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Extract of Scutellaria baicalensis inhibits dengue virus replication
Abstract and Figures
Background
Scutellaria baicalensis (S. baicalensis) is one of the traditional Chinese medicinal herbs that have been shown to possess many health benefits. In the present study, we evaluated the in vitro antiviral activity of aqueous extract of the roots of S. baicalensis against all the four dengue virus (DENV) serotypes.
Methods
Aqueous extract of S. baicalensis was prepared by microwave energy steam evaporation method (MEGHE™), and the anti-dengue virus replication activity was evaluated using the foci forming unit reduction assay (FFURA) in Vero cells. Quantitative real-time polymerase chain reaction (qRT-PCR) assay was used to determine the actual dengue virus RNA copy number. The presence of baicalein, a flavonoid known to inhibit dengue virus replication was determined by mass spectrometry.
Results
The IC50 values for the S. baicalensis extract on Vero cells following DENV adsorption ranged from 86.59 to 95.19 μg/mL for the different DENV serotypes. The IC50 values decreased to 56.02 to 77.41 μg/mL when cells were treated with the extract at the time of virus adsorption for the different DENV serotypes. The extract showed potent direct virucidal activity against extracellular infectious virus particles with IC50 that ranged from 74.33 to 95.83 μg/mL for all DENV serotypes. Weak prophylactic effects with IC50 values that ranged from 269.9 to 369.8 μg/mL were noticed when the cells were pre-treated 2 hours prior to virus inoculation. The concentration of baicalein in the S. baicalensis extract was ~1% (1.03 μg/gm dried extract).
Conclusions
Our study demonstrates the in vitro anti-dengue virus replication property of S. baicalensis against all the four DENV serotypes investigated. The extract reduced DENV infectivity and replication in Vero cells. The extract was rich in baicalein, and could be considered for potential development of anti-DENV therapeutics.
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... Figueiredo et al. (2021) reported that cold aqueous root extracts of Solanum sisymbriifolium Lam., Solanaceae, commonly used in Paraguayan folk medicine, exhibited virucidal effects against dengue virus serotype 2 (Figueiredo et al. 2021). Furthermore, Zandi et al. (2013) also identified anti-dengue characteristics in root extracts from Scutellaria baicalensis Georgi, Lamiaceae, a traditional Chinese medicinal herb, towards all dengue serotypes (Zandi et al. 2013). ...
... Figueiredo et al. (2021) reported that cold aqueous root extracts of Solanum sisymbriifolium Lam., Solanaceae, commonly used in Paraguayan folk medicine, exhibited virucidal effects against dengue virus serotype 2 (Figueiredo et al. 2021). Furthermore, Zandi et al. (2013) also identified anti-dengue characteristics in root extracts from Scutellaria baicalensis Georgi, Lamiaceae, a traditional Chinese medicinal herb, towards all dengue serotypes (Zandi et al. 2013). ...
Dengue fever is caused by the Aedes mosquito-borne dengue virus, which is a global threat with 400 million cases reported annually and 5–20% mortality rate. Currently, there is no effective treatment available for dengue fever. Natural products like withanolides, which are steroidal lactones, have shown many good properties, including antiviral activity against other viruses. This study aimed to evaluate the anti-dengue virus serotype 2 activity of withanolide A and withanone in Vero cells. Withanolide A and withanone were well-tolerated in Vero cells with a half-maximal cytotoxic concentration of 0.4982 and 1.186 µM, respectively. Withanolide A and withanone exhibited good direct virus-inactivating effects against dengue virus serotype 2 with a half-maximal inhibitory concentration of 0.017 and 0.353 µM, respectively. Based on the selectivity index, withanolide A (selectivity index, 29.31) was determined to be safer and more effective in inhibiting dengue virus serotype 2 infection in Vero cells than withanone (selectivity index, 3.36). Further investigations conducted with withanolide A showed that it inhibited dengue virus serotype 2 during the pre- and post-infection stages in a dose-dependent manner. Withanolide A also effectively blocked dengue virus serotype 2 attachment and entry into Vero cells in a dose-dependent manner. These findings suggest that withanolide A showed potent anti-dengue activity and could serve as a promising antiviral agent for treatment of dengue infections.
