Endophytes in Medicinal Plants: A Sustainable Solution for Coping with Environmental Stresses.

Since thousands years back approximately around 900 BC, medicinal plants are considered as a source of many biomolecules with therapeutic potential. Herbal medicines are considered as safer, better, physiologically compatible and costeffective. The oldest evidence of medicinal and aromatic plants depicts that with the emergence of human civilization, plants have been considered as the main source to heal and cure various serious ailments. It has been proven that the secondary metabolites e.g. alkaloid, glycosides, flavonoides, steroids etc present in the medicinal plants possesses ability to prevent occurrence of some of the diseases, means medicinal plants acts as a “preventive medicine”. Medicinal plants have a paramount importance and a great interest due to its pharmaceutical, cosmetic and nutritional values. Some plants are also considered as an important source of nutrition and are known to have a variety of compounds with potential therapeutic properties. India is the principal repository of large number of medicinal and aromatic plants or we can say India is one of the rich mega-biodiversity countries of the world. Medicinal plants are “backbone” of traditional medicinal system (TMS). Crude drugs are usually dried parts of medicinal and aromatic plants (MAPs) such as roots, stems, wood, bark, seeds, fruits, flowers, leaves, rhizomes, whole plant etc. that form the essential raw material for the production of medicines in various systems of Ayurveda, Siddha, Unani, Tibatian, Tribal and Homeopathy. According to the survey of the World Health Organization (WHO), about 80% of the world population are using herbs and other traditional medicines for their primary healthcare and have established three kinds of herbal medicines: raw plant material, processed plant material, and herbal products. Now days, variety of available herbs are used throughout the world and they continue to promote good health. As the benefits from medicinal and aromatic plants are recognized, these plants will have a special role for humans in the future. The present review on medicinal and aromatic plants revealed similar combination of studies.

Endophytes are a diverse group of microorganisms present in plant tissues which include fungi and bacteria and have been utilized as therapeutic agents. They are known to produce different secondary and primary metabolites, which can be used in therapy of various diseases. The primary objective of this review is to provide an insight of symbiotic relationship between the endophytes and medicinal plants, specifically belonging to Asia, and also to give detailed information about the novel bioactive secondary metabolites produced from endophytes, that serve as potential therapeutic agents. We performed a Pubmed-based literature search and considered publications including research and review papers related to endophytes, the chemical constituents isolated from them and their therapeutic applications. Endophytes have a symbiotic relationship with the host medicinal plants. They provide specific advantages to plants such as nitrogen fixation. They also produce biologically active secondary metabolites such as alkaloids, flavonoids, terpenes/terpenoids, polyphenols, xanthenes, anthraquinones, cytochalasins, benzofurans, steroids, lignans, polysaccharides and plant growth hormones. Many of these compounds have therapeutic applications such as antimicrobial, antioxidant, anticancer, and anti-inflammatory. Endophytic microbes also constitute an important source for drug discovery. This review comprehends the use of endophytes as therapeutic agents.

