Aliphatic and alicyclic camphor imines as effective inhibitors of influenza virus H1N1

Natural Product-Derived Phytochemicals for Influenza A Virus (H1N1) Prevention and Treatment

Influenza A (H1N1) viruses are prone to antigenic mutations and are more variable than other influenza viruses. Therefore, they have caused continuous harm to human public health since the pandemic in 2009 and in recent times. Influenza A (H1N1) can be prevented and treated in various ways, such as direct inhibition of the virus and regulation of human immunity. Among antiviral drugs, the use of natural products in treating influenza has a long history, and natural medicine has been widely considered the focus of development programs for new, safe anti-influenza drugs. In this paper, we focus on influenza A (H1N1) and summarize the natural product-derived phytochemicals for influenza A virus (H1N1) prevention and treatment, including marine natural products, flavonoids, alkaloids, terpenoids and their derivatives, phenols and their derivatives, polysaccharides, and derivatives of natural products for prevention and treatment of influenza A (H1N1) virus. We further discuss the toxicity and antiviral mechanism against influenza A (H1N1) as well as the druggability of natural products. We hope that this review will facilitate the study of the role of natural products against influenza A (H1N1) activity and provide a promising alternative for further anti-influenza A drug development.

Conformational and Supramolecular Aspects in Chirality of Flexible Camphor-Containing Schiff Base as an Inducer of Helical Liquid Crystals

The experimental and theoretical study of influence of the conformational state and association on the chirality of the stereochemically nonrigid biologically active bis-camphorolidenpropylenediamine (CPDA) and its ability to induce the helical mesophase of alkoxycyanobiphenyls liquid-crystalline binary mixture was carried out. On the basis of quantum-chemical simulation of the CPDA structure, four relatively stable conformers were detected. A comparison of the calculated and experimental electronic circular dichroism (ECD) and ¹H, ¹³C, ¹⁵N NMR spectra, as well as specific optical rotation and dipole moments, allowed to establish the most probable trans-gauche conformational state (tg) of dicamphorodiimine and CPDA dimer with a predominantly mutually parallel arrangement of molecular dipoles. The induction of helical phases in LC mixtures based on cyanobiphenyls and bis-camphorolidenpropylenediamine was studied by polarization microscopy. The clearance temperatures and the helix pitch of the mesophases were measured. The helical twisting power (HTP) was calculated. The decrease in HTP with increasing dopant concentration was shown to be connected with the CPDA association process in the LC phase. The effect of camphor-containing chiral dopants of various structures on nematic LCs was compared. The values of the permittivity and birefringence components of the CPDA solutions in CB-2 were measured experimentally. A strong effect of this dopant on the anisotropic physical properties of the induced chiral nematic was established. A significant decrease in the dielectric anisotropy was associated with the 3D compensation of the LC dipoles during the formation of the helix.

Borneol Ester Derivatives as Entry Inhibitors of a Wide Spectrum of SARS-CoV-2 Viruses

In the present work we studied the antiviral activity of the home library of monoterpenoid derivatives using the pseudoviral systems of our development, which have glycoproteins of the SARS-CoV-2 virus strains Wuhan and Delta on their surface. We found that borneol derivatives with a tertiary nitrogen atom can exhibit activity at the early stages of viral replication. In order to search for potential binding sites of ligands with glycoprotein, we carried out additional biological tests to study the inhibition of the re-receptor-binding domain of protein S. For the compounds that showed activity on the pseudoviral system, a study using three strains of the infectious SARS-CoV-2 virus was carried out. As a result, two leader compounds were found that showed activity on the Wuhan, Delta, and Omicron strains. Based on the biological results, we searched for the potential binding site of the leader compounds using molecular dynamics and molecular docking methods. We suggested that the compounds can bind in conserved regions of the central helices and/or heptad repeats of glycoprotein S of SARS-CoV-2 viruses.

