Antiviral effect of flavonol glycosides isolated from the leaf of Zanthoxylum piperitum on influenza virus

Determination of Biologically Active Compounds and Antioxidant Capacity In Vitro in Fruit of Small Cranberries (Vaccinium oxycoccos L.) Growing in Natural Habitats in Lithuania

The composition of flavonols, proanthocyanidins, anthocyanins, triterpene compounds, and chlorogenic acid in small cranberry fruit samples collected in natural habitats in Lithuania and variation in the antioxidant capacity of cranberry fruit extracts was determined. This study showed that in the flavonol group, hyperoside and myricetin-3-O-galactoside predominated in cranberry fruit samples; in the anthocyanin group, the predominant compounds were cyanidin-3-O-galactoside, cyanidin-3-O-arabinoside, peonidin-3-O-galactoside, and peonidin-3-O-arabinoside, and in the group of triterpene compounds, ursolic acid was predominant. The highest total amounts of flavonols and anthocyanins were found in the samples collected in Čepkeliai State Strict Nature Reserve (2079.44 ± 102.99 μg/g and 6993.79 ± 350.22 μg/g, respectively). Cluster analysis of the chemical composition of small cranberry fruit samples revealed trends in the accumulation of bioactive compounds in cranberry fruit. Cranberry fruit samples collected in central Lithuania had higher levels of triterpene compounds. Statistical correlation analysis showed the strongest correlation between the quantitative composition of cyanidin-3-O-arabinoside and peonidin-3-O-arabinoside and the reducing capacity of the ethanolic extracts of the cranberry fruit samples assessed in vitro by the FRAP assay (r = 0.882, p < 0.01 and r = 0.805, p < 0.01, respectively). Summarizing the results, the geographical factor affects the variation of the quantitative composition of biologically active compounds in cranberry fruit samples.

A mini review on the prospects of Fagara zanthoxyloides extract based composites: a remedy for COVID-19 and associated replica?

Studies are still being conducted to find a sustainable and long-lasting solution to the lethal consequences of the feared virus characterized as coronavirus disease (Covid-19) and its accompanying pathogenic replication, which pose a serious threat to human survival in the wake of its broad distribution. Since its emergence, researchers have investigated synthetic approaches in search of a dependable vaccine or treatment and curtail the spread of the virus and also enhance the health of a patient who has been affected. Unfortunately, the infection is yet to be entirely eradicated in many parts of the world. Despite the introduction of synthetic pharmaceuticals like remdesivir and derivatives of chloroquine, plant extracts may be an alternative reliable strategy that could successfully combat the operation of the virus. Herein, we investigated the prospects of fagara zanthoxyloides lam. (rutaceae) (syn. zanthoxylum zanthoxyloides), a well-known medicinal tree whose extracts have demonstrated success in treating many microbiological and viral-related infections. The distinctive plant extracts contain several bioactive phytochemicals with promising biological activity with minimal or no side effects and are being researched for a variety of applications, particularly in the pharmaceutical and medicinal industries. Consequently, in this review, we examined the crude extracts from the Fagara species and suggested that careful consideration should be given to its independent use or combination with other bioactive molecules, such as biopolymers and nano-metallic composites, to combat the terrifying Covid-19 virus and its associates.

Hydroxy-β-sanshool isolated from Zanthoxylum piperitum (Japanese pepper) shortens the period of the circadian clock

We showed that an ethanol extract from Zanthoxylum piperitum can shorten the circadian rhythm at the cellular level and that this activity was due to hydroxy-β-sanshool, a secondary metabolite in this plant. An ethanol extract of Z. piperitum was repeatedly fractionated using solid phase extraction and reverse-phase HPLC, then the circadian rhythms of cells to which the fractions were loaded were monitored using real-time reporter gene assays. We purified one HPLC peak and identified it as hydroxy-β-sanshool using liquid chromatography (LC)-precision-mass spectrometry (MS). This compound shortened the period of Bmal1 and Per2 at the cellular level. Incubation cells for 24 h with hydroxy-β-sanshool resulted in upregulated Per2 promoter activity. Hydroxy-β-sanshool also dose-dependently upregulated expression of the clock genes Bmal1, Per1, Per2 and Cry1 and the clock-controlled oxidative stress responsive genes Gpx1and Sod2.

