Deacetylation biocatalysis and elicitation by immobilized Penicillium canescens in Astragalus membranaceus hairy root cultures: towards the enhanced and sustainable production of astragaloside IV

Progress on metabolites of Astragalus medicinal plants and a new factor affecting their formation: Biotransformation of endophytic fungi

It is generally believed that the main influencing factors of plant metabolism are genetic and environmental factors. However, the transformation and catalysis of metabolic intermediates by endophytic fungi have become a new factor and resource attracting attention in recent years. There are over 2000 precious plant species in the Astragalus genus. In the past decade, at least 303 high-value metabolites have been isolated from the Astragalus medicinal plants, including 124 saponins, 150 flavonoids, two alkaloids, six sterols, and over 20 other types of compounds. These medicinal plants contain abundant endophytic fungi with unique functions, and nearly 600 endophytic fungi with known identity have been detected, but only about 35 strains belonging to 13 genera have been isolated. Among them, at least four strains affiliated to Penicillium roseopurpureum, Alternaria eureka, Neosartorya hiratsukae, and Camarosporium laburnicola have demonstrated the ability to biotransform four saponin compounds from the Astragalus genus, resulting in the production of 66 new compounds, which have significantly enhanced our understanding of the formation of metabolites in plants of the Astragalus genus. They provide a scientific basis for improving the cultivation quality of Astragalus plants through the modification of dominant fungal endophytes or reshaping the endophytic fungal community. Additionally, they open up new avenues for the discovery of specialized, green, efficient, and sustainable biotransformation pathways for complex pharmaceutical intermediates.

Exploring Steroidal Saponin Composition and Morphometric Characteristics of Rhizomes from Trillium govanianum Wall. ex D. Don: Inference for Medicinal Properties and Genetic Stock Improvement

Trillium govanianum, a medicinal herb, exhibiting diverse morphometric traits and phytochemicals across developmental stages of plants. The changes in the chemical profile and steroidal saponin levels in the rhizome of T. govanianum across different developmental stages were previously unknown. This study categorizes rhizomes into three types based on scar presence: juvenile (5-10 scars, Type I), young (11-19 scars, Type II), and mature (21-29 scars, Type III). Rhizomes show varying sizes (length 1.2-4.7 cm, girth 0.3-1.6 cm), weight (0.18-5.0 g), and extractive yields (9.7-16.1 % w w-1), with notable differences in saponin content (5.95-21.9 mg g-1). Ultra-high performance liquid chromatography-MS/MS (UHPLC-QTOF-MS/MS)-based chemical profiling identifies 31 phytochemicals, mainly including diverse saponins. Ultra-high performance liquid chromatography coupled with evaporative light scattering detection (UHPLC-ELSD)-based quantitative analysis of seven key saponins reveals stage-specific accumulation patterns, with protodioscin (P) and dioscin (DS) predominant in mature rhizomes. Statistical analysis confirms significant variation (p=0.001) in saponin levels across developmental stages with chemical constituent protodioscin (P=4.03±0.03-15.76±0.14 mg g-1, PAve=9.79±3.03 mg g-1) and dioscin (DS=1.23±0.06-3.93±0.07 mg g-1, DSAve=2.59±0.70 mg g-1), with acceptable power (p=0.738; |δ|>0.5) statistics for effective sample size (n=27 samples used in the study) of T. govanianum. Principal Component Analysis (PCA) and Euclidean clustering further highlighted chemotype distinctions.

Advances in Biotechnological Production and Metabolic Regulation of Astragalus membranaceus

Legume medicinal plants Astragalus membranaceus are widely used in the world and have very important economic value, ecological value, medicinal value, and ornamental value. The bioengineering technology of medicinal plants is used in the protection of endangered species, the rapid propagation of important resources, detoxification, and the improvement of degraded germplasm. Using bioengineering technology can effectively increase the content of secondary metabolites in A. membranaceus and improve the probability of solving the problem of medicinal plant resource shortage. In this review, we focused on biotechnological research into A. membranaceus, such as the latest advances in tissue culture, including callus, adventitious roots, hairy roots, suspension cells, etc., the metabolic regulation of chemical compounds in A. membranaceus, and the research progress on the synthetic biology of astragalosides, including the biosynthesis pathway of astragalosides, microbial transformation of astragalosides, and metabolic engineering of astragalosides. The review also looks forward to the new development trend of medicinal plant biotechnology, hoping to provide a broader development prospect for the in-depth study of medicinal plants.

