Production of bioactive ginsenoside Rg3(S) and compound K using recombinant Lactococcus lactis

Triterpenoid saponin from Panax ginseng increases the sensitivity of methicillin-resistant Staphylococcus aureus to β-lactam and aminoglycoside antibiotics

The triterpenoid saponins, ginsenosides, are the major bioactive compound of red ginseng and can exert various physiological activities. In the present study, we examined whether red ginseng extract (RGE) exerts antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA). RGE had no bactericidal activity, at least in the range of dissolvable concentration. However, RGE reduced 0.03-0.25-fold the minimum inhibitory concentration (MIC) values of β-lactam antibiotics (oxacillin, ampicillin, carbenicillin, and cefazolin) and aminoglycoside antibiotics (kanamycin and gentamicin) against the two laboratory strains of MRSA. Moreover, the fractional inhibitory concentration index indicated the synergistic activity of RGE with each of the antibiotics. RGE also increased the kanamycin sensitivity of 15 MRSA strains isolated from human volunteers and increased the ampicillin sensitivity of five MRSA strains isolated from dairy cows diagnosed with bovine mastitis. In contrast, RGE did not alter the MIC values of fosfomycin, tetracycline, and erythromycin, suggesting that RGE acts selectively. In contrast, Triton X-100, which was reported to reduce the MIC value of β-lactam antibiotics to MRSA by increasing membrane permeability, reduced the MIC values of fosfomycin and tetracycline. These results indicate that RGE increases the bactericidal effect of antibiotics via a mechanism different from that used by Triton X-100. We found that ginsenoside Rg3 (Rg3), a component of RGE, was an essential compound that exhibits synergy activity with antibiotics. Furthermore, the non-natural compound K, which contains a common protopanaxadiol aglycon moiety with Rg3, also showed synergistic activity with antibiotics. Thus, Rg3 and compound K are potentially new antibiotic adjuvants against MRSA.IMPORTANCEMethicillin-resistant Staphylococcus aureus (MRSA) is a multidrug-resistant organism that is prevalent worldwide. Therefore, the research and development of new agents against MRSA are required. We first found that ginsenoside Rg3 (Rg3) in red ginseng, made from the roots of Panax ginseng C. A. Meyer, increased the sensitivity of β-lactam antibiotics and aminoglycoside antibiotics to MRSA. Furthermore, we identified that compound K, an unnatural ginsenoside analog, also increased the sensitivity of antibiotics to MRSA, similar to Rg3. By contrast, neither Rg3 nor compound K increased the sensitivity of fosfomycin, tetracycline, and erythromycin to MRSA, suggesting that these act selectively. In the present study, the natural compound Rg3 and its structural isomer, compound K, are potentially new antibiotic adjuvants against MRSA. Currently, multiple antibiotics are used to treat MRSA, but the use of these adjuvants is expected to enable the treatment of MRSA with a single antibiotic and low concentrations of antibiotics.

Increased Accumulation of Ginsenosides in Panax ginseng Sprouts Cultivated with Kelp Fermentates

Currently, new agri-tech has been developed and adapted for the cultivation of crops using smart farming technologies, e.g., plant factories and hydroponics. Kelp (Laminaria japonica), which has a high industrial value, was considered as an alternative to chemicals for its eco-friendly and sustainably wide use in crop cultivation. In this study, a fermented kelp (FK) was developed for use in hydroponics. The FK contained various free and protein-bound amino acid compositions produced by fermenting the kelp with Saccharomyces cerevisiae. Supplementing FK as an aeroponic medium when cultivating ginseng sprouts (GSs) elevated the total phenolic and flavonoid contents. Additionally, seven ginsenosides (Rg1, Re, Rb1, Rc, Rg2, Rb2, and Rd) in GSs cultivated with FK in a smart-farm system were identified and quantified by a high-performance liquid chromatography-evaporative light scattering detector/mass spectrometry analysis. Administering FK significantly increased the ginsenosides in the GSs compared to the control group, which was cultivated with tap water. These results indicate the FK administration contributed to the increased accumulation of ginsenosides in the GSs. Overall, this study suggests that FK, which contains abundant nutrients for plant growth, can be used as a novel nutrient solution to enhance the ginsenoside content in GSs during hydroponic cultivation.