Tale of Viruses in Male Infertility

Male infertility is a condition where the males either become sterile or critically infertile. The World Health Organisation assessed that approximately 9% of the couple have fertility issues where the contribution of the male partner was estimated to be 50%. There are several factors that can amalgamate to give rise to male infertility. Among them are lifestyle factors, genetic factors and as well as several environmental factors. The causes of male infertility may be acquired, congenital or sometimes idiopathic. All these factors adversely affect the spermatogenesis process as well as they impart serious threats to male genital organs thus resulting in infertility. Viruses are submicroscopic pathogenic agents that rely on host for their replication and survival. They enter the host cell, hijack the host cell machinery to aid their own replication and exit the cell for a new round of infection. With the growing abundance of different types of viruses and the havoc they have stirred in the form of pandemics, it is very essential to decipher their route of entry inside the human body and understand their diverse functional roles in order to combat them. In this chapter, we will review how viruses invade the male genital system thus in turn leading to detrimental consequence on male fertility. We will discuss the tropism of various viruses in the male genital organs and explore their sexual transmissibility. This chapter will summarise the functional and mechanistic approaches employed by the viruses in inducing oxidative stress inside spermatozoa thus leading to male infertility. Moreover, we will also highlight the various antiviral therapies that have been studied so far in order to ameliorate viral infection in order to combat the harmful consequences leading to male infertility.

Preclinical evaluation of Zanthoxylum piperitum Benn., traditional muscle pain remedy, for joint inflammation

ETHNOPHARMACOLOGICAL RELEVANCE

Zanthoxylum piperitum has been used as a traditional Asian medicine to treat hypertension, stroke, bruise and muscle pain. It has been known to induce detoxification; affect anti-bacterial, anti-oxidant, and tyrosinase activity; inhibit osteosarcoma proliferation; anti-osteoarthritis inflammation. In this study, we aim to identify the therapeutic effect of Z. piperitum 90% EtOH extract (ZPE-LR) on rheumatoid arthritis.

MATERIAL AND METHODS

We investigated the anti-rheumatoid arthritis and -immunomodulatory activities of the ZPE-LR in collagen-induced arthritic (CIA) mice, a rheumatoid arthritis animal model. In order to assess the analgesic effects of ZPE-LR in vivo, acetic acid injection, formaldehyde injection, hot plate model was used. The mechanism for anti-inflammatory activity of ZPE-LR was identified with LPS-stimulated Raw 264.7 cells.

RESULTS

Pharmacologically, oral administration of ZPE-LR into CIA mice resulted in a significant and dose-dependent decrease in clinical arthritis score and paw swelling compared to untreated negative control. Pathologic examination showed that ZPE-LR prevented morphological change in cartilage and destruction of phalanges in CIA mice. This protective effect was associated with reduced pain, inflammatory mediators such as NO, TNF-α, IL-1β, and IL-6, as well as COX-2 and iNOS expression. Furthermore, reduction of phosphor-ERK and BDNF indicates a novel rheumatoid arthritis-regulating mechanism by ZPE-LR treatment.

CONCLUSIONS

These data suggest that the administration of ZPE-LR remarkably inhibited CIA progression and might be helpful in suppressing inflammation and pain in rheumatoid arthritis.

Novel Anti-Hepatitis B Virus Activity of Euphorbia schimperi and Its Quercetin and Kaempferol Derivatives

Natural or plant products, because of their structural diversity, are a potential source for identifying new anti-hepatitis B virus (HBV) agents. Here, we report the anti-HBV activity of Euphorbia schimperi and its quercetin (QRC) and kaempferol derivatives. The anti-HBV-active methanol fraction of E. schimperi was subjected to chromatographic techniques, leading to isolation of three flavonols, following their structure determination by ¹H and ¹³C NMR spectroscopies. Their cytotoxicity and anti-HBV potential were assessed using HBV reporter HepG2.2.15 cells, and their modes of action were delineated by molecular docking. The isolated compounds identified as quercetin-3-O-glucuronide (Q3G), quercetin-3-O-rhamnoside (Q3R), and kaempferol-3-O-glucuronide (K3G) were non-cytotoxic to HepG2.2.15 cells. The viral HBsAg/HBeAg production on day 5 was significantly inhibited by K3G (∼70.2/∼73.4%), Q3G (∼67.8/∼72.1%), and Q3R (∼63.2%/∼68.2%) as compared to QRC (∼70.3/∼74.8%) and lamivudine (∼76.5/∼84.5%) used as standards. The observed in vitro anti-HBV potential was strongly supported by in silico analysis, which suggested their structure-based activity via interfering with viral Pol/RT and core proteins. In conclusion, this is the first report on the anti-HBV activity of E. schimperi-derived quercitrin-3-O-glucuronide, quercitrin-3-O-rhamnoside, and kaempferol-3-O-glucuronide, most likely through interfering with HBV proteins.

