Introduction/Overview
Diabetes and its complications, especially hyperglycemia, have become a major global public health challenge. Long term hyperglycemia can lead to various serious health problems such as cardiovascular disease, neuropathy, kidney disease, and cognitive impairment. At present, although there are many first-line hypoglycemic drugs in clinical practice, such as metformin, SGLT2 inhibitors, DPP-4 inhibitors, etc., there are still limitations such as insufficient efficacy, side effects, or long-term medication safety. Therefore, discovering natural active ingredients with novel mechanisms of action and multi-target synergistic effects from traditional medicinal plants has become an important direction for new drug development. Zhimu（Anemarrhena asphodeloides Bunge, as a traditional Chinese medicine that clears heat and eliminates fire, nourishes yin and moistens dryness, has attracted much attention for its hypoglycemic activity. Timosaponin BI, also known as Timosaponin E, is an important steroid saponin compound isolated from the rhizome of Anemarrhena. In recent years, a large number of studies have shown that Anemarrhena asphodeloides BI shows significant pharmacological activity in improving insulin resistance, reducing blood sugar, and potentially interfering with diabetes related complications. Its mechanism of action involves activation of the AMPK signaling pathway, inhibition of SGLT2, and impact on multiple targets related to glucose metabolism and neuroprotection, such as EHMT2 and BACE1, exhibiting a multi pathway, multi target characteristic of action. This article aims to systematically review the chemical structure, plant origin, pharmacological activity, molecular mechanism of action, pharmacological evaluation, and clinical application prospects of saponins BI from Anemarrhena chinensis, in order to provide comprehensive scientific references for the in-depth research and development of this natural product.
Chemical structure and physicochemical properties
Timosaponin BI is a steroid saponin with the chemical name (25R) -26-O - β - D-glucopyranosyl-5 β - furostan-20 (22) - ene-3 β, 26 diol 3-O - β - D-glucopyranosyl - (1 → 2) - β - D-galactopyranoside. Its CAS number is 136565-73-6, molecular formula is C45H74O19, and molecular weight is 935.1110 Da.
Structurally, Zhimu saponin BI has a typical furostane type saponin skeleton. Its parent nucleus is 5 β - furostane-20 (22) - ene, connected to a triple sugar chain at C-3 position. The sugar chain is composed of β - D-galactose and β - D-glucose, which are connected by a (1 → 2) glycosidic bond from the inside out. In addition, there is also a β - D-glucopyranosyl group attached to the C-26 position (hydroxymethyl on the furan ring), forming another glycosidic bond, which is a key structural feature that distinguishes it from other saponins of Anemarrhena (such as Anemarrhena saponin AIII). This dual sugar chain structure has a significant impact on its water solubility and biological activity.
The physical and chemical properties parameters are as follows: the calculated lipid water partition coefficient (LogP) is 1.5391, indicating that the compound has a certain lipophilicity, but overall it still tends to be hydrophilic. The topologically polar surface area (TPSA) is as high as 296.3700 Å ², which is mainly attributed to the presence of multiple hydroxyl groups and oxygen atoms on the sugar ring in the molecule. The huge polar surface area is the structural basis for its good water solubility. The calculated water solubility is 0.1437 mg/mL, which belongs to the range of slightly soluble to soluble, which is beneficial for its absorption and distribution in organisms. Overall, Zhimu saponin BI is a highly polar and water-soluble steroid saponin compound.
Plant sources and extraction methods
Zhimu saponin BI mainly comes from the lily family plant Zhimu（Anemarrhena asphodeloides Bunge's dried rhizomes. Zhimu is mainly distributed in China, South Korea, and Japan, and has a long history of medicinal use in China. Zhimu rhizome contains abundant steroidal saponins, among which Zhimu saponin BI is one of the active ingredients with high content, often coexisting with Zhimu saponins AIII, BII, etc.