Optimization of application schedule of camphecene, a novel anti-influenza compound, based on its pharmacokinetic characteristics

Due to high variability and rapid life cycle, influenza virus is able to develop drug resistance against direct-acting antivirals. Development of novel virus-in113039hibiting drugs is therefore important goal. Previously, we identified camphor derivative, camphecene, as an effective anti-influenza compound. In the present study, we optimize the regimen of its application to avoid high sub-toxic concentrations. The protective activity of camphecene was assessed on the model of lethal pneumonia of mice caused by influenza viruses. Camphecene was administered either once a day or four times a day, alone or in combination with Tamiflu. Mortality and viral titer in the lungs were studied. Pharmacokinetics of camphecene was studied in rabbits. We have demonstrated that camphecene, being used every 6 h at a dose of 7.5 mg/kg/day, results in antiviral effect that was statistically equal to the effect of 100 mg/kg/day once a day, that is, the same effect was achieved by 13 times lower daily dose of the drug. This effect was manifested in decrease of mortality and decrease of virus' titer in the lungs. The studies of pharmacokinetics of camphecene have demonstrated that it does not accumulate in blood plasma and that its m ultiple applications with dosage interval of 65 min are safe. In addition, the results of the study demonstrate also that camphecene possesses additive effect with Tamiflu, allowing to decrease the dose of the latter. The results suggest that due to safety and efficacy, camphecene can be further developed as potential anti-influenza remedy.

Promoted Electron Transfer and Surface Absorption by Single Nickel Atoms for Photocatalytic Cross-Coupling of Aromatic Alcohols and Aliphatic Amines under Visible Light

The preparation of imines has drawn increasing attention as they are fundamental intermediates in the production of pharmaceuticals, agricultures, and fine chemicals. Nevertheless, current approaches for imines synthesis mainly focus on thermally driven reactions which always involve the consumption of high price noble metal catalysts, expensive ligands, strong base, and harsh reaction conditions. Herein, we demonstrate single atom nickel anchored on polymeric carbon nitride (Ni-SA@PCN) in Ni-N₄ structure for visible light-promoted crossed coupling between aromatic alcohols and aliphatic amines. As expected, the Ni atoms dispersed carbon nitride demonstrates an obviously improved charge separation and transfer as reflected in UV-vis, fluorescence intensity and lifetime, photocurrent density, and electrochemical impedance characterizations. More impressively, the density functional theory (DFT) calculations also reveals that the presence of Ni atoms can dramatically accelerate the absorption of reactive substrates on the surface of PCN. The decreased absorption energy from -0.51 to -3.35 eV, associated with increased O═O bond length from 1.226 to 1.371 Å indicates a huge advantage of single Ni atom on oxygen activation. As a result, the obtained Ni-SA@PCN photocatalyst shows a prominent catalytic efficiency in imines formation with a reaction conversion of 73% and selectivity of >99%. Lastly, the photocatalytic reactions displays an excellent compatibility with various imines being achieved with high yield.

Modelling the DFT structural and reactivity study of feverfew and evaluation of its potential antiviral activity against COVID-19 using molecular docking and MD simulations

Abstract

The unavailability of a proper drug against SARS-CoV-2 infections and the emergence of various variants created a global crisis. In the present work, we have studied the antiviral behavior of feverfew plant in treating COVID-19. We have reported a systematic in silico study with the antiviral effects of various phytoconstituents Borneol (C₁₀H₁₈O), Camphene (C₁₀H₁₆), Camphor (C₁₀H₁₆O), Alpha-thujene (C₁₀H₁₆), Eugenol (C₁₀H₁₄O), Carvacrol (C₁₀H₁₄O) and Parthenolide (C₁₅H₂₀O₃) of feverfew on the viral protein of SARS-CoV-2. Parthenolide shows the best binding affinity with both main protease (M^pro) and papain-like protease (PL^pro). The molecular electrostatic potential and Mulliken atomic charges of the Parthenolide molecule shows the high chemical reactivity of the molecule. The docking of Parthenolide with PL^pro give score of −8.0 kcal/mol that validates the good binding of Parthenolide molecule with PL^pro. This complex was further considered for molecular dynamics simulations. The binding energy of the complex seems to range in between −3.85 to −11.07 kcal/mol that is high enough to validate the stability of the complex. Free energy decomposition analysis have been also performed to understand the contribution of residues that reside into the binding site. Good binding affinity and reactivity response suggested that Parthenolide can be used as a promising drug against the COVID-19.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11696-022-02067-6.