Identification of anti-TMV active flavonoid glycosides and their mode of action on virus particles from Clematis lasiandra Maxim

BACKGROUND

Tobacco mosaic virus (TMV) is a disreputable plant pathogen that causes a decline in the quality and yield of various economic crops. Natural products are important potential sources of biopesticides to control TMV. This study focuses on the discovery of anti-TMV active flavonoid glycosides and their mode of action on TMV particles from Clematis lasiandra Maxim.

RESULTS

A new benzoyl acylated flavonoid glycoside, kaempferol 3-O-(2''-benzoyl)-β-d-glucopyranosyl-7-O-α-l-rhamnopyranoside (1), and nine known flavonoids (2-10) were identified first from C. lasiandra. The hydroxyl group at C-7, E-p-coumarate at C-6'' in the Glc of C-6, and the glucuronic acid at C-3 were functional groups for the antiviral flavonoid glycosides. Flavonoids 2, 5, and 6 showed higher inactivation efficacies of 64.62% to 82.54% compared with ningnanmycin at 500 μg ml^-1 . The protective and curative efficacies for 2 and 5 were 57.44-59.00% and 41.17-43.92% at 500 μg ml^-1 , respectively. Compound 5 showed higher TMV systemic resistance with control efficacies of 41.64%, 36.56% and 27.62% at concentrations of 500, 250 and 125 μg ml^-1 compared with ningnanmycin in K326 tobaccos, respectively. Compound 5 can directly fracture TMV particles into small fragments combining with the fusion phenomena, and TMV-CP was an important target for 5 to break TMV particles.

CONCLUSION

Flavonoid glycosides from C. lasiandra showed potent antiviral activities against TMV with multiple modes of action including inactivation, protective and curative effects, and inducing systemic resistance. TMV-CP was an important target for active flavonoid glycosides to fracture TMV particles. The results provided evidence that flavonoid glycosides from C. lasiandra have the potential to control TMV.

Multifaceted antiviral therapeutic potential of dietary flavonoids: Emerging trends and future perspectives

Phytochemicals are the natural biomolecules produced by plants via primary or secondary metabolism, which have been known to have many potential health benefits to human beings. Flavonoids or phytoestrogens constitute a major group of such phytochemicals widely available in variety of vegetables, fruits, herbs, tea, and so forth, implicated in a variety of bio-pharmacological and biochemical activities against diseases including bacterial, viral, cancer, inflammatory, and autoimmune disorders. More recently, these natural biomolecules have been shown to have effective antiviral properties via therapeutically active ingredients within them, acting at different stages of infection. Current review emphasizes upon the role of these flavonoids in physiological functions, prevention and treatment of viral diseases. More so the review focuses specifically upon the antiviral effects exhibited by these natural biomolecules against RNA viruses including coronaviruses. Furthermore, the article would certainly provide a lead to the scientific community for the effective therapeutic antiviral use of flavonoids using potential cost-effective tools for improvement of the pharmacokinetics, bioavailability, and biodistribution of such compounds for the concrete action along with the promotion of human health.

