Inhibition of Herpes Simplex Virus-1 Replication by Natural Compound Honokiol

Novel Pesticide Candidates Inspired by Natural Neolignan: Preparation and Insecticidal Investigation of Honokiol Analogs Containing 2-Aminobenzoxazole-Fused Core Scaffold

As a continuation of our efforts to develop new agrochemicals with typical architecture and efficient bioactivity from plant natural products, natural neolignan honokiol was used as a lead compound to prepare novel analogs bearing the core 2-aminobenzoxazole scaffold. Their insecticidal potency against two representative agricultural pests, Plutella xylostella Linnaeus and Mythimna separata (Walker), were evaluated in vivo. The pesticide bioassay results revealed that compounds 7″a, 9, 10d, and 10j exhibited prominent larvicidal activity against the larvae of P. xylostella (LC50 = 7.95, 11.85, 15.51, and 12.06 μg/mL, respectively), superior to the precursor honokiol (LC50 = 43.35 μg/mL) and two botanical insecticides, toosendanin (LC50 = 26.20 μg/mL) and rotenone (LC50 = 23.65 μg/mL). Compounds 7d, 10d, and 10j displayed a more pronounced nonchoice antifeedant effect (AFC50 = 9.48, 9.14, and 12.41 μg/mL, respectively) than honokiol (AFC50 = 54.81 μg/mL) on P. xylostella. Moreover, compounds 7b, 7″a, 9, 10d, 10f, and 10j showed better growth inhibitory activity against M. separata (LC50 = 0.36, 0.34, 0.28, 0.16, 0.26, and 0.11 mg/mL, respectively) than honokiol, toosendanin, and rotenone (LC50 = 1.48, 0.53, and 0.46 mg/mL, respectively). A potted plant assay under greenhouse conditions illustrated that compounds 10d and 10j continued to provide good control efficacy against P. xylostella and an apparent protective effect on plants. Further cytotoxicity assay revealed that the aforementioned potent compounds showed relatively moderate toxicity and a good safety profile for non-target mammalian cells. Overall, the current work provides valuable insight into the agrochemical innovation of honokiol-derived analogs for use as natural-inspired pesticides in agricultural pest management.

Harmol used for the treatment of herpes simplex virus induced keratitis

Herpes simplex virus type 1 (HSV-1) infection of the eyes results in herpes simplex keratitis (HSK), which has led to vision loss and even blindness in patients. However, the rate of drug resistance in HSV is on the rise; therefore, new antiviral agents with sufficient safety profiles must be developed. At present, we assessed the anti-HSV-1 activity of 502 natural compounds and their ability to reduce the HSV-1-induced cytopathic effect. We chose harmol for further studies because it exhibited the highest antiviral activity. We found that harmol inhibited both HSV-1 F and HSV-1/153 (a clinical drug-resistant strain) replication, with an EC50 of 9.34 µM and 5.84 µM, respectively. Moreover, harmol reduced HSV-1 replication in corneal tissues and viral progeny production in tears, and also alleviated early corneal surface lesions related to HSK. For example, harmol treatment preserved corneal thickness and nerve density in HSK mice. Interestingly, harmol also showed a promising antiviral effect on HSV-1/153 induced HSK in mouse model. Furthermore, harmol combined with acyclovir (ACV) treatment showed a greater antiviral effect than either one alone in vitro. Therefore, harmol may be a promising therapeutic agent for managing HSK.