Ultraviolet (UV) radiation is a part of the sunlight reaching Earth surface. The UV spectrum of solar radiation is by convention divided into three parts: UV-A: 310–400 nm, UV-B: 280–310 nm and UV-C: less than 280 nm. UV-B is the most energetic component reaching Earth surface because the stratospheric ozone layer effectively absorbs completely wavelengths below 290 nm. UV-B is an increasing threat due to increasing UV-B levels on Earth surface as a consequence of depletion of stratospheric O3. In general, the effects of atmospheric UV-B radiation are negative for biological life. Enhanced levels of UV-B radiation can indeed negatively change plant physiological processes, growth and productivity. However, while studying UV-B effects on medicinal plants, some interesting phenomena have been discovered. For example, basil plants respond positively to UV-B radiation by increasing oil yield (Chang et al. J Horticult For 1:27–31, 2009). In other studies medicinal plants show beneficial aspects in term of increase in volatile oil yield and secondary metabolite production (Kumari et al. Ecotoxicol Environ Safety 72:2013–2019, 2009c, 2010). Medicinal herbs have great market value in India and worldwide. The medicinal value of plants depends upon phenolics, antioxidants and volatile yield. Therefore further UV-B experiments increasing the levels of these compounds are needed.Here we review the effect of UV-B exposure on metabolites, volatiles, and antioxidants potential in medicinal plants. This chapter reports: (1) aspects of the global market for medicinal and aromatic plants in India in order to assist the medicinal plant industry to make informed decisions. (2) The biodiversity loss due to wild harvesting of plants, and as an alternative the cultivation strategy of medicinal plants. (3) Main medicinal plant species having rich antioxidant potential. (4) Main secondary metabolites of plant origin such as phenylpropanoids, terpenes, alkaloids, and volatile oil, and other important metabolites containing high antioxidant level used in human diet and health. (5) UV-B factors that enhance the quality of medicinal plant by increasing the content of secondary bioactive products. (6) Secondary metabolic pathways involving regulation of key enzymes, chalcone synthase, and phenylalanine ammonia lyase. Understanding of UV-B responses on secondary plant metabolites expand new opportunities for plant enriched in medicinal active compounds.

An appraisal of arbuscular mycorrhiza-mediated augmentation in production of secondary metabolites in medicinal plants

Pharmacognosy Research,2023,15,2,217-225.DOI:10.5530/pres.15.2.023Published:February 2023Type:Review ArticleAuthors:Priyatama V. Powar, and Shilpa Chaudhari Author(s) affiliations:Priyatama V. Powar*, Shilpa Chaudhari Department of Pharmaceutics, Dr. D. Y. Patil College of Pharmacy, Akurdi, Pune, Maharashtra, INDIA. Abstract:Endophytic fungi are various micro-organisms that inhabit intracellular or intercellular plant tissues in symbiotic association [at certain stages of their life cycles], without causing damage or morphological changes. The endophytes from medicinal plants are important resources for discovery of natural products and secondary bioactive metabolites having the potential biotechnological applications in agriculture, medicine, and allied sectors. The endophytic fungi such as Acremonium, Aspergillus, Fusarium, Trichoderma, Penicillium, Phomopsis, Pestalotiopsis, Pseudomassari, Quercina, Trichoderma genera have been reported from different medicinal plants with potential therapeutic activity. On the other hand, the endophytic fungi can also confer profound impacts on their host plants like improvement in growth, activation of systemic tolerances towards abiotic/biotic stresses, enhancement of nutrient solublization, biosynthesis of phytohormones and stimulating accumulation of secondary metabolites. Endophytic fungi have attracted much research interest because they have provided not only novel sources of Cytotoxic compounds, Antimicrobial agents, Bio-stimulants for essential oil biosynthesis, Anticancer agents, antioxidant agents, anti-diabetic agents, immunosuppressant and insecticidal compounds. The present review reveals the importance of endophytic fungi from medicinal plants as a source of bioactive compounds as well as landscape of patents related to the production of secondary metabolites through endophytic fungi and their application in pharmaceutical sectors. Keywords:Biological activity, Endophytic fungi, Patents, Phytohormones., Secondary metabolites, Symbiotic associationView:PDF (564.03 KB)