Zanthoxylum Species: A Review of Traditional Uses, Phytochemistry and Pharmacology in Relation to Cancer, Infectious Diseases and Sickle Cell Anemia

The health benefits and toxicity of plant products are largely dependent on their secondary metabolite contents. These compounds are biosynthesized by plants as protection mechanisms against environmental factors and infectious agents. This review discusses the traditional uses, phytochemical constituents and health benefits of plant species in genus Zanthoxylum with a focus on cancer, microbial and parasitic infections, and sickle cell disease as reported in articles published from 1970 to 2021 in peer-reviewed journals and indexed in major scientific databases. Generally, Z. species are widely distributed in Asia, America and Africa, where they are used as food and for disease treatment. Several compounds belonging to alkaloids, flavonoids, terpenoids, and lignans, among others have been isolated from Z. species. This review discusses the biological activities reported for the plant species and their phytochemicals, including anticancer, antibacterial, antifungal, antiviral, anti-trypanosomal, antimalarial and anti-sickling properties. The safety profiles and suggestions for conservation of the Z. species were also discussed. Taken together, this review demonstrates that Z. species are rich in a wide range of bioactive phytochemicals with multiple health benefits, but more research is needed towards their practical application in the development of functional foods, nutraceuticals and lead compounds for new drugs.

Zanthoxylum Species: A Comprehensive Review of Traditional Uses, Phytochemistry, Pharmacological and Nutraceutical Applications

Zanthoxylum species (Syn. Fagara species) of the Rutaceae family are widely used in many countries as food and in trado-medicinal practice due to their wide geographical distribution and medicinal properties. Peer reviewed journal articles and ethnobotanical records that reported the traditional knowledge, phytoconstituents, biological activities and toxicological profiles of Z. species with a focus on metabolic and neuronal health were reviewed. It was observed that many of the plant species are used as food ingredients and in treating inflammation, pain, hypertension and brain diseases. Over 500 compounds have been isolated from Z. species, and the biological activities of both the plant extracts and their phytoconstituents, including their mechanisms of action, are discussed. The phytochemicals responsible for the biological activities of some of the species are yet to be identified. Similarly, biological activities of some isolated compounds remain unknown. Taken together, the Z. species extracts and compounds possess promising biological activities and should be further explored as potential sources of new nutraceuticals and drugs.

Flavonoids as Promising Antiviral Agents against SARS-CoV-2 Infection: A Mechanistic Review

A newly diagnosed coronavirus in 2019 (COVID-19) has affected all human activities since its discovery. Flavonoids commonly found in the human diet have attracted a lot of attention due to their remarkable biological activities. This paper provides a comprehensive review of the benefits of flavonoids in COVID-19 disease. Previously-reported effects of flavonoids on five RNA viruses with similar clinical manifestations and/or pharmacological treatments, including influenza, human immunodeficiency virus (HIV), severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and Ebola, were considered. Flavonoids act via direct antiviral properties, where they inhibit different stages of the virus infective cycle and indirect effects when they modulate host responses to viral infection and subsequent complications. Flavonoids have shown antiviral activity via inhibition of viral protease, RNA polymerase, and mRNA, virus replication, and infectivity. The compounds were also effective for the regulation of interferons, pro-inflammatory cytokines, and sub-cellular inflammatory pathways such as nuclear factor-κB and Jun N-terminal kinases. Baicalin, quercetin and its derivatives, hesperidin, and catechins are the most studied flavonoids in this regard. In conclusion, dietary flavonoids are promising treatment options against COVID-19 infection; however, future investigations are recommended to assess the antiviral properties of these compounds on this disease.

Elucidation of Japanese pepper (Zanthoxylum piperitum De Candolle) domestication using RAD-Seq

Japanese pepper, Zanthoxylum piperitum, is native to Japan and has four well-known lineages (Asakura, Takahara, Budou, and Arima), which are named after their production area or morphology. Restriction-site associated DNA sequencing (RAD-Seq) was used to analyse 93 accessions from various areas, including these four lineages. Single nucleotide variant analysis was used to classify the plants into eight groups: the Asakura and Arima lineages each had two groups, the Takahara and Budou lineages each had one group, and two additional groups were present. In one Asakura group and two Arima groups, the plants were present in agricultural fields and mountains, thus representing the early stage of domestication of the Japanese pepper. The second Asakura lineage group was closely related to plants present in various areas, and this represents the second stage of domestication of this plant because, after early domestication, genetically related lineages with desirable traits spread to the periphery. These results demonstrate that domestication of Japanese pepper is ongoing. In addition, this study shows that spineless plants are polyphyletic, despite the spineless lineage being considered a subspecies of Japanese pepper.