... Figueiredo et al. (2021) reported that cold aqueous root extracts of Solanum sisymbriifolium Lam., Solanaceae, commonly used in Paraguayan folk medicine, exhibited virucidal effects against dengue virus serotype 2 (Figueiredo et al. 2021). Furthermore, Zandi et al. (2013) also identified anti-dengue characteristics in root extracts from Scutellaria baicalensis Georgi, Lamiaceae, a traditional Chinese medicinal herb, towards all dengue serotypes (Zandi et al. 2013). ...
... Figueiredo et al. (2021) reported that cold aqueous root extracts of Solanum sisymbriifolium Lam., Solanaceae, commonly used in Paraguayan folk medicine, exhibited virucidal effects against dengue virus serotype 2 (Figueiredo et al. 2021). Furthermore, Zandi et al. (2013) also identified anti-dengue characteristics in root extracts from Scutellaria baicalensis Georgi, Lamiaceae, a traditional Chinese medicinal herb, towards all dengue serotypes (Zandi et al. 2013). ...
Dengue fever is caused by the Aedes mosquito-borne dengue virus, which is a global threat with 400 million cases reported annually and 5–20% mortality rate. Currently, there is no effective treatment available for dengue fever. Natural products like withanolides, which are steroidal lactones, have shown many good properties, including antiviral activity against other viruses. This study aimed to evaluate the anti-dengue virus serotype 2 activity of withanolide A and withanone in Vero cells. Withanolide A and withanone were well-tolerated in Vero cells with a half-maximal cytotoxic concentration of 0.4982 and 1.186 µM, respectively. Withanolide A and withanone exhibited good direct virus-inactivating effects against dengue virus serotype 2 with a half-maximal inhibitory concentration of 0.017 and 0.353 µM, respectively. Based on the selectivity index, withanolide A (selectivity index, 29.31) was determined to be safer and more effective in inhibiting dengue virus serotype 2 infection in Vero cells than withanone (selectivity index, 3.36). Further investigations conducted with withanolide A showed that it inhibited dengue virus serotype 2 during the pre- and post-infection stages in a dose-dependent manner. Withanolide A also effectively blocked dengue virus serotype 2 attachment and entry into Vero cells in a dose-dependent manner. These findings suggest that withanolide A showed potent anti-dengue activity and could serve as a promising antiviral agent for treatment of dengue infections.
... An antiviral agent can act by masking the viral proteins E and M necessary for adsorption and entry into the host cell or by blocking intracellular replication [9]. In addition, it can mask viral receptors on the cell surface, due to competitive binding [10]. Other attractive targets are the different cycle steps of viral replication where the agents interfere with non-structural proteins [6]. ...
Dengue is an emerging disease of high impact on human health. Plants are an important source of new antivirals and Arachis hypogaea stands for its biological properties. The aim of this study was to evaluate the cytotoxicity and antiviral activity and elucidate the antiviral mechanism of ethanolic extracts from A. hypogaea against dengue virus 2 (DENV-2). The skin or tegument ethanolic extract (TEEs) and seed ethanolic extract (SEEs) were obtained. Cytotoxicity was evaluated by MTT and Neutral Red Uptake (NRU). Antiviral activity was evaluated at different stages of the viral replication cycle by the lysis plaque reduction method. The 50% inhibitory concentration (IC50) and selectivity index (SI) were determined. Antiviral activity was further determined by RT-qPCR. The CC50 values were 169 (NRU) and 65 (MTT) µg/mL for TEE. In addition, the CC50 values were >1400 (NRU) and 636 (MTT) µg/mL for SEE. The TEE demonstrated 99.9 ± 0.1% viral inhibition. The TEE presented an IC50 = 3.47 and SI of 48.7 (NRU) and 18.73 (MTT). Its mechanism of antiviral action is broad and it acts in the viral adsorption–penetration stage and inhibits the first steps of infection in the post-penetration stage. It is also capable of acting as virucidal and as prophylactic. Studies of RT-qPCR indicated that the TEE inhibited viral RNA synthesis. These findings suggest that the TEE from A. hypogaea could be a promising antiviral candidate for treating DENV-2 infections.