Research progress of natural medicine Astragalus mongholicus Bunge in treatment of myocardial fibrosis

ETHNOPHARMACOLOGICAL RELEVANCE

Myocardial fibrosis (MF) is a common pathological manifestation of many cardiovascular diseases at a certain stage, with excessive accumulation of collagen fibers, excessive increase in collagen content, and a significant increase in collagen volume as the main pathological changes. There are currently no effective drugs for the treatment of myocardial fibrosis. Traditional Chinese medicine (TCM), the main component of the medical practice used for more than 5000 years, especially in China, often exerts a wider action spectrum than previously attempted options in treating human diseases. In recent times, the great potential of TCM in the treatment of MF has received much attention. Especially many experimental studies on the treatment of MF by Astragalus mongholicus Bunge have been conducted, and the effect is remarkable, which may provide more comprehensive database and theoretical support for the application of Astragalus mongholicus Bunge in the treatment of MF and could be considered a promising candidate drug for preventing MF.

AIM OF THE REVIEW

This review summarizes the chemical components of Astragalus mongholicus Bunge, Astragalus mongholicus Bunge extract, Astragalus mongholicus Bunge single prescription, and Astragalus mongholicus Bunge compound preparation in the treatment of MF, and provides comprehensive information and a reliable basis for the exploration of new treatment strategies of botanical drugs in the therapy of MF.

METHODS

The literature information was obtained from the scientific databases on ethnobotany and ethnomedicines (up to August 2022), mainly from the PubMed, Web of Science, and CNKI databases. The experimental studies on the anti-myocardial fibrosis role of the effective active components of Astragalus mongholicus Bunge and the utility of its compound preparation and the involved mechanisms were identified. The search keywords for such work included: "myocardial fibrosis" or "Cardiac fibrosis ", and "Astragalus mongholicus Bunge", "extract," or "herb".

RESULTS

Several studies have shown that the effective active components of Astragalus mongholicus Bunge and its formulas, particularly Astragaloside IV, Astragalus polysaccharide, total saponins of Astragalus mongholicus Bunge, triterpenoid saponins of Astragalus mongholicus Bunge, and cycloastragenol, exhibit potential benefits against MF, the mechanisms of which appear to involve the regulation of inflammation, oxidant stress, and pro-fibrotic signaling pathways, etc. Conclusion: These research works have shown the therapeutic benefits of Astragalus mongholicus Bunge in the treatment of MF. However, further research should be undertaken to clarify the unconfirmed chemical composition and regulatory mechanisms, conduct standard clinical trials, and evaluate the possible side effects. The insights in the present review provided rich ideas for developing new anti-MF drugs.

THESIS

Myocardial fibrosis (MF) with excessive accumulation of collagen fibers, excessive increase in collagen content, and a significant increase in collagen volume as the main pathological changes is a common pathological manifestation of many cardiovascular diseases at a certain stage, which seriously affects cardiac function. At present, there is still a lack of effective drugs for the treatment of MF. Traditional Chinese medicine (TCM), the main component of the medical practice used for more than 5000 years especially in China, often exerts wider action spectrum than previously attempted options in treating human diseases. In recent times, the great potential of TCM in the treatment of MF has received much attention. Especially many experimental studies on the treatment of MF by Astragalus mongholicus Bunge have been conducted, and the effect is remarkable, which may provide more comprehensive data base and theoretical support for the application of Astragalus mongholicus Bunge in the treatment of MF and could be considered a promising candidate drug for preventing MF.

