Introduction/Overview
As an important treasure trove for drug discovery, natural products continue to provide modern medicine with lead compounds with novel structures and diverse activities. Among them, isoquinoline alkaloids have always been a hot topic in medicinal chemistry and pharmacology research due to their extensive pharmacological activity and unique chemical structure. Roemerine (CAS number: 548-08-3) is a compound derived from the plant Polygonatum sibiricum in the family Menispermaceae（Fibraurea recisa The aporphine type isoquinoline alkaloids isolated from various plants such as Pierre. Early research focused more on its basic antibacterial activity, but in recent years, with the deepening of research technology, the significant activities of berberine in anti-tumor, antidepressant, sedative, and reversal of multidrug resistance have gradually been revealed, exhibiting multi-target and multi pathway characteristics. Its pharmacological effects involve regulating the cAMP signaling pathway, affecting the expression of brain-derived neurotrophic factor (BDNF), regulating the serotonergic and glutamatergic systems, and intervening in the drug resistance mechanism of tumor cells. These findings have broad research prospects in the treatment of cancer, central nervous system diseases and infectious diseases. This article aims to systematically review the chemical characteristics, plant sources, pharmacological activities, mechanisms of action, and medicinal properties of lotus alkaloids, in order to provide comprehensive scientific references for the in-depth research and development of this compound.
Chemical structure and physicochemical properties
The chemical name of lotus alkaloid is 1,2-dimethoxy-6a β - aporphin-7-one, with a molecular formula of C ₁₇ H ₁₇ NO ₂ and a molecular weight of 279.34 g/mol. Its core structure is the aporphine skeleton, which belongs to the tetracyclic isoquinoline alkaloids. Specifically, it is composed of two benzene rings (A ring and D ring) fused together through a dihydroisoquinoline system (B ring and C ring). In the molecule of lotus alkaloids, the 1st and 2nd positions of the A ring are each connected to a methoxy group (- OCH ∝), which is an important functional group; There is a carbonyl group (C=O) on the D ring, forming a lactam structure.
These structural features determine its physicochemical properties. The lipid water partition coefficient (LogP) of berberine is 3.16, indicating its good lipid solubility, which is consistent with its ability to efficiently penetrate cell membranes and the blood-brain barrier. Its topological polar surface area (TPSA) is relatively low, only 21.7 Å ², further confirming its characteristics of low molecular polarity and strong lipophilicity. The water-soluble data (approximately 0.0184 mg/mL) indicates that it is a poorly soluble compound, which may pose challenges in formulation development. From the perspective of stereochemistry, the 6a position in its molecule is in the β configuration, which may be closely related to its precise binding and biological activity with certain target proteins. Overall, berberine is a typical lipophilic small molecule alkaloid, and its structure lays the foundation for its diverse biological activities.
Plant sources and extraction methods
Lianalkaloid is mainly found in plants of the Menispermaceae family, with the main source being Huangteng（Fibraurea recisa Pierre）， The stem, leaves, and root bark all contain this alkaloid. In addition, in lotus plants such as lotus flowers（Nelumbo nucifera）It has also been found in the embryo of plants, as well as in various plants such as the poppy family and the lychee family. There are differences in the content of berberine in different plant sources and parts, which provides a space for resource development and sustainable utilization.
The extraction and separation of lotus alkaloids from plant materials usually follow the conventional process of natural product chemistry. Firstly, dry and crushed plant materials (such as rattan leaves) are extracted or refluxed using polar organic solvents (such as methanol, ethanol, or chloroform), and alkaloids are preliminarily enriched in the extraction solution using the principle of similar solubility. Subsequently, crude extract was obtained by vacuum concentration. The crude extract needs to be further separated and purified, and classic methods include acid-base treatment: using alkaloids to form salts and dissolve in water under acidic conditions, and the characteristics of downstream separation under alkaline conditions for preliminary enrichment. More precise separation relies on modern chromatographic techniques, such as silica gel column chromatography and alumina column chromatography, using gradient elution with different ratios of organic solvents (such as chloroform methanol). High performance liquid chromatography (HPLC), especially preparative HPLC, is currently the key technology for obtaining high-purity lotus alkaloid monomers. It often uses a reverse phase C18 chromatography column with methanol water or acetonitrile water (often adjusted with a small amount of trifluoroacetic acid or formic acid to adjust pH) as the mobile phase. Structural identification involves the comprehensive use of mass spectrometry (MS), nuclear magnetic resonance (NMR, including ¹ H-NMR and ¹ ³ C-NMR), and X-ray single crystal diffraction techniques.
Pharmacological activity research
A large number of in vitro and in vivo pharmacological studies have shown that berberine has various biological activities, covering multiple fields such as anti infection, anti-tumor, and neuropsychiatric regulation.
