Dihuang glycoside C: a neuroprotective potential molecule derived from Rehmannia glutinosa
1. Overview
Rhmannioside C, CAS number 81720-07-2, is a traditional medicinal plant derived from Rehmannia glutinosa（Rehmannia glutinosa）Natural iridoid glycosides isolated from the middle. Its molecular formula is C21H34O14, with a molecular weight of 510.4890 g/mol. As one of the important active ingredients in Rehmannia glutinosa, Rehmannia glutinosa glycoside C has shown potential in recent years due to its neuroprotection The activity has attracted widespread attention in the field of natural product pharmacology research. Dihuang, as one of the "Four Great Huai Medicines", has a history of over a thousand years of clinical application in traditional Chinese medicine. It is commonly used to nourish yin and kidney, clear heat and cool blood. Modern pharmacological research is gradually revealing the material basis and molecular mechanism behind its traditional efficacy, and digoxin C is one of the representative research objects. Current research suggests that digoxin C may exert neuroprotective effects by acting on multiple key targets related to neuronal survival, synaptic plasticity, and inflammatory response, such as SIRT1, MAPK1, CREB1, BDNF, and NGF. This demonstrates its potential application value in the prevention and treatment of neurodegenerative and damaging diseases such as Alzheimer's disease, Parkinson's disease, and cerebral ischemia-reperfusion injury. This article will provide a systematic professional popularization of Dihuang Glycoside C from its chemical structure, plant origin, pharmacological mechanism, medicinal evaluation, and research prospects.
2. Chemical structure and physicochemical properties
The chemical structure of Dihuang glycoside C belongs to the class of iridoid glycosides, and its SMILES structural formula clearly demonstrates its complex stereochemical characteristics: a iridoid core is connected to two sugar groups (presumably glucose or similar hexose) through glycosidic bonds. This structure is an important material basis for its biological activity. Analyze its physicochemical properties based on the provided pharmacological parameters:
- Molecular weight (MW)：510.49 g/mol， Slightly higher than conventional small molecule drugs (usually<500 Da), but still within an acceptable range.
- Lipid water partition coefficient (LogP/LogD)-2.01 indicates that the compound has extremely strong hydrophilicity Almost insoluble in lipids. This is closely related to the presence of multiple hydroxyl groups (- OH) and glycosyl structures in its molecule.
- Topological Polarity Surface Area (TPSA)Up to 228.22 Å ², far exceeding the threshold typically considered easy to penetrate cell membranes (approximately 140 Å ²). High TPSA is a typical characteristic of glycoside compounds, originating from their multiple hydrogen bond donors and acceptors.
- Water solubility The value is 28.17 (usually measured in mg/mL or log mol/L, which is not specified here, but the value is high), confirming its good water solubility.
- Permeability Caco-2 cells have low permeability (0.37 × 10 ⁻⁶ cm/s) and effective permeability (Peff, 0.46), indicating poor passive absorption through the intestine. The blood-brain barrier (BBB) penetration is marked as "low", which poses a major challenge for its central nervous system protective effect.
In summary, Dihuang Glycoside C is a High polarity, high hydrophilicity, low fat solubility Glycoside compounds. Its physicochemical properties determine that its oral bioavailability may not be high and it is difficult to freely pass through the blood-brain barrier. This suggests that in drug development, strategies such as structural modification (such as preparing prodrugs), developing novel drug delivery systems (such as nano delivery), or utilizing peripheral effects to indirectly affect the central nervous system may be needed to overcome these obstacles.
3. Plant sources and traditional applications
The plant source of Dihuang Glycoside C is single and clear, that is, it comes from Orobanchaceae family Plant Rehmannia glutinosa（Rehmannia glutinosa）Dihuang is mainly distributed in China, and its root tuber is a famous traditional Chinese medicinal herb. According to different processing methods, it can be divided into fresh Rehmannia glutinosa, raw Rehmannia glutinosa, and cooked Rehmannia glutinosa, each with its own emphasis on efficacy.
- Fresh Rehmannia glutinosa Clearing heat and generating fluids, cooling blood and stopping bleeding.
- Sheng Dihuang Clearing heat and cooling blood, nourishing yin and generating fluids.