Upgrading the accumulation of ginsenoside Rd in Panax notoginseng by a novel glycosidase-producing endophytic fungus G11-7

A novel endophytic fungus producing beta-glucosidase was isolated and characterized from pigeon pea (Cajanus cajan [L.] Millsp.), which has excellent properties in converting ginsenoside Rb1 to ginsenoside Rd in Panax notoginseng. According to the 16S rDNA gene sequence, the G11-7 strain was identified as Fusarium proliferatum, and the accession number KY303906 was confirmed in GenBank. The G11-7 immobilized spores, in which the activity of beta-glucosidase could reach 0.95 U/mL, were co-cultured with P. notoginseng plant material to obtain a continuous beta-glucosidase supply for the biotransformation of ginsenoside Rb1 to Rd. Under the liquid-solid ratio (20:1), initial pH (6.0), and temperature (30 °C) constituents, the maximum ginsenoside Rd yield was obtained as 9.15 ± 0.65 mg/g, which was 3.67-fold higher than that without fungal spore co-culture (2.49 ± 0.98 mg/g). Furthermore, immobilized G11-7 spores showed significant beta-glucosidase producing ability which could be recovered and reused for 6 cycles. Overall, these results suggested that immobilized G11-7 offered a promising and effective approach to enhance the production of ginsenoside Rd for possible nutraceutical and pharmaceutical uses.

Research progress on the antitumor effects of astragaloside IV

One of the most important and effective components of Astragalus membranaceus is astragaloside IV (AS-IV), which can exert anti-tumor effects through various pathways. For instance, AS-IV exerts an anti-tumor effect by acting at the cellular level, regulating the phenotype switch of tumor-associated macrophages, or inhibiting the development of tumor cells. Furthermore, AS-IV inhibits tumor cell progression by enhancing its sensitivity to antitumor drugs or reversing the drug resistance of tumor cells. This article reviews the different mechanisms of AS-IV inhibition of epithelial-mesenchymal transition (EMT), migration, proliferation, and invasion of tumor cells, inducing apoptosis and improving the sensitivity of anti-tumor drugs. This review summarizes recent progress in the current research into AS-IV anti-tumor effect and provides insight on the next anti-tumor research of AS-IV.

Heterologous Expression of Three Transcription Factors Differently Regulated Astragalosides Metabolic Biosynthesis in Astragalus membranaceus Hairy Roots

Astragalus membranaceus has been used as a highly popular Chinese herbal medicine for centuries. Triterpenoids, namely astragalosides I, II, III, and IV, represent the main active compounds in this plant species. Transcription factors have a powerful effect on metabolite biosynthesis in plants. We investigated the effect of the Arabidopsis MYB12, production of anthocyanin pigment 1 (PAP1), and maize leaf color (LC) transcription factors in regulating the synthesis of astragaloside metabolites in A. membranaceus. Overexpression of these transcription factors in hairy roots differentially up-regulated these active compounds. Specifically, the overexpression of LC resulted in the accumulation of astragalosides I–IV. The content of astragalosides I and IV were, in particular, more highly accumulated. Overexpression of MYB12 increased the accumulation of astragaloside I in transgenic hairy roots, followed by astragaloside IV, and overexpression of PAP1 resulted in the increased synthesis of astragalosides I and IV. In addition, we found that overexpression of PAP1 together with LC increased astragaloside III levels. At the transcriptional level, several key genes of the mevalonate biosynthetic pathway, especially HMGR1, HMGR2, and HMGR3, were up-regulated differentially in response to these transcription factors, resulting in astragaloside synthesis in the hairy roots of A. membranaceus. Overall, our results indicated that heterologous expression of Arabidopsis MYB12, PAP1, and maize LC differentially affected triterpenoids biosynthesis, leading to the increased biosynthesis of active compounds in A. membranaceus.