1. Antibacterial activity: Lotus alkaloids exhibit inhibitory activity against various Gram positive bacteria (such as Staphylococcus aureus) and some fungi. Its function is not simply cell membrane disruption. Studies suggest that its antibacterial mechanism may be related to interfering with the second messenger cAMP signaling pathway inside bacteria, thereby affecting bacterial metabolism, virulence, or biofilm formation.
2. Antitumor and reversal of multidrug resistance activity: Lotus alkaloid has the effect of inhibiting proliferation and inducing apoptosis in many human cancer cell lines (such as breast cancer, liver cancer, lung cancer cells). What is particularly noteworthy is that berberine can effectively reverse the multidrug resistance (MDR) phenotype of tumor cells. MDR is the main cause of chemotherapy failure, often mediated by overexpression of efflux pumps such as P-glycoprotein (P-gp). Lianalkaloid itself is not a classic substrate for P-gp, but studies have shown that it may increase the accumulation of chemotherapy drugs (such as doxorubicin) in cells by inhibiting the function or expression of P-gp, thereby restoring the sensitivity of drug-resistant cells to chemotherapy drugs.
3. Neuropsychiatric system activity:
* Anti depression and anti anxiety: Animal behavioral experiments, such as forced swimming test, tail suspension test, and elevated maze test, have shown that administration of berberine can significantly reduce immobility time in mice, increase arm opening exploration behavior, and exhibit clear antidepressant and anti anxiety like effects. Its strength of action is comparable to the classic antidepressant fluoxetine.
* Sedative effect: Lianjian can synergistically enhance the sedative and hypnotic effects of barbiturates, prolong sleep time, and exhibit central sedative activity. This is closely related to its regulation of the gamma aminobutyric acid (GABA) system.
4. Other activities: Some studies have also reported that lotus alkaloids have anti-inflammatory, antioxidant and other activities, providing potential clues for their multi-purpose development.
Mechanism of action and molecular targets
The multiple pharmacological activities of lotus alkaloids stem from their regulation of multiple nodes in the cellular signaling network. Currently, it has been preliminarily revealed that they act on the following key targets and pathways:
1. Neuro psychiatric system related targets:
* Monoamine transporters and receptors: Lianalkaloid can significantly inhibit the function of serotonin transporter (SLC6A4, also known as 5-HTT), reduce the reuptake of 5-HT in synaptic cleft, and thus increase the level of 5-HT neurotransmission, which is one of the core mechanisms of its antidepressant effect. At the same time, it is also a partial agonist of the 5-HT1A receptor (HTR1A), whose activation is directly related to antidepressant and anti anxiety effects.
* GABA_A receptor: Lotus alkaloids can bind to GABA_A receptor complexes, particularly targeting receptor subtypes containing α 1 (GABRA1), β 2 (GABRB2), and γ 2 (GABRG2) subunits. It enhances the binding of GABA to receptors through allosteric regulation, promotes chloride ion influx, and strengthens central inhibitory neurotransmission, which reasonably explains its sedative, anti anxiety, and anticonvulsant potential.
* Neurotrophic factor system: Lianjian can upregulate the protein expression of BDNF in brain regions such as hippocampus. BDNF is a key regulatory factor for neuronal survival, growth, and plasticity, and its increased expression is closely related to synaptic function improvement and antidepressant efficacy.
* Glutamate energy system: Research suggests that berberine may regulate the function of NMDA receptors, maintain the homeostasis of the glutamatergic system, and prevent excitotoxicity, which may play an important role in its neuroprotective effects.
2. Mechanisms related to anti-tumor and reversal of drug resistance:
* Inducing cell apoptosis: Lianalkaloid can activate the Caspase cascade reaction and induce tumor cell apoptosis through the mitochondrial pathway (reducing mitochondrial membrane potential, releasing cytochrome c) and death receptor pathway.
* Regulating the cell cycle: It can arrest the cell cycle in G0/G1 or G2/M phase and inhibit cell proliferation.
* Reversing multidrug resistance: As mentioned earlier, its reversal of MDR is mainly related to directly inhibiting the efflux pump function of P-gp or downregulating its expression, and specific signaling pathways may involve NF - κ B, MAPK, etc.
3. Antibacterial mechanism:
Preliminary research suggests its regulation of intracellular cAMP levels in bacteria. cAMP is an important second messenger in bacteria that affects the expression of virulence genes and adaptability, but the specific target proteins are yet to be elucidated.
Evaluation of drug properties and pharmacokinetics
Preliminary drug like analysis and pharmacokinetic (PK) evaluation of berberine can help determine its potential for development as a drug.
