Storage conditions：Short-term storage at 2~8℃, long-term storage at -20 ~ -80℃

Introduction/Overview

Guanosine, CAS number 118-00-3, is an important natural nucleoside compound, formed by the connection between guanine and ribose in a purine base via β-N9-glycoside bonds. As one of the basic building blocks of nucleic acids, guanine nucleoside plays a key role in nucleic acid metabolism, energy conversion, and signal transduction within cells. In recent years, with the deepening development of natural product pharmacology, guanine nucleoside has become an important candidate for antiviral drug development due to its remarkable antiviral activity, especially its inhibitory effect on herpes simplex virus (HSV). In addition, guanine's potential role in regulating immune responses, neuroprotection, and cellular metabolism has also attracted widespread attention.

This paper aims to systematically review the chemical structure and physicochemical properties of guanoside, plant origin and extraction methods, pharmacological activity and mechanism of action, druggability evaluation, and pharmacokinetic characteristics, and to explore its clinical application prospects and future research directions, providing comprehensive and in-depth reference materials for researchers in the field of natural product pharmacology.

Chemical structure and physicochemical properties

The chemical structure of guanine nucleoside consists of purine base guanine and ribose, which are connected by β-N9 glycan bonds to form a typical nucleoside structure. Its molecular formula is C10H13N5O5, and its molecular weight is 283.2440. The guanine part of the structure contains multiple nitrogen atoms, giving it strong polarity and hydrogen bond donor/acceptor capabilities; The hydroxyl group of the ribose ring enhances its water solubility.

In terms of physicochemical properties, the LogP value of guanine nucleoside was -1.8247, indicating strong hydrophilicity and easy solubility in water (solubility about 4.1618 mg/mL). Its polar surface area (TPSA) is 159.5100 Ų, indicating high molecular polarity that may limit its passive diffusion ability through lipid membranes. The blood-brain barrier has low permeability, indicating limited distribution in the central nervous system. The hERG channel inhibition test was negative, indicating a low risk of cardiotoxicity. The Ames-induced mutagenic test result was 1.2, indicating a low genotoxicity risk and a solid safety foundation.

Plant Origins and Extraction Methods

Guan is widely present in various organisms, especially in higher plants, microorganisms, and animal tissues. In plants, it mainly exists as an intermediate in nucleic acid metabolism, with relatively low levels. Common plant sources include the nuclei and cytoplasm of certain medicinal plants, such as ginkgo leaves, goji berries, and astragalus, but purity and content are greatly affected by plant species, growing environment, and harvest time.

In terms of extraction methods, traditional guanyin extraction mostly uses water extraction or buffer extraction combined with organic solvent separation. The specific steps include:

1. Sample pretreatment: Drying and crushing plant tissue to increase surface area.
2. Water extraction: Extraction using hot water or buffer solution to promote nucleoside dissolution.
3. Organic solvent extraction: Ethanol, methanol, and other substances are used to remove fat-soluble impurities.
4. Column chromatography separation: purifies guanine nucleoside using ion exchange, reversed-phase high-performance liquid chromatography (RP-HPLC), and other techniques.
5. Crystallization: High-purity crystalline products are obtained through cooling or solvent evaporation.

In recent years, the application of modern technologies such as ultrasound-assisted extraction, microwave-assisted extraction, and enzymatic hydrolysis-assisted extraction has improved extraction efficiency and purity, providing technical support for industrial production.

Pharmacological activity research

Antiviral activity

Guanyin is best known for its pharmacological activity, especially its antiviral effect, particularly its inhibitory effect on herpes simplex virus (HSV). Multiple in vitro experiments have shown that guanyin can effectively reduce the replication of HSV-1 and HSV-2, inhibit viral DNA synthesis, and slow down the process of viral infection. Its antiviral activity is not limited to HSV, but also involves various viruses such as human immunodeficiency virus (HIV) and cytomegalovirus (CMV).

Immunomodulatory effects

Guanyin exerts certain immunomodulatory effects by regulating immune cell function. Research shows that guanine nucleoside can influence macrophage peroxidase (MPO) activity, regulate inflammatory responses, and reduce oxidative stress levels. Additionally, its regulation of chemokine receptors CCR5 and CXCR4 helps inhibit HIV virus cell invasion.

Neuroprotective effects

In recent years, research on guanine nucleoside in the field of neuroprotection has gradually increased. By regulating neuronal energy metabolism, antioxidant stress, and promoting nerve regeneration, it demonstrates potential neuroprotective functions. In animal models, guanyin has a certain alleviating effect on cerebral ischemia and neurodegenerative diseases.

