Contribution of endophytes towards improving plant bioactive metabolites: a rescue option against red-taping of medicinal plants

Antimicrobial, Quorum Sensing Inhibition, and Anti-Cancer Activities of Silver Nanoparticles Synthesized from Kenyan Bacterial Endophytes of Teclea nobilis

Untapped bioactive compounds from microbial endophytes offer a promising solution to counter antimicrobial and chemotherapeutic drug resistance when complexed as silver nanoparticles (AgNPs). AgNPs were biosynthesized using cell-free supernatants from endophytic Streptomyces sp. KE4D and Bacillus safensis KE4K isolated from the Kenyan medicinal plant Teclea nobilis, following fermentation in three different media. Bacterial extracts were analyzed using gas chromatography-mass spectrometry. AgNPs were characterized using Fourier-transform infrared spectroscopy and high-resolution transmission electron microscopy. Antimicrobial activity was assessed using agar well diffusion assays, and quorum sensing inhibition (QSI) was investigated using Chromobacterium violaceum. Anti-cancer potential was evaluated against breast (MCF-7) and prostate cancer (DU-145) cell lines using MTT assays. AgNPs were 5-55 nm in size, with KE4D AgNPs being spherical and KE4K AgNPs exhibiting various shapes. Cyclopropane acetic acids and fatty acids were identified as possible capping agents. Medium-dependent antimicrobial activity was observed, with medium Mannitol and medium 5294 AgNPs displaying stronger activity, particularly against Gram-negative indicators. KE4D medium 5294 AgNPs demonstrated 85.12% violacein inhibition at 140 µg/mL and better QSI activity, whilst KE4K AgNPs were better antimicrobials. The AgNPs IC50 values were <3.5 µg/mL for MCF-7 and <2.5 µg/mL for DU-145 cells. The bioactivity of biosynthesized AgNPs is influenced by the bacterial isolate and fermentation medium, suggesting that AgNP synthesis can be tailored for specific bioactivity.

Characterization of bioactive compounds in fenugreek genotypes in varying environments: diosgenin, trigonelline, and 4-hydroxyisoleucine

This study investigates the effects of irrigated and non-irrigated conditions on the bioactive compound content in fenugreek (Trigonella foenum-graecum) across 31 diverse genotypes from various geographical regions. The study was conducted at Atatürk University Research and Extension Center, Türkiye (N 39°55'59.9", E 41°14'10.6", altitude 1789 m) during the 2021 and 2022 growing seasons. The levels of diosgenin, trigonelline, and 4-hydroxyisoleucine analyzed under irrigated and non-irrigated conditions were found to be significantly influenced by genotype, environment, and their interaction (Genotype × Environment), with a highly significant effect observed at the p < 0.001 level. The compounds analyzed included diosgenin (0.50-0.93%), trigonelline (5.22-13.65 mg g-¹), and 4-hydroxyisoleucine (0.41-1.90%). Notably, genotypes such as Sivas/TR, Amasya/TR, Konya/TR and Samsun/TR exhibited higher diosgenin content across all conditions, while Spain, Malaysia, France, and India showed higher trigonelline content under irrigation. Variability in 4-hydroxyisoleucine content was observed, with some genotypes showing stability across different environmental conditions. A negative correlation between diosgenin and trigonelline was observed in fenugreek. Furthermore, Principal Component Analysis (PCA) and cluster analysis were found to be effective in revealing genetic diversity, morphological differences, and genotype adaptability. The findings highlight the potential for selecting superior genotypes for breeding programs focused on enhancing bioactive compound yields, especially under varying irrigation and non-irrigated conditions. This research emphasizes the critical role of environmental and genetic factors in optimizing the production of health-benefiting compounds in fenugreek.