Rare ginsenosides: A unique perspective of ginseng research

BACKGROUND

Rare ginsenosides (Rg3, Rh2, C-K, etc.) refer to a group of dammarane triterpenoids that exist in low natural abundance, mostly produced by deglycosylation or side chain modification via physicochemical processing or metabolic transformation in gut, and last but not least, exhibited potent biological activity comparing to the primary ginsenosides, which lead to a high concern in both the research and development of ginseng and ginsenoside-related nutraceutical and natural products. Nevertheless, a comprehensive review on these promising compounds is not available yet.

AIM OF REVIEW

In this review, recent advances of Rare ginsenosides (RGs) were summarized dealing with the structurally diverse characteristics, traditional usage, drug discovery situation, clinical application, pharmacological effects and the underlying mechanisms, structure-activity relationship, toxicity, the stereochemistry properties, and production strategies.

KEY SCIENTIFIC CONCEPTS OF REVIEW

A total of 144 RGs with diverse skeletons and bioactivities were isolated from Panax species. RGs acted as natural ligands on some specific receptors, such as bile acid receptors, steroid hormone receptors, and adenosine diphosphate (ADP) receptors. The RGs showed promising bioactivities including immunoregulatory and adaptogen-like effect, anti-aging effect, anti-tumor effect, as well as their effects on cardiovascular and cerebrovascular system, central nervous system, obesity and diabetes, and interaction with gut microbiota. Clinical trials indicated the potential of RGs, while high quality data remains inadequate, and no obvious side effects was found. The stereochemistry properties induced by deglycosylation at C (20) were also addressed including pharmacodynamics behaviors, together with the state-of-art analytical strategies for the identification of saponin stereoisomers. Finally, the batch preparation of targeted RGs by designated strategies including heating or acid/ alkaline-assisted processes, and enzymatic biotransformation and biosynthesis were discussed. Hopefully, the present review can provide more clues for the extensive understanding and future in-depth research and development of RGs, originated from the worldwide well recognized ginseng plants.

Compound K Production: Achievements and Perspectives

Compound K (CK) is one of the major metabolites found in mammalian blood and organs following oral administration of Panax plants. CK, also known as minor ginsenoside, can be absorbed in the systemic circulation. It has garnered significant attention in healthcare and medical products due to its pharmacological activities, such as antioxidation, anticancer, antiproliferation, antidiabetics, neuroprotection, and anti-atherogenic activities. However, CK is not found in natural ginseng plants but in traditional chemical synthesis, which uses toxic solvents and leads to environmental pollution during the harvest process. Moreover, enzymatic reactions are impractical for industrial CK production due to low yield and high costs. Although CK could be generated from major ginsenosides, most ginsenosides, including protopanaxatriol-oleanane and ocotillol-type, are not converted into CK by catalyzing β-glucosidase. Therefore, microbial cell systems have been used as a promising solution, providing a safe and efficient approach to CK production. This review provides a summary of various approaches for the production of CK, including chemical and enzymatic reactions, biotransformation by the human intestinal bacteria and endophytes as well as engineered microbes. Moreover, the approaches for CK production have been discussed to improve the productivity of target compounds.

β-Glucosidase and Its Application in Bioconversion of Ginsenosides in Panax ginseng

Ginsenosides are a group of bioactive compounds isolated from Panax ginseng. Conventional major ginsenosides have a long history of use in traditional medicine for both illness prevention and therapy. Bioconversion processes have the potential to create new and valuable products in pharmaceutical and biological activities, making them both critical for research and highly economic to implement. This has led to an increase in the number of studies that use major ginsenosides as a precursor to generate minor ones using β-glucosidase. Minor ginsenosides may also have useful properties but are difficult to isolate from raw ginseng because of their scarcity. Bioconversion processes have the potential to create novel minor ginsenosides from the more abundant major ginsenoside precursors in a cost-effective manner. While numerous bioconversion techniques have been developed, an increasing number of studies have reported that β-glucosidase can effectively and specifically generate minor ginsenosides. This paper summarizes the probable bioconversion mechanisms of two protopanaxadiol (PPD) and protopanaxatriol (PPT) types. Other high-efficiency and high-value bioconversion processes using complete proteins isolated from bacterial biomass or recombinant enzymes are also discussed in this article. This paper also discusses the various conversion and analysis methods and their potential applications. Overall, this paper offers theoretical and technical foundations for future studies that will be both scientifically and economically significant.

