Introduction/Overview
In the field of natural product chemistry and pharmacology research, flavonoids have attracted much attention due to their extensive biological activity and low toxicity. Kaempferol-3-O-sambubioside, also known as Leucoside (CAS number: 27661-51-4), is an important glycosylated derivative of kaempferol-3-O-sambubioside, mainly isolated from tea seeds and other plants. As a natural flavonoid glycoside, it not only inherits the active basis of kaempferol parent nucleus, but its unique mulberry disaccharide (composed of xylose and glucose) substituent is more likely to significantly affect its physicochemical properties, bioavailability, and pharmacological effects. In recent years, as the core role of oxidative stress in various pathological processes such as aging, neurodegenerative diseases, cardiovascular diseases, and cancer has been continuously revealed, natural compounds with strong antioxidant potential have become a research hotspot. Leucoside has shown significant research value and application potential due to its regulatory role in antioxidant and related pathways. This article aims to systematically review the chemical properties, plant sources, pharmacological activities, especially the antioxidant mechanism and molecular targets of Leucoside, and to provide a comprehensive academic reference for its pharmacological properties and future application prospects, in order to provide in-depth research and development of this compound.
Chemical structure and physicochemical properties
The molecular formula of kaempferol-3-O-Sambucoside is C26H28O15, with a molecular weight of 580.4950. Its chemical structure is based on the flavonol compound kaempferol as the aglycone, which is connected to a mulberry disaccharide through a glycosidic bond on the 3-hydroxyl group of the mother nucleus. Sambucan is a disaccharide composed of one molecule of xylose and one molecule of glucose connected in a specific manner. This glycosylation modification significantly alters the polarity of kaempferol.
From the analysis of parameters related to drug properties, this compound has a high topological polar surface area (TPSA: 249.2000 Å ²), which is determined by the multiple hydroxyl and sugar structures in its molecule. The calculated LogP value (-0.6136) indicates that the compound has strong hydrophilicity and good theoretical water solubility (2.8159 mg/mL). These data collectively indicate that Leucoside is a polar molecule with good water solubility. However, high polarity and large molecular weight also pose challenges to its biofilm permeability, with a predicted "low" blood-brain barrier permeability, suggesting that it may be difficult to enter the central nervous system and exert its effects. In early toxicity screening, the compound showed no inhibitory activity on hERG potassium channels, indicating a low potential risk of cardiac toxicity; The Ames test result was 0.6, indicating a low risk of mutagenicity and providing preliminary positive data for its safety evaluation.
Plant sources and extraction methods
Kaempferol-3-O-Sambucoside is relatively widely distributed in nature, but mainly exists as a secondary metabolite in various plants. One of its most commonly reported sources is tea plants, especially those isolated from tea seed extracts. In addition, it has also been detected in the leaves and fruits of mulberry trees (Morus alba L.), flowers and fruits of elderberry (Sambucus spp.) (from which the name "sambubioside" comes), and some medicinal plants such as Smilax china.
The extraction of Leucoside from plant materials usually follows the conventional process of natural product chemistry. Firstly, suitable solvents are used for extraction, including methanol, ethanol, or their aqueous solutions. Heating reflux, ultrasound assisted, or microwave-assisted methods are used to improve extraction efficiency. Subsequently, preliminary enrichment and purification were carried out using macroporous adsorption resin column chromatography, followed by further separation and purification using techniques such as silica gel column chromatography, reverse phase silica gel column chromatography (such as ODS-C18), and high performance liquid chromatography (HPLC). Structural identification involves the comprehensive use of spectroscopic methods such as ultraviolet spectroscopy (UV), mass spectrometry (MS), and nuclear magnetic resonance spectroscopy (NMR, including 1H-NMR and 13C-NMR). In recent years, green extraction techniques such as supercritical fluid extraction have also been explored for the extraction of polar flavonoid glycosides, in order to improve efficiency while reducing the use of organic solvents.
Pharmacological activity research
The pharmacological activity research of Leucoside is currently mainly focused on antioxidant and its extended biological effects, and its spectrum of activities is constantly expanding.
1. Core antioxidant activity
The most prominent pharmacological activity of Leucoside is its strong antioxidant capacity. A large number of in vitro chemical model evaluations have shown that the compound can effectively scavenge 1,1-diphenyl-2-trinitrophenylhydrazine (DPPH) free radicals, 2,2 '- diazobis (3-ethylbenzothiazoline-6-sulfonic acid) cationic free radicals, superoxide anions (O2 •−), and hydroxyl free radicals (• OH), and its scavenging ability is positively correlated with concentration. In cell models, Leucoside can significantly alleviate the increase in intracellular reactive oxygen species (ROS) levels induced by oxidative stressors such as hydrogen peroxide (H2O2), tert butyl hydroperoxide (t-BHP), or ultraviolet radiation, protecting cells from oxidative damage. This direct free radical scavenging ability is the first line of defense against its protective effect.