Natural product honokiol exhibits antiviral effects against Micropterus salmoides rhabdovirus (MSRV) both in vitro and in vivo

Micropterus salmoides rhabdovirus (MSRV) is a formidable pathogen, presenting a grave menace to juvenile largemouth bass. This viral infection frequently leads to epidemic outbreaks, resulting in substantial economic losses within the aquaculture industry. Unfortunately, at present, there are no commercially available vaccines or pharmaceutical treatments to combat this threat. In order to address the urgent need for therapeutic strategy to resist MSRV infection, the antiviral activity of natural product honokiol against MSRV was explored in this study. Firstly, cellular morphology was directly observed in an inverted microscope when treated with honokiol after MSRV infection. The results clarified that honokiol significantly lessened cytopathic effect (CPE) induced by MSRV and protected the integrity of GCO cells. Furthermore, the viral nucleic acid expression (G gene) was detected by reverse transcription real-time quantitative PCR (RT-qPCR) and the results indicated that honokiol significantly decreased the viral loads of MSRV in a concentration-dependent manner, and honokiol showed a high antiviral activity with IC50 of 2.92 μM. Besides, honokiol significantly decreased the viral titre and suppressed apoptosis caused by MSRV. Mechanistically, honokiol primarily inhibited the initial replication of MSRV and discharge of progeny virus to exert anti-MSRV activity. More importantly, in vivo experiments suggested that honokiol (40 mg/kg) expressed a fine antiviral activity against MSRV when administrated with intraperitoneal injection, which led to a notable 40% improvement in the survival rate among infected largemouth bass. In addition, it also resulted in significant reduction in the viral nucleic acid expression within liver, spleen and kidney at 2, 4 and 6 days following infection. What is more, 100 mg/kg honokiol with oral administration also showed certain antiviral efficacy in MSRV-infected largemouth bass via improving the survival rate by 10.0%, and decreasing significantly the viral nucleic acid expression in liver, spleen and kidney of largemouth bass on day 2. In summary, natural product honokiol is a good candidate to resist MSRV infection and has promising application prospects in aquaculture.

Identification of Na+/K+-ATPase Inhibitor Bufalin as a Novel Pseudorabies Virus Infection Inhibitor In Vitro and In Vivo

Pseudorabies virus (PRV), an alpha herpesvirus, induces significant economic losses to the swine industry and infects multiple kinds of animals. Therefore, it is of great importance to explore anti-PRV compounds. In this study, to explore the anti-PRV compounds, a library of natural compounds was screened through a cell-based ELISA assay, and it was discovered that bufalin, a Na+/K+-ATPase inhibitor, had a robust inhibitory effect on PRV replication. A time-of-addition experiment and temperature-shift assay showed that bufalin significantly inhibited the entry stage of PRV. NaCl- or KCl-treatment showed that NaCl could enhance the inhibitory effect of bufalin on PRV replication, whereas there was no significant effect under the treatment of KCl. Meanwhile, it was also found that bufalin possessed antiviral activity against other alpha herpesviruses, including human herpes simplex virus type 1 (HSV-1) and chicken Marek's disease virus (MDV). Finally, it was found that bufalin could decrease the viral load in multiple tissues, and reduce the morbidity and mortality in PRV-challenged BALB/c mice. Overall, our findings demonstrated that bufalin has the potential to be developed as an anti-PRV compound.

