Proanthocyanidin-enriched extract from Myrothamnus flabellifolia Welw. exerts antiviral activity against herpes simplex virus type 1 by inhibition of viral adsorption and penetration

Institute of Pharmaceutical Biology and Phytochemistry, University of Muenster, Hittorfstr. 56, D-48149 Muenster, Germany.
Journal of ethnopharmacology (Impact Factor: 3). 03/2011; 134(2):468-74. DOI: 10.1016/j.jep.2010.12.038
Source: PubMed


Extracts from the aerial parts of the South African resurrection plant Myrothamnus flabellifolia Welw. have been used traditionally against infections of the upper respiratory tract and skin diseases. A polyphenol-enriched extract was investigated for potential antiviral effects against herpes simplex virus type 1 (HSV-1) and adenovirus, and the underlying mode of action was to be studied.
Antiviral effects of an acetone-water extract (MF) from Myrothamnus flabellifolia on HSV-1 and adenovirus type 3 were tested in infected Vero cells by plaque reduction assay, MTT test and immunofluorescence. The influence of the extract on the HSV-1 envelope glycoprotein D was shown by Western blot. Organotypic full thickness skin models consisting of multilayer skin equivalents were used for the investigation of MF effects on HSV-1 replication.
MF exhibited strong antiviral activity against HSV-1. The HSV-1-specific inhibitory concentration (IC(50)) was determined as 0.4 μg/mL and the cytotoxic concentration (CC(50)) against Vero cells as 50 μg/mL. A selectivity index (SI) (ratio of CC(50) to IC(50)) of approximately 120 was calculated when MF was added to the virus inoculum for 1h at 37°C prior to infection. The replication of adenovirus 3 was not affected by MF. MF abolished virus entry into the host cell by blocking viral attachment to the cell surface. When added after attachment at a concentration of >6 μg/mL, the extract also inhibited penetration of HSV-1 into the host cell. Polyphenolic compounds from MF directly interacted with viral particles, leading to the oligomerisation of envelope proteins as demonstrated for the essential viral glycoprotein D (gD). Using organotypic full thickness tissue cultures, it was shown that treatment of HSV-1 infected cultures with the MF resulted in reduced viral spread.
A polyphenol-enriched extract from Myrothamnus flabellifolia strongly acts against HSV-1 by blocking viral entry into the cells.

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    • "Not only the daily intake has to be taken into account, but also the content of proanthocyanidins can differ between different extracts, with concern to the herb-extract ratio as well as to the respective solvent used for manufacture. From this point of view it has to be considered that especially the galloylated oligomeric proanthocyanidins can exert cell toxicity (Gescher et al., 2011b). The content of these compounds depends strongly on the details of the manufacturing process. "
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    • "Similarly, the aqueous extract from Rhododendron ferrugineum L., blackberry extract, and proanthocyanidin-enriched extract from Myrothamnus flabellifolia Welw. have been reported to inhibit HSV-1 infection.[838485] Another example is glucoevatromonoside, a cardenolide from Digitalis lanata, which has been suggested to alter cellular electrochemical gradient and block HSV-1 and HSV-2 propagation in cells.[86] "
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