Microorganisms for Ginsenosides Biosynthesis: Recent Progress, Challenges, and Perspectives

Ginsenosides are major bioactive compounds present in the Panax species. Ginsenosides exhibit various pharmaceutical properties, including anticancer, anti-inflammatory, antimetastatic, hypertension, and neurodegenerative disorder activities. Although several commercial products have been presented on the market, most of the current chemical processes have an unfriendly environment and a high cost of downstream processing. Compared to plant extraction, microbial production exhibits high efficiency, high selectivity, and saves time for the manufacturing of industrial products. To reach the full potential of the pharmaceutical resource of ginsenoside, a suitable microorganism has been developed as a novel approach. In this review, cell biological mechanisms in anticancer activities and the present state of research on the production of ginsenosides are summarized. Microbial hosts, including native endophytes and engineered microbes, have been used as novel and promising approaches. Furthermore, the present challenges and perspectives of using microbial hosts to produce ginsenosides have been discussed.

Novel Split Intein-Mediated Enzymatic Channeling Accelerates the Multimeric Bioconversion Pathway of Ginsenoside

Cascade reaction systems, such as protein fusion and synthetic protein scaffold systems, can both spatially control the metabolic flux and boost the productivity of multistep enzymatic reactions. Despite many efforts to generate fusion proteins, this task remains challenging due to the limited expression of complex enzymes. Therefore, we developed a novel fusion system that bypasses the limited expression of complex enzymes via a post-translational linkage. Here, we report a split intein-mediated cascade system wherein orthogonal split inteins serve as adapters for protein ligation. A genetically programmable, self-assembled, and traceless split intein was utilized to generate a biocatalytic cascade to produce the ginsenoside compound K (CK) with various pharmacological activities, including anticarcinogenic, anti-inflammatory, and antidiabetic effects. We used two types of split inteins, consensus atypical (Cat) and Rma DnaB, to form a covalent scaffold with the three enzymes involved in the CK conversion pathway. The multienzymatic complex with a size greater than 240 kDa was successfully assembled in a soluble form and exhibited specific activity toward ginsenoside conversion. Furthermore, our split intein cascade system significantly increased the CK conversion rate and reduced the production time by more than 2-fold. Our multienzymatic cascade system that uses split inteins can be utilized as a platform for regulating multimeric bioconversion pathways and boosting the production of various high-value substances.

Advances and challenges in ginseng research from 2011 to 2020: the phytochemistry, quality control, metabolism, and biosynthesis

Covering: 2011 to the end of 2020Panax species (Araliaceae), particularly P. ginseng, P. quinquefolius, and P. notoginseng, have a long history of medicinal use because of their remarkable tonifying effects, and currently serve as crucial sources for various healthcare products, functional foods, and cosmetics, aside from their vast clinical preparations. The huge market demand on a global scale prompts the continuous prosperity in ginseng research concerning the discovery of new compounds, precise quality control, ADME (absorption/disposition/metabolism/excretion), and biosynthesis pathways. Benefitting from the ongoing rapid development of analytical technologies, e.g. multi-dimensional chromatography (MDC), personalized mass spectrometry (MS) scan strategies, and multi-omics, highly recognized progress has been made in driving ginseng analysis towards "systematicness, integrity, personalization, and intelligentization". Herein, we review the advances in the phytochemistry, quality control, metabolism, and biosynthesis pathway of ginseng over the past decade (2011-2020), with 410 citations. Emphasis is placed on the introduction of new compounds isolated (saponins and polysaccharides), and the emerging novel analytical technologies and analytical strategies that favor ginseng's authentic use and global consumption. Perspectives on the challenges and future trends in ginseng analysis are also presented.