Dengue fever, caused by the Dengue virus (DENV) and transmitted by Aedes aegypti mosquitoes, has become endemic in over 100 countries. Despite considerable research, there is a lack of specific drugs for clinical use against dengue. Hence, further exploration to identify anti-- dengue compounds is essential. In recent years, natural products have gained attention for their antiviral properties. Plant-based medicines are particularly appealing due to their safety and low toxicity. This review summarizes natural compounds with potential antiviral activity against DENV, highlighting their mechanisms of action. Various compounds, from traditional herbal remedies to novel plant isolates, show promise against dengue, targeting crucial viral proteins like the envelope protein, proteases, and RNA polymerase. Exploring natural sources of antiviral agents against dengue is crucial. These compounds offer hope for effective treatments and mitigating dengue's global impact.
Mosquitoes are insects with slender bodies, three pairs of jointed legs, a pair of wings, and an elongated mouthpart for sucking the blood of vertebrate animals including humans. The saliva of mosquitoes causes itchy rashes when deposited on the skin of humans during blood feeding. Many female mosquito species are
capable of ingesting and/or transmitting infectious pathogens such as viruses that cause diseases like chikungunya fever, dengue fever, Japanese encephalitis, West Nile fever, yellow fever, Zika fever, and others to humans. These viral diseases are primarily transmitted through the bites of infected female mosquitoes (Aedes, Anopheles, and Culex) species in the Culicidae family. The listed viruses are
endemic in the tropics and subtropics of Africa and Southeast Asia, where they cause the emergence and re-emergence of mosquito-borne viral diseases. These diseases are responsible for thousands of deaths reported annually within the affected regions. Treatment and management of mosquito-borne viral diseases with orthodox medicines are common in several parts of the world. However, due to the toxicity of synthetic drugs, their alternatives (mainly from medicinal plants) are beginning to receive wider attention. Therefore, the age-long practice of using plants and herbs by herbalists in the tropics to treat different ailments with believable reports from patients and herbalists is being empirically evaluated presently. Based on verifiable reports of the antiviral properties of some medicinal plants, this chapter intends to discuss medicinal plant diversity in the tropics, highlight recent updates on their use in the treatment and management of mosquito-borne viral diseases, and succinctly espouse some isolated and identified phytochemicals that are potentially active against the listed mosquito-borne viral diseases.
Dengue fever is a mosquito-borne viral illness that affects over 100 nations around the world, including Africa, America, the Eastern Mediterranean, Southeast Asia, and the Western Pacific. Those who get infected by virus for the second time are at greater risk of having persistent dengue symptoms. Dengue fever has yet to be treated with a long-lasting vaccination or medication. Because of their ease of use, mosquito repellents have become popular as a dengue prevention technique. However, this has resulted in environmental degradation and harm, as well as bioaccumulation and biomagnification of hazardous residues in the ecosystem. Synthetic pesticides have caused a plethora of serious problems that were not foreseen when they were originally introduced. The harm caused by the allopathic medications/synthetic pesticides/chemical mosquito repellents has paved the door to employment of eco-friendly/green approaches in order to reduce dengue cases while protecting the integrity of the nearby environment too. Since the cases of dengue have become rampant these days, hence, starting the medication obtained from green approaches as soon as the disease is detected is advisable. In the present paper, we recommend environmentally friendly dengue management strategies, which, when combined with a reasonable number of vector control approaches, may help to avoid the dengue havoc as well as help in maintaining the integrity of the ecosystem.
