Hydrangea leaf extracts may inhibit coronavirus infection: Japan research

KITAKAMI, Iwate — Extracts from hydrangea leaves produced in northeast Japan for “amacha” sweet tea may prevent the bonding of proteins involved in coronavirus infection, a research team here has found.

The team from the Iwate Biotechnology Research Center will now proceed with empirical studies at the cellular level, and eventually confirm whether it is effective in preventing infection in humans.

Coronaviruses’ surfaces are covered with a protruding “spike protein.” It is believed that when this protein binds to a cell surface protein, or receptor, called ACE2, the virus enters and infects the cell.

The Iwate Prefectural Government-established research center has taken extracts from about 500 kinds of plants, including vegetables and wild herbs grown in the prefecture, and stores them in an “extract library” to search for new, useful ingredients.

In an attempt to find components from familiar materials that can inhibit coronavirus infection, the research team mixed 110 kinds of extracts from the library with the two proteins and examined their effects.

As a result, they found a strong reaction to prevent the bonding of the spike protein and ACE2 produced by the compounds phyllodulcin and hydrangenol, which are contained in amacha leaves produced in the prefecture’s village of Kunohe.

According to the researchers, the same effect was observed in both the omicron strain and the original Wuhan strain seen when COVID-19 first broke out. They expect it will be effective at suppressing infection even after the virus mutates.

Akira Yano, general manager of the Department of Bioresource Sciences at the research center, said, “There have been components that attack spike proteins, but there have been few reports of components found in agricultural, forestry and marine products that protect ACE2 like a shield.” The research paper was published in the English-language journal of the Japan Society for Bioscience, Biotechnology, and Agrochemistry.

The village of Kunohe began producing amacha in 1983 after introducing seedlings from Nagano Prefecture as part of revitalization efforts. About 2 metric tons of the leaves were produced in 2022, apparently making the village one of a few major production areas in the country. A municipal government official expressed joy over the discovery, saying, “This is a bright source of hope to secure people to work (in production).”

(Japanese original by Seiichi Yuasa, Morioka Bureau)