Enhanced biotransformation of the minor ginsenosides in red ginseng extract by Penicillium decumbens β-glucosidase

Compound K (C-K) and Rh2, which are present at low levels in ginseng and ginseng extracts, have higher intestinal absorption rates than other ginsenosides. Here, we attempted to convert ginsenoside Rb1 to C-K using a β-glucosidase from Penicillium decumbens. Ten commercially available enzymes were screened to identify enzymes that can convert ginsenoside Rb1 to C-K, resulting in the selection of a P. decumbens-derived β-glucosidase. β-Glucosidase showed maximum activity at pH 4.0 and 60 °C; its substrate specificity for ginsenoside Rb1 was investigated. The main glucoside-hydrolyzing pathways were as follows: ginsenoside Rb1 or Rd → gypenoside XVII → F2 → C-K and ginsenoside Rg3 → Rh2. The P. decumbens-derived β-glucosidase was used to generate C-K and Rh2 using protopanaxadiol-type ginsenosides as substrates. Additionally, to apply this enzyme to the commercialized red ginseng extract products, the contents of C-K and Rh2 in the total ginsenosides significantly (p < 0.05) increased up to 36-fold and 8.9-fold, respectively, higher than prior to subjecting to biotransformation. To the best of our knowledge, this is the first report of the dual biotransformation of C-K and Rh2 by a food-grade commercial enzyme. This study demonstrates that the use of a specific β-glucosidase may increase C-K and Rh2 contents in the ginseng extract through a simple biotransformation process and, thus, enhance its health benefits.

Elucidation of interaction between serum albumin and ginsenoside CK along with cytotoxic study

As a main metabolite of ginsenosides, compound K (CK) has a vast array of pharmacological effects. However, due to its low polarity and insoluble in water, its oral application has been greatly limited. In this work, the interaction between serum albumin and ginsenoside CK was elucidated by multi-spectroscopic studies. The result of ultraviolet/visible absorption spectroscopy showed that the conformation of serum albumin could be changed via binding with CK. The result of fluorescence spectroscopy suggested that CK could form complex with serum albumin. CK could quench the fluorescence and the fluorescence residues of serum albumin were located in or near the binding position. Molecular docking indicated that CK bound at Sudlow's site II of serum albumin and formed hydrogen-bonding interactions with three residues. Furthermore, the flexible side chain of CK was difficult to be stabilized at the binding site, resulting in its serious perturbation during dynamics simulation. This work also performed the cytotoxic study and the result showed that serum albumin enhanced the inhibitory effect of CK on the proliferation of both Caco-2 and HCT-116 cells. To sum up, this work revealed that serum albumin might be an appropriate carrier of hydrophobic compounds, with the advantage of improving their biocompatibility.

Cumulative Production of Bioactive Rg3, Rg5, Rk1, and CK from Fermented Black Ginseng Using Novel Aspergillus niger KHNT-1 Strain Isolated from Korean Traditional Food

Ginseng is an ancient herb widely consumed due to its healing property of active ginsenosides. Recent researchers were explored to increase its absorption and bioavailability of ginsenosides at the metabolic sites, due to its pharmacological activity. The purpose of this study was to investigate the isolation and characteristics of components obtained by a shorter steaming cycle (seven cycles) of white ginseng to fermented black ginseng, using a novel strain of Aspergillus niger KHNT-1 isolated from fermented soybean. The degree of bioactive of Rg3 increased effectively during the steaming process, and biotransformation converted the color towards black along active ginsenosides. Glycol moiety associated with C-3, C-6, or C-20 underwent rapid biotransformation and hydrolysis, such as Rb1, Rb2, Rc, Rd → Rg3, F2, and was converted to CK. Dehydration produces Rg3 → Rk1, Rg5. Rh2 → Rk2; thus, converted fermented black ginseng was solvent-extracted, and the isolated components were identified by TLC, HPLC, and quantification by LCMS. The unique composition obtained during this process with Rk1, Rg3, Rg5, and CK is nontoxic to HaCaT cell line up to 200 ug/mL for 24 h and was found to be effective in B16BL6 cell lines, in a dose- and time-dependent manner. Thus, it is a suitable candidate for nutraceuticals and cosmeceuticals.