Viruses, the smallest microorganisms, continue to present an escalating threat to human health, being the leading cause of mortality worldwide. Over the decades, although significant progress has been made in the development of therapies and vaccines against viral diseases, the need for effective antiviral interventions remains urgent. This urgency stems from the lack of effective vaccines, the severe side effects associated with current drugs, and the emergence of drug-resistant viral strains. Natural plants, particularly traditionally-used herbs, are often considered an excellent source of medicinal drugs with potent antiviral efficacy, as well as a substantial safety profile. Scutellaria baicalensis, a traditional Chinese medicine, has garnered considerable attention due to its extensive investigation across diverse therapeutic areas and its demonstrated efficacy in both preclinical and clinical trials. In this review, we mainly focused on the potential antiviral activities of ingredients in Scutellaria baicalensis, shedding light on their underlying mechanisms of action and therapeutic applications in the treatment of viral infections.
Arboviruses have caused several epidemics worldwide, resulting in significant global health problems. Dengue virus (DENV), Zika virus (ZIKV), and Chikungunya virus (CHIKV) are endemic arboviruses throughout Brazil and have a significant impact on public health. Major gaps in protection against the most significant emerging arboviruses remain, as no antivirals are currently available, and vaccines are only available in a few countries. A potential source of antiviral compounds can be found in natural products, of which several compounds have been documented to have antiviral activities and are expected to have good efficacy and low side effects. Polyphenols and plant extracts have been studied for their antiviral properties against arboviruses and have shown promising results. Natural products continue to play an essential role in drug production and development. This study evaluated the antiviral potential of natural substances and extracts against DENV, ZIKV, and CHIKV. Original articles published between 2018 and 2022 in Portuguese and English on the antiviral activity of natural substances against arboviruses were reviewed. A total of 70 natural substances were evaluated against DENV, ZIKV, and CHIKV, and the potential antiviral activity against these viruses was analyzed. Some of these substances have shown promise in developing new antiviral compounds. With abundant natural products to screen for new antiviral compounds, they play an important role in developing new antiviral drugs and reducing arbovirus cases.
Background
Dengue is a serious arboviral disease currently with no effective antiviral therapy or approved vaccine available. Therefore, finding the effective compound against dengue virus (DENV) replication is very important. Among the natural compounds, bioflavonoids derived mainly from plants are of interest because of their biological and medicinal benefits.
Methods
In the present study, antiviral activity of a bioflavonoid, baicalein, was evaluated against different stages of dengue virus type 2 (DENV-2) replication in Vero cells using focus forming unit reduction assay and quantitative RT-PCR.
Results
Baicalein inhibited DENV-2 replication in Vero cells with IC50= 6.46 μg/mL and SI= 17.8 when added after adsorption to the cells. The IC50 against DENV-2 was 5.39 μg/mL and SI= 21.3 when cells were treated 5 hours before virus infection and continuously up to 4 days post infection. Baicalein exhibited direct virucidal effect against DENV-2 with IC 50= 1.55 μg/mL and showed anti-adsorption effect with IC50 = 7.14 μg/mL.
Conclusions
Findings presented here suggest that baicalein exerts potent antiviral activity against DENV. Baicalein possesses direct virucidal activity against DENV besides its effects against dengue virus adsorption and intracellular replication of DENV-2. Baicalein, hence, should be considered for in vivo evaluation in the development of an effective antiviral compound against DENV.
