Okayama University discovers the liver injury suppression effects of wild grape juice

The research group of Associate Professor Sakae Arimoto-Kobayashi of the Graduate School of Medicine, Dentistry, and Pharmaceutical Sciences at Okayama University and Professor Ryosuke Mochioka, Director of University Farm of Faculty of Agriculture at Kagawa University examined the functional properties, such as anti-carcinogenic effects, of the juice of the wild grape known as Ryukyu-ganebu, which grows naturally in Nansei Islands, compared to the wild grape, Vitis coignetiae (crimson glory vine), known as "yamabudo" in Japan (from Okayama Prefecture) that had been previously studied. Their results revealed that the juice of Ryukyu-ganebu from Kuchinoshima Island of the Tokara Islands has antimutagenic and antioxidant properties, similar to those of yamabudo, and it has an anti-inflammatory effect on mouse skin.

Many wild grapes grow naturally in Japan, where seven species and eight varieties have been identified to date. During the course of their investigation, the research group identified the wild grape called yamabudo in Kuchinoshima Island to be Ryukyu-ganebu.

Then, they examined the functionality of the juice of Ryukyu-ganebu (from Kuchinoshima Island) compared to that to the yamabudo from Okayama. The juice of Ryukyu-ganebu (from Kuchinoshima Island) showed antimutagenic, antioxidant, and radical-scavenging activities against carcinogens, similar to the juice of yamabudo (from Okayama). It also showed an anti-inflammatory effect on mouse skin.

Moreover, to investigate its novel functionality that had not been found in yamabudo, the research group examined whether the juice of Ryukyu-ganebu had protective activity against liver injury. They found that, while the injection of the liver injury substance CCL4 into mice increased the liver dysfunction index GOT, oral administration of wild grape juice (Ryukyu-ganebu or yamabudo) suppressed the increase in GOT in mice even when CCL4 was administered. The study showed that wild grape juice protected the liver, decreasing the extent of liver injury and preventing hepatocyte death. In mice orally administered wild grape juice, the mechanism of action was suggested to be the reduction in lipid peroxidation in the liver.

Associate Professor Arimoto-Kobayashi said, "Ryukyu-ganebu is widely distributed across the Nansei Islands south of Kuchinoshima Island. However, Ryukyu-ganebu on each island may not necessarily have the same functionality. In the future, we would like to compare the functionalities of Ryukyu-ganebu from islands south of Kuchinoshima Island, such as Okinawa. We would also like to explore the potential preventive effects of Ryukyu-ganebu against lung and skin cancers, which have been observed in yamabudo. We have now clarified the functionality of Ryukyu-ganebu, a naturally-grown product that has been self-consumed, and shown the usefulness of a product of remote islands, which we expect will lead to the promotion of its use in the future."