Endophytes, biotransforming microorganisms, and engineering microbial factories for triterpenoid saponins production

Triterpenoid saponins are structurally diverse secondary metabolites. They are the main active ingredient of many medicinal plants and have a wide range of pharmacological effects. Traditional production of triterpenoid saponins, directly extracted from cultivated plants, cannot meet the rapidly growing demand of pharmaceutical industry. Microorganisms with triterpenoid saponins production ability (especially Agrobacterium genus) and biotransformation ability, such as fungal species in Armillaria and Aspergillus genera and bacterial species in Bacillus and Intestinal microflora, represent a valuable source of active metabolites. With the development of synthetic biology, engineering microorganisms acquired more potential in terms of triterpenoid saponins production. This review focusses on potential mechanisms and the high yield strategies of microorganisms with inherent production or biotransformation ability of triterpenoid saponins. Advances in the engineering of microorganisms, such as Saccharomyces cerevisiae, Yarrowia lipolytica, and Escherichia coli, for the biosynthesis triterpenoid saponins de novo have also been reported. Strategies to increase the yield of triterpenoid saponins in engineering microorganisms are summarized following four aspects, that is, introduction of high efficient gene, optimization of enzyme activity, enhancement of metabolic flux to target compounds, and optimization of fermentation conditions. Furthermore, the challenges and future directions for improving the yield of triterpenoid saponins biosynthesis in engineering microorganisms are discussed.

Diversity of Ginsenoside Profiles Produced by Various Processing Technologies

Ginseng is a traditional medicinal herb commonly consumed world-wide owing to its unique family of saponins called ginsenosides. The absorption and bioavailability of ginsenosides mainly depend on an individual's gastrointestinal bioconversion abilities. There is a need to improve ginseng processing to predictably increase the pharmacologically active of ginsenosides. Various types of ginseng, such as fresh, white, steamed, acid-processed, and fermented ginsengs, are available. The various ginseng processing methods produce a range ginsenoside compositions with diverse pharmacological properties. This review is intended to summarize the properties of the ginsenosides found in different Panax species as well as the different processing methods. The sugar moiety attached to the C-3, C-6, or C-20 deglycosylated to produce minor ginsenosides, such as Rb1, Rb2, Rc, Rd→Rg3, F2, Rh2; Re, Rf→Rg1, Rg2, F1, Rh1. The malonyl-Rb1, Rb2, Rc, and Rd were demalonylated into ginsenoside Rb1, Rb2, Rc, and Rd by dehydration. Dehydration also produces minor ginsenosides such as Rg3→Rk1, Rg5, Rz1; Rh2→Rk2, Rh3; Rh1→Rh4, Rk3; Rg2→Rg6, F4; Rs3→Rs4, Rs5; Rf→Rg9, Rg10. Acetylation of several ginsenosides may generate acetylated ginsenosides Rg5, Rk1, Rh4, Rk3, Rs4, Rs5, Rs6, and Rs7. Acid processing methods produces Rh1→Rk3, Rh4; Rh2→Rk1, Rg5; Rg3→Rk2, Rh3; Re, Rf, Rg2→F1, Rh1, Rf2, Rf3, Rg6, F4, Rg9. Alkaline produces Rh16, Rh3, Rh1, F4, Rk1, ginsenoslaloside-I, 20(S)-ginsenoside-Rh1-60-acetate, 20(R)-ginsenoside Rh19, zingibroside-R1 through hydrolysis, hydration addition reactions, and dehydration. Moreover, biological processing of ginseng generates the minor ginsenosides of Rg3, F2, Rh2, CK, Rh1, Mc, compound O, compound Y through hydrolysis reactions, and synthetic ginsenosides Rd12 and Ia are produced through glycosylation. This review with respect to the properties of particular ginsenosides could serve to increase the utilization of ginseng in agricultural products, food, dietary supplements, health supplements, and medicines, and may also spur future development of novel highly functional ginseng products through a combination of various processing methods.

Advances in the Production of Minor Ginsenosides Using Microorganisms and Their Enzymes

Abstract Minor ginsenodes are of great interest due to their diverse pharmacological activities such as their anti-cancer, anti-diabetic, neuroprotective, immunomodulator, and anti-inflammatory effects. The miniscule amount of minor ginsenosides in ginseng plants has driven the development of their mass production methods. Among the various production methods for minor ginsenosides, the utilization of microorganisms and their enzymes are considered as highly specific, safe, and environmentally friendly. In this review, various minor ginsenosides production strategies, namely utilizing microorganisms and recombinant microbial enzymes, for biotransforming major ginsenosides into minor ginsenoside, as well as constructing synthetic minor ginsenosides production pathways in yeast cell factories, are described and discussed. Furthermore, the present challenges and future research direction for producing minor ginsenosides using those approaches are discussed.