Binding of baicalein, wogonin and baicalin to fish sperm DNA was studied by using ethidium bromide dye as a fluorescence probe. To study the binding mechanism, the absorption, fluorescence, melting temperature and viscosity measurement were carried out. The experimental results indicated that the planar of flavonoids intercalated to the DNA helix. When bound to DNA, flavonoids showed hyperchromic and blue shift in the absorption spectra and fluorescence quenching (>50%) in the fluorescence spectra. Furthermore, the intercalative binding was consistent with the red shift in the position of λmax in the fluorescence spectra. It was also found that ionic strength had little or no effect on the binding of flavonoids and DNA. Stern–Volmer plots at 25 and 37 °C showed that the quenching of fluorescence by flavonoids was a combined quenching process. The binding site number n, apparent binding constant KA at 25 and 37 °C, and the corresponding thermodynamic parameters ΔG, ΔH, ΔS at 25 °C were obtained. The interaction of flavonoid–metal complexes with DNA was also studied by spectral methods, and the results suggested that the complexes intercalated into DNA.
This study investigates the effects of 2-phenyl-1-benzopyran-4-one (flavone) on DENV-2 infectivity in Vero cells. Virus adsorption and attachment and intracellular virus replication were investigated using a foci forming unit assay (FFUA) and quantitative RT-PCR, respectively. Addition of flavone (100 μg/mL) significantly increased the number of DENV-2 foci by 35.66% ± 1.52 and 49.66% ± 2.51 when added during and after virus adsorption to the Vero cells, respectively. The average foci size after 4 days of infection increased by 33% ± 2.11 and 89% ± 2.13. The DENV-2 specific RNA copy number in the flavone-treated infected cells increased by 6.41- and 23.1-fold when compared to the mock-treated infected cells. Flavone (100 μg/mL) did not promote or inhibit Vero cell proliferation. The CC₅₀ value of flavone against Vero cells was 446 µg/mL. These results suggest that flavone might enhance dengue virus replication by acting antagonistically towards flavonoids known to inhibit dengue virus replication.
Patients seek an effective alternative to pharmacotherapy including herbal treatment options for allergic rhinitis and rhinosinusitis.
Material and Methods. Nasal mucosal tissue was obtained from 12 patients, fragmented, preincubated with tissue culture medium, S. baicalensis and/or E. senticosus and/or vitamin C (each compound 0.2 mu g/mL and 2 mu g/mL) for 1 hour at 37 degrees C/5% CO2, and stimulated with anti-IgE for 30 minutes and 6 hours to imitate the allergic early and late phases. Furthermore, Staphylococcus aureus superantigen B (SEB) stimulation for 6 hours was used to imitate T-cell activation.
Results. The combination of S. baicalensis and E. senticosus had a more potent suppressive effect on the release of PGD2, histamine, and IL-5 than S. baicalensis alone. The combination also resulted in a significant inhibition of SEB-induced cytokines comparable or superior to an established topical corticosteroid, fluticasone propionate. Vitamin C increased ciliary beat frequency, but had no anti-inflammatory effects.
Discussion. The combination of S. baicalensis and E. senticosus may be able to significantly block allergic early-and late-phase mediators and substantially suppress the release of proinflammatory, and Th1-, Th2-, and Th17-derived cytokines.
Dengue fever regardless of its serotypes has been the most prevalent arthropod-borne viral diseases among the world population. The development of a dengue vaccine is complicated by the antibody-dependent enhancement effect. Thus, the development of a plant-based antiviral preparation promises a more potential alternative in combating dengue disease.
Present studies investigated the antiviral effects of standardised methanolic extracts of Andrographis paniculata, Citrus limon, Cymbopogon citratus, Momordica charantia, Ocimum sanctum and Pelargonium citrosum on dengue virus serotype 1 (DENV-1).
O. sanctum contained 88.6% of total flavonoids content, an amount that was the highest among all the six plants tested while the least was detected in M. charantia. In this study, the maximum non-toxic dose (MNTD) of the six medicinal plants was determined by testing the methanolic extracts against Vero E6 cells in vitro. Studies also determined that the MNTD of methanolic extract was in the decreasing order of M. charantia >C. limon >P. citrosum, O. sanctum >A. paniculata >C. citratus. Antiviral assay based on cytopathic effects (CPE) denoted by degree of inhibition upon treating DENV1-infected Vero E6 cells with MNTD of six medicinal plants showed that A. paniculata has the most antiviral inhibitory effects followed by M. charantia. These results were further verified with an in vitro inhibition assay using MTT, in which 113.0% and 98.0% of cell viability were recorded as opposed to 44.6% in DENV-1 infected cells. Although methanolic extracts of O. sanctum and C. citratus showed slight inhibition effect based on CPE, a significant inhibition was not reflected in MTT assay. Methanolic extracts of C. limon and P. citrosum did not prevent cytopathic effects or cell death from DENV-1.
