Rare ginsenosides: A unique perspective of ginseng research

Ginsenoside Rg3 Alleviates Xerostomia in Orchiectomized Mice via AR/AQP5

Sjögren's disease (SjD), an autoimmune inflammatory disease, is associated with reduced androgen levels. Testosterone replacement therapy alleviates SjD progression, but the exact mode of action is unclear and adverse effects are reported. Our present study found that dihydrotestosterone (DHT) enhances the transcription and expression of aquaporin 5 (AQP5) in human salivary gland epithelial cells via androgen receptor (AR) signaling. The DHT/AR complex binds to the androgen response element of the AQP5 promoter, upregulating AQP5 expression. Using orchiectomized mice, we observed that reduced levels of DHT resulted in hyposalivation and SjD progression. By screening compounds with similar structures to DHT, we identified that DHT-like ginsenoside Rg3, a natural product, upregulates AQP5 expression in salivary gland epithelial cells via binding with AR. The Rg3/AR complex acts like DHT/AR and binds to the androgen response element of the AQP5 promoter to promote AQP5 transcription in salivary gland epithelial cells. Gavage of Rg3 restored saliva secretion and submandibular gland morphology in orchiectomized and nonobese diabetic mice. Transcriptome analysis revealed that Rg3 treatment upregulates saliva secretion-related signaling and downregulates inflammation and immune activation-related signaling in the submandibular glands of orchiectomized mice. In conclusion, our results indicated that Rg3 restores androgen deficiency-triggered xerostomia via AR-mediated AQP5 upregulation.

Structural Insights into the Substrate Recognition of Ginsenoside Glycosyltransferase Pq3-O-UGT2

Ginsenosides are a group of tetracyclic triterpenoids with promising health benefits, consisting of ginseng aglycone attached to various glycans. Pq3-O-UGT2, an important UDP-dependent glycosyltransferase (UGT), catalyzes the production of Ginsenoside Rg3 and Rd by extending the glycan chain of Ginsenoside Rh2 and F2, respectively, with higher selectivity for F2. However, the mechanism underlying its substrate recognition remains unclear. In this study, the crystal structures of Pq3-O-UGT2 in complex with its acceptor substrates are solved. The structures revealed a Nα5-oriented acceptor binding pocket in Pq3-O-UGT2, shaped by the unique conformation of the Nα5-Nα6 linker. Hydrophobic interactions play a pivotal role in the recognition of both Rh2 and F2, while hydrogen bonds specifically aid in F2 recognition due to its additional glucose moiety. The hydrophobic nature of the acceptor binding pocket also enables Pq3-O-UGT2 to recognize flavonoids. Overall, this study provides novel insights into the substrate recognition mechanisms of ginsenoside UGTs, advancing the understanding of their function and specificity.

Preparation of Rare Dehydrated Protopanaxadiol Ginsenosides from Panax notoginseng Leaves by Confined Microwave-Driven Transformation

Rare dehydrated ginsenosides barely exist in natural ginseng plants. Herein, the confined microwave technique was utilized to transform the main ginsenosides of Panax notoginseng leaves (PNL) into dehydrated ginsenosides. The main microwave-treated products of dried PNL are dehydrated ginsenoside Rk1, Rg5, notoginsenoside SFt3, and SFt4. Comparatively, the main microwave-treated products of water preimmersed PNL are dehydrated ginsenoside Rk2, Rh3, notoginsenoside SFt3, and SFt4. The impacts of solvent, solid-liquid ratio, microwave temperature and duration on the yield of dehydrated ginsenosides were explored. Based on theoretical calculation, primary ginsenosides in water preimmersed PNL are more prone to deglycosylation at the C-20 site and dehydration elimination reactions at the side chain during microwave treatment. Moreover, reference compounds were used to verify ginsenoside transformation pathway, and the dehydrated ginsenosides were individually purified and identified. In short, this study elucidates novel approach for preparing rare Δ20(21)- and Δ20(22)-dehydrated protopanoxadiol ginsenosides.

