The antimicrobial properties of ginseng and ginseng extracts.

Ginseng is commonly used in traditional Chinese medicine as a tonic and an adaptogen to reduce fatigue and boost the immune system. In recent years, ginseng extracts are shown to have both bacteriostatic and bactericidal actions and seem to exert their effects by several mechanisms, including disruption of biofilms, inhibition of quorum-sensing and virulence factors, and altering motility. Also, ginseng extracts are shown to have antifungal properties as demonstrated by their ability to inhibit the growth of several mold and yeast species. Extracts from ginseng root have a strong antiviral activity against the RNA viruses in cell cultures and animal models. In addition to the antimicrobial activities, ginseng extracts are shown to possess immunomodulatory properties involved in the amelioration of infections. The present paper describes the antimicrobial effects of ginseng and its extracts.

Anti-influenza virus activity of Ginkgo biloba leaf extracts.

We examined the influence of Ginkgo biloba leaf extract (EGb) on the infectivity of influenza viruses in Madin-Darby canine kidney (MDCK) cells. Plaque assays demonstrated that multiplication of influenza viruses after adsorption to host cells was not affected in the agarose overlay containing EGb. However, when the viruses were treated with EGb before exposure to cells, their infectivity was markedly reduced. In contrast, the inhibitory effect was not observed when MDCK cells were treated with EGb before infection with influenza viruses. Hemagglutination inhibition assays revealed that EGb interferes with the interaction between influenza viruses and erythrocytes. The inhibitory effect of EGb was observed against influenza A (H1N1 and H3N2) and influenza B viruses. These results suggest that EGb contains an anti-influenza virus substance(s) that directly affects influenza virus particles and disrupts the function of hemagglutinin in adsorption to host cells. In addition to the finding of the anti-influenza virus activity of EGb, our results demonstrated interesting and important insights into the screening system for anti-influenza virus activity. In general, the plaque assay using drug-containing agarose overlays is one of the most reliable methods for detection of antiviral activity. However, our results showed that EGb had no effects either on the number of plaques or on their sizes in the plaque assay. These findings suggest the existence of inhibitory activities against the influenza virus that were overlooked in past studies.

Attenuation of influenza virus infectivity with herbal-marine compound (HESA-A): an in vitro study in MDCK cells.

BACKGROUND: The influenza virus is still one of the most important respiratory risks affecting humans which require effective treatments. In this case, traditional medications are of interest. HESA-A is an active natural biological compound from herbal-marine origin. Previous studies have reported that the therapeutic properties of HESA-A are able to treat psoriasis vulgaris and cancers. However, no antiviral properties have been reported. METHODS: This study was designed to investigate the potential antiviral properties of HESA-A and its effects in modulating TNF-α and IL-6 cytokine levels. HESA-A was prepared in normal saline as a stock solution (0.8 mg/ml, pH = 7.4). Percentages of cell survival when exposed to different concentrations of HESA-A at different time intervals was determined by MTT assay. To study the potential antiviral activity of HESA-A, Madin-Darby Canine Kidney (MDCK) cells were treated with the effective concentration (EC50) of HESA-A (0.025 mg/ml) and 100 TCID50/0.1 ml of virus sample under different types of exposure. RESULTS: Based on the MTT method and hemagglutination assay (HA), HESA-A is capable of improving cell viability to 31% and decreasing HA titre to almost 99% in co-penetration exposures. In addition, based on quantitative real-time PCR (qRT-PCR) and enzyme-linked immunosorbent assay (ELISA), it was found that HESA-A causes decrements in TNF-α and IL-6 cytokine expressions, which was significant for TNF-α (p ≤ 0.05) but not for IL-6. CONCLUSION: In conclusion, HESA-A was effective against influenza infection through suppressing cytokine expression.

Synthesis and biological evaluation of pyrimidine nucleoside monophosphate prodrugs targeted against influenza virus.

Uridine-based nucleoside analogues have often been found to have relatively poor antiviral activity. Enzymatic assays, evaluating inhibition of influenza virus RNA polymerase, revealed that some uridine triphosphate derivatives displayed inhibitory activity on UTP incorporation into viral RNA. Here we report the synthesis, antiviral activity and enzymatic evaluation of novel ProTides designed to deliver the activated (monophosphorylated) uridine analogues inside the influenza virus-infected cells. After evaluation of the activation profile we identified two ProTides with moderate antiviral activity in MDCK cells (23a, EC(99)=49 ± 38 µM and 23b, EC(99)≥81 µM) while the corresponding nucleoside analogue (2'-fluoro-2'-deoxyuridine) was inactive. Thus, at least in these cases the poor antiviral activity of the uridine analogues may be ascribed to poor phosphorylation.

Inhibitory activity of a standardized elderberry liquid extract against clinically-relevant human respiratory bacterial pathogens and influenza A and B viruses.