Honokiol Inhibits SARS-CoV-2 Replication in Cell Culture at a Post-Entry Step

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) emerged in 2019, and the resulting pandemic has already caused the death of over 6 million people. There are currently few antivirals approved for treatment of the 2019 coronavirus disease (COVID-19), and more options would be beneficial, not only now but also to increase our preparedness for future coronavirus outbreaks. Honokiol is a small molecule from magnolia trees for which several biological effects have been reported, including anticancer and anti-inflammatory activities. Honokiol has also been shown to inhibit several viruses in cell culture. In this study, we determined that honokiol protected Vero E6 cells from SARS-CoV-2-mediated cytopathic effect, with a 50% effective concentration of 7.8 μM. In viral load reduction assays, honokiol decreased viral RNA copies as well as viral infectious progeny titers. The compound also inhibited SARS-CoV-2 replication in the more relevant human A549 cells expressing angiotensin converting enzyme 2 and transmembrane protease serine 2. Time-of-addition and other assays showed that honokiol inhibited virus replication at a post-entry step of the replication cycle. Honokiol was also effective against more recent variants of SARS-CoV-2, including Omicron, and it inhibited other human coronaviruses as well. Our study suggests that honokiol is an interesting molecule to be evaluated further in animal studies and, when successful, maybe even in clinical trials to investigate its effect on virus replication and pathogenic (inflammatory) host responses. IMPORTANCE Honokiol is a compound that shows both anti-inflammatory and antiviral effects, and therefore its effect on SARS-CoV-2 infection was assessed. This small molecule inhibited SARS-CoV-2 replication in various cell-based infection systems, with up to an ~1,000-fold reduction in virus titer. In contrast to earlier reports, our study clearly showed that honokiol acts on a postentry step of the replication cycle. Honokiol also inhibited different recent SARS-CoV-2 variants and other human coronaviruses (Middle East respiratory syndrome CoV and SARS-CoV), demonstrating its broad spectrum of antiviral activity. The anticoronavirus effect, combined with its anti-inflammatory properties, make honokiol an interesting compound to be further explored in animal coronavirus infection models.

Insights into Antiviral Properties and Molecular Mechanisms of Non-Flavonoid Polyphenols against Human Herpesviruses

Herpesviruses are one of the most contagious DNA viruses that threaten human health, causing severe diseases, including, but not limited to, certain types of cancer and neurological complications. The overuse and misuse of anti-herpesvirus drugs are key factors leading to drug resistance. Therefore, targeting human herpesviruses with natural products is an attractive form of therapy, as it might improve treatment efficacy in therapy-resistant herpesviruses. Plant polyphenols are major players in the health arena as they possess diverse bioactivities. Hence, in this article, we comprehensively summarize the recent advances that have been attained in employing plant non-flavonoid polyphenols, such as phenolic acids, tannins and their derivatives, stilbenes and their derivatives, lignans, neolignans, xanthones, anthraquinones and their derivatives, curcuminoids, coumarins, furanocoumarins, and other polyphenols (phloroglucinol) as promising anti-herpesvirus drugs against various types of herpesvirus such as alpha-herpesviruses (herpes simplex virus type 1 and 2 and varicella-zoster virus), beta-herpesviruses (human cytomegalovirus), and gamma-herpesviruses (Epstein-Barr virus and Kaposi sarcoma-associated herpesvirus). The molecular mechanisms of non-flavonoid polyphenols against the reviewed herpesviruses are also documented.

Honokiol and Alpha-Mangostin Inhibit Mayaro Virus Replication through Different Mechanisms

Mayaro virus (MAYV) is an emerging arbovirus with an increasing circulation across the Americas. In the present study, we evaluated the potential antiviral activity of the following natural compounds against MAYV and other arboviruses: Sanguinarine, (R)-Shikonin, Fisetin, Honokiol, Tanshinone IIA, and α-Mangostin. Sanguinarine and Shikonin showed significant cytotoxicity, whereas Fisetin, Honokiol, Tanshinone IIA, and α-Mangostin were well tolerated in all the cell lines tested. Honokiol and α-Mangostin treatment protected Vero-E6 cells against MAYV-induced damage and resulted in a dose-dependent reduction in viral progeny yields for each of the MAYV strains and human cell lines assessed. These compounds also reduced MAYV viral RNA replication in HeLa cells. In addition, Honokiol and α-Mangostin disrupted MAYV infection at different stages of the virus life cycle. Moreover, Honokiol and α-Mangostin decreased Una, Chikungunya, and Zika viral titers and downmodulated the expression of E1 and nsP1 viral proteins from MAYV, Una, and Chikungunya. Finally, in Honokiol- and α-Mangostin-treated HeLa cells, we observed an upregulation in the expression of type I interferon and specific interferon-stimulated genes, including IFNα, IFNβ, MxA, ISG15, OAS2, MDA-5, TNFα, and IL-1β, which may promote an antiviral cellular state. Our results indicate that Honokiol and α-Mangostin present potential broad-spectrum activity against different arboviruses through different mechanisms.

