Threats to Murasaki Plant Highlighted in Study: Hanging on a Purple Thread

Purple is a color that has historically been associated with nobility around the world. Japan is no exception. However, Murasaki’s distinctive color is threatened because the native gromwell plant—synonymous with Murasaki—has become an endangered species.

Disease and hybridization with non-native species are partly to blame for Murasaki’s increasing demise.

Now, a research group that includes Kyoto University is leading a movement to raise awareness of Gromwell’s importance in preserving Japanese culture. For example, Murasaki revitalization projects currently underway across Japan are investigating the origins of the seeds and educating the public about the importance of protecting plant homogeneity.

Team paper appeared May 18, 2023 in Plant and cell physiology.

“Many of the nonprofit organizations involved in Gromwell’s revival are also keen to preserve the silk-staining technique by collaborating with botanists,” says lead author Kazufumi Yazaki.

Purple gromwell – or Lithospermum erythrorhizon – contains shikonin derivatives in the root surfaces of the plant, which are red naphthoquinones. This natural dye and medicinal properties are linked to ancient East Asian traditions. Among the set of colors, dark purple was the dark purple color reserved for members at the higher levels of the government and the imperial family, as well as high-ranking Buddhist monks, among the set of colors.

“Purple was also used in a national treasure called Koku-Bun-Ji Kyo, the ten-volume sheets of Buddhist scripture on which the letters are lettered in gold,” says co-author Ryosuke Munakata of the Kyoto Research Institute for Sustainable Human Surroundings in Kyoto.

For medicinal purposes, the roots are prescribed in several remedies as an ointment called shi-en-koh, which is still popular today in the treatment of hemorrhoids, burns, frostbite, and other wounds.

Recovery initiatives, such as the Mitaka Gromwell Restoration Project, focus on ensuring the survival of the original Gromwell, affected by the spread of the cucumber mosaic virus and sudden environmental changes. Hybridization with the European species L officinale is another factor in the uncertain future of this plant.

Official wooden documents excavated from Kyushu—which were found to have been used to transport goods during the Asuka dynasty—were unexpectedly associated with Gromwell, highlighting the crucial administrative role of the purple dye.

“We hope that our research will raise awareness of the importance of Murasaki in the history and culture of Japan,” comments co-author Emi Ito of Ochanomizu University.