Effects of Metal Nanoparticles and Other Preparative Materials in the Environment on Plants: From the Perspective of Improving Secondary Metabolites

The influence of preparation material residues in wastewater and soil on plants has been paid more and more attention by researchers. Secondary metabolites play an important role in the application of plants. It was found that nanomaterials can increase the content of plant secondary metabolites in addition to their role in pharmaceutical preparations. For example, 800 mg/kg copper oxide nanoparticles (NPs) increased the content of p-coumaric acid in cucumber by 225 times. Nanoparticles can cause oxidative stress in plants, increase signal molecule, and upregulate the synthase gene expression, increasing the content of secondary metabolites. The increase of components such as polyphenols and total flavonoids may be related to oxidative stress. This paper reviews the application and mechanism of metal nanomaterials (Ag-NP, ZnO-NP, CeO₂-NP, Cds-NP, Mn-NP, CuO-NP) in promoting the synthesis of secondary metabolites from plants. In addition, the effects of some other preparative materials (cyclodextrins and immobilized molds) on plant secondary metabolites are also involved. Finally, possible future research is discussed.

Elicitation of (E)-2-Hexenal and 2,3-Butanediol on the Bioactive Compounds in Adventitious Roots of Astragalus membranaceus var. mongholicus

This study aimed to investigate the elicitation of volatile organic compounds (E)-2-hexenal and 2,3-butanediol on bioactive metabolites in Astragalus membranaceus var. mongholicus adventitious root cultures by adding them into the medium. The experiment was performed for 72 h and the roots were dynamically sampled for quantification of representative astragaloside IV, calycosin-7-O-β-d-glucoside (CG), ononin, and the gene expression. Compared with the controls, the combination of 2,3-butanediol and (E)-2-hexenal advanced the peak accumulation of astragaloside IV and was the most effective, but their individual application delayed it. Meanwhile, 2,3-butanediol and (E)-2-hexenal had no obviously promoting effect on the production of CG and ononin but chronologically changed their accumulation patterns. The underlying mechanism was uncovered by the correlation analysis between the metabolites and the gene expression, as did the identification of the target genes. Collectively, 2,3-butanediol and (E)-2-hexenal were important cues shaping the production of bioactive products in the herbal plant.

Transcriptome analysis of Paris polyphylla var. yunnanensis illuminates the biosynthesis and accumulation of steroidal saponins in rhizomes and leaves

Paris polyphylla var. yunnanensis can synthesize Paris saponins with multiple effective therapies, and its rhizome has become an indispensable ingredient in many patented drugs. However, how Paris saponin content changes in tissues at different stages and the molecular mechanisms underlying the production and accumulation of the bioactive compounds are unclear. This study aimed to uncover the mechanisms underlying the biosynthesis and accumulation by integrating transcriptome sequencing and phytochemical investigation of the leaves and rhizomes at different growth stages. Paris saponin content in leaves was lower during the fruiting stage than the vegetative stage, whereas the content in rhizomes increased during the fruiting stage. The candidate genes related to Paris saponin biosynthesis were determined by transcriptome analyses. Most biosynthetic genes were found to be abundantly expressed in the leaves during the vegetative stage in the light of expression profiles and functional enrichment results. The expression patterns of the differentially expressed genes related to the biosynthesis were positively correlated with the accumulation of saponins in tissues. These findings suggest that both leaves and rhizomes are capable of biosynthesizing Paris saponins, and that aerial plant parts can be used to extract them. The different patterns of biosynthesis and accumulation in the leaves and rhizomes were also determined here. This study will help improve our understanding of the mechanisms underlying the biosynthesis and accumulation of Paris saponins, and aid in the comprehensive development and utilization of this medicinal plant.

Penicillium sp. YJM-2013 induces ginsenosides biosynthesis in Panax ginseng adventitious roots by inducing plant resistance responses

Objective

Fusarium oxysporum is a common pathogenic fungus in ginseng cultivation. Both pathogens and antagonistic fungi have been reported to induce plant resistance responses, thereby promoting the accumulation of secondary metabolites. The purpose of this experiment is to compare the advantages of one of the two fungi, in order to screen out more effective elicitors. The mechanism of fungal elicitor-induced plant resistance response is supplemented.