Ginsenoside Rk2 alleviates hepatic ischemia/reperfusion injury by enhancing AKT membrane translocation and activation

Hepatic ischemia-reperfusion injury (IRI) poses a significant threat to clinical outcomes and graft survival during hemorrhagic shock, hepatic resection, and liver transplantation. Current pharmacological interventions for hepatic IRI are inadequate. In this study, we identified ginsenoside Rk2 (Rk2), a rare dehydroprotopanaxadiol saponin, as a promising agent against hepatic IRI through high-throughput screening. The pharmacological effects and molecular mechanisms of Rk2 on hepatic IRI were further evaluated and elucidated in vitro and in vivo. Rk2 significantly reduced inflammation and apoptosis caused by oxygen-glucose deprivation and reperfusion in hepatocytes and dose dependently protected against hepatic I/R-induced liver injury in mice. Integrated approaches, including network pharmacology, molecular docking, transcriptome analysis, and isothermal titration calorimetry, along with experimental validation, indicated that Rk2 protects against hepatic IRI by targeting and activating the AKT (RAC serine/threonine protein kinase) signaling pathway. Pharmacological inhibition of AKT pathway or knockdown of AKT1 effectively diminished protective effects of Rk2. Rk2 directly binds to AKT1, facilitating its translocation from the cytoplasm to plasma membrane. This process markedly enhanced AKT interaction with PDPK1, promoting the activation of AKT1 and its downstream signaling. Our findings demonstrate that Rk2 protects against hepatic IRI by activating AKT signaling through direct binding to AKT1 and facilitating its membrane translocation.

A GH1 β-glucosidase from the Fervidobacterium pennivorans DSM9078 showed extraordinary thermostability and distinctive ability in the efficient transformation of ginsenosides

A novel GH1 β-glucosidase Fpglu1 from Fervidobacterium pennivorans DSM9078 was successfully cloned and expressed in Escherichia coli. This hyperthermophilic enzyme possesses unique features that make it valuable in biochemistry and pharmacology. It exhibited optimal activity at temperatures exceeding 100 °C, a trait rarely observed in other enzymes, and demonstrated extraordinary thermostability. It displayed multifunctional activity, with the highest activity observed for p-nitrophenyl-β-d-glucopyranoside (pNPGlu) at 92.47 U/mg. Furthermore, the distinctive capacity of Fpglu1 to transform ginsenosides (Rb1, Rb2, and Rc) into Compound-K (C-K) sets it apart from the other enzymes. It effectively cleaved the external β-(1-6) glycosidic linkage at the C-20 position of ginsenosides Rb1, Rb2, and Rc, followed by hydrolysis ofthe internal glycosidic bond connected to the C-3 position. The kcat/Km value of Fpglu1 for Rb1 was 453 ± 1.27 mM-1/s, significantly higher than those of Fpglu1 for other ginsenosides. The crystal structure of Fpglu1, determined at 1.85 Å resolution, provided a deeper understanding of its catalysis and substrate specificity. The evaluation of the binding conformation, hydrogen bond, and key amino acids of β-glucosidase Fpglu1 with different ginsenosides (Rb1, Rb2, and Rc) further elucidated the structural basis of its substrate-binding preference. In summary, Fpglu1, which had excellent thermostability and unique ginsenoside-transforming ability, was a highly promising catalyst for the industrial production of ginsenoside C-K. Additionally, structural studies have laid a theoretical foundation for further improving the catalytic properties of the enzyme through directed evolution in the future.

Quantitative Changes and Transformation Mechanisms of Saponin Components in Chinese Herbal Medicines during Storage and Processing: A Review

Saponins are an important class of active components in Chinese herbal medicines (CHMs), which are present in large quantities in Ginseng Radix et Rhizoma, Notoginseng Radix et Rhizoma, Polygonati Rhizoma, etc., and have immune regulation, anti-tumor, anti-inflammatory, anti-cardiovascular disease, and hypoglycemic activities. Storage and processing are essential processes in the production process of CHMs which affect the stability of saponin components and then reduce the medicinal and economic value. Therefore, it is of great importance to investigate the effects of storage and processing conditions on the content of saponin components in CHMs. In this paper, the effects of various storage and processing factors, including temperature, pH, enzymes, meta lions, extraction methods, etc., on the saponin content of CHMs are investigated and the underlying mechanisms for the quantitative changes of saponin are summarized. These findings may provide technical guidance for the production and processing of saponin-rich CHMs.