Analysis of pharmacological parameters: According to its physical and chemical properties, berberine conforms to Lipinski's "Five Rules" (Ro5), with a molecular weight of<500, LogP<5, and the number of hydrogen bond donors (structural implications) and acceptors not exceeding the standard, indicating that it has good oral absorption potential. Its high lipid solubility (LogP 3.16) and low TPSA enable it to efficiently penetrate the blood-brain barrier (BBB permeability predicted as "high"), which is crucial for its central nervous system activity. In terms of safety warning, the key cardiac toxicity target hERG channel inhibition experiment showed a negative result ("no"), reducing the risk of QT interval prolongation and apical torsion type ventricular tachycardia. The preliminary screening result of genetic toxicity (Ames test) is 1.2 (usually considered negative if the number of revertant mutant colonies is less than twice that of the control), indicating no obvious mutagenicity, but more complete genetic toxicity testing is needed to confirm.
Current status of pharmacokinetic research: At present, there are relatively limited reports on pharmacokinetic studies of the lotus alkaloid system. Based on its physicochemical properties, it can be inferred that it is well absorbed in the small intestine after oral administration, but its bioavailability may be affected to some extent due to the first pass effect. It is expected to have a wide distribution in the body and can quickly enter the central nervous system. In terms of metabolism, as an isoquinoline alkaloid, the liver cytochrome P450 enzyme system (especially CYP3A4, CYP2D6) may be involved in its oxidative metabolism, and methoxy groups may undergo demethylation reactions. The main pathways of excretion may be through bile and urine. However, these speculations require specific in vitro and in vivo ADME (absorption, distribution, metabolism, excretion) experimental data to support, including key parameters such as absolute bioavailability, plasma protein binding rate, identification of major metabolites, major excretion pathways, and half-life, which are research gaps that must be filled before preclinical development.
Clinical application prospects and prospects
The rich pharmacological activity and unique multi-target mechanism of action of lotus alkaloids have drawn attractive prospects for their application in multiple disease fields, but also face challenges.
Potential application directions:
1. Antitumor adjuvant therapy: Its ability to reverse multidrug resistance makes it a potential sensitizer for tumor chemotherapy, which can be used in combination with existing chemotherapy drugs to overcome resistance issues and improve efficacy, especially for advanced cancer patients who have developed tolerance to conventional chemotherapy.
2. Treatment of central nervous system diseases: It has multiple effects of increasing 5-HT levels, enhancing GABA function, and upregulating BDNF expression, providing candidate molecules for the development of novel multimodal antidepressant and anti anxiety drugs. Compared with existing selective 5-HT reuptake inhibitors (SSRIs), they may have a faster onset of action, broader therapeutic efficacy, or be effective for refractory patients. Its sedative properties can also be used for anxiety related insomnia disorders.
3. Antibiotic resistant bacterial infections: In response to the increasingly serious problem of bacterial resistance, berberine exerts antibacterial effects through a novel mechanism of non direct sterilization, such as interfering with cAMP signaling, which may not easily lead to cross resistance and is expected to serve as a lead compound for novel antibacterial agents.
Challenges and future research directions:
1. In depth mechanism clarification: Many targets of action (especially in antibacterial aspects) and upstream and downstream signaling pathways are still unclear. Molecular docking, surface plasmon resonance, gene knockout/knockdown and other technologies are needed for target validation and mechanism deepening research.
2. System pharmacokinetics and safety evaluation: Comprehensive preclinical pharmacokinetic studies must be conducted to clarify its in vivo processes. At the same time, standardized safety pharmacology evaluations such as acute toxicity, long-term toxicity, and reproductive toxicity need to be conducted to ensure their safety.
3. Structural optimization and formulation development: To address its poor water solubility, structural modification (such as preparing water-soluble prodrug salts) or the development of novel drug delivery systems (such as nanoparticles, liposomes, cyclodextrin inclusion complexes) can be used to improve its solubility and bioavailability. Based on structure-activity relationship research, optimize its activity, selectivity, and pharmacokinetic properties.
4. Clinical translational studies: After completing sufficient preclinical research, gradually advancing clinical trials to verify its effectiveness, safety, and pharmacokinetic characteristics in humans is an essential step towards achieving its clinical application.
Conclusion
Lianjian, as a natural aporphine alkaloid derived from traditional medicinal plants, has shown significant potential in various fields such as anti-tumor, antidepressant, sedative, and antibacterial applications due to its unique chemical structure and multi-target pharmacological effects. Substantial progress has been made in the study of the mechanisms of action of SLC6A4 inhibition, HTR1A activation, and allosteric modulation of GABA_A receptors to improve neuropsychiatric function, as well as P-gp inhibition to reverse tumor multidrug resistance. Preliminary pharmacological analysis also shows that it has a good foundation for development as a central nervous system drug and chemotherapy sensitizer. However, successfully transforming it from a potential natural active molecule into a clinical drug is still a long way to go. Future research needs to focus on in-depth analysis of its molecular mechanisms of action, systematic and standardized preclinical pharmacokinetic and toxicological evaluations, and rational drug design based on structure-activity relationships. With the continuous deepening of these studies, berberine is expected to provide new strategies and weapons for the treatment of major public health issues such as cancer and neurological and psychiatric disorders, continuing the glory of natural products in the history of drug discovery.