2. Skin photoprotection and anti-aging effects
Based on its antioxidant properties, Leucoside has shown potential in skin pharmacology. Research suggests that it can inhibit the activity of tyrosinase (TYR), which may be related to intervening in skin pigmentation. More importantly, it can downregulate the expression of matrix metalloproteinase-1 and MMP-3 (MMP-1, MMP-3). MMPs are key enzymes that degrade collagen and elastin in the dermis of the skin, and their overexpression is the main mechanism of UV induced skin photoaging and wrinkle formation. Therefore, Leucoside shows promising application prospects in combating skin photoaging through dual pathways of antioxidant and MMP inhibition.
3. Potential anti-inflammatory and cell protective effects
Oxidative stress is closely coupled with inflammatory response. Preliminary studies suggest that the antioxidant effect of Leucoside may extend to the anti-inflammatory field. By reducing ROS levels, it can indirectly inhibit the excessive activation of pro-inflammatory signaling pathways such as nuclear factor kappa B (NF - κ B), thereby reducing the production of inflammatory mediators. In models such as liver cells and endothelial cells, Leucoside exhibits protective effects against oxidative stress-induced cell apoptosis and damage, suggesting its potential for protection in organs such as the liver and cardiovascular system.
Mechanism of action and molecular targets
The pharmacological effects of Leucoside, especially its core antioxidant and cell protective effects, are not solely achieved through direct chemical quenching of free radicals. More importantly, it can activate or regulate the endogenous antioxidant defense system within cells, which involves multiple clear molecular targets and signaling pathways.
1. Activate the KEAP1-NRF2/ARE core antioxidant pathway
This is the most critical molecular mechanism by which Leucoside exerts antioxidant effects. In the basal state, transcription factor NF-E2-related factor 2 (NRF2, encoded by the NFE2L2 gene) binds to its cytoplasmic inhibitory protein Kelch like ECH associated protein 1 (KEAP1) and is degraded by ubiquitination. When Leucoside enters the cell, its active groups may directly modify key cysteine residues on KEAP1, or cause conformational changes in KEAP1 by generating slight oxidative stress, thereby dissociating the binding of NRF2. Stable NRF2 translocates to the nucleus and binds to antioxidant response elements (ARE), initiating transcriptional expression of a series of phase II detoxifying enzymes and antioxidant proteins. The key downstream targets of Leucoside include:
* antioxidant enzyme Superoxide dismutase 1/2 (SOD1, SOD2), catalase (CAT), glutathione peroxidase 1 (GPX1). These enzymes work together to convert superoxide anions into hydrogen peroxide, which is further broken down into harmless water and oxygen.
* Heme oxygenase-1 (HMOX1)The induction of HMOX1 not only has antioxidant effects, but its products bilirubin and CO also have anti-inflammatory and cell protective functions.
2. Inhibit oxidative stress-related damage factors
* Matrix metalloproteinases (MMPs)As mentioned earlier, Leucoside can downregulate the expression of MMP-1 and MMP-3. The mechanism may be related to the inhibition of the AP-1 signaling pathway activated by oxidative stress, as well as the enhancement of antioxidant status through the NRF2 pathway, indirectly inhibiting the transcription of MMPs.
* Tyrosinase (TYR)The inhibition of TYR by Leucoside may be achieved through its molecular structure chelating with copper ions in the enzyme active center, or competitive binding to substrate sites.
3. Networked regulation
The mechanism of action of Leucoside exhibits networked characteristics. Activating NRF2 not only enhances overall antioxidant capacity, but also affects other pathways through cross-talk, such as reducing NF - κ B-mediated inflammatory responses. Its multi-target nature enables it to intervene from multiple links such as the source of oxidative damage (free radicals), intermediate processes (inflammation), and end effects (extracellular matrix degradation), forming a synergistic protective effect.
Evaluation of drug properties and pharmacokinetics
Although Leucoside exhibits good biological activity in vitro and at the cellular level, its drug like and pharmacokinetic (PK) properties in vivo are key factors determining its clinical application.
1. Analysis of drug properties
According to its physicochemical parameters, Leucoside meets some of the requirements in the Rule of Five for class drugs (the number of hydrogen bond donors and acceptors may exceed the standard), and belongs to the "Beyond Rule of 5" compound. Its high water solubility and low fat solubility (low LogP) mean that it may have poor passive cell membrane diffusion ability, and oral bioavailability may face challenges. The glycosidic structure makes it easily broken down by gastrointestinal microbiota and hydrolytic enzymes on the intestinal mucosa (such as β - glucosidase) into aglycone kaempferol and glycosyl groups. Although this may increase the absorption of aglycone, it also alters the in vivo exposure and distribution of the prototype drug. The low permeability of the blood-brain barrier limits its potential for direct treatment of central nervous system diseases. The preliminary safety indicators (no hERG inhibition, Ames negative) are relatively optimistic.