Theacrine and strictinin, two major ingredients for the anti-influenza activity of Yunnan Kucha tea

ETHNOPHARMACOLOGICAL RELEVANCE

Kucha tea plant (Camellia assamica var. kucha Chang et Wang) is regarded as a mutant variety of wild Pu'er tea plant found in few mountain areas of Yunnan, China. Its fresh young leaves and shoots are picked by the indigenous aborigines in these local areas to prepare an herbal tea for the treatment of common cold empirically.

MATERIALS AND METHODS

Two extra compounds of relative abundance were detected in Kucha tea in comparison with Pu'er tea, and their chemical structures were identified as chlorogenic acid and theacrine. These two compounds as well as two major compounds, strictinin and caffeine, in Kucha tea were evaluated for their cytotoxicity and inhibitory effects on human influenza virus A/Puerto Rico/8/34 by analyzing viral protein expression and progeny production.

RESULTS

No or low cytotoxicity was detected for the four Kucha compounds when their concentrations were below 100 μM. Expression of viral NS1 protein was significantly inhibited by chlorogenic acid, theacrine or strictinin, but not caffeine at a concentration of 100 μM. The relative inhibitory potency was detected as chlorogenic acid < theacrine < strictinin, and both theacrine and strictinin displayed significant inhibition at a concentration of 50 μM. According to a plaque assay, viral progeny production was significantly reduced by theacrine or strictinin, but not by chlorogenic acid or caffeine under the same concentration of 100 μM.

CONCLUSION

It is suggested that theacrine and strictinin are two major ingredients responsible for the anti-influenza activity of Yunnan Kucha tea traditionally used for the treatment of common cold.

Investigation of Brassica juncea, Forsythia suspensa, and Inula britannica: phytochemical properties, antiviral effects, and safety

BACKGROUND

General antiviral agents such as oseltamivir are associated with certain adverse effects and the emergence of resistance. This study investigated the phytochemical properties, antiviral activities, and safety of three herbs used in traditional Korean medicine.

METHODS

Extracts of three medicinal herbs (Brassica juncea, Forsythia suspensa, and Inula britannica) were prepared using ethanol or water. The total phenolic, flavonoid, and saponin content, condensed tannin content, and reducing sugar content of the herb extracts were determined via phytochemical screening. Tandem mass analysis was performed using an ultra-performance liquid chromatography (UPLC)-electrospray ionization (ESI)-Q/Orbitrap instrument. Virus titrations were determined via tissue culture infective dose (TCID50) and cytotoxicity assays. Hemolysis and hepatotoxicity were measured to determine safety.

RESULTS

Among the three medicinal herbs, F. suspensa showed the highest concentration of phenolic compounds, flavonoids, and saponins. The number of phytochemical compounds detected via tandem mass analysis of B. juncea, F. suspensa, and I. britannica was 5 (including sinigrin, m/z [M-H] = 358.02), 14 (including forsythoside A, m/z [M-H] = 623.19), and 18 (including chlorogenic acid, m/z [M-H] = 353.20), respectively. The antiviral effects of the B. juncea extracts (ethanol and water) and I. britannica extract (ethanol) were further investigated. The ethanol extract of B. juncea showed a 3 Log TCID50/25 μL virus titration reduction and the water extract showed a selectivity index of 13.668 against infected influenza H1N1 virus A/NWS/33. The B. juncea extracts did not show hemolysis activities and hepatotoxicity (< 20%). The ethanol extract of I. britannica showed the most effective virus titration decrease, whereas its hemolytic and hepatotoxicity values were the most significantly different compared to the control. Despite the high concentration of phytochemicals detected in F. suspensa, the extract showed approximately 1 Log TCID50/25 μL at the highest concentration.

CONCLUSION

B. juncea may show antiviral effects against H1N1 in a host. In addition, B. juncea may also show decreased disadvantages compared to other antiviral agents.