The extraction of saponins BI from Anemarrhena usually follows the conventional process of natural product separation. Firstly, dry and crush the rhizomes of Anemarrhena asphodeloides, and use polar solvents such as methanol, ethanol, or aqueous ethanol for heating reflux or ultrasound assisted extraction to fully extract saponin components. After vacuum concentration, the crude extract is preliminarily enriched and decolorized using macroporous adsorption resins (such as D101, AB-8). Water ethanol gradient elution is commonly used, and saponin components are mostly concentrated in the 30% -70% ethanol elution site. Subsequently, multiple chromatographic techniques such as normal phase silica gel column chromatography, reverse phase silica gel column chromatography (such as ODS), and high performance liquid chromatography (HPLC) were used for repeated separation and purification. Semi preparative or preparative HPLC, using a C18 chromatographic column with methanol water or acetonitrile water as the mobile phase, is a key step in obtaining high-purity Anemarrhenoside BI monomers. Modern technologies such as high-speed countercurrent chromatography (HSCCC) have also been applied to the separation and purification of saponins from Anemarrhena due to their high recovery rate and avoidance of irreversible adsorption. During the extraction process, attention should be paid to the characteristics that saponins are easy to produce foam and may be hydrolyzed when heated.
Pharmacological activity research
A large number of pharmacological studies both in vitro and in vivo have confirmed that saponins from Anemarrhena asphodeloides have a wide range of biological activities, especially in the intervention of hyperglycemia and its related metabolic disorders and complications.
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Lowering blood sugar and improving insulin resistance activity This is the core pharmacological effect of Zhimu saponin BI. In the model of streptozotocin (STZ) induced diabetes mice or the model of type 2 diabetes rats induced by high-fat diet combined with STZ, oral administration of anemarroside BI can significantly reduce the levels of fasting blood glucose, postprandial blood glucose and glycosylated hemoglobin (HbA1c). Meanwhile, it can improve oral glucose tolerance (OGTT) and insulin tolerance (ITT), enhance insulin sensitivity, and alleviate insulin resistance. Its strength of action is comparable or slightly weaker than the positive drugs metformin or glibenclamide, but it shows the potential for multi-target action.
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Regulating lipid metabolism In the hyperglycemic animal model, Anemarrhena asphodeloides saponin BI can also reduce the levels of serum total cholesterol (TC), triglyceride (TG) and low-density lipoprotein cholesterol (LDL-C), and increase high-density lipoprotein cholesterol (HDL-C), which has a good regulatory effect on the lipid metabolism disorder associated with diabetes.
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Anti inflammatory and antioxidant effects Chronic low-grade inflammation and oxidative stress are the important pathological basis of insulin resistance and complications of diabetes. Studies have shown that saponin BI of Anemarrhena asphodeloides can inhibit the expression of proinflammatory factors such as tumor necrosis factor - α (TNF - α) and interleukin-6 (IL-6) in the liver and adipose tissue of diabetes animals, increase the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH Px), and reduce the content of malondialdehyde (MDA), thereby alleviating oxidative damage.
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Neuroprotection and potential anti Alzheimer's disease activity: Since diabetes is an important risk factor for Alzheimer's disease (AD), the protective effect of Anemarrhena saponin BI on the nervous system has attracted attention. The study found that it can improve the cognitive dysfunction of diabetes model animals. Its mechanism may be related to inhibiting the activity of β - secretase (BACE1), reducing the production of β - amyloid protein (A β) (target APP, BACE1), and alleviating neuroinflammation and oxidative stress, suggesting that it has potential intervention value in diabetes encephalopathy and AD.
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Other activities In addition, there are also research reports that Anemarrhena asphodeloides BI has anti platelet aggregation, protection of vascular endothelial function and other beneficial effects on cardiovascular and cerebrovascular health, which are of great significance for the prevention and treatment of macrovascular complications in diabetes.
Mechanism of action and molecular targets
The hypoglycemic and pleiotropic effects of Zhimu saponin BI are not achieved through a single target, but involve a complex signaling network. The molecular targets and pathways revealed by existing research mainly include:
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Activate AMPK signaling pathway Adenosine activated protein kinase (AMPK) is a core regulatory factor in cellular energy metabolism. Zhimu saponin BI has been shown to significantly activate AMPK in the liver, skeletal muscle, and adipose tissue. The activation of AMPK promotes the translocation of glucose transporter 4 (GLUT4), increasing the uptake and utilization of glucose by peripheral tissues; On the other hand, inhibiting the expression of key enzymes involved in gluconeogenesis, such as phosphoenolpyruvate carboxykinase PEPCK and glucose-6-phosphatase G6Pase, reduces liver glucose output. This is one of the core mechanisms by which it improves insulin resistance and lowers blood sugar.