The methanol extracts of A. paniculata and M. charantia possess the ability of inhibiting the activity of DENV-1 in in vitro assays. Both of these plants are worth to be further investigated and might be advantageous as an alternative for dengue treatment.
In vitro antiviral activities of three flavonoids; fisetin, naringenin and rutin against DENV-2 (NGC strain) were evaluated. Inhibitory effects of each compound at the different stages of DENV-2 infection were examined using foci forming unit reduction assay (FFURA) and quantitative real-time polymerase chain amplification (qRT-PCR). Fisetin, rutin and naringenin showed cytotoxic effects against Vero cells with 50% cytotoxicity (CC50) values of 247, >1000, and 87 µg/mL, respectively. Fisetin when added to Vero cells after virus adsorption inhibited DENV replication with a half maximal inhibition concentration (IC50) value of 55 µg/mL and selectivity index (SI) of 4.49. The IC50 value of fisetin was 43.12 µg/mL with SI=5.72 when Vero cells were treated for 5 h before virus infection and continuously up to 4 days postinfection. There was no direct virucidal activity or prophylactic activity of fisetin against DENV-2. Rutin and naringenin did not inhibit DENV-2 replication in Vero cells. Naringenin however, exhibited direct virucidal activity against DENV-2 with IC50 = 52.64 µg/mL but the SI was <1. The present study suggests that among the flavonoids examined, only fisetin showed significant in vitro anti dengue virus replication activity.
Dengue is a major mosquito-borne disease currently with no effective antiviral or vaccine available. Effort to find antivirals for it has focused on bioflavonoids, a plant-derived polyphenolic compounds with many potential health benefits. In the present study, antiviral activity of four types of bioflavonoid against dengue virus type -2 (DENV-2) in Vero cell was evaluated. Anti-dengue activity of these compounds was determined at different stages of DENV-2 infection and replication cycle. DENV replication was measured by Foci Forming Unit Reduction Assay (FFURA) and quantitative RT-PCR. Selectivity Index value (SI) was determined as the ratio of cytotoxic concentration 50 (CC50) to inhibitory concentration 50 (IC50) for each compound.
The half maximal inhibitory concentration (IC50) of quercetin against dengue virus was 35.7 μg mL-1 when it was used after virus adsorption to the cells. The IC50 decreased to 28.9 μg mL-1 when the cells were treated continuously for 5 h before virus infection and up to 4 days post-infection. The SI values for quercetin were 7.07 and 8.74 μg mL-1, respectively, the highest compared to all bioflavonoids studied. Naringin only exhibited anti-adsorption effects against DENV-2 with IC50 = 168.2 μg mL-1 and its related SI was 1.3. Daidzein showed a weak anti-dengue activity with IC50 = 142.6 μg mL-1 when the DENV-2 infected cells were treated after virus adsorption. The SI value for this compound was 1.03. Hesperetin did not exhibit any antiviral activity against DENV-2. The findings obtained from Foci Forming Unit Reduction Assay (FFURA) were corroborated by findings of the qRT-PCR assays. Quercetin and daidzein (50 μg mL-1) reduced DENV-2 RNA levels by 67% and 25%, respectively. There was no significant inhibition of DENV-2 RNA levels with naringin and hesperetin.