Advancements in enzymatic biotransformation and bioactivities of rare ginsenosides: A review

Ginsenoside, the principal active constituent of ginseng, exhibits enhanced bioavailability and medicinal efficacy in rare ginsenosides compared to major ginsenosides. Current research is focused on efficiently and selectively removing sugar groups attached to the major ginsenoside sugar chains to convert them into rare ginsenosides that meet the demands of medical industry and functional foods. The methods for preparing rare ginsenosides encompass chemical, microbial, and enzymatic approaches. Among these, the enzyme conversion method is highly favored by researchers due to its exceptional specificity and robust efficiency. This review summarizes the biological activities of different rare ginsenosides, explores the various glycosidases used in the biotransformation of different major ginsenosides as substrates, and elucidates their respective corresponding biotransformation pathways. These findings will provide valuable references for the development, utilization, and industrial production of ginsenosides.

Production and pharmaceutical research of minor saponins in Panax notoginseng (Sanqi): Current status and future prospects

Panax notoginseng (Burk.) F.H. Chen is a traditional medicinal herb known as Sanqi or Tianqi in Asia and is commonly used worldwide. It is one of the main raw ingredients of Yunnan Baiyao, Fu fang dan shen di wan, and San qi shang yao pian. It is also a source of cardiotonic pill used to treat cardiovascular diseases in China, Korea, and Russia. Approximately 270 Panax notoginseng saponins have been isolated and identified as the major active components. Although the absorption and bioavailability of saponins are predominantly dependent on the gastrointestinal biotransformation capacity of an individual, minor saponins are better absorbed into the bloodstream and act as active substances than major saponins. Notably, minor saponins are absent or are present in minimal quantities under natural conditions. In this review, we focus on the strategies for the enrichment and production of minor saponins in P. notoginseng using physical, chemical, enzyme catalytic, and microbial methods. Moreover, pharmacological studies on minor saponins derived from P. notoginseng over the last decade are discussed. This review serves as a meaningful resource and guide, offering scholarly references for delving deeper into the exploration of the minor saponins in P. notoginseng.

Ginsenoside Rg5 as an anticancer drug: a comprehensive review on mechanisms, structure-activity relationship, and prospects for clinical advancement

Cancer remains one of the leading causes of death in the world. Despite the considerable success of conventional treatment strategies, the incidence and mortality rates are still high, making developing new effective anticancer therapies an urgent priority. Ginsenoside Rg5 (Rg5) is a minor ginsenoside constituent obtained exclusively from ginseng species and is known for its broad spectrum of pharmacological activities. This article aimed to comprehensively review the anticancer properties of Rg5, focusing on action mechanisms, structure-activity relationship (SAR), and pharmacokinetics attributes. The in vitro and in vivo activities of Rg5 have been proven against several cancer types, such as breast, liver, lung, bone, and gastrointestinal (GI) cancers. The modulation of multiple signaling pathways critical for cancer growth and survival mediates these activities. Nevertheless, human clinical studies of Rg5 have not been addressed before, and there is still considerable ambiguity regarding its pharmacokinetics properties. In addition, a significant shortage in the structure-activity relationship (SAR) of Rg5 has been identified. Therefore, future efforts should focus on further optimization by performing extensive SAR studies to uncover the structural features essential for the potent anticancer activity of Rg5. Thus, this review highlights the value of Rg5 as a potential anticancer drug candidate and identifies the research areas requiring more investigation.

Ginsenoside Rg3: A Review of its Anticancer Mechanisms and Potential Therapeutic Applications

BACKGROUND

Traditional Chinese Medicine (TCM) has a long history of treating various diseases and is increasingly being recognized as a complementary therapy for cancer. A promising natural compound extracted from the Chinese herb ginseng is ginsenoside Rg3, which has demonstrated significant anticancer effects. It has been tested in a variety of cancers and tumors and has proven to be effective in suppressing cancer.

OBJECTIVES

This work covers various aspects of the role of ginsenoside Rg3 in cancer treatment, including its biological functions, key pathways, epigenetics, and potential for combination therapies, all of which have been extensively researched and elucidated. The study aims to provide a reference for future research on ginsenoside Rg3 as an anticancer agent and a support for the potential application of ginsenoside Rg3 in cancer treatment.