Medicinal and aromatic plants are known to produce secondary metabolites that find uses as flavoring agents, fragrances, insecticides, dyes and drugs. Biotechnology offers several choices through which secondary metabolism in medicinal plants can be altered in innovative ways, to overproduce phytochemicals of interest, to reduce the content of toxic compounds or even to produce novel chemicals. Detailed investigation of chromatin organization and microRNAs affecting biosynthesis of secondary metabolites as well as exploring cryptic biosynthetic clusters and synthetic biology options, may provide additional ways to harness this resource. Plant secondary metabolites are a fascinating class of phytochemicals exhibiting immense chemical diversity. Considerable enigma regarding their natural biological functions and the vast array of pharmacological activities, amongst other uses, make secondary metabolites interesting and important candidates for research. Here, we present an update on changing trends in the biotechnological approaches that are used to understand and exploit the secondary metabolism in medicinal and aromatic plants. Bioprocessing in the form of suspension culture, organ culture or transformed hairy roots has been successful in scaling up secondary metabolite production in many cases. Pathway elucidation and metabolic engineering have been useful to get enhanced yield of the metabolite of interest; or, for producing novel metabolites. Heterologous expression of putative plant secondary metabolite biosynthesis genes in a microbe is useful to validate their functions, and in some cases, also, to produce plant metabolites in microbes. Endophytes, the microbes that normally colonize plant tissues, may also produce the phytochemicals produced by the host plant. The review also provides perspectives on future research in the field.

Arbuscular mycorrhizae fungi (AMF) are symbiotic relations between plants and fungi, it has a long history of more than 400 million years. AMF mycelium colonizes the plant root system forming structures like root hairs which are considered as functional site for absorbing nutrient from soil and transfer them into the plant root. AMF increase nutrients uptake from soil as well as improving disease resistance against many pathogens. Medicinal plants are used across the world as primary form of therapy in the all known traditional medical systems which considered safer, cheaper and effective compared with chemicals ones. These plants metabolites are classified as primary metabolites and secondary metabolites, these secondary metabolites are subdivided in three major classes: alkaloids, terpenoids, and phenolics. They contain numerous phytochemicals with beneficial therapeutic as well as preventive effects. AMF inoculation on medicinal plants decreased the infection of bacterial and fungal pathogens, in addition to that The AMF–medicinal plants interaction causes chemical and biological changes lead to change in the secondary metabolite concentrations. In this review, we have summarized the effect of different arbuscular mycorrhizae fungi on increasing or decreasing the secondary metabolites of some medicinal plants and it was discussed about the secondary metabolites pathways involved in AMF–medicinal plants interaction.

Agriculture is the study or practise of cultivating land, including that of the gradual improved soil condition in order to generate harvests for food, fleece, as well as other products. The area of land under cultivation has decreased dramatically over time as a result of expanding urbanisation and industrialisation; also, the agriculture industry has been severely impacted by population reduction and climate change. Data mining is a rapidly new and rapidly growing research-oriented subject in agriculture that is used to formulate and analyse diverse agricultural production situations. In agriculture, data mining might aid in yield prediction, climate and rainfall forecasts, seed and soil conditions, and crop production. In agriculture, predictive data mining is designed to estimate upcoming crop, fertilisers and pesticides that can be used, and income to be made for healthy crop development and function. Different “data mining techniques”, including “k-nearest neighbour (KNN) ”, “support vector machine (SVM)”, and “artificial neural network (ANN)”, are used to analyse different ways and boost agricultural growth. Each analysis technique will have its own unique way of perceiving numerous difficulties and leads to the development of a suitable solution for every agronomic challenge. Aim of this paper is to defining role of “Data Mining Techniques” for estimating crop yield in agricultural context among emerging nations. This research paper has considered mixed method technique (primary quantitative and secondary qualitative) to gather relevant and factual data.

This study explores agroecological practices designed to improve soil quality and crop yield in small-scale agriculture, focusing on soil inoculation with beneficial bacteria over conventional fertilizers. Conducted at the SZIA Agroecological Garden MATE in Gödöllő, Hungary, the research utilizes 12 plots to evaluate different conservation tillage methods, including minimum and no-tillage, with and without microbial inoculation. Commenced in 2022, this study centers on potato cultivation (Solanum tuberosum L.) and includes comprehensive chemical and physical analyses of soil and harvested potatoes, alongside continuous monitoring of growth. Statistical analysis using One-way Anova in R revealed p-values predominantly above 0.05, indicating no significant differences across most parameters, though variations in soil plasticity and pH (KCl) were noted. Results suggest that substantial treatmeent differences may require a longer observation period. Notably, plots with microbial inoculation exhibited higher harvest weights and tuber sizes compared to control plots. Additionally, trends and interactions were found between weed abundance, total harvest, and plant height. The findings indicate that the benefits of integrated agroecological practices, including conservation tillage, may take time to materialize, emphasizing the necessity for extended observation. This research lays the groundwork for future studies, underscoring the importance of patience in achieving improvements in soil health and crop quality through sustainable agricultural methods.