2. Prospects for pharmacokinetics
At present, there are few reports on the Leucoside system and complete in vivo pharmacokinetic studies. Based on the study of its structural analogues, its pharmacokinetic characteristics can be inferred as follows:
* absorb After oral administration, the absorption of the prototype drug in the gastrointestinal tract may be limited and unstable. Part of it is absorbed in its original form, while the majority may undergo hydrolysis in the intestine.
* distribution The distribution volume of the prototype drug may be small, mainly distributed in the blood and extracellular fluid, making it difficult to enter adipose tissue and cross the blood-brain barrier.
* Metabolism In addition to hydrolysis, it may undergo II binding reactions (such as glucuronidation and sulfation) in the liver, and the polarity of metabolites is greater, making them easier to excrete.
* excretion The prototype drug and its metabolites are mainly excreted from the urine through the kidneys.
In order to improve its pharmacological properties, future research may need to consider the following strategies: ① Developing prodrugs, such as esterification modification to enhance lipid solubility and membrane permeability; ② Adopting new drug delivery systems such as liposomes, nanoparticles, phospholipid complexes, etc. to improve their stability, promote absorption, and target delivery; ③ Explore non oral routes of administration, such as transdermal administration for skin diseases or injection administration.
Clinical application prospects and prospects
Leucoside, as a natural product with a clear antioxidant mechanism, has broad clinical application prospects, but requires in-depth research and key technological breakthroughs.
1. Potential application areas
* Functional cosmetics and topical preparations for the skin This is the field closest to achieving conversion. Add it to sunscreen, anti-aging essence, repair lotion and other products, and use its efficacy of inhibiting MMPs, eliminating free radicals and potential whitening (inhibiting TYR) to prevent and improve skin photoaging, wrinkles and pigmentation. It has good water solubility and is easy to formulate.
* Dietary supplements and health foods As one of the active ingredients in plant extracts such as tea seeds, it is used to develop health products that have antioxidant properties and enhance the body's ability to resist stress. Attention should be paid to the actual bioavailability and in vivo effects after oral administration.
* Adjuvant therapy drugs In the diseases where oxidative stress plays an important role, such as metabolic syndrome, nonalcoholic fatty liver disease, early atherosclerosis, tissue damage caused by chemotherapy drugs, Leucoside may be used as an auxiliary treatment drug to play an organ protection role by regulating the NRF2 pathway.
* Adjuvant therapy for inflammatory skin diseases Such as atopic dermatitis, psoriasis, etc., their antioxidant and potential anti-inflammatory properties may help alleviate symptoms.
2. Future research prospects
To promote the research and development of Leucoside, future work should focus on:
* In depth mechanism research By utilizing techniques such as gene knockout, molecular docking, and proteomics, we aim to more accurately elucidate the details of its interactions with targets such as KEAP1, and explore its role in specific disease models such as liver fibrosis and myocardial ischemia-reperfusion.
* Systematic pharmacokinetic study Conduct research on ADME in animals to clarify the pharmacokinetic characteristics, absolute bioavailability, and tissue distribution of its prototype and major metabolites.
* Security system evaluation Complete preclinical safety pharmacology studies on acute toxicity, subchronic toxicity, reproductive toxicity, etc.
* Innovation in formulation technology Actively developing new drug delivery systems that can overcome their physical and chemical defects, improve bioavailability and targeting.
* Exploration of clinical research After completing sufficient preclinical research, gradually conduct clinical trials on the effectiveness and safety of topical application on the skin, as well as research on human tolerance and biomarkers as oral health ingredients.
Conclusion
Leucoside, a flavonoid glycoside with significant antioxidant activity, is extracted from tea seeds and other plants. Its mechanism of action goes beyond simple free radical scavenging, and its core lies in activating the key switch of cell self-protection - the KEAP1-NRF2/ARE signaling pathway, thereby upregulating the expression of a series of endogenous antioxidant enzymes and cell protective proteins such as SOD, CAT, GPX1, HMOX1, and inhibiting damage factors such as MMPs. Although its strong polarity and glycosidic structure may pose challenges to oral bioavailability, its clear multi-target mechanism of action, good preliminary safety, and advantages in water-soluble formulations make it have clear development potential in the fields of functional cosmetics, topical skin treatments, and health products for preventing oxidative stress-related diseases. Future research should focus on deepening the understanding of its molecular mechanisms, overcoming its pharmacological bottlenecks, and transforming this promising natural molecule into products that benefit human health through rigorous preclinical and clinical studies.