Other pharmacological effects

Guanyin is also involved in various biological processes such as cell proliferation, apoptosis regulation, and metabolic regulation, demonstrating broad biological activity. Its potential in tumors, metabolic diseases, and other fields is worth further exploration in the future.

Mechanism of action and molecular targets

The antiviral mechanism of guanine mainly operates by interfering with key enzymes and proteins in the viral replication cycle. Specific targets include:

• UL42 and UL54: cofactors and catalytic subunits of HSV DNA polymerase. Guanine nucleoside inhibits viral DNA synthesis through competitive binding or structural mimicry.
• ICP27: HSV transcription regulatory protein that affects viral gene expression. Guannine nucleoside may block viral transcription by modulating ICP27 activity.
• TK (thymidine kinase): a virus-specific enzyme, guanyin nucleoside acts as a nucleoside analog that interferes with phosphorylation and activation, blocking viral DNA synthesis.
• gD (glycoprotein D): a key protein for viral invasion of host cells; guanine nucleoside regulates its binding or expression, hindering viral entry.
• CCR5 and CXCR4: The main cellular receptors of the HIV virus, guanine nucleoside, inhibits viral infection by regulating its expression or function.
• HIV1-PR (HIV protease) and INT (integrase): Guannine may bind to these enzymes through molecular mimicry, inhibiting viral protein processing and genomic integration.

Additionally, guanyin enhances antiviral defenses by regulating the host's immune system. It inhibits macrophage MPO activity, reduces the release of inflammatory mediators, and decreases tissue damage.

Druggability evaluation and pharmacokinetics

The druggability evaluation of guanine nucleoside shows it has certain advantages and challenges:

• Molecular weight and polarity: A molecular weight of 283.2440 and high polarity (TPSA 159.51 Ų) give it good water solubility, but limit oral absorption and membrane penetration.
• LogP value of -1.8247 indicates strong hydrophilicity, making it difficult to pass through the lipid bilayer membrane and affecting bioavailability.
• Low blood-brain barrier permeability: limiting its application in central nervous system diseases but reducing the risk of central nervous system side effects.
• Safety: hERG channel inhibition is negative and Ames test has low mutagenicity, indicating a solid safety foundation.
• Pharmacokinetic characteristics: Guan nucleoside is absorbed orally with limited absorption. Its metabolism in the body is mainly through ribosididase hydrolysis and hepatic metabolism, with a short half-life. Optimization of administration is needed to improve efficacy.

Based on these characteristics, developing guanine nucleoside derivatives or using nanocarrier systems to improve their pharmacokinetic performance is a key direction to enhance their clinical application value.

Prospects and outlooks for clinical applications

Although guanine nucleoside has demonstrated good antiviral and immunomodulatory activity in basic research, its clinical application is still in its early stages. Future development directions include:

1. Antiviral drug development: Based on structural optimization of guanine, design highly effective, low-toxicity nucleoside analogs to develop novel antiviral drugs targeting HSV, HIV, and other viral infections.
2. Combination therapy strategy: Combined with existing antiviral drugs to achieve synergistic effects, reduce resistance risk, and improve treatment outcomes.
3. Neuroprotection and immune regulation: Explore its potential applications in neurodegenerative diseases, multiple sclerosis, and autoimmune diseases, expanding its indications.
4. Innovation in drug delivery systems: Enhancing bioavailability and tissue specificity through nanotechnology, liposomes, and targeted delivery systems, overcoming druggability limitations.
5. Clinical trial design: Strengthen preclinical safety and efficacy evaluations, promote clinical trials, and verify their therapeutic potential and safety.

With advances in molecular biology and medicinal chemistry, guanine nucleoside and its derivatives are expected to become important components of future antiviral and multifunctional therapeutic drugs.

Conclusion

As a natural nucleoside compound, guanine nucleoside demonstrates broad pharmacological potential due to its unique chemical structure and diverse biological activities. Its research achievements in antiviral, immunomodulatory, and neuroprotective fields provide a valuable theoretical and practical foundation for natural product pharmacology. Despite challenges in druggability and pharmacokinetics, the application of structural modification and advanced drug delivery technologies is expected to overcome existing limitations and achieve clinical translation. In the future, in-depth mechanistic research and application development around guanine will promote its important position in new drug development and contribute new therapeutic strategies to human health.