and bacteria, colonise the intercellular spaces of the plant tissues. The mutual relationship between endophytic microorganisms and their host plants, taxanomy and ecology of endophytes are being studied. Some of these microorganisms produce bioactive secondary metabolites that may be involved in a host-endophyte relationship. Recently, many endophytic bioactive metabolites, known as well as new substances, possesing a wide variety of biological activities as antibiotic, antitumor, antiinflammatory, antioxidant, etc. have been identified. The microorganisms such as endophytes may be very interesting for biotechnological production of bioactive substances as medicinally important agents. Therefore the aim of this review is to briefly characterize endophytes and summarize the structuraly different bioactive secondary metabolites produced by endophytic microorganisms as well as microbial sources of these metabolites and their host plants.     

药用植物内生真菌研究现状及其应用前景

随着对药用植物内生真菌研究的深入,从药用植物内生真菌中寻找新的生物活性成分已成为研究热点。内生真菌对药用植物的生长及活性成分的形成都有影响,内生真菌活性成分已成为发现新颖结构化合物及新药物的潜在资源。简要综述了近年来在内生真菌的分离鉴定、发酵、次生代谢产物、与宿主的关系等方面的研究进展。     

The Diversity and Anti-Microbial Activity of Endophytic Actinomycetes Isolated from Medicinal Plants in Panxi Plateau,China

Traditional Chinese medicinal plants are sources of biologically active compounds, providing raw material for pharmaceutical, cosmetic and fragrance industries. The endophytes of medicinal plants participate in biochemical pathways and produce analogous or novel bioactive compounds. Panxi plateau in South-west Sichuan in China with its unique geographical and climatological characteristics is a habitat of a great variety of medicinal plants. In this study, 560 endophytic actinomycetes were isolated from 26 medicinal plant species in Panxi plateau. 60 isolates were selected for 16S rDNA-RFLP analysis and 14 representative strains were chosen for 16S rDNA sequencing. According to the phylogenetic analysis, seven isolates were Streptomyces sp., while the remainder belonged to genera Micromonospora, Oerskovia, Nonomuraea, Promicromonospora and Rhodococcus. Antimicrobial activity analysis combined with the results of amplifying genes coding for polyketide synthetase (PKS-I, PKS-II) and nonribosomal peptide synthetase (NRPS) showed that endophytic actinomycetes isolated from medicinal plants in Panxi plateau had broad-spectrum antimicrobial activity and potential natural product diversity, which further proved that endophytic actinomycetes are valuable reservoirs of novel bioactive compounds.     

Fungal growth promotor endophytes: a pragmatic approach towards sustainable food and agriculture

Agricultural productivity suffers a heavy loss due to plant pathogens, insect pests and various abiotic stresses. Agriculture being the world’s largest economic sector, it is the need of time to find and establish the ideal strategy for sustainable agriculture and improvement in crop growth. Endophytes are microorganisms that asymptomatically grow within the plant tissues without causing any disease to the host. Endophytic fungi live in symbiotic association with plants and play an important role in plant growth promotion, higher seed yield and plants resistant to various biotic, abiotic stresses and diseases. Many are able to produce antimicrobial compounds, plant growth hormones and various agrochemical bioactive metabolites. These mycoendophytes hold enormous potential for the development of eco-friendly and economically viable agricultural products. In this review we focused on the endophytic fungi recovered from different medicinal plants, their active principles involved in plant growth enhancement and the applications of fungal endophytes in agriculture. Moreover, we also discussed about endophytic fungi and their pragmatic approach towards sustainable food and agriculture.     

Endophytic fungi: resource for gibberellins and crop abiotic stress resistance

The beneficial effects of endophytes on plant growth are important for agricultural ecosystems because they reduce the need for fertilizers and decrease soil and water pollution while compensating for environmental perturbations. Endophytic fungi are a novel source of bioactive secondary metabolites; moreover, recently they have been found to produce physiologically active gibberellins as well. The symbiosis of gibberellins producing endophytic fungi with crops can be a promising strategy to overcome the adverse effects of abiotic stresses. The association of such endophytes has not only increased plant biomass but also ameliorated plant-growth during extreme environmental conditions. Endophytic fungi represent a trove of unexplored biodiversity and a frequently overlooked component of crop ecology. The present review describes the role of gibberellins producing endophytic fungi, suggests putative mechanisms involved in plant endophyte stress interactions and discusses future prospects in this field.     