Novel O-acylated amidoximes and substituted 1,2,4-oxadiazoles synthesised from (+)-ketopinic acid possessing potent virus-inhibiting activity against phylogenetically distinct influenza A viruses

This article describes the synthesis and antiviral activity evaluation of new substituted 1,2,4-oxadiazoles containing a bicyclic substituent at position 5 of the heterocycle and O-acylated amidoximes as precursors for their synthesis. New compounds were obtained from the (+)-camphor derivative (+)-ketopinic acid. The chemical library was tested in vitro for cytotoxicity against the MDCK cell line and for antiviral activity against influenza viruses of H1N1 and H7N9 subtypes. The synthesised compounds exhibited high virus-inhibiting activity against the H1N1 influenza virus. Some synthesised compounds were also active against the influenza virus of a different antigenic subtype: H7N9. The mechanism of the virus-inhibiting activity of these compounds is based on their interference with the fusion activity of viral hemagglutinin (HA). No interference with the receptor-binding activity of HA has been demonstrated. According to molecular docking results, the selective antiviral activity of O-acylated amidoximes and 1,2,4-oxadiazoles is associated with their structural features. O-Acylated amidoximes are likely more complementary to the binding site located at the site of the fusion peptide, and 1,2,4-oxadiazoles are more complimentary to the site located at the site of proteolysis. Significant differences in the amino acid residues of the binding sites of HA's of different types allow us to explain the selective antiviral activity of the compounds under study.

Discovery of New Ginsenol-Like Compounds with High Antiviral Activity

A number of framework amides with a ginsenol backbone have been synthesized using the Ritter reaction. We named the acetamide as Ginsamide. A method was developed for the synthesis of the corresponding amine and thioacetamide. The new compounds revealed a high activity against H1N1 influenza, which was confirmed using an animal model. Biological experiments were performed to determine the mechanism of action of the new agents, a ginsamide-resistant strain of influenza virus was obtained, and the pathogenicity of the resistant strain and the control strain was studied. It was shown that the emergence of resistance to Ginsamide was accompanied by a reduction in the pathogenicity of the influenza virus.

From longevity grass to contemporary soft gold: Explore the chemical constituents, pharmacology, and toxicology of Artemisia argyi H.Lév. & vaniot essential oil

ETHNOPHARMACOLOGICAL RELEVANCE

Artemisia argyi H.Lév. & Vaniot is known as the longevity grass in eastern countries for its warm effect to cure many cold diseases. It has been widely used in medicine, food, bathing, moxibustion, and fumigation for more than two thousand years. Nowadays it even becomes the cultural symbol of the Dragon Boat Festival. In traditional application, A. argyi is considered to be an important hemostatic drug and a common drug for gynecological diseases. In modern application, the Artemisia argyi H.Lév. & Vaniot essential oil (AAEO) is regarded as the important medicinal substance of A. argyi, and has been made into many health products, forming a large-scale A. argyi industry.

AIM OF THE REVIEW

This review aims to summarize the research status of AAEO and evaluate its application value. The manuscript focuses on the reported extraction methods, chemical components and influencing factors, pharmacological action, and toxicity.

MATERIALS AND METHODS

In the literature search, several databases, such as Google Scholar, Science Direct, PubMed, Elsevier, CNKI, and Wanfang, were searched for key words, including "Artemisia argyi H.Lév. & Vaniot essential oil," "Artemisia argyi H.Lév. & Vaniot," "cineole," "caryophyllene," "cyclamen," "borneol," and "camphor."

RESULTS

At present, more than 200 kinds of chemical components have been detected in AAEO, including terpenes, ketones (aldehydes), alcohols (phenols), acids (esters), alkanes (olefins) hydrocarbons, and so on. It has great anti-disease-resistant microorganism, anti-inflammatory, analgesic, and anti-cancer effects in clinical treatment and has good development potential and application prospects.

CONCLUSION

Present review provides an insight into chemical composition, extraction method, quality influencing factors, pharmacological action and toxicological action of AAEO. As an important traditional medicine herb, remarkable efficacy has been demonstrated in comprehensive literature reports, which has shown the great medicinal potential of this plant. However, the toxicity of AAEO cannot be ignored, the exact mechanism of action remains to be elucidated.

