Influenza is a serious public health concern worldwide, as it causes significant morbidity and mortality. The emergence of drug-resistant viral strains requires new approaches for the treatment of influenza. In this study, Rubus coreanus seed (RCS) that is left over from the production of wine or juice was found to show antiviral activities against influenza type A and B viruses. Using the time-of-addition plaque assay, viral replication was almost completely abolished by simultaneous treatment with the RCS fraction of less than a 1-kDa molecular weight (RCSF1). One of the polyphenols derived from RCSF1, gallic acid (GA), identified by liquid chromatography-tandem mass spectrometry, showed inhibitory effects against both influenza type A and B viruses, albeit at relatively high concentrations. RCSF1 was bound to hemagglutinin protein, inhibited hemagglutination significantly and disrupted viral particles, whereas GA was found to only disrupt the viral particles by using transmission electron microscopy. In BALB/c mice infected with influenza virus, oral administration of RCSF1 significantly improved the survival rate and reduced the viral titers in the lungs. Our results demonstrate that RCSF1 and GA show potent and broad antiviral activity against influenza A and B type viruses and are promising sources of agents that target virus particles.

Helicobacter pylori specifically adheres to host cells, mainly based on carbohydrate-mediated cell-cell interactions. Previously, we investigated the anti-adhesive effect of polysaccharide fractions from Artemisia capillaris and Panax ginseng, using hemagglutination and enzyme-linked glycosorbent assays. In the present study, each active polysaccharide fraction was further purified, resulting in a single peak (fraction F2) using gel filtration FPLC, in which no protein content was detectable. Using scanning electron microscopy, we examined the inhibitory effects of these polysaccharides on the attachment of H. pylori to the human gastric adenocarcinoma epithelial cell line. The bacterial attachment to the cell line was inhibited by these polysaccharides in the range of the concentrations studied (0.2 - 2.8 mg/mL), showing their minimum inhibitory concentration at as low as 0.2 mg/mL. The bacterial binding was inhibited more effectively by P. ginseng polysaccharides, than by those from A. capillaris. The purified polysaccharides contain similar sugar compositions and have high amounts of uronic acids. Our results suggest that acidic carbohydrates may play an important role in the inhibitory activity on H. pylori adhesion to host cells and that our established purification protocol can be applied to obtain active acidic polysaccharides from plant sources.

Human noroviruses (HuNoVs) are the most frequent cause of foodborne viral gastroenteritis, causing approximately 90% of non-bacterial epidemic outbreaks around the world. Rubus coreanus is a species of black raspberry, rich in polyphenols, and known to exert anti-inflammatory, antibacterial, and antiviral activities. In the present study, the antiviral effects of R . coreanus juice (black raspberry [BRB] juice) on foodborne viral surrogates, murine norovirus-1 (MNV-1) and feline calicivirus-F9 (FCV-F9), were compared with those of cranberry juice, grape juice, and orange juice by plaque assays. Among the four juices tested, BRB juice was the most effective in reducing plaques formation of these viruses. Time-of-addition experiments were designed to determine the mechanism of action of BRB juice on MNV-1 and FCV-F9. The maximal antiviral effect of BRB juice against MNV-1 was observed when it was added to RAW 264.7 cells (mouse leukemic monocyte macrophage cell line) simultaneously with the virus. Pre-treatment of either Crandell Reese Feline Kidney cells or FCV-F9 with BRB juice exhibited significant antiviral activity. The inhibition of viral infection by BRB juice on MNV-1 and FCV-F9 probably occurs at the internalization of virions into the cell or the attachment of the viral surface protein to the cellular receptor. The polyphenol components in BRB (i.e., gallic acid and quercetin), however, did not show any activity against these viruses. Our data provide great promise for the utilization of BRB in the prevention of foodborne viral outbreaks.