Fungal endophytes and bioprospecting

Horizontally transmitted fungal endophytes are an ecological group of fungi, mostly belonging to the Ascomycota, that reside in the aerial tissues and roots of plants without inducing any visual symptoms of their presence. These fungi appear to have a capacity to produce an array of secondary metabolites exhibiting a variety of biological activity. Although the ability of fungi to produce unique bioactive metabolites is well known, endophytes have not been exploited, perhaps because we are only beginning to understand their distribution and biology. This review emphasizes the need to routinely include endophytic fungi in the screening of organisms for bioactive metabolites and novel drugs; it also underscores the need to use information obtained concerning fungal secondary metabolite production from other groups of fungi for a targeted screening approach.     

药用植物内生真菌及活性物质多样性研究进展

药用植物具有丰富的物种多样性,是人类生存与发展的重要自然资源。内生真菌广泛存在于健康植物组织内部,是植物微生态系统的重要组成部分,各种药用植物中蕴藏着非常丰富的内生真菌。通过与药用植物的“协同进化”,某些内生真菌具有了产生与宿主植物相同或相似的生物活性物质的能力。内生真菌产生的各种活性物质,在生物制药、农业生产、工业发酵等方面都表现出美好的应用前景,受到世界各国专家的广泛关注。利用内生真菌发酵实现生物活性物质的工业化生产,可以提高产量、降低产品成本,满足人们日益增长的需求;同时有利于珍稀、濒危药用植物资源的保护,对减少野生药用植物多样性的破坏具有重要意义。本文从药用植物内生真菌物种多样性与产生生物活性物质多样性等方面总结近年最新的研究进展,提出了内生真菌及活性物质研究的未来发展方向。     

Piperine production by endophytic fungus Colletotrichum gloeosporioides isolated from Piper nigrum

Many endophytic fungi have been reported with the biosynthetic potential to produce same or similar metabolites present in host plants. The adaptations that might have acquired by these fungi as a result of the long-term association with their host plants can be the possible basis of their biosynthetic potential. The bioactive compounds originated from endophytes are currently explored for their potential applications in pharmaceutical, agriculture and food industries. Piper nigrum, a plant of the Piperaceae is very remarkable because of the presence of the alkaloid piperine. Piperine has been reported to have broad bioactive properties ranging from antimicrobial, antidepressant, anti-inflammatory, antioxidative to anticancer activities. Interestingly, piperine also plays a vital role in increasing the bioavailability of many drugs which again is a promising property. The current study was carried out to identify piperine producing endophytic fungus from Piper nigrum L. By screening various endophytic fungi, the isolate which was identified as member of Colletotrichum gloeosporioides was found to have the ability to form piperine and was confirmed by HPLC and LCMS. Considering the broad bioactive potential of piperine, the piperine producing fungi identified in the study can expect to have much industrial potential.     

Rainforest Endophytes and Bioactive Products

ABSTRACT:?

An increase in the number of people in the world having health problems caused by certain cancers, drug-resistant bacteria, parasitic protozoans, and fungi has caused alarm. An intensive search for newer and more effective agents to deal with these problems is now underway. Endophytes are a potential source of novel chemistry and biology to assist in helping solve not only human health, but plant and animal health problems also. Endophytes reside in the tissues between living plant cells. The relationship that they establish with the plant varies from symbiotic to bordering on pathogenic. Of all of the world's plants, it seems that only a few grass species have had their complete complement of endophytes studied. As a result, the opportunity to find new and interesting endophytes among the myriad of plants is great. Sometimes extremely unusual and valuable organic substances are produced by these endophytes. These compounds may contribute to the host-microbe relationship. The initial step in dealing with endophytic microorganisms is their successful isolation from plant materials. Then, the isolation and characterization of bioactive substances from culture filtrates is done using bioassay guided fractionation and spectroscopic methods. Some of the more interesting compounds produced by endophytic microbes with which we have dealt are taxol, cryptocin, cryptocandin, jesterone, oocydin, isopestacin, the pseudomycins and ambuic acid. This review discusses an approach for bio-prospecting the rainforests, not only to harvest their endophytic microorganisms, but to eventually build a better understanding of the importance and value they have to humankind.     