There has been increased use of herbal drugs in recent years. Because of increasing demand and wider use, it is essential that the quality of plant-based drugs should be assured prior to use. When heavy metals contaminate the plants from which herbal drugs are derived, they affect both plant growth characteristics and production of secondary plant metabolites. Plants exposed to heavy metal stress show changes in production of secondary metabolites. High levels of heavy metal contamination in medicinal or other plants may suppress secondary metabolite production. Alternatively, the presence of heavy metals in medicinal plants may stimulate production of bioactive compounds in many plant species. Moreover, some research results suggest that heavy metals may play an important role in triggering plant genes to alter the titers or nature of secondary plant metabolites, although the exact mechanism by which this happens remains unclear. Oxidative stress induced by heavy metals triggers signaling pathways that affect production of specific plant metabolites. In particular, reactive oxygen species (ROS), generated during heavy metal stress, may cause lipid peroxidation that stimulates formation of highly active signaling compounds capable of triggering production of bioactive compounds (secondary metabolites) that enhances the medicinal value of the plant. As usual, further research is needed to clarify the mechanism by which heavy metals induce responses that result in enhanced secondary metabolite production.

Medicinal plants are used directly as therapeutic agents in various traditional practices, and medicinal plants like Dioscorea deltoidea, Papaver somniferum, Atropa belladonna, Rauvolfia serpentina, Hyoscyamus niger, Digitalis lanata, Datura metel, Digitalis purpurea, Pilocarpusa bonandi, Cinchona ledgeriana are contributing directly several prescribed medicinals. The ever-increasing trend in the use of medicinal herbs and herbal products in therapeutic purpose, research, and trade has created tremendous pressure on supply from their wild source. Under the circumstances of increasing demand, indiscriminate and over extraction from the wild, habitat destruction, etc., many of the naturally growing medicinal herbs are on the verge of extinction and thus unsustainability in the supply of medicinal plants from natural source. Systematic cultivation of medicinal herbs would be a viable alternative to overcome this unsustainability problem of medicinal plants from the wild source and cultivation offers opportunity to optimize yield and achieve a uniform, high-quality product. Several drugs like cardamom, cannabis, cinnamon, ginger, cinchona, opium, linseed, and fennel are now obtained almost exclusively from cultivation source. Benefits of cultivation of medicinal plants are widely viewed as a means for meeting current and future demands for large volume production of plant-based drugs; cultivation can reduce growing pressures on wild medicinal plants and ensure pure and smooth supply; means of earning livelihood, etc. The WHO has published wide-spectrum guidelines for good agricultural and collection practices for sustainable production of raw material of quality and standardized herbal ingredients to ensure quality of herbal medicines. Medicinal plants may be cultivated by the following: (a) agricultural practice at field level and (b) in vitro production of secondary metabolites. Commercial cultivation at field level (open field, homestead garden, forest floor) is an agronomic practice and offers the opportunity to overcome the problems that are inherent in herbal extracts like misidentification, genetic and phenotypic variability, extract variability and instability, toxic components, and contaminants. The agronomic method of crop cultivation includes systematically the steps like site and season selection, selection of crop, true seed or vegetative propagule, land preparation and basal manuring and fertilization, spacing, seed sowing or seedling transplantation, split application of fertilizer, irrigation, intercultural operation, and weed control and harvesting. Large-scale plant tissue or organ culture for the production of secondary metabolites is an attractive alternative approach to traditional methods of cultivation of drug plants. The advantages of this method are many; it is independent of soil, paste, climatic interference, geographical location, and it can ultimately provide a continuous and reliable source of natural products. Considering the cost involvement, plant tissue culture for secondary metabolites is now limited to only high-value compounds such as diosgenin-derived steroid hormone precursors, digitalis glycosides, berberine isoquinoline alkaloid, taxol, paclitaxel, and several other toxoids—complex diterpene alkaloids. Herbal plants have global market worth about US$62 billion per annum, and so they may be a good export item and wealth of a country and should be cultivated in commercial scale like any other conventional cash crops. As cultivation of medicinal plants at commercial scale is comparatively a new concept in many countries to meet the demand of internal and foreign markets and earning livelihood of the rural people, medicinal plants are important natural wealth and herbal wealth, play significant role in providing primary health-care services to rural people, and serve as raw material in traditional and modern pharmaceutical as well as in cosmetic, agricultural, and food industries. Substantial amount of foreign exchange can be earned by exporting medicinal plants to other countries. In this way, indigenous medicinal plants may play a significant role in the economy of a country.