Methods

A gradient dilution and the dural culture were carried out to screen strains. The test strain was identified by morphology and 18 s rDNA. The effect of different concentrations (0, 50, 100, 200, 400 mg/L) of Penicillium sp. YJM-2013 and F. oxysporum on fresh weight and ginsenosides accumulation were tested. Signal molecules transduction, expression of transcription factors and functional genes were investigated to study the induction mechanism of fungal elicitors.

Results

Antagonistic fungi of F. oxysporum was identified as Penicillium sp. YJM-2013, which reduced root biomass. The total ginsenosides content of Panax ginseng adventitious roots reached the maximum (48.95 ± 0.97 mg/g) treated with Penicillium sp. YJM-2013 at 200 mg/L, higher than control by 2.59-fold, in which protopanoxadiol-type ginsenosides (PPD) were increased by 4.57 times. Moreover, Penicillium sp. YJM-2013 activated defense signaling molecules, up-regulated the expression of PgWRKY 1, 2, 3, 5, 7, 9 and functional genes in ginsenosides synthesis.

Conclusion

Compared with the pathogenic fungi F. oxysporum, antagonistic fungi Penicillium sp. YJM-2013 was more conducive to the accumulation of ginsenosides in P. ginseng adventitious roots. Penicillium sp. YJM-2013 promoted the accumulation of ginsenosides by intensifying the generation of signal molecules, activating the expression of transcription factors and functional genes.

Highly efficient production of diverse rare ginsenosides using combinatorial biotechnology

The rare ginsenosides are recognized as the functionalized molecules after the oral administration of Panax ginseng and its products. The sources of rare ginsenosides are extremely limited because of low ginsenoside contents in wild plants, hindering their application in functional foods and drugs. We developed an effective combinatorial biotechnology approach including tissue culture, immobilization, and hydrolyzation methods. Rh2 and nine other rare ginsenosides were produced by methyl jasmonate-induced culture of adventitious roots in a 10 L bioreactor associated with enzymatic hydrolysis using six β-glycosidases and their combination with yields ranging from 5.54 to 32.66 mg L^-1 . The yield of Rh2 was furthermore increased by 7% by using immobilized BglPm and Bgp1 in optimized pH and temperature conditions, with the highest yield reaching 51.17 mg L^-1 (17.06% of protopanaxadiol-type ginsenosides mixture). Our combinatorial biotechnology method provides a highly efficient approach to acquiring diverse rare ginsenosides, replacing direct extraction from Panax plants, and can also be used to supplement yeast cell factories.

Elicitation: A biotechnological tool for enhanced production of secondary metabolites in hairy root cultures

Elicitation is a possible aid to overcome various difficulties associated with the large-scale production of most commercially important bioactive secondary metabolites from wild and cultivated plants, undifferentiated or differentiated cultures. Secondary metabolite accumulation in vitro or their efflux in culture medium has been elicited in the undifferentiated or differentiated tissue cultures of several plant species by the application of a low concentration of biotic and abiotic elicitors in the last three decades. Hairy root cultures are preferred for the application of elicitation due to their genetic and biosynthetic stability, high growth rate in growth regulator-free media, and production consistence in response to elicitor treatment. Elicitors act as signal, recognized by elicitor-specific receptors on the plant cell membrane and stimulate defense responses during elicitation resulting in increased synthesis and accumulation of secondary metabolites. Optimization of various parameters, such as elicitor type, concentration, duration of exposure, and treatment schedule is essential for the effectiveness of the elicitation strategies. Combined application of different elicitors, integration of precursor feeding, or replenishment of medium or in situ product recovery from the roots/liquid medium with the elicitor treatment have showed improved accumulation of secondary metabolites due to their synergistic effect. This is a comprehensive review about the progress in the elicitation approach to hairy root cultures from 2010 to 2019 and the information provided is valuable and will be of interest for scientists working in this area of plant biotechnology.