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Inhibit SGLT2 Sodium glucose cotransporter 2 (SGLT2) is the main transporter responsible for glucose reabsorption in the renal proximal tubules. Computational simulations and partial biochemical experiments suggest that saponins BI from Anemarrhena chinensis may inhibit SGLT2 activity through competitive or conformational mechanisms, thereby increasing urinary glucose excretion and achieving hypoglycemic effects, similar to clinical SGLT2 inhibitor drugs.
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Regulating epigenetic target EHMT2 Histone lysine methyltransferase 2 (EHMT2, also known as G9a) is an epigenetic regulatory factor involved in silencing genes related to the insulin signaling pathway. Research has found that saponins BI from Anemarrhena chinensis may improve insulin signaling by inhibiting the activity or expression of EHMT2, thereby relieving its inhibition of genes such as insulin receptor substrate 1 (IRS1).
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Affects deubiquitinase UBP2 and serine protease inhibitor PAI1 Both deubiquitinase UBP2 (USP2) and plasminogen activator inhibitor-1 (PAI-1) are associated with insulin resistance and inflammation. Zhimu saponin BI may affect the stability of related proteins by regulating UBP2, and improve fibrinolysis and alleviate vascular inflammation by downregulating PAI-1 expression.
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Intervention of Glucokinase (GCK) and Protein Tyrosine Phosphatase 1B (PTPN1)GCK is the rate limiting enzyme for liver glucose sensing and metabolism, while PTPN1 is a key negative regulator of insulin receptor signaling. Zhimu saponin BI may promote the efficiency of the insulin signaling pathway by positively regulating GCK activity and inhibiting PTPN1 activity.
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Targeting neurodegenerative proteins In the nervous system, Zhimu saponin BI reduces the production of neurotoxic A β by targeting the key enzyme BACE1 in the processing of amyloid precursor protein (APP). In addition, the potential regulatory effect of carboxylesterase 1 (CES1) may also affect lipid metabolism and neuroinflammation in the brain.
In summary, Zhimu saponin BI exerts a comprehensive anti hyperglycemic effect and its complications through synergistic action on multiple targets such as AMPK, SGLT2, EHMT2, PTPN1, BACE1, etc., from promoting glucose utilization, inhibiting reabsorption and production, improving insulin sensitivity, reducing inflammatory oxidative stress, to protecting nerves, and other aspects.
Evaluation of drug properties and pharmacokinetics
Based on its calculations and preliminary experimental data, a preliminary evaluation of the pharmacological properties of Zhimu saponin BI is conducted
Absorption, distribution, metabolism, excretion (ADME) characteristics：
* absorb As a saponin compound with a high molecular weight (>900 Da) and extremely high TPSA (>250 Å ²), its oral bioavailability is expected to be low. This is mainly limited by poor intestinal permeability (which conforms to the characteristics of high polarity molecules in "Class Rule Five") and the possibility of hydrolysis or first pass effects by intestinal microbiota. Formulation technologies such as nanocrystals, liposomes, phospholipid complexes, or in combination with absorption enhancers may be key to improving their oral absorption.
* distribution The calculation shows that its blood-brain barrier (BBB) permeability is "low", which is consistent with most polar macromolecules. However, under pathological conditions such as diabetes or AD, the integrity of the blood-brain barrier may be damaged, and its amount entering the central nervous system may increase. The study of its tissue distribution in the body is not yet sufficient, and further radioactive labeling or high-sensitivity mass spectrometry research is needed to clarify.
* Metabolism The main metabolic pathways of steroidal saponins in the body may include: ① hydrolysis of glycans in the gastrointestinal tract and liver, gradually removing glycans and converting them into secondary glycosides or aglycones (such as salsa saponin); ② Oxidation and binding reactions of hydroxyl groups (such as glucuronidation and sulfation). These metabolites may have different or stronger activity than the prototype drug.
* excretion The prototype drug and its metabolites may be mainly excreted through the kidneys and bile.
Preliminary evaluation of safety：
* HERG inhibition The calculated prediction shows' no ', indicating a low risk of potential cardiac toxicity (causing long QT syndrome), which is a favorable safety feature.