Stability study of the antiviral agent camphecene in dried blood spots at different temperatures

In this study, an optimized procedure of sample preparation for quantitative determination of the antiviral agent camphecene in dried rat blood spots was developed. It has been shown that when using methanol containing 0.1% HCOOH as an extractant, the recovery of the substance increases in comparison with the previously developed method. In addition to this, there is no need to dilute the obtained solutions with water for the analysis of the sample by high-performance liquid chromatography (HPLC) on a column with a reversed-phase sorbent. By using the developed method, the stability of samples of dried rat blood spots containing camphecene in different concentrations at different temperatures was studied. It was found that while the samples were stored at room temperature, apparently, desorption of the substance occurs leading to a loss of more than 15% of its initial amount after 5-10 days. Lowering the temperature increases the stability of samples and their storage at -70°C is possible for 4 weeks.

Quaternary ammonium salts based on (-)-borneol as effective inhibitors of influenza virus

A series of compounds containing a 1,7,7-trimethylbicyclo[2.2.1]heptane fragment were evaluated for their antiviral activity against influenza A virus strain A/Puerto Rico/8/34 (H1N1) in vitro. The most potent antiviral compound proved to be a quaternary ammonium salt based on (-)-borneol, 10a. In in vitro experiments, compound 10a inhibited influenza A viruses (H1, H1pdm09, and H3 subtypes), with an IC₅₀ value of 2.4-16.8 µM (depending on the virus), and demonstrated low toxicity (CC₅₀ = 1311 µM). Mechanism-of-action studies for compound 10a revealed it to be most effective when added at the early stages of the viral life cycle. In direct haemolysis inhibition tests, compound 10a was shown to decrease the membrane-disrupting activity of influenza A virus strain A/Puerto Rico/8/34. According to molecular modelling results, the lead compound 10a can bind to different sites in the stem region of the viral hemagglutinin.

New chemical agents based on adamantane-monoterpene conjugates against orthopoxvirus infections

Currently, the spectrum of agents against orthopoxviruses, in particular smallpox, is very narrow. Despite the fact that smallpox is well controlled, there is, for many reasons, a real threat of epidemics associated with this or a similar virus. In order to search for new low molecular weight orthopoxvirus inhibitors, a series of amides combining adamantane and monoterpene moieties were synthesized using 1- and 2-adamantanecarboxylic acids as well as myrtenic, citronellic and camphorsulfonic acids as acid components. The produced compounds exhibited high activity against the vaccinia virus (an enveloped virus belonging to the poxvirus family), which was combined with low cytotoxicity. Some compounds had a selectivity index higher than that of the reference drug cidofovir; the highest SI = 1123 was exhibited by 1-adamantanecarboxylic acid amide containing the (-)-10-amino-2-pinene moiety. The produced compounds demonstrated inhibitory activity against other orthopoxviruses: cowpox virus (SI = 30-406) and ectromelia virus (mousepox virus, SI = 39-707).

Monoterpenes and Their Derivatives-Recent Development in Biological and Medical Applications

Monoterpenes, comprising hydrocarbons, are the largest class of plant secondary metabolites and are commonly found in essential oils. Monoterpenes and their derivatives are key ingredients in the design and production of new biologically active compounds. This review focuses on selected aliphatic, monocyclic, and bicyclic monoterpenes like geraniol, thymol, myrtenal, pinene, camphor, borneol, and their modified structures. The compounds in question play a pivotal role in biological and medical applications. The review also discusses anti-inflammatory, antimicrobial, anticonvulsant, analgesic, antiviral, anticancer, antituberculosis, and antioxidant biological activities exhibited by monoterpenes and their derivatives. Particular attention is paid to the link between biological activity and the effect of structural modification of monoterpenes and monoterpenoids, as well as the introduction of various functionalized moieties into the molecules in question.

Monoterpenoid-based inhibitors of filoviruses targeting the glycoprotein-mediated entry process

In this study, we screened a large library of (+)-camphor and (-)-borneol derivatives to assess their filovirus entry inhibition activities using pseudotype systems. Structure-activity relationship studies revealed several compounds exhibiting submicromolar IC₅₀ values. These compounds were evaluated for their effect against natural Ebola virus (EBOV) and Marburg virus. Compound 3b (As-358) exhibited the good antiviral potency (IC₅₀ = 3.7 μM, SI = 118) against Marburg virus, while the hydrochloride salt of this compound 3b·HCl had a strong inhibitory effect against Ebola virus (IC₅₀ = 9.1 μM, SI = 31) and good in vivo safety (LD₅₀ > 1000 mg/kg). The results of molecular docking and in vitro mutagenesis analyses suggest that the synthesized compounds bind to the active binding site of EBOV glycoprotein similar to the known inhibitor toremifene.