Seed bacterization with siderophore-producing bacteria: a strategy to enhance growth and alkaloid content in Catharanthus roseus

Catharanthus roseus is a medicinal plant widely known for producing monoterpenoid indole alkaloids (MIAs), including therapeutic compounds such as vinblastine and vincristine, which are crucial for cancer treatment. However, the naturally low concentration of these alkaloids in plant tissues poses a significant challenge for large-scale production. This study explores the application of siderophore-producing bacteria for seed bacterization of Catharanthus roseus to enhance the production of MIAs, including vindoline, catharanthine, and vinblastine. Utilizing High-Performance Liquid Chromatography (HPLC), we observed a significant increase in the concentration of these alkaloids in bacterized plants compared to controls. FTIR spectra of treated plants showed strong correlations with standard alkaloid mixtures, confirming higher alkaloid accumulation. Our findings demonstrate that bacterial siderophores play a vital role in optimizing iron uptake, which is crucial for secondary metabolite biosynthesis. This research highlights the potential of using microbial biotechnology to improve the yield of valuable pharmaceutical compounds in medicinal plants. Enhancing the biosynthetic pathways of MIAs offers a sustainable and efficient strategy for boosting the production of key therapeutic alkaloids in Catharanthus roseus, paving the way for advanced biotechnological applications in plant-based drug production.

Deciphering the endomicrobiome of Podophyllum hexandrum to reveal the endophytic bacterial-association of in-planta podophyllotoxin biosynthesis

Understanding the change in plant-associated microbial diversity and secondary metabolite biosynthesis in medicinal plants due to their cultivation in non-natural habitat (NNH) is important to maintain their therapeutic importance. Here, the bacterial endomicrobiome of Podophyllum hexandrum plants of natural habitat (NH; Kardang and Triloknath locations) and NNH (Palampur location) was identified and its association with the biosynthesis of podophyllotoxin (PTOX) was revealed. Rhizomes (source of PTOX) of plants of NH had highest endophytic bacterial diversity compared to NNH-plants. Presence of plant-location and tissue-specific distinct and common taxa were also identified. Acinetobacter, Ralstonia and Pseudomonas were identified as core taxa, present in plants of both NH and NNH. Predictive functional analysis of endophytic communities revealed abundant presence of genes encoding initial enzymes of PTOX biosynthesis and plant growth promotion in the rhizomes and roots of Kardang locations. Higher accumulations of secondary metabolites such as PTOX (2.78 and 2.11 folds in Kardang and Triloknath rhizomes, respectively; 1.48 and 1.71 fold in Kardang and Triloknath roots, respectively), Picropodophyllotoxin (3.08 fold in Kardang rhizomes), Quercetin (1.65 fold in Kardang and 1.32 fold in Triloknath rhizomes; 3.07-fold in Kardang and 1.60 fold in Triloknath roots) and Kaempferol (1.66 and 1.24-fold in Kardang and Triloknath rhizomes, respectively; 2.91 and 1.94-fold in Kardang and Triloknath roots, respectively) were also found in NH compared to NNH. This study provides novel insight into the change in the endomicrobiome of NH and NNH-plants and their correlation to secondary metabolites biosynthesis, and that must be considered for cultivation practices.

Unlocking specialized metabolism in medicinal plant biotechnology through plant-microbiome interactions

Medicinal plants produce specialized metabolites (SM) that are used as drugs. However, due to low yields of field cultivation and the increasing market demand, this production method often failed to meet supply needs. Biotechnological alternatives, such as in vitro plant cultures, offer promising solutions. Nonetheless, SM production in these systems remains too low for industrial exploitation, necessitating an elicitation step to induce the plant defense metabolism. Traditional elicitation methods mimic environmental conditions that trigger plant-specialized metabolism, often with an artificial signal that mimics microbial interaction. Recent insights into the essential role of the plant microbiota, provides new opportunities for elicitation strategies by microbial coculture in a controlled environment. The successful co-culture of in vitro medicinal plants with synthetic microbial communities could enable sustainable production of pharmaceutically important SM.