Screening for Endophytic Fungi with Antitumour and Antifungal Activities from Chinese Medicinal Plants

Summary One hundred and thirty endophytic fungi isolated from 12 Chinese traditional medicinal plants collected at Yuanmou county and Dawei Mountain, Yunnan province, southwest China, were tested for antitumour and antifungal activities by MTT assay on human gastric tumour cell line BGC-823 and the growth inhibition test against 7 phytopathogenic fungi. The results showed that fermentation broths from 9.2% of the isolates exhibited antitumour activity and 30% exhibited antifungal activity, moreover, some of them exhibited broad-spectrum antifungal activity. The active isolates were identified to 32 taxa. The results indicate that the endophytic fungi of Chinese traditional medicinal plants are promising sources of novel bioactive compounds.     

Rainforest endophytes and bioactive products

An increase in the number of people in the world having health problems caused by certain cancers, drug-resistant bacteria, parasitic protozoans, and fungi has caused alarm. An intensive search for newer and more effective agents to deal with these problems is now underway. Endophytes are a potential source of novel chemistry and biology to assist in helping solve not only human health, but plant and animal health problems also. Endophytes reside in the tissues between living plant cells. The relationship that they establish with the plant varies from symbiotic to bordering on pathogenic. Of all of the world's plants, it seems that only a few grass species have had their complete complement of endophytes studied. As a result, the opportunity to find new and interesting endophytes among the myriad of plants is great. Sometimes extremely unusual and valuable organic substances are produced by these endophytes. These compounds may contribute to the host-microbe relationship. The initial step in dealing with endophytic microorganisms is their successful isolation from plant materials. Then, the isolation and characterization of bioactive substances from culture filtrates is done using bioassay guided fractionation and spectroscopic methods. Some of the more interesting compounds produced by endophytic microbes with which we have dealt are taxol, cryptocin, cryptocandin, jesterone, oocydin, isopestacin, the pseudomycins and ambuic acid. This review discusses an approach for bio-prospecting the rainforests, not only to harvest their endophytic microorganisms, but to eventually build a better understanding of the importance and value they have to humankind.     

Endophytic fungi and their metabolites isolated from Indian medicinal plant

Endophytic fungi have been creating a considerable interest and curiosity among researchers since past three decades globally, owing to their recognition as an inexhaustible source of structurally and biologically novel compounds, alternative source of metabolites functionally identical to plant produced metabolites and their ability to impart resistance in host plants against various biotic and abiotic stresses. In this review, we have earnestly attempted to compile a vast array of endophytic fungi assemblages harbored inside Indian medicinal plants which have been reported during last decade from India.     

植物内生真菌抗肿瘤活性代谢产物研究进展

癌症已成为全球头号杀手,迫切需要从自然界寻找更新、更有效的抗肿瘤药物。植物内生真菌是指生活在宿主植物体内,不会对宿主植物组织引起明显病害症状的一类真菌。众多研究表明,植物内生真菌在寻找抗肿瘤药物中起着至关重要的作用。随着植物内生真菌研究的深入,从植物内生真菌中寻找新的抗肿瘤活性成分已成为研究的热点。大量的抗肿瘤活性成分从植物内生真菌中分离出来,并表现出良好的抗肿瘤活性。目前,植物内生真菌抗肿瘤活性代谢产物主要有紫杉醇、喜树碱、长春新碱,鬼臼毒素等等,本文主要对近年来植物内生真菌抗肿瘤活性成分的研究进展进行了综述。     

Endophyte research: going beyond isolation and metabolite documentation

Many fungi belonging to mostly Ascomycota inhabit living tissues of plants of all major lineages without causing any visible symptoms. Termed horizontally transmitted endophytes, they have been investigated mostly for their capacity to produce bioactive secondary metabolites. However, many questions regarding the interactions between endophytes and their plant hosts, phytophagous insects and other fungi remain unanswered. This review highlights some of these areas of endophyte biology about which very little or no knowledge exists. Information garnered' using modern methodologies' on these grey areas of ‘endophytism’ (endophytic mode of lifestyle) would help immensely in understanding the evolution of endophytes of aerial plant tissues and in exploiting endophytes in various fields of biotechnology.     