Discovery of honokiol thioethers containing 1,3,4-oxadiazole moieties as potential α-glucosidase and SARS-CoV-2 entry inhibitors

Honokiol, isolated from a traditional Chinese medicine (TCM) Magnolia officinalis, is a biphenolic compound with several biological activities. To improve and broaden its biological activity, herein, two series of honokiol thioethers bearing 1,3,4-oxadiazole moieties were prepared and assessed for their α-glucosidase and SARS-CoV-2 entry inhibitory activities. Among all the honokiol thioethers, compound 7l exhibited the strongest α-glucosidase inhibitory effect with an IC₅₀ value of 18.9 ± 2.3 µM, which was superior to the reference drug acarbose (IC₅₀ = 24.4 ± 0.3 µM). Some interesting results of structure–activity relationships (SARs) have also been discussed. Enzyme kinetic study demonstrated that 7l was a noncompetitive α-glucosidase inhibitor, which was further supported by the results of molecular docking. Moreover, honokiol thioethers 7e, 9a, 9e, and 9r exhibited potent antiviral activity against SARS-CoV-2 pseudovirus entering into HEK-293 T-ACE2^h. Especially 9a displayed the strongest inhibitory activity against SARS-CoV-2 pseudovirus entry with an IC₅₀ value of 16.96 ± 2.45 μM, which was lower than the positive control Evans blue (21.98 ± 1.98 μM). Biolayer interferometry (BLI) binding and docking studies suggested that 9a and 9r may effectively block the binding of SARS-CoV-2 to the host ACE2 receptor through dual recognition of SARS-CoV-2 spike RBD and human ACE2. Additionally, the potent honokiol thioethers 7l, 9a, and 9r displayed relatively no cytotoxicity to normal cells (LO2). These findings will provide a theoretical basis for the discovery of honokiol derivatives as potential both α-glucosidase and SARS-CoV-2 entry inhibitors.

The application prospects of honokiol in dermatology

Honokiol is one of the natural extracts of Magnolia officinalis. It is a small molecule, lipophilic compound with extensive biological effects. It has been used in the treatment of multisystem diseases, including digestive diseases, endocrine diseases, nervous system diseases, and various tumors. This paper reviews the biological effects of honokiol on the treatment of skin diseases in recent years, including anti-microbial, anti-oxidant, anti-inflammatory, anti-tumor, anti-fibrosis, anti-allergy, photo-protection, and immunomodulation. Most current researches are focused on the effects of anti-melanoma and photo-protection. Therefore, we summarized the specific mechanisms about these two effects. On the other side of treating skin diseases, the advantages of topical drugs cannot be replaced. As a small molecule fat-soluble compound, honokiol is suitable for external use. We reviewed the advantages and disadvantages of the topical mixed cream and various improved methods. These improvements include physical and chemical penetration enhancers, drug carriers, and chemical derivatives. In conclusion, honokiol has a wide range of effects, and its topical preparation provides a safe and effective way for treating skin diseases.

Inhibitory activity and mechanism of silver nanoparticles against herpes simplex virus type 1

Herpes simplex virus type 1 (HSV-1) is a common pathogen that infects 50-90% of the world's population and causes a variety of diseases, some of which can be life-threatening. Silver nanoparticles (AgNPs) have been shown to have broad-spectrum antiviral activity. In this study, we investigated the activity of AgNPs against HSV-1 and found that AgNPs effectively inhibited plaque formation and HSV-1 progeny production, reduced the genomic load, and interfered with HSV-1 mRNA expression and protein synthesis. Transmission electron microscopy showed that AgNPs interacted with HSV-1 and altered the shape of the viral particles. Furthermore, AgNPs affected the entry of HSV-1 into cells as well as their release and cell-to-cell spread. AgNPs were also found to downregulate the expression of pro-inflammatory cytokines upon HSV-1 infection. Combined treatment with AgNPs and acyclovir (ACV) confirmed that AgNPs significantly enhanced the inhibitory effect of ACV against HSV-1. Our findings may contribute to an understanding of the mechanism of the antiviral effect of AgNPs against HSV-1 and help to provide a theoretical basis for their clinical application.

