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Persimmon tannins may weaken coronavirus: west Japan university researchers

A powder made of persimmon tannins is seen at Nara Medical University in Kashihara, Nara Prefecture, on Sept. 15, 2020. (Mainichi/Honsu Kan)

KASHIHARA, Nara -- Tannins from persimmon are effective at weakening the infectivity of new coronavirus samples in saliva, according to the results of tests by a research group at Nara Medical University, in the western Japan city of Kashihara, on Sept. 15.

    Next, the university intends to proceed with clinical trials to prove whether the tannins' preventative ability remains when inside a human mouth, and it is also looking to publicly recruit companies to help develop the findings into a product as soon as possible.

    The group that confirmed the results is headed by Toshihiro Ito, a professor in immunology at the university, and professor Yano Hisakazu, who studies microbial infections. In their tests, they added a high concentration of persimmon tannins to a sample of human saliva with the new coronavirus in it. After 10 minutes, they then compared the sample with another where the tannins had not been introduced, and found that the virus's infectivity had reduced to one-ten thousandth or less of what it was before.

    Speaking at a press conference, professor Ito said that while they have yet to be able to explain the mechanism that weakens the new coronavirus, they currently think the tannins attach to the virus's surface and prevent it from entering cells.

    Professor Toshihiro Ito, right, is seen with professor Yano Hisakazu announcing the test results at a press conference at Nara Medical University in Kashihara, Nara Prefecture, on Sept. 15, 2020. (Mainichi/Honsu Kan)

    The research group did confirm in tests that the effects of the tannins are reduced if they are diluted. The tannins need to be in the mouth for a set amount of time if they are to begin suppressing the virus, and so it is currently envisaged that they could be used in products such as candies or gum.

    Yet despite the development, professor Ito struck a note of caution, saying, "It's absolutely not the case that just having persimmon tannins present in something means they're effective, or that if you eat persimmons you'll be fine." He added, "At the moment we only have results under test conditions, and a clinical trial is required. Next we'll test what is a suitable concentration (of the tannins) and we hope this leads to some kind of product."

    (Japanese original by Honsu Kan, Kashihara Resident Bureau)

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