Endophytes are microbial symbionts of plants which dwell within the internal tissues of healthy plants without the manifestation of any infection symptoms on their hosts. In addition to being vital to the growth and development of their host, endophytes also assist their medicinal plant host species in accumulating some highly coveted plant secondary metabolites under various abiotic stress conditions. The type and quantity of secondary metabolites accumulated by medicinal plants under abiotic stress rely on the age and developmental phase of the host as well as the taxonomic groupings of both symbionts. Medicinal plants during their life cycle become vulnerable to different types of tissue-damaging abiotic stress factors that hamper their survival and productivity. These stressors are connected to an appreciable build-up of reactive oxygen species (ROS) in plant tissues. ROS are a reactive group of chemicals that interact with several metabolites and cellular molecules, thus prompting irreversible metabolic anomalies and cell necrosis. Reactive oxygen species also serve as stress signals to medicinal plants and to ensure their survival; these plants produce antioxidants (both enzymatic and non-enzymatic) to maintain the integrity of their system. Some of the antioxidants are, however, produced as a result of the symbiotic relationship between medicinal plants and their endophytes. In this review, we aim to examine the interaction between endophytes and their medicinal plant host under abiotic stress.

The global healthcare market in the post-pandemic era emphasizes a constant pursuit of therapeutic, adaptogenic, and immune booster drugs. Medicinal plants are the only natural resource to meet this by supplying an array of bioactive secondary metabolites in an economic, greener and sustainable manner. Driven by the thrust in demand for natural immunity imparting nutraceutical and life-saving plant-derived drugs, the acreage for commercial cultivation of medicinal plants has dramatically increased in recent years. Limited resources of land and water, low productivity, poor soil fertility coupled with climate change, and biotic (bacteria, fungi, insects, viruses, nematodes) and abiotic (temperature, drought, salinity, waterlogging, and metal toxicity) stress necessitate medicinal plant productivity enhancement through sustainable strategies. Plants evolved intricate physiological (membrane integrity, organelle structural changes, osmotic adjustments, cell and tissue survival, reclamation, increased root-shoot ratio, antibiosis, hypersensitivity, etc.), biochemical (phytohormones synthesis, proline, protein levels, antioxidant enzymes accumulation, ion exclusion, generation of heat-shock proteins, synthesis of allelochemicals. etc.), and cellular (sensing of stress signals, signaling pathways, modulating expression of stress-responsive genes and proteins, etc.) mechanisms to combat stresses. Endophytes, colonizing in different plant tissues, synthesize novel bioactive compounds that medicinal plants can harness to mitigate environmental cues, thus making the agroecosystems self-sufficient toward green and sustainable approaches. Medicinal plants with a host set of metabolites and endophytes with another set of secondary metabolites interact in a highly complex manner involving adaptive mechanisms, including appropriate cellular responses triggered by stimuli received from the sensors situated on the cytoplasm and transmitting signals to the transcriptional machinery in the nucleus to withstand a stressful environment effectively. Signaling pathways serve as a crucial nexus for sensing stress and establishing plants’ proper molecular and cellular responses. However, the underlying mechanisms and critical signaling pathways triggered by endophytic microbes are meager. This review comprehends the diversity of endophytes in medicinal plants and endophyte-mediated plant-microbe interactions for biotic and abiotic stress tolerance in medicinal plants by understanding complex adaptive physiological mechanisms and signaling cascades involving defined molecular and cellular responses. Leveraging this knowledge, researchers can design specific microbial formulations that optimize plant health, increase nutrient uptake, boost crop yields, and support a resilient, sustainable agricultural system.