- prepared rehmannia root Nourish blood and yin, nourish essence and fill marrow.
In traditional Chinese medicine theory, Rehmannia glutinosa is commonly used to treat various diseases caused by "kidney yin deficiency" or "blood heat", such as dizziness, tinnitus, soreness and weakness of the waist and knees, bone steaming and hot flashes, thirst quenching, blood heat bleeding, etc. Many classic kidney tonifying formulas, such as Liuwei Dihuang Wan, Zuogui Wan, Yougui Wan, etc., all use Dihuang as their main medicine or important component.
Modern plant chemistry research has isolated and identified hundreds of compounds from Rehmannia glutinosa, including iridoid glycosides (such as catalpol, Rehmannia glycosides A, B, C, D, etc.), sugars, amino acids, organic acids, etc. Among them, iridoid glycosides are considered to be the main active ingredient group of Rehmannia glutinosa. As one of them, although the content of Dihuang Glycoside C is not the highest, its unique structure gives it specific biological activity, which is one of the modern scientific entry points to explain the traditional effects of Dihuang in nourishing yin and kidney, nourishing essence and filling marrow, especially its potential benefits to the nervous system.
4. Pharmacological activity and mechanism of action
Existing research data focuses on the activity of digoxin C neuroprotection The field identified five key targets that it may act on, including SIRT1, MAPK1, CREB1, BDNF, and NGF. These targets form a complex and interconnected signaling network that collectively regulates the survival, differentiation, synaptic function, and ability to cope with stress of neurons.
1. Core target analysis:
- SIRT1 (Silent Information Regulatory Factor 1)This is a histone deacetylase that relies on NAD+and is a core regulatory factor for cellular energy metabolism and stress response. In the nervous system, SIRT1 activation can promote mitochondrial biosynthesis, enhance antioxidant defense, inhibit inflammatory response and apoptosis pathways, thereby protecting neurons from various damages. Dihuang glycoside C may act as an activator or modulator of SIRT1.
- MAPK1 (mitogen activated protein kinase 1, also known as ERK2)The MAPK/ERK signaling pathway is a key pathway for cell proliferation, differentiation, and survival. Moderate activation of ERK is crucial for neuronal survival, synaptic plasticity, and learning and memory mediated by neurotrophic factors such as BDNF and NGF in neurons.
- CREB1 (cAMP response element binding protein 1)This is a key transcription factor that, after being phosphorylated and activated by various kinases (including ERK), enters the nucleus and initiates transcription of specific genes. Its downstream target genes include BDNF and Bcl-2 Anti apoptotic proteins are core molecules that connect extracellular signals with long-term neural adaptive changes.
- BDNF (brain-derived neurotrophic factor) and NGF (nerve growth factor)Both are important neurotrophic factors. BDNF is highly expressed in the hippocampus and cerebral cortex, and plays a decisive role in neuronal survival, differentiation, synaptic formation, and plasticity (such as long-term potentiation, LTP). NGF is crucial for the survival and functional maintenance of cholinergic neurons in the basal forebrain, and the degeneration of this neuronal group is closely related to cognitive impairment in Alzheimer's disease.
2. Integration of mechanism of action and association with neuroprotection:
Based on the above targets, the mechanism framework of the neuroprotective effect of digoxin C can be outlined:
- Activate SIRT1 mitochondrial functional axis Dihuang glycoside C may upregulate the expression of mitochondrial related genes, improve neuronal energy metabolism, and enhance its resistance to oxidative stress by activating SIRT1, deacetylating, and activating transcription co activators such as PGC-1 α. SIRT1 can also inhibit neuroinflammation by deacetylating proteins such as NF - κ B.
- Regulating the MAPK/CREB/neurotrophic factor pathway Dihuang glycoside C may activate or regulate MAPK (ERK) signaling in some way (possibly indirectly through antioxidant or anti-inflammatory effects). Activated ERK can phosphorylate and activate CREB. Activated CREB enters the nucleus, initiating processes including BDNF Transcription of various protective genes within.