* Genotoxicity The Ames test predicted a value of 0.0, indicating that it has no mutagenic risk under the current model prediction, but experimental verification is needed.
* Other The acute toxicity experiment showed that within the effective dose range, there were no significant acute toxic side effects of Zhimu saponin BI on experimental animals. However, systematic evaluations of long-term toxicity and reproductive toxicity still need to be conducted.
Challenges and optimization directions in drug development：
The main challenges lie in low oral bioavailability and chemical stability (such as glycosidic bonds that may be sensitive to acids and enzymes). Future research should focus on: ① systematic pharmacokinetic studies to clarify their in vivo processes; ② Develop new drug delivery systems (such as oral nano formulations, transdermal drug delivery); ③ Perform structural modifications to optimize the lipid water partition coefficient and metabolic stability while retaining the pharmacophore, and prepare prodrugs or derivatives.
Clinical application prospects and prospects
Zhimu saponin BI, as a multi-target natural compound for anti hyperglycemic effects, has broad clinical application prospects but also faces many challenges.
Potential application directions：
1. First line or auxiliary treatment of type 2 diabetes: It can be developed as a single ingredient drug, especially suitable for new onset and mild type 2 diabetes patients, or as a component of combined use with existing drugs (such as metformin) to achieve synergy and reduce side effects.
2. Prevention and treatment of complications of diabetes: Based on its multiple effects of anti-inflammatory, antioxidant, lipid regulating, neuroprotective and endothelial protection, it has special potential to be developed to prevent and treat diabetes nephropathy, diabetes peripheral neuropathy, diabetes cardiovascular disease and diabetes related cognitive decline.
3. Comprehensive management of metabolic syndrome Its comprehensive effects of lowering blood sugar, regulating lipids, and improving insulin resistance meet the multiple intervention needs of metabolic syndrome.
4. Preventive interventions for Alzheimer's disease: In view of diabetes, an important risk factor of AD, the dual role of Anemarrhena asphodeloides BI (hypoglycemic+neuroprotective) makes it a candidate drug to prevent or delay the progression of AD.
Future research prospects：
1. In depth mechanism research It is necessary to use techniques such as gene knockout/knock in animals, chemical probes, proteomics, etc. to more accurately verify its direct interactions with targets such as EHMT2, UBP2, PAI1, and elucidate the cross dialogue between its multi-target network.
2. System drug development Comprehensive preclinical pharmacokinetic and toxicological studies must be conducted. We will focus on using pharmaceutical and medicinal chemistry methods to solve the bottleneck problem of low bioavailability.
3. Clinical translational research: On the basis of completing standard preclinical research, gradually promote human clinical trials, and evaluate their effectiveness, safety and optimal administration scheme in different populations (such as patients with different stages of diabetes and complications).
4. Examples of Modernization of Traditional Chinese Medicine The in-depth study of Zhimu saponin BI is a typical case of clarifying the "pharmacological substance basis" from traditional Chinese medicine and interpreting its scientific connotation of "multi-component multi-target multi pathway", which helps to promote the modernization and international recognition of Zhimu and even the entire traditional Chinese medicine.
Conclusion
Zhimu saponin BI is a steroid saponin with significant hypoglycemic activity isolated from traditional Chinese medicine Zhimu. Research has shown that it not only effectively reduces blood sugar, improves insulin resistance and lipid metabolism, but also has multiple pharmacological effects such as anti-inflammatory, antioxidant, and neuroprotective effects. Its mechanism of action involves the regulation of multiple key targets such as AMPK, SGLT2, EHMT2, PTPN1, BACE1, etc., showing a distinct characteristic of multi pathway synergistic effects. Although it faces challenges in developing drug properties in terms of oral bioavailability, it is expected to overcome these obstacles through the optimization of modern drug development technologies, such as structural modifications and the application of novel drug delivery systems. To sum up, Anemarrhena asphodeloides saponin BI is a natural lead compound with great development potential against diabetes and its complications. Its in-depth research is of great significance for innovative drug research and development and for interpreting the scientific value of traditional Chinese medicine. In the future, interdisciplinary collaboration is needed to accelerate the transition from basic research to clinical applications.