Phospholipase A2 inhibitor and LY6/PLAUR domain-containing protein PINLYP regulates type I interferon innate immunity

Type I interferons (IFNs) are the first frontline of the host innate immune response against invading pathogens. Herein, we characterized an unknown protein encoded by phospholipase A2 inhibitor and LY6/PLAUR domain-containing (PINLYP) gene that interacted with TBK1 and induced type I IFN in a TBK1- and IRF3-dependent manner. Loss of PINLYP impaired the activation of IRF3 and production of IFN-β induced by DNA virus, RNA virus, and various Toll-like receptor ligands in multiple cell types. Because PINLYP deficiency in mice engendered an early embryonic lethality in mice, we generated a conditional mouse in which PINLYP was depleted in dendritic cells. Mice lacking PINLYP in dendritic cells were defective in type I IFN induction and more susceptible to lethal virus infection. Thus, PINLYP is a positive regulator of type I IFN innate immunity and important for effective host defense against viral infection.

The rich pharmacological activities of Magnolia officinalis and secondary effects based on significant intestinal contributions

ETHNOPHARMACOLOGICAL RELEVANCE

Magnolia officinalis Cortex (M. officinalis) is a traditional herbal drug widely used in Asian countries. Depending on its multiple biological activities, M. officinalis is used to regulate gastrointestinal (GI) motility, relieve cough and asthma, prevent cardiovascular and cerebrovascular diseases, and treat depression and anxiety.

AIM OF THE REVIEW

We aimed to review the abundant form of pharmacodynamics activity and potential mechanisms of action of M. officinalis and the characteristics of the internal processes of the main components. The potential mechanisms of local and distance actions of M. officinalis based on GI tract was provided, and it was used to reveal the interconnections between traditional use, phytochemistry, and pharmacology.

MATERIALS AND METHODS

Published literatures about M. officinalis and its main components were collected from several scientific databases, including PubMed, Elsevier, ScienceDirect, Google Scholar and Web of Science etc. RESULTS: M. officinalis was shown multiple effects including effects on digestive system, respiratory system, central system, which is consistent with traditional applications, as well as some other activities such as cardiovascular system, anticancer, anti-inflammatory and antioxidant effects and so on. The mechanisms of these activities are abundant. Its chief ingredients such as magnolol and honokiol can be metabolized into active metabolites in vivo, which can increase water solubility and bioavailability and exert pharmacological activity in the whole body. In the GI tract, M. officinalis and its main ingredient can regulate GI hormones and substance metabolism, protect the intestinal barrier and affect the gut microbiota (GM). These actions are effective to improve local discomfort and some distal symptoms such as depression, asthma, or metabolic disorders.

CONCLUSIONS

Although M. officinalis has rich pharmacological effects, the GI tract makes great contributions to it. The GI tract is not only an important place for absorption and metabolism but also a key site to help M. officinalis exert local and distal efficacy. Pharmacodynamical studies on the efficacies of distal tissues based on the contributions of the GI tract hold great potential for understanding the benefits of M. officinalis and providing new ideas for the treatment of important diseases.