Odoriferous Therapy: A Review Identifying Essential Oils against Pathogens of the Respiratory Tract

This review explores the body of scientific information available on the antimicrobial properties of essential oils against pathogens responsible for respiratory infections and critically compares this to what is recommended in the Layman's aroma-therapeutic literature. Essential oils are predominantly indicated for the treatment of respiratory infections caused by bacteria or viruses (total 79.0 %), the efficacy of which has not been confirmed through clinical trials. When used in combination, they are often blended for presumed holistic synergistic effects. Of the essential oils recommended, all show some degree of antioxidant activity, 50.0 % demonstrate anti-inflammatory effects and 83.3 % of the essential oils showed antihistaminic activity. Of the essential oils reviewed, 43.8 % are considered non-toxic while the remaining essential oils are considered slightly to moderately toxic (43.7 %) or the toxicity is unknown (12.5 %). Recommendations are made for further research into essential oil combinations.

Visible-Light-Driven Selective Oxidative Coupling of Amines to Imines by Bismuth-Rich Bismuth Oxybromide in Water

Photocatalytic selective oxidative coupling of amines is a promising method for imine synthesis. Bismuth-rich bismuth oxybromide photocatalysts have been found to exhibit improved conversion and selectivity for the visible-light-driven selective oxidative coupling of amines to imines in water. Benzylamines with either electron-withdrawing or electron-donating groups undergo good conversion (94-99 %) and excellent selectivity (93-98 %) to the corresponding imines. The average apparent quantum efficiency at 455 nm is 57.4 %. Active species trapping experiments, isotope experiments, and in situ infrared spectroscopy reveal that water both serves as solvent and participates in the coupling reaction as a reactant. This work provides a green and environmentally friendly method for the efficient synthesis of imines with bismuth-rich bismuth oxyhalides and reveals water is involved in the oxidative coupling mechanism of benzylamines.

Synthesis of d-(+)-camphor-based N-acylhydrazones and their antiviral activity

The design and synthesis of a series of novel d-(+)-camphor N-acylhydrazones exhibiting inhibitory activity against vaccinia and influenza viruses are presented. An easy pathway to camphor-based N-acylhydrazones containing in their structure aliphatic, aromatic, and heterocyclic pharmacophore scaffolds has been developed. The conformation and configuration of the synthesized hydrazones were thoroughly characterized by a complete set of spectral characterization techniques, including 2D NMR spectroscopy, mass spectrometry, and X-ray diffraction analysis. In vitro screening for activity against vaccinia virus (VV) and influenza H1N1 virus was carried out for the obtained compounds. It was revealed that the derived N-acylhydrazones exhibited significant antiviral activity with a selectivity index >280 against VV for the most promising compound.

Silver Camphor Imine Complexes: Novel Antibacterial Compounds from Old Medicines

The emergence of bacterial resistance to available antimicrobials has prompted the search for novel antibacterial compounds to overcome this public health problem. Metal-based complexes have been much less explored than organic compounds as antimicrobials, leading to investigations of the antimicrobial properties of selected complexes in which silver may occupy the frontline due to its use as medicine since ancient times. Like silver, camphor has also long been used for medicinal purposes. However, in both cases, limited information exists concerning the mechanisms of their antimicrobial action. This work reviews the present knowledge of the antimicrobial properties of camphor-derived silver complexes, focusing on recent research on the synthesis and antimicrobial properties of complexes based on silver and camphor imines. Selected examples of the structure and antimicrobial activity relationships of ligands studied so far are presented, showing the potential of silver camphorimine complexes as novel antimicrobials.