Herbal Medicines with Antiviral Activity Against the Influenza Virus, a Systematic Review

The rapidly changing influenza virus has remained a consistent threat to the well-being of a variety of species on the planet. Influenza virus' high mutation rate has allowed the virus to rapidly and continuously evolve, as well as generate new strains that are resistant to the current commercially available antivirals. Thus, the increased resistance has compelled the scientific community to explore alternative compounds that have antiviral effects against influenza virus. In this paper, the authors systematically review numerous herbal extracts that were shown to have antiviral effects against the virus. Specifically, the herbal antiviral targets mainly include hemagglutinin, neuraminidase and matrix 2 proteins. In some instances, herbal extracts inhibited the replication of oseltamivir-resistant strains and certain pentacyclic triterpenes exhibited higher antiviral activity than oseltamivir. This paper also explores the possibility of targeting various host-cell signaling pathways that are utilized by the virus during its replication process. Infected cell pathways are hijacked by intracellular signaling cascades such as NF-kB signaling, PI3K/Akt pathway, MAPK pathway and PKC/PKR signaling cascades. Herbal antivirals have been shown to target these pathways by suppressing nuclear export of influenza vRNP and thus inhibiting the phosphorylation signaling cascade. In conclusion, copious amounts of herbal antivirals have been shown to inhibit influenza virus, however further studies are needed for these new compounds to be up to modern pharmacological standards.

The Cranberry Extract Oximacro® Exerts in vitro Virucidal Activity Against Influenza Virus by Interfering With Hemagglutinin

The defense against influenza virus (IV) infections still poses a series of challenges. The current antiviral arsenal against influenza viruses is in fact limited; therefore, the development of new anti-influenza strategies effective against antigenically different viruses is an urgent priority. Bioactive compounds derived from medicinal plants and fruits may provide a natural source of candidates for such broad-spectrum antivirals. In this regard, cranberry (Vaccinium macrocarpon Aiton) extracts on the basis of their recognized anti-adhesive activities against bacteria, may provide potential compounds able to prevent viral attachment to target cells. Nevertheless, only few studies have so far investigated the possible use of cranberry extracts as an antiviral tool. This study focuses on the suitability of a cranberry extract as a direct-acting anti-influenza compound. We show that the novel cranberry extract Oximacro® inhibits influenza A and B viruses (IAV, IBV) replication in vitro because of its high content of A-type proanthocyanidins (PAC-A) dimers and trimers. Mechanistic studies revealed that Oximacro® prevents attachment and entry of IAV and IBV into target cells and exerts a virucidal activity. Oximacro® was observed to interact with the ectodomain of viral hemagglutinin (HA) glycoprotein, thus suggesting the interference with HA functions and a consequent loss of infectivity of IV particles. Fluorescence spectroscopy revealed a reduction in the intrinsic fluorescence of HA protein after incubation with purified dimeric PAC-A (PAC-A2), thus confirming a direct interaction between HA and Oximacro® PAC-A2. In silico docking simulations further supported the in vitro results and indicated that among the different components of the Oximacro® chemical profile, PAC-A2 exhibited the best binding propensity with an affinity below 10 nM. The role of PAC-A2 in the anti-IV activity of Oximacro® was eventually confirmed by the observation that it prevented IAV and IVB replication and caused the loss of infectivity of IV particles, thus indicating PAC-A2 as the major active component of Oximacro®. As a whole, these results suggest Oximacro® as a potential candidate to create novel antiviral agents of natural origin for the prevention of IV infections.

Zanthoxylum fruit extract from Japanese pepper promotes autophagic cell death in cancer cells

Zanthoxylum fruit, obtained from the Japanese pepper plant (Zanthoxylum piperitum De Candolle), and its extract (Zanthoxylum fruit extract, ZFE) have multiple physiological activities (e.g., antiviral activity). However, the potential anticancer activity of ZFE has not been fully examined. In this study, we investigated the ability of ZFE to induce autophagic cell death (ACD). ZFE caused remarkable autophagy-like cytoplasmic vacuolization, inhibited cell proliferation, and ultimately induced cell death in the human cancer cell lines DLD-1, HepG2, and Caco-2, but not in A549, MCF-7, or WiDr cells. ZFE increased the level of LC3-II protein, a marker of autophagy. Knockdown of ATG5 using siRNA inhibited ZFE-induced cytoplasmic vacuolization and cell death. Moreover, in cancer cells that could be induced to undergo cell death by ZFE, the extract increased the phosphorylation of c-Jun N-terminal kinase (JNK), and the JNK inhibitor SP600125 attenuated both vacuolization and cell death. Based on morphology and expression of marker proteins, ZFE-induced cell death was neither apoptosis nor necrosis. Normal intestinal cells were not affected by ZFE. Taken together, our findings show that ZFE induces JNK-dependent ACD, which appears to be the main mechanism underlying its anticancer activity, suggesting a promising starting point for anticancer drug development.