A rapid method for sensitive profiling of bioactive triterpene and flavonoid from Astragalus mongholicus and Astragalus membranaceus by ultra-pressure liquid chromatography with tandem mass spectrometry

Astragalus is one of the most popular Chinese herbal. Control of Astragalus quantity is most important, since that various varieties and ages largely affect bioactive metabolites and different pharmacological effects. Astragalus mongholicus and Astragalus membranaceus are both major sources of Astragalus according to the provisions in the Chinese Pharmacopoeia. Thus, a sensitive and rapid UPLC-MS/MS method for the simultaneous determination of l-Phenylalanine, Isoliquiritigenin, Liquiritigenin, Daidzein, Formononetin, Ononin, Calycosin, Calycosin-7-glucoside, Cycloastragenol, Astragaloside I, Astragaloside II, Astragaloside III and Astragaloside IV was established in this study. The detection was accomplished by MRM scanning in the positive ionization mode. Calibration curves offered linear ranges with r² > 0.999. The method was successfully validated for the linearity, intra-day and inter day precisions, accuracy, recovery, matrix effect and stability. Then this method was successfully applied to detect the contents of 13 target flavonoids and triterpenoids metabolites in different organs and ages of A. mongholicus and A. membranaceus. Significant organs-, ages- and varieties- specificity of the 13 target metabolites were observed and discussed. The results provided basis and support for further exploration of the distribution of bioactive metabolites, namely flavonoids and triterpenoids, in different organs and ages of two Astragalus varieties. This method should be applicable to various Astragalus matrices for the quantitative analysis of the target flavonoids and triterpenoids.

Remarkable enhancement of flavonoid production in a co-cultivation system of Isatis tinctoria L. hairy root cultures and immobilized Aspergillus niger

The dried roots of Isatis tinctoria L. are highly traded in the pharmaceutical industry due to their notable anti-influenza efficacy. For the first time, I. tinctoria hairy root cultures (ITHRCs) were co-cultured with two immobilized live GRAS (Generally Recognized as Safe) fungi, i.e. Aspergillus niger and Aspergillus niger, for the elevated production of pharmacologically active flavonoids. Immobilized A. niger (IAN) was exhibited as the superior elicitor in the plant-fungus co-cultivation system. The highest flavonoid production (3018.31 ± 48.66 μg/g DW) were achieved in IAN-treated ITHRCs under the optimal conditions of IAN spore concentration ca.10⁴ spores/mL, temperature 30 °C, initial pH value of media 7.0 and time 72 h, which remarkably increased 6.83-fold relative to non-treated control (441.91 ± 7.35 μg/g DW). Also, this study revealed that IAN elicitation could trigger the sequentially transient accumulation of signal molecules and intensify the oxidative stress in ITHRCs, which both contributed to the up-regulated expression of associated genes involved in flavonoid biosynthetic pathway. Moreover, IAN could be reused at least five cycles with satisfactory performance. Overall, the coupled culture of IAN and ITHRCs is a promising and effective approach for the enhanced production of flavonoids, which allows for the improved applicability of these valuable compounds in pharmaceutical fields.

Enhanced Production of Two Bioactive Isoflavone Aglycones in Astragalus membranaceus Hairy Root Cultures by Combining Deglycosylation and Elicitation of Immobilized Edible Aspergillus niger

A cocultivation system of Astragalus membranaceus hairy root cultures (AMHRCs) and immobilized food-grade fungi was established for the enhanced production of calycosin (CA) and formononetin (FO). The highest accumulations of CA (730.88 ± 63.72 μg/g DW) and FO (1119.42 ± 95.85 μg/g DW) were achieved in 34 day-old AMHRCs cocultured with immobilized A. niger (IAN) for 54 h, which were 7.72- and 18.78-fold higher than CA and FO in nontreated control, respectively. IAN deglycosylation could promote the formation of CA and FO by conversion of their glycoside precursors. IAN elicitation could intensify the generation of endogenous signal molecules involved in plant defense response, which contributed to the significantly up-regulated expression of genes in CA and FO biosynthetic pathway. Overall, the coupled culture of IAN and AMHRCs offered a promising and effective in vitro approach to enhance the production of two health-promoting isoflavone aglycones for possible nutraceutical and pharmaceutical uses.