N-Heterocyclic borneol derivatives as inhibitors of Marburg virus glycoprotein-mediated VSIV pseudotype entry

There is currently no approved antiviral therapy for treatment of Marburg virus disease (MVD). Although filovirus infection outbreaks are quite rare, the high mortality rates in such outbreaks make the development of anti-filoviral drugs an important goal of medical chemistry and virology. Here, we performed screening of a large library of natural derivatives for their virus entry inhibition activity using pseudotype systems. The bornyl ester derivatives containing saturated N-heterocycles exhibited the highest antiviral activity. It is supposed that compounds with specific inhibitory activity toward MarV-GP-dependent virus entry will inhibit the rVSIV-ΔG-MarV-GP pseudotype much more efficiently than the control rVSIV-ΔG-G pseudotype. At the same time, the compounds similarly inhibiting both pseudotypes will likely affect rVSIV capsid replication or the cellular mechanisms common to the entry of both viruses. Borneol itself is not active against both pseudotypes and is nontoxic, whereas its derivatives have varying toxicity and antiviral activity. Among low-toxic borneol derivatives, six compounds turned out to be relatively specific inhibitors of MarV-GP-mediated infection (SC > 10). Of them, compound 6 containing a methylpiperidine moiety exhibited the highest virus-specific activity. Notably, the virus-specific activity of this compound is twice as high as that of the reference.

Monoterpenes as a renewable source of biologically active compounds

Monoterpenes and their derivatives play an important role in the creation of new biologically active compounds including drugs. The review focuses on the data on various types of biological activity exhibited by monoterpenes and their derivatives, including analgesic, anti-inflammatory, anticonvulsant, antidepressant, anti-Alzheimer, anti-Parkinsonian, antiviral, and antibacterial (anti-tuberculosis) effects. Searching for novel potential drugs among monoterpene derivatives shows great promise for treating various pathologies. Special attention is paid to the effect of absolute configuration of monoterpenes and monoterpenoids on their activity.

Synthesis and in vitro study of novel borneol derivatives as potent inhibitors of the influenza A virus

Herein, we present the design and synthesis of a series of novel heterocyclic derivatives of (-)-borneol and (-)-isoborneol as potent inhibitors of the influenza A virus. All compounds were tested for their toxicity against MDCK cells and for virus-inhibiting activity against the influenza virus A/Puerto Rico/8/34 (H1N1). Compounds 7, 16 and 26 containing a morpholine fragment exhibited the highest efficiency as agents inhibiting the replication of the influenza virus A(H1N1) with selectivity indices of 82, 45 and 65, correspondingly. Derivatives 9 (SI = 23) and 18 (SI = 25) containing a 1-methylpiperazine motif showed moderate antiviral activity. Structure-activity analysis of this new series of borneol derivatives revealed that a 1,7,7-trimethylbicyclo[2.2.1]heptan scaffold is required for the antiviral activity.

Anti-influenza activity of monoterpene-containing substituted coumarins

Compounds simultaneously carrying the monoterpene and coumarin moieties have been tested for cytotoxicity and inhibition of activity against influenza virus A/California/07/09 (H1N1)pdm09. The structure of substituents in the coumarin framework, as well as the structure and the absolute configuration of the monoterpenoid moiety, are shown to significantly influence the anti-influenza activity and cytotoxicity of the compounds under study. The compounds with a bicyclic pinane framework exhibit the highest selectivity indices (the ratios between the cytotoxicity and the active dose). The derivative of (-)-myrtenol 15c, which is characterized by promising activity, low cytotoxicity, and synthetic accessibility, has the greatest potential among this group of compounds. It exhibited the highest activity when added to the infected cell culture at early stages of viral reproduction.

Synthesis of camphecene derivatives using click chemistry methodology and study of their antiviral activity

A series of seventeen tetrazole derivatives of 1,7,7-trimethyl-[2.2.1]bicycloheptane were synthesized using click chemistry methodology and characterized by spectral data. Studies of cytotoxicity and in vitro antiviral activity against influenza virus A/Puerto Rico/8/34 (H1N1) in MDCK cells of the compounds obtained were performed. The structure-activity relationship analysis suggests that to possess virus-inhibiting activity, the compounds of this group should bear oxygen atom with a short linker (C2-C4), either as a hydroxyl group (18, 19, 29), keto-group (21) or as a part of a heterocycle (24). These compounds demonstrated low cytotoxicity along with high anti-viral activity.