Results from the study suggest that only quercetin demonstrated significant anti-DENV-2 inhibitory activities. Other bioflavonoids, including daidzein, naringin and hesperetin showed minimal to no significant inhibition of DENV-2 virus replication. These findings, together with those previously reported suggest that select group of bioflavonoids including quercetin and fisetin, exhibited significant inhibitory activities against dengue virus. This group of flavonoids, flavonol, could be investigated further to discover the common mechanisms of inhibition of dengue virus replication.
This study evaluates published clinical trials of Chinese herbal medicine (CHM) for chronic obstructive pulmonary disease (COPD) that employ a health-related quality of life (HRQoL) outcome measure.
Searches were conducted in April 2011 on MEDLINE, Embase, the Cochrane Controlled Trials Register, CINAHL, Scopus, and Chinese databases (CNKI, CQVIP, WANFANG). Randomized controlled trials involving oral administration of CHM formulae or single herb, with or without blinding, compared to placebo, no treatment, routine pharmacotherapy control, or CHM plus routine pharmacotherapy versus routine pharmacotherapy, with a HRQoL questionnaire as an outcome measure were identified. The methodological quality was assessed using the Cochrane risk of bias assessment.
A total of 27 studies involving 1966 patients were identified. St. George Respiratory Questionnaire (SGRQ) or Cai's QoLQ were used in 13 and 14 studies, respectively. Assessment of the Cochrane risk of bias revealed adequate sequence of generation in 10 studies and adequate allocation concealment in 1 study; double blinding was not described adequately in any studies. Seventeen (17) studies addressed incomplete outcome data, and 17 studies were free of selective reporting. The main results of meta-analysis showed improvement of total HRQoL scores (SGRQ and Cai's QoLQ) when CHM was compared to no treatment (-6.07 [-9.21, -2.93] and -0.20 [-32, -0.07], respectively) and for CHM plus routine pharmacotherapy versus routine pharmacotherapy (-5.15 [-7.26, -3.05]) and (-0.25 [-0.37, -0.13]).
While the results of CHM on HRQoL for stable COPD sufferers were promising, they need to be interpreted with caution due to methodological problems, which should be addressed in future trials.
Flavonoids are an interesting group of natural polyphenolic compounds that exhibit extensive bioactivities such as scavenging free radical, antitumor and antiproliferative effects. The anticancer and antiviral effects of these natural products are attributed to their potential biomedical applications. While flavonoids complexation with DNA is known, their bindings to RNA are not fully investigated. This study was designed to examine the interactions of three flavonoids; morin (Mor), apigenin (Api) and naringin (Nar) with yeast RNA in aqueous solution at physiological conditions, using constant RNA concentration (6.25 mM) and various pigment/RNA (phosphate) ratios of 1/120 to 1/1. FTIR, UV–visible spectroscopic methods were used to determine the ligand binding modes, the binding constant and the stability of RNA in flavonoid-RNA complexes in aqueous solution. Spectroscopic evidence showed major binding of flavonoids to RNA with overall binding constants of Kmorin = 9.150 × 103 M−1, Kapigenin = 4.967 × 104 M−1, and Knaringin = 1.144 × 104 M−1. The affinity of flavonoid-RNA binding is in the order of apigenin > naringin > morin. No biopolymer secondary structural changes were observed upon flavonoid interaction and RNA remains in the A-family structure in these pigment complexes.
Human enterovirus 71 infection causes hand, foot and mouth disease in children under 6 years of age and has caused mortalities in large-scale outbreaks in the Asia-Pacific region. No effective vaccine or antiviral drugs currently exist against enterovirus 71 in the clinic. In this study, we investigated the antiviral effect of geraniin on enterovirus 71 both in vitro and in vivo. The results showed that geraniin effectively inhibited virus replication in rhabdomyosarcoma cells with an IC(50) of 10 μg/ml. Moreover, geraniin treatment of mice that were challenged with a lethal dose of enterovirus 71 resulted in a reduction of mortality, relieved clinical symptoms, and inhibited virus replication in muscle tissues. The results suggest that geraniin may be used as a potential drug for anti-enterovirus 71.