Inhibitory effect of honokiol on furin-like activity and SARS-CoV-2 infection

The coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged as a pandemic and has caused damage to the lives of the people and economy of countries. However, the therapeutic reagents against SARS-CoV-2 remain unclear. The spike (S) protein of SARS-CoV-2 contains a cleavage motif at the S1/S2 boundary, known to be cleaved by furin. As cleavage is essential for S protein activation and viral entry, furin was selected as the target compound. In this study, we examined the inhibitory effects of two lignans (honokiol and magnolol) on furin-like enzymatic activity using a fluorogenic substrate with whole-cell lysates. Of two compounds tested, honokiol partially inhibited furin-like enzymatic activity. We further examined the anti-SARS-CoV-2 activity of honokiol using VeroE6 cell line, which is stably expressing a transmembrane protease serine 2 (TMPRSS2). It was shown that honokiol exhibited remarkable inhibition of SARS-CoV-2 infection. Therefore, honokiol and crude drugs which contain honokiol such as Magnolia species have a potential therapeutic reagents for SARS-CoV-2.

2-O-Methylhonokiol Suppresses HCV Replication via TRAF6-Mediated NF-kB Activation

Hepatitis C virus (HCV) is associated with various liver diseases. Chronic HCV infection is characterized by an abnormal host immune response. Therefore, it is speculated that to suppress HCV, a well-regulated host immune response is necessary. 2-O-methylhonokiol was identified by the screening of anti-HCV compounds using Renilla luciferase assay in Huh 7.5/Con 1 genotype 1b replicon cells. Here, we investigated the mechanism by which 2-O-methylhonokiol treatment inhibits HCV replication using real-time PCR. Our data shows that treatment with 2-O-methylhonokiol activated innate immune responses via nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB) pathway. Additionally, the immunoprecipitation result shows that treatment with 2-O-methylhonokiol augmented tumor necrosis factor receptor (TNFR)-associated factor 6 (TRAF6) by preventing p62 from binding to TRAF6, resulting in reduced autophagy caused by HCV. Finally, we reproduced our data with the conditioned media from 2-O-methylhonokiol-treated cells. These findings strongly suggest that 2-O-methylhonokiol enhances the host immune response and suppresses HCV replication via TRAF6-mediated NF-kB activation.

Akt Kinase Intervenes in Flavivirus Replication by Interacting with Viral Protein NS5

Arthropod-borne flaviviruses, such as Zika virus (ZIKV), Usutu virus (USUV), and West Nile virus (WNV), are a growing cause of human illness and death around the world. Presently, no licensed antivirals to control them are available and, therefore, search for broad-spectrum antivirals, including host-directed compounds, is essential. The PI3K/Akt pathway controls essential cellular functions involved in cell metabolism and proliferation. Moreover, Akt has been found to participate in modulating replication in different viruses including the flaviviruses. In this work we studied the interaction of flavivirus NS5 polymerases with the cellular kinase Akt. In vitro NS5 phosphorylation experiments with Akt showed that flavivirus NS5 polymerases are phosphorylated and co-immunoprecipitate by Akt. Polymerase activity assays of Ala- and Glu-generated mutants for the Akt-phosphorylated residues also indicate that Glu mutants of ZIKV and USUV NS5s present a reduced primer-extension activity that was not observed in WNV mutants. Furthermore, treatment with Akt inhibitors (MK-2206, honokiol and ipatasertib) reduced USUV and ZIKV titers in cell culture but, except for honokiol, not WNV. All these findings suggest an important role for Akt in flavivirus replication although with specific differences among viruses and encourage further investigations to examine the PI3K/Akt/mTOR pathway as an antiviral potential target.

Antiviral Role of Phenolic Compounds against Dengue Virus: A Review

Phenolic compounds have been related to multiple biological activities, and the antiviral effect of these compounds has been demonstrated in several viral models of public health concern. In this review, we show the antiviral role of phenolic compounds against dengue virus (DENV), the most widespread arbovirus globally that, after its re-emergence, has caused multiple epidemic outbreaks, especially in the last two years. Twenty phenolic compounds with anti-DENV activity are discussed, including the multiple mechanisms of action, such as those directed against viral particles or viral proteins, host proteins or pathways related to the productive replication viral cycle and the spread of the infection.