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Title: Inhibition of HIV-1 infection by aqueous extracts of Prunella vulgaris L

Author
item Oh, Choonsheok - University Of Iowa
item Price, Jason - University Of Iowa
item Brindley, Melinda - University Of Iowa
item Widrlechner, Mark
item Qu, Luping
item Mccoy, Joe-ann - Bent Creek Institute
item Murphy, Patricia - Iowa State University
item Hauck, Cathy - Iowa State University
item Maury, Wendy - University Of Iowa

Submitted to: Virology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/29/2011
Publication Date: 5/18/2011
Citation: Oh, C., Price, J., Brindley, M., Widrlechner, M.P., Qu, L., Mccoy, J., Murphy, P., Hauck, C., Maury, W. 2011. Inhibition of HIV-1 infection by aqueous extracts of Prunella vulgaris L. Virology Journal. 8:118.

Interpretive Summary: Many members of the mint family are used as medicinal plants. Several species have antiviral activity, including lemon balm, peppermint, hyssop, basil, sage and self-heal. Self-heal is known to inhibit equine infectious anemia virus (EIAV), and we wanted to determine if it was also effective against a related virus, HIV-1, the causal agent of AIDS. So we tested water and ethanol extracts of self-heal against HIV-1 infection. Water extracts displayed more antiviral activity than did ethanol extracts, with strong activity against HIV-1 at very low concentrations and little toxicity to human cells at levels 100-times higher. Water extracts were 40 times more potent against HIV-1 infection than against EIAV. Experiments testing different times of extract addition showed that water extracts worked best when added during the first 5 hours after initiation of HIV-1 infection, suggesting that they targeted viral entry. We then showed that extracts prevented viral particles from binding to the cell surface. But levels needed to inhibit HIV binding were much greater than those needed to inhibit infection. In contrast, water extracts inhibited the virus after binding at levels resembling those that blocked infection, indicating that they interfered with one or more of these steps in the virus's life cycle. Our results show that water extracts of self-heal limited HIV-1 infection, mostly by inhibiting the viral life cycle shortly after the virus binds to human cells. This suggests that self-heal extracts (or the most active purified components from those extracts) would be promising microbicides and/or antivirals against HIV-1. This information is valuable to medical researchers developing AIDS therapies and to those studying the bioactivity of medicinal plants.

Technical Abstract: The mint family produces many metabolites with medicinal properties. Several species are reported to have antiviral activity, including lemon balm, peppermint, hyssop, basil, sage and self-heal. To further characterize the anti-lentiviral activity of self-heal (Prunella vulgaris), we tested water and ethanol extracts against HIV-1 infection. Aqueous extracts displayed more antiviral activity than did ethanol extracts, with potent antiviral activity against HIV-1 at sub-microgram/mL concentrations and little to no cytotoxicity at concentrations >100 times higher. Aqueous extracts were ~40 times more potent against HIV-1 infectivity than against equine infectious anemia virus. Time-of-addition studies showed that aqueous extracts were effective when added during the first 5 hours after initiation of infection, suggesting that they were targeting entry events. We then demonstrated that extracts prevented viral particles from binding to the surface of permissive cells. But extract concentrations required to inhibit HIV binding were significantly higher than those needed to inhibit infectivity. In contrast, aqueous extracts inhibited post-binding events at concentrations near those blocking infection, indicating that they interfered with one or more of these steps of the HIV-1 life cycle. As extracts inhibited both X4 and R5 viral strains, it's unlikely that they interfere with specific gp120-co-receptor interactions. Our findings indicate that aqueous extracts inhibited HIV-1 infectivity, primarily by inhibiting early, post-virion binding events. The ability of these extracts to inhibit early events in the life cycle suggests that they (or the purified constituents responsible for antiviral activity) are promising microbicides and/or antivirals against HIV-1.