Flavonoids: promising natural compounds against viral infections

Flavonoids are widely distributed as secondary metabolites produced by plants and play important roles in plant physiology, having a variety of potential biological benefits such as antioxidant, anti-inflammatory, anticancer, antibacterial, antifungal and antiviral activity. Different flavonoids have been investigated for their potential antiviral activities and several of them exhibited significant antiviral properties in in vitro and even in vivo studies. This review summarizes the evidence for antiviral activity of different flavonoids, highlighting, where investigated, the cellular and molecular mechanisms of action on viruses. We also present future perspectives on therapeutic applications of flavonoids against viral infections.

Evaluation of Antiviral Activity of Zanthoxylum Species Against Picornaviruses

Human rhinoviruses and enteroviruses (family Picornaviridae) infect millions of people worldwide each year, but little is known about effective therapeutical treatment for the infection caused by these viruses. We sought to determine whether or not Zanthoxylum (Rutaceae) species can exhibit antiviral activity against picornaviruses. The leaf parts of four Zanthoxylum species were extracted with methanol, and the extracts were investigated for their antiviral activity against picornaviruses using cytopathic effects by cytopathic effect reduction. Leaf extracts of Zanthoxylum piperitum among four Zanthoxylum species were found to possess only broad-spectrum antipicornavirus activity against human rhninovirus 2 with a 50% inhibitory concentration (IC50) value of 59.48 μg/mL, human rhinovirus 3 with an IC50 value of 39.94 μg/mL, coxsackie A16 virus with an IC50 value of 45.80 μg/mL, coxsackie B3 virus with an IC50 value of 68.53 μg/mL, coxsackie B4 virus with an IC50 value of 93.58 μg/mL, and enterovirus 71 virus with an IC50 value of 4.48 μg/mL. However, ribavirin did not possess antiviral activity against human rhinovirus 3 and four enteroviruses. Therefore, leaves of Z. piperitum showed broad-spectrum antipicornavirus activity, and may be useful as a candidate for studying picornavirus agents and development of pharmaceuticals.

Apigenin inhibits African swine fever virus infection in vitro

African swine fever virus (ASFV) is one of the most devastating diseases of domestic pigs for which no effective vaccines are available. Flavonoids, natural products isolated from plants, have been reported to have significant in vitro and in vivo antiviral activity against different viruses. Here, we tested the antiviral effect of five flavonoids on the replication of ASFV in Vero cells. Our results showed a potent, dose-dependent anti-ASFV effect of apigenin in vitro. Time-of-addition experiments revealed that apigenin was highly effective at the early stages of infection. Apigenin reduced the ASFV yield by more than 99.99 % when it was added at 1 hpi. The antiviral activity of apigenin was further investigated by evaluation of ASFV protein synthesis and viral factories. This flavonoid inhibited ASFV-specific protein synthesis and viral factory formation. ASFV-infected cells continuously treated with apigenin did not display a cytopathic effect. Further studies addressing the use of apigenin in vivo are needed.

Quercetin as an Antiviral Agent Inhibits Influenza A Virus (IAV) Entry

Influenza A viruses (IAVs) cause seasonal pandemics and epidemics with high morbidity and mortality, which calls for effective anti-IAV agents. The glycoprotein hemagglutinin of influenza virus plays a crucial role in the initial stage of virus infection, making it a potential target for anti-influenza therapeutics development. Here we found that quercetin inhibited influenza infection with a wide spectrum of strains, including A/Puerto Rico/8/34 (H1N1), A/FM-1/47/1 (H1N1), and A/Aichi/2/68 (H3N2) with half maximal inhibitory concentration (IC₅₀) of 7.756 ± 1.097, 6.225 ± 0.467, and 2.738 ± 1.931 μg/mL, respectively. Mechanism studies identified that quercetin showed interaction with the HA2 subunit. Moreover, quercetin could inhibit the entry of the H5N1 virus using the pseudovirus-based drug screening system. This study indicates that quercetin showing inhibitory activity in the early stage of influenza infection provides a future therapeutic option to develop effective, safe and affordable natural products for the treatment and prophylaxis of IAV infections.