Enzymatic Biotransformation of Ginsenoside Rb2 into Rd by Recombinant α-L-Arabinopyranosidase from Blastococcus saxobsidens

In this study, we used a novel α-L-arabinopyranosidase (AbpBs) obtained from ginsenoside-converting Blastococcus saxobsidens that was cloned and expressed in Escherichia coli BL21 (DE3), and then applied it in the biotransformation of ginsenoside Rb₂ into Rd. The gene, termed AbpBs, consisting of 2,406 nucleotides (801 amino acid residues), and with a predicted translated protein molecular mass of 86.4 kDa, was cloned into a pGEX4T-1 vector. A BLAST search using the AbpBs amino acid sequence revealed significant homology with a family 2 glycoside hydrolase (GH2). The over-expressed recombinant AbpBs in Escherichia coli BL21 (DE3) catalyzed the hydrolysis of the arabinopyranose moiety attached to the C-20 position of ginsenoside Rb2 under optimal conditions (pH 7.0 and 40°;C). Kinetic parameters for α-Larabinopyranosidase showed apparent K_m and V_max values of 0.078 ± 0.0002 micrometer and 1.4 ± 0.1 μmol/min/mg of protein against p-nitrophenyl-α-L-arabinopyranoside. Using a purified AbpBs (1 μg/ml), 0.1% of ginsenoside Rb₂ was completely converted to ginsenoside Rd within 1 h. The recombinant AbpBs could be useful for high-yield, rapid, and low-cost preparation of ginsenoside Rd from Rb₂.

Exploration and Characterization of Novel Glycoside Hydrolases from the Whole Genome of Lactobacillus ginsenosidimutans and Enriched Production of Minor Ginsenoside Rg3(S) by a Recombinant Enzymatic Process

Background: Several studies have reported that ginsenoside Rg3(S) is effective in treating metastatic diseases, obesity, and various cancers, however, its presence in white ginseng cannot be estimated, and only a limited amount is present in red ginseng. Therefore, the use of recombinant glycosidases from a Generally Recognized As Safe (GRAS) host strain is a promising approach to enhance production of Rg3(S), which may improve nutritional activity, human health, and quality of life. Method: Lactobacillus ginsenosidimutans EMML 3041^T, which was isolated from Korean fermented pickle (kimchi), presents ginsenoside-converting abilities. The strain was used to enrich the production of Rg3(S) by fermenting protopanaxadiol (PPD)-mix-type major ginsenosides (Rb1, Rb2, Rc, and Rd) in four different types of food-grade media (1, MRS; 2, Basel Food-Grade medium; 3, Basel Food-Grade medium-I, and 4, Basel Food-Grade medium-II). Due to its tendency to produce Rg3(S), the presence of glycoside hydrolase in Lactobacillus ginsenosidimutans was proposed, the whole genome was sequenced, and the probable glycoside hydrolase gene for ginsenoside conversion was cloned. Results: The L. ginsenosidimutans EMML 3041^T strain was whole genome sequenced to identify the target genes. After genome sequencing, 12 sets of glycoside hydrolases were identified, of which seven sets (α,β-glucosidase and α,β-galactosidase) were cloned in Escherichia coli BL21 (DE3) using the pGEX4T-1 vector system. Among the sets of clones, only one clone (BglL.gin-952) showed ginsenoside-transforming abilities. The recombinant BglL.gin-952 comprised 952 amino acid residues and belonged to glycoside hydrolase family 3. The enzyme exhibited optimal activity at 55 °C and a pH of 7.5 and showed a promising conversion ability of major ginsenoside Rb1→Rd→Rg3(S). The recombinant enzyme (GST-BglL.gin-952) was used to mass produce Rg3(S) from major ginsenoside Rb1. Scale-up of production using 50 g of Rb1 resulted in 30 g of Rg3(S) with 74.3% chromatography purity. Conclusion: Our preliminary data demonstrated that this enzyme would be beneficial in the preparation of pharmacologically active minor ginsenoside Rg3(S) in the functional food and pharmaceutical industries.