- Form a positive feedback loop The newly synthesized BDNF is secreted into the extracellular space and binds to its receptor TrkB in an autocrine or paracrine manner, further strongly activating downstream PI3K/Akt and MAPK/ERK pathways, forming a positive feedback loop that promotes neuronal survival and synaptic function. Meanwhile, the potential promotion of NGF signaling may help maintain the health of cholinergic neurons.
- synergy The activation of SIRT1 is not isolated from the activation of the CREB/BDNF pathway. Studies have shown that SIRT1 can enhance the transcriptional activity of CREB and may have a cross dialogue with the BDNF signaling pathway, jointly constructing a powerful neuroprotective network.
Therefore, the neuroprotective effect of digoxin C is likely to be Multi target and multi pathway synergy The result. It may provide comprehensive protection for neurons from multiple levels, such as enhancing cellular energy metabolism (SIRT1), inhibiting oxidative stress and inflammation (SIRT1), promoting the expression of neurotrophic factors and their downstream survival signals (CREB/BDNF/ERK), etc., to combat neural damage caused by aging, toxic proteins (such as A β), ischemia and hypoxia. This provides a theoretical basis for its development for the treatment of Alzheimer's disease, Parkinson's disease, post-stroke nerve repair, and other conditions.
5. Evaluation of drug properties
Drug efficacy assessment aims to predict the likelihood of a compound becoming a successful drug. We analyzed digoxin C using Lipinski's Rule of Five (Ro5) and other key parameters:
1. Lipinski's Five Rules Compliance Status:
-Molecular weight MW<500 Da: not conform to（510.49 > 500）。
-Lipid water partition coefficient LogP<5: Comply with（-2.01 << 5）。
-Number of hydrogen bond donors (HBD)<5: not conform to(According to the structure, the glycoside portion contains a large amount of - OH and far more than 5 HBDs).
-Number of hydrogen bond acceptors (HBA)<10: not conform to There are 14 oxygen atoms in the molecule, most of which can be used as HBAs.
-The number of rotatable bonds: usually requires<10, and its glycosidic structure may result in a higher number of rotatable bonds.
Conclusion: Dihuang glycoside C seriously violates three of Lipinski's rules (MW, HBD, HBA). Ro5 is mainly used to predict small molecules with good oral absorption, and digoxin C is used as Natural glycosides Its properties have exceeded the scope of application of Ro5. These compounds usually have low oral bioavailability.
2. In depth interpretation of specific pharmacological parameters:
- Absorption and penetration Extremely low LogP (-2.01), extremely high TPSA (228 Å ²), and low Caco-2 permeability (0.37) all point to it Extremely poor membrane permeability This means that it is difficult for it to be absorbed through intestinal epithelial cells through passive diffusion, which also explains the reason for its "low" BBB penetration.
- distribution The plasma protein binding rate (PPB) is about 32.5%, which is a relatively low level. Low PPB means that there is a higher proportion of free drugs available for distribution to tissues, but due to its extremely poor membrane penetration, actual tissue distribution (especially in the central nervous system) will still be very limited.
- Metabolism and toxicity Preliminary data from Ames test (0.0), chromosomal aberration (none), hERG inhibition (no), and skin/respiratory sensitization (no) indicate that digoxin C is Low risk of genetic toxicity and cardiac toxicity It has a good foundation of security. However, 'phototoxicity' is marked as' none ', while' Ser_LK/GGT/AST/ALT 'is marked as' yes', which may indicate that it has an impact on liver related enzymes in specific models or at high doses, and its potential liver cell effects need to be addressed in subsequent studies.
- Comprehensive score of drug properties SyneAccessibility is 5.39, which is a moderate value; MRTD (Maximum Recommended Treatment Dose) is marked as "Yes", indicating that its treatment window may still be acceptable.
Overall evaluation：
Dihuang glycoside C, as a lead compound Advantage It lies in: clear plant sources, multi-target neuroprotective mechanisms, and preliminary demonstrated good safety characteristics.
its Main challenges Due to poor drug properties, especially Extremely poor oral bioavailability and blood-brain barrier penetration ability This severely limits its potential for direct development as an oral neuroprotective drug.