Bioprospecting Endophytic Fungi of Forest Plants for Bioactive Metabolites with Antibacterial, Antifungal, and Antioxidant Potentials

The growing emergence of multi-drug resistant microbial strains has kept the scientific world searching for novel bioactive compounds with specific chemical characteristics. Accordingly, researchers have started exploring the understudied metabolites from endophytes as a new source of bioactive compounds. In this context, the current study was designed to evaluate the bioactive properties of endophytic fungi from the Mokrzański forest in Wrocław, Poland that have not yet been fully researched. Forty-three endophytic fungi were isolated from twelve distinct plants. Following their cultivation, fungal extracts were separately prepared from biomass and cell-free filtrates, and their antibacterial, antifungal (against human and plant pathogens), and antioxidant properties were examined. Five promising fungi after screening were identified to possess all of these activities. These strains and their respective plant hosts were Trichoderma harzianum BUK-T (Fagus sylvatica), Aspergillus ochraceus ROB-L1 (Robinia pseudoacacia), Chaetomium cochliodes KLON-L1, Fusarium tricinctum KLON-L2 (Acer platanoides), and Penicillium chrysogenum SOS-B2 (Pinus sylvestris). Moreover, gamma irradiation at several doses (Gy) was separately applied to the fungal cultures to study their effects on the recorded activities. Finally, compounds after preparative thin-layer chromatography fractionation of the five fungal strains were identified by GC-MS. These findings suggest that the isolated endophytic fungi could serve as novel sources of bioactive metabolites with antibacterial, antifungal, and antioxidant properties, potentially paving the way for future research and the development of new bioactive compounds.

A review on endophytic bacteria of orchids: functional roles toward synthesis of bioactive metabolites for plant growth promotion and disease biocontrol

MAIN CONCLUSION

In this review, we have discussed the untapped potential of orchid endophytic bacteria as a valuable reservoir of bioactive metabolites, offering significant contributions to plant growth promotion and disease protection in the context of sustainable agriculture. Orchidaceae is one of the broadest and most diverse flowering plant families on Earth. Although the relationship between orchids and fungi is well documented, bacterial endophytes have recently gained attention for their roles in host development, vigor, and as sources of novel bioactive compounds. These endophytes establish mutualistic relationships with orchids, influencing plant growth, mineral solubilization, nitrogen fixation, and protection from environmental stress and phytopathogens. Current research on orchid-associated bacterial endophytes is limited, presenting significant opportunities to discover new species or genetic variants that improve host fitness and stress tolerance. The potential for extracting bioactive compounds from these bacteria is considerable, and optimization strategies for their sustainable production could significantly enhance their commercial utility. This review discusses the methods used in isolating and identifying endophytic bacteria from orchids, their diversity and significance in promoting orchid growth, and the production of bioactive compounds, with an emphasis on their potential applications in sustainable agriculture and other sectors.

Impact of Heavy Metal Pollution in the Environment on the Metabolic Profile of Medicinal Plants and Their Therapeutic Potential

The paper provides a comprehensive examination of heavy metal stress on medicinal plants, focusing on its impact on antioxidant capacity and biosynthetic pathways critical to their therapeutic potential. It explores the complex relationship between heavy metals and the physiological and biochemical responses of medicinal plants, highlighting how metal stress disrupts biosynthetic pathways, altering concentrations of secondary metabolites. This disruption may compromise the overall quality and efficacy of medicinal plants, requiring a holistic understanding of its cumulative impacts. Furthermore, the study discusses the potential of targeted genetic editing to enhance plant resilience against heavy metal stress by manipulating genes associated with antioxidant defenses. This approach represents a promising frontier in safeguarding medicinal plants in metal-contaminated environments. Additionally, the research investigates the role of phytohormone signaling in plant adaptive mechanisms to heavy metal stress, revealing its influence on biochemical and physiological responses, thereby adding complexity to plant adaptation. The study underscores the importance of innovative technologies and global cooperation in protecting medicinal plants' therapeutic potential and highlights the need for mitigation strategies to address heavy metal contamination effectively.