The Preparation of Ginsenoside Rg5, Its Antitumor Activity against Breast Cancer Cells and Its Targeting of PI3K

Ginsenosides have been reported to possess various pharmacological effects, including anticancer effects. Nevertheless, there are few reports about the antitumor activity and mechanisms of ginsenoside Rg5 against breast cancer cells. In the present study, the major ginsenoside Rb1 was transformed into the rare ginsenoside Rg5 through enzymatic bioconversion and successive acid-assisted high temperature and pressure processing. Ginsenosides Rb1, Rg3, and Rg5 were investigated for their antitumor effects against five human cancer cell lines via the MTT assay. Among them, Rg5 exhibited the greatest cytotoxicity against breast cancer. Moreover, Rg5 remarkably suppressed breast cancer cell proliferation through mitochondria-mediated apoptosis and autophagic cell death. LC3B-GFP/Lysotracker and mRFP-EGFP-LC3B were utilized to show that Rg5 induced autophagosome-lysosome fusion. Western blot assays further illustrated that Rg5 decreased the phosphorylation levels of PI3K, Akt, mTOR, and Bad and suppressed the PI3K/Akt signaling pathway in breast cancer. Moreover, Rg5-induced apoptosis and autophagy could be dramatically strengthened by the PI3K/Akt inhibitor LY294002. Finally, a molecular docking study demonstrated that Rg5 could bind to the active pocket of PI3K. Collectively, our results revealed that Rg5 could be a potential therapeutic agent for breast cancer treatment.

Complete Biotransformation of Protopanaxadiol-Type Ginsenosides into 20-O-β-Glucopyranosyl-20(S)-protopanaxadiol by Permeabilized Recombinant Escherichia coli Cells Coexpressing β-Glucosidase and Chaperone Genes

The ginsenoside 20-O-β-glucopyranosyl-20(S)-protopanaxadiol or compound K is an essential ingredient in functional food, cosmetics, and traditional medicines. However, no study has reported the complete conversion of all protopanaxadiol (PPD)-type ginsenosides from ginseng extract into compound K using whole-cell conversion. To increase the production of compound K from ginseng extract using whole recombinant cells, the β-glucosidase enzyme from Caldicellulosiruptor bescii was coexpressed with a chaperone expression system (pGro7), and the cells expressing the coexpression system were permeabilized with ethylenediaminetetraacetic acid. The permeabilized cells carrying the chaperone coexpression system showed a 2.6-fold increase in productivity and yield as compared with nontreated cells, and completely converted all PPD-type ginsenosides from ginseng root extract into compound K with the highest productivity among the results reported so far. Our results will contribute to the industrial biological production of compound K.

Antifeedant and ovicidal activities of ginsenosides against Asian corn borer, Ostrinia furnacalis (Guenee)

Introduction

Ginsenosides, including protopanaxdiol (PPD) and protopanaxtriol (PPT) type ginsenosides, have been identified as natural insecticidess. This study aimed to investigate the antifeedant and ovicidal activities of total ginsenosides, protopanaxdiol saponins (PDS) and protopanaxtriol saponins (PTS) against Asian corn borer, O. furnacalis (Guenee).

Methods and results

O. furnacalis egg masses (> 40 eggs) at 0-, 1- and 2-day-old were dipped into ginsenosides and egg hatchability was significantly inhibited by total ginsenosides, PDS, and PTS in dose and egg-age dependent manners. 100 mg/ml PDS had the strongest ovicidal activity against 0- (80.58 ± 0.95%), 1- (71.48 ± 5.70%), and 2-day-old eggs (64.31 ± 3.20%). In no-choice and choice feeding tests, we observed that the 3^rd instar larvae consumed decreased area of leaves treated with ginsenosides, and the antifeedant activities of total ginsenosides, PDS, and PTS against the 3^rd instar larvae were time and dose-dependent, with higher activities at 48 h. 100 mg/ml PDS had relative higher antifeedant activity (88.39 ± 3.43% in no-choice and 80.9±4.36% in choice) than total ginsenosides and PTS at all time intervals, except at 48 h in no-choice test. In further experiments, we found PPD ginsenosides (Rb1, Rb2, Rc, and Rd) had relative higher time and dose dependent antifeedant activities than PPT ginsenosides (Re and Rg1).

Conclusions

Our results suggested the insecticidal action of total ginsenosides, PDS, and PTS on O. furnacalis. All ginsenosides, especially PDS, showed antifeedant and ovicidal activities against O. furnacalis.