BACKGROUND: Black elderberries (Sambucus nigra L.) are well known as supportive agents against common cold and influenza. It is further known that bacterial super-infection during an influenza virus (IV) infection can lead to severe pneumonia. We have analyzed a standardized elderberry extract (Rubini, BerryPharma AG) for its antimicrobial and antiviral activity using the microtitre broth micro-dilution assay against three Gram-positive bacteria and one Gram-negative bacteria responsible for infections of the upper respiratory tract, as well as cell culture experiments for two different strains of influenza virus. METHODS: The antimicrobial activity of the elderberry extract was determined by bacterial growth experiments in liquid cultures using the extract at concentrations of 5%, 10%, 15% and 20%. The inhibitory effects were determined by plating the bacteria on agar plates. In addition, the inhibitory potential of the extract on the propagation of human pathogenic H5N1-type influenza A virus isolated from a patient and an influenza B virus strain was investigated using MTT and focus assays. RESULTS: For the first time, it was shown that a standardized elderberry liquid extract possesses antimicrobial activity against both Gram-positive bacteria of Streptococcus pyogenes and group C and G Streptococci, and the Gram-negative bacterium Branhamella catarrhalis in liquid cultures. The liquid extract also displays an inhibitory effect on the propagation of human pathogenic influenza viruses. CONCLUSION: Rubini elderberry liquid extract is active against human pathogenic bacteria as well as influenza viruses. The activities shown suggest that additional and alternative approaches to combat infections might be provided by this natural product.

Anti-influenza virus principles from Muehlenbeckia hastulata.

Extracts of Chilean medicinal plants were evaluated in vitro for their activities against influenza virus proliferation in MDCK cells. The most potent extract obtained was from Muehlenbeckia hastulata (Polygonaceae), known as Quilo in Chile, from which three active principles were isolated and identified as pheophorbide a (1), hypericin (2) and protohypericin (3). Minimum inhibitory concentration (MIC) values of 42 ng/ml for compound 1, 2.1 ng/ml for compound 2 and 1.5 ng/ml for the authentic hypericin were determined by using an endpoint assay which comprises pre-incubation of serially diluted specimens with a given amount of the influenza virus, incubation of the pre-incubated virus/specimen with MDCK cells and determination of the hemagglutination (HA) titer of the culture supernatant. Compound 3 was easily converted to 2 on exposure to visible light and, in due course, showed an anti-influenza virus activity (3.1 ng/ml) similar to 2. Although compounds 1-3 were previously isolated from other plants, this is the first report of their isolation from M. hastulata. The high content of 1 (0.06% dry weight of whole plant) is noteworthy. In addition, this is the first report on the isolation of compounds 2 and 3 from a plant other than the genus Hypericum.

Anti-influenza virus activity of Myrica rubra leaf ethanol extract evaluated using Madino-Darby canine kidney (MDCK) cells.

Myrica rubra leaf ethanol extract was added to culture medium of Madino-Darby canine kidney (MDCK) cells inoculated with influenza virus, and the inhibition of influenza virus replication was measured. Myrica rubra leaf ethanol extract showed anti-influenza virus activity irrespective of the hemagglutinin antigen type in the influenza virus type A (H1N1), its subtype (H3N2), and type B.

Structure-based identification of an inducer of the low-pH conformational change in the influenza virus hemagglutinin: irreversible inhibition of infectivity.

Past efforts to employ a structure-based approach to design an inhibitor of the fusion-inducing conformational change in the influenza virus hemagglutinin (HA) yielded a family of small benzoquinones and hydroquinones. The most potent of these, tert-butyl hydroquinone (TBHQ), inhibits both the conformational change in HA from strain X:31 influenza virus and viral infectivity in tissue culture cells with 50% inhibitory concentrations in the micromolar range (D. L. Bodian, R. B. Yamasaki, R. L. Buswell, J. F. Stearns, J. M. White, and I. D. Kuntz, Biochemistry 32:2967-2978, 1993). A new structure-based inhibitor design search was begun which involved (i) the recently refined crystal structure (2.1-A resolution) of the HA ectodomain, (ii) new insights into the conformational change, and (iii) improvements in the molecular docking program, DOCK. As a result, we identified new inhibitors of HA-mediated membrane fusion. Like TBHQ, most of these molecules inhibit the conformational change. One of the new compounds, however, facilitates rather than inhibits the HA conformational change. Nonetheless, the facilitator, diiodofluorescein, inhibits HA-mediated membrane fusion and, irreversibly, infectivity. We further characterized the effects of inhibitors from both searches on the conformational change and membrane fusion activity of HA as well as on viral infectivity. We also isolated and characterized several mutants resistant to each class of inhibitor. The implications of our results for HA-mediated membrane fusion, anti-influenza virus therapy, and structure-based inhibitor design are discussed.