Traditional Japanese dye shows skin-protective effects

Professor Toshio Morikawa and Professor Koji Kakutani of the Pharmaceutical Research and Technology Institute, Kindai University as well as Doctoral Student Ryuya Takada (second year) in the Department of Pharmacy at the Graduate School of Pharmacy, in a joint study with the Japanese Madder Regeneration Organization, clarified that red pigment components contained in Rubia argyi (Japanese Akane), a traditional Japanese plant dye material, may suppress skin aging and inflammatory responses by inhibiting enzymes that break down collagen and hyaluronic acid. Application to functional materials that lead to skin condition improvement effects is expected in the future. The study was published online in Natural Products: Chemistry, Pharmacology and Nutrition.

Although R. argyi has been used in Japan as a red (scarlet) dye since ancient times, its commercial production ceased due to the alternative use of introduced species (Rubia tinctorum and Rubia cordifolia) and synthetic dyes. The research group at the Pharmaceutical Research and Technology Institute, Kindai University, has been conducting research on the conservation and cultivation of the plant since around 2003. They published research results in 2024 regarding propagation technology via tissue culture of R. argyi and molecular phylogenetic analysis via DNA authentication in prior research with the Japanese Madder Regeneration Organization. The research group has been energetically advancing efforts toward its revival as an agricultural product.

In addition, plants belonging to the family Rubiaceae contain diverse components and have been used for the treatment of diseases such as arthritis, skin disorders, cardiovascular diseases, and liver disorders. The research group had also previously identified components with anti-inflammatory and anti-allergic effects from Chinese Rubiaceae plants, but the effects brought about by the components contained in R. argyi remained unclear.

The group clarified that R. argyi extract and its red pigment components, purpurin and munjistin, exhibit inhibitory activity against collagenase and hyaluronidase. First, analyzing the activity of an 80% aqueous acetone extract of the plant revealed collagenase inhibitory activity and hyaluronidase inhibitory activity. Investigating the contained components using activity as an indicator led to the isolation and identification of eight anthraquinone compounds, among which purpurin was identified as a collagenase inhibitory component. On the other hand, munjistin was identified as a hyaluronidase inhibitory component. Furthermore, the activity intensity of these components was revealed to be stronger than that of alizarin, a red pigment contained in introduced species such as Rubia tinctorum and Rubia cordifolia.

These results suggest that R. argyi extract and its red pigment components, purpurin and munjistin, suppress skin aging and inflammatory responses by inhibiting enzymes that degrade collagen and hyaluronic acid in the extracellular matrix, offering skin-friendly effects.

Morikawa stated: "In this study, we clarified that the red pigment components 'purpurin' and 'munjistin' contained in Rubia argyi inhibit enzymes involved in the degradation of collagen and hyaluronic acid. This study identified components that may bring skin-friendly effects from R. argyi, which has a long history of being used in botanical dyeing since ancient times in Japan. Moving forward, we would like to pursue research aiming for applications to functional dye materials and the development of functional pigments useful for improving skin problems."

Kakutani stated: "In advancing the propagation and promotion activities of R. argyi, finding new functionality in its major red pigments is a highly significant achievement. This research result demonstrates the possibility of utilizing R. argyi not only as a botanical dye, but also as a functional material or cosmetic raw material. Furthermore, by conducting cultivation and promotion activities together with students from the Kindai University Academic Theater Project 'Japanese Akane Charm Discovery Project', we hope to widely convey the new value of R. argyi to society."

Journal Information
Publication: Natural Products: Chemistry, Pharmacology and Nutrition
Title: Anthraquinones with Collagenase and Hyaluronidase Inhibitory Activities Obtained from Japanese Akane, the Roots of Rubia argyi (H. Lév. & Vaniot) H. Hara