Biodiversity and antimicrobial potential of bacterial endophytes from halophyte Salicornia brachiata

Extreme natural habitats like halophytes, marsh land, and marine environment are suitable arena for chemical ecology between plants and microbes having environmental impact. Endophytes are an ecofriendly option for the promotion of plant growth and to serve as sustainable resource of novel bioactive natural products. The present study, focusing on biodiversity of bacterial endophytes from Salicornia brachiata, led to isolation of around 336 bacterial endophytes. Phylogenetic analysis of 63 endophytes revealed 13 genera with 27 different species, belonging to 3 major groups: Firmicutes, Proteobacteria, and Actinobacteria. 30% endophytic isolates belonging to various genera demonstrated broad-spectrum antibacterial and antifungal activities against a panel of human, plant, and aquatic infectious agents. An endophytic isolate Bacillus amyloliquefaciens 5NPA-1, exhibited strong in-vitro antibacterial activity against human pathogen Staphylococcus aureus and phytopathogen Xanthomonas campestris. Investigation through LC–MS/MS-based molecular networking and bioactivity-guided purification led to the identification of three bioactive compounds belonging to lipopeptide class based on ¹H-, ¹³C-NMR and MS analysis. To our knowledge, this is the first report studying bacterial endophytic biodiversity of Salicornia brachiata and the isolation of bioactive compounds from its endophyte. Overall, the present study provides insights into the diversity of endophytes associated with the plants from the extreme environment as a rich source of metabolites with remarkable agricultural applications and therapeutic properties.

     

Fungal endophytes: unique plant inhabitants with great promises

Fungal endophytes residing in the internal tissues of living plants occur in almost every plant on earth from the arctic to the tropics. The endophyte–host relationship is described as a balanced symbiotic continuum ranging from mutualism through commensalism to parasitism. This overview will highlight selected aspects of endophyte diversity, host specificity, endophyte–host interaction and communication as well as regulation of secondary metabolite production with emphasis on advanced genomic methods and their role in improving our current knowledge of endophytic associations. Furthermore, the chemical potential of endophytic fungi for drug discovery will be discussed with focus on the detection of pharmaceutically valuable plant constituents as products of fungal biosynthesis. In addition, selected examples of bioactive metabolites reported in recent years (2008–2010) from fungal endophytes residing in terrestrial plants are presented grouped according to their reported biological activities.     

植物内生真菌及其活性代谢产物研究进展

植物内生真菌是一大类未被充分研究过的真菌,其物种及代谢产物均具有生物多样性,现今从植物内生真菌中得到的活性物质种类远比从土壤微生物中得到的多。对植物内生真菌的研究具有重要的生态学意义和经济学意义,在各个领域中应用前景广泛。作者主要综述了植物内生真菌及其活性物质研究的最新进展。     

植物内生菌及其防治植物病害的研究进展

综述了植物内生菌及其防治植物病害的研究进展.植物内生菌分布广,种类多,几乎存在于所有目前已研究过的陆生及水生植物中,目前全世界至少已在80个属290多种禾本科植物中发现有内生真菌,在各种农作物及经济作物中发现的内生细菌已超过120种.感染内生菌的植物宿主往往具有生长快速、抗逆境、抗病害、抗动物危害等优势,比未感染内生菌的植株更具生存竞争力.植物内生菌的防病机理主要表现在通过产生抗生素类,水解酶类,植物生长调节剂和生物碱类物质,与病原菌竞争营养物质,增强宿主植物的抵抗力以及诱导植物产生系统抗性等途径抑制病原菌生长.另外,对植物内生真菌和内生细菌的分离、筛选和检测方法;利用植物内生菌控制植物病害的途径如人工接种内生菌,利用内生菌代谢产生的抗生素以及将内生菌作为基因工程的载体菌等进行了综述.同时,对植物内生菌作为生物防治因子未来发展前景及存在的问题进行了讨论.利用植物内生菌作为生物防治因子进行大田防病,需要考虑它的病理学、生态学和形态学等方面的影响.