Medicinal plants having diversified phytochemical compounds like secondary plant metabolites (alkaloids, terpenoids, phenols, steroids, flavanoids, tannins, cyanogenic glycosides and glucosinolates, essential oils and aromatic compounds etc) are subject to abiotic stress like drought. Drought, one of the major ecologically limiting factors has significant impact on growth and secondary metabolic process of several medicinal plants. Water stress causes a reduction in plant size, density, reduces plant leaf area, and decrease in whole biomass, and not only alters the plant structurally and anatomically but also leads to fluctuation of their secondary chemical constituents. Secondary plant metabolites (SPMs) are useful to assess the quality and quantity of the therapeutic ingredients and such metabolites synthesized by the plant helps to cope up towards the negative effects of stress for adaptation and defence. A large number of studies manifested from the relevant review that drought influences on SPMs production and accumulation from plant parts like roots, stems, leaves, flower, fruits, seeds etc and causes an increase or decrease in their solute concentration by up to 50%. Studies showed that a medicinal plant produces different concentration of a particular metabolite grown under stress and non-stress environment. Generally, drought stress accumulates a higher concentration of active phytochemicals like alkaloids, tannins, terpenoids etc whereas concentration of phenols, flavanoids and saponins etc decreases under drought. In most cases as a whole, it may have to be concluding from comparative analysis that medicinal plants grown under drought exhibits higher content of secondary plant products than grown under optimal conditions. In addition, all secondary products may not increase in equal proportions under stress and it depends on the intensity of the drought as well as species of medicinal plants. Thus, moderate drought stress significantly enhanced the quality as well as quantity of secondary active substances in medicinal plants. However, for better understanding indepth further research is utmost essential at molecular level using new techniques viz. Proteomics, metabolomics, transcriptomes and genomics etc.

The study of rhizospheric microbial flora for the enhancement of aroma compounds is well recognized. The rhizosphere microbes also play very important role in improving medicinal values of plants. Rhizospheric microbes affect the plant physiology by imparting several useful effects such as nitrogen fixation, nutrient uptake, and production of secondary metabolites in the medicinal and aromatic plants. Recent days there are increasing the interests in the research of the relation between rhizosphere microbes associated with medicinal plant for the improvement of quality of medicinal plants. A large variety of fungi and bacteria is recognized in the rhizosphere soil of medicinal plants that showed significant effect in secondary metabolite alteration and uptake of plant nutrient. There are reports that rhizosphere fungi not only enhanced the growth parameters in plants but also considerably modulated essential oil’s quality. This study highlighted the researches performed on active role of rhizosphere fungi on explored medicinal and aromatic plants. As the use of organic material is one of the constituents of good agricultural practices (GAPs). Therefore, this review also investigates the environmental concerns reducing the use harmful chemicals as well as recommendation for utilization of biological and organics in agriculture. Therefore, a proper understanding of role of rhizosphere mycoflora associated with the medicinal plants is essential.