Future development strategies may need to focus on:
1. structural optimization Modify its sugar moiety (such as preparing prodrugs) or simplify its structure to search for essential active pharmacophores, aiming to improve lipid solubility and membrane penetration.
2. delivery system Using novel drug delivery systems such as liposomes, nanoparticles, and polymer micelles to encapsulate digoxin C, improving its stability, promoting intestinal absorption, and enhancing its BBB penetration ability through functional modifications (such as brain targeting peptides).
3. Further exploration of the mechanism of action Study whether it can produce indirect neuroprotective effects by acting on the peripheral system (such as the immune system, gut brain axis), thereby avoiding BBB problems.
6. Research Status and Application Prospects
Research status：
At present, there is relatively limited independent and in-depth pharmacological research literature on Rehmannia glutinosa C, and its activity data mostly comes from high-throughput screening or speculation based on the study of Rehmannia glutinosa whole extract. It is often mentioned as a member of the iridoid glycoside group in Rehmannia glutinosa. Known studies have mainly confirmed its in vitro or preliminary in vivo neuroprotective activity, and associated it with targets such as SIRT1, CREB, BDNF, etc. However, there are still many gaps in specific direct target validation, signaling pathway details, in vivo pharmacokinetics, and pharmacodynamic system research. The synthesis route, derivative preparation, and structure-activity relationship research are also in their early stages.
Application Prospects：
1. As a neuroprotective lead compound Despite facing challenges in drug development, its unique multi-target mechanism of action makes it a valuable lead compound. Through Medicinal Chemistry By means of structural modification, it is expected to significantly improve its pharmacokinetic properties while retaining its activity, and develop innovative drugs with independent intellectual property rights.
2. As a Quality Marker for Traditional Chinese Medicine (Q-Marker)In the quality control of Radix Rehmanniae and its compound preparations (such as Liuwei Radix Rehmanniae Pills), Radix Rehmanniae Glycoside C can be used as one of the characteristic components to evaluate the origin, processing technology, and stability of the quality of medicinal materials.
3. Development of functional foods and health products Under the modern interpretation of the traditional "nourishing" effects of Rehmannia glutinosa, Rehmannia glutinosa extracts or refined parts rich in Rehmannia glycosides C can be used to develop health foods with the potential to assist in improving memory and anti-aging. At this point, the pursuit of oral absorption rate can be appropriately relaxed, with more emphasis on the safety and overall regulatory effect of long-term use.
4. Combination therapy and multi-component therapy Following the compatibility concept of "Jun Chen Zuo Shi" in traditional Chinese medicine, Dihuang Glycoside C can synergize with other active ingredients (such as catalpol and verbascoside in Rehmannia) or be used in combination with other drugs to exert a multi pathway and multi link integrated therapeutic effect, which may be more effective in dealing with complex neurological diseases than a single ingredient.
Future research directions：
- basic research Experiments need to be conducted to clarify whether Huangdi C directly acts on targets such as SIRT1 or indirectly regulates through upstream events; Elucidate its complete intracellular signal transduction network.
- Pharmacokinetic study Systematically study its absorption, distribution, metabolism, and excretion processes in different animal models, clarify its bioavailability, major metabolites, and tissue distribution characteristics.
- Structural optimization and formulation research This is the key to pushing it towards clinical application. Experts in medicinal chemistry and pharmacy are needed to intervene, design and synthesize a series of derivatives, or develop advanced brain targeted delivery systems.
- Disease model validation Strictly evaluate the therapeutic or preventive effects on mature animal models such as Alzheimer's disease, Parkinson's disease, and stroke.
In short, Dihuang glycoside C is a natural molecule with clear neuroprotective potential discovered from the treasure trove of traditional Chinese medicine. It is like a multi toothed key, with the potential to simultaneously unlock multiple signal locks that protect nerve cells. Although the road to becoming a traditional Chinese medicine is full of obstacles, especially its inherent physical and chemical properties, with the advancement of modern drug development technology, especially the integration of structural biology, computer-aided drug design, and new delivery technologies, digoxin C and its derivatives are expected to occupy a place in the future field of neurodegenerative disease prevention and treatment, providing a modern scientific example for interpreting and developing traditional Chinese medicine theory.
