Inhibitory effects of extracts from Eucalyptus gunnii on α-synuclein amyloid fibrils

Masatomo So, Misaki Ono, Shigeki Oogai, Minako Kondo, Kaede Yamazaki, Charlotte Nachtegael, Hiroshi Hamajima, Risa Mutoh, Masaki Kato, Hisaya Kawate, Tomoyuki Oki, Yasushi Kawata, Shiho Kumamoto, Noritaka Tokui, Toshiki Takei, Kuniyoshi Shimizu, Akio Inoue, Naoki Yamamoto, Motoko Unoki, Kenichi Tanabe, Kinichi Nakashima, Hiroyuki Sasaki, Hironobu Hojo, Yasuo Nagata, Isao Suetake

Amyloid fibril formation is associated with various amyloidoses, including neurodegenerative diseases such as Alzheimer's and Parkinson's diseases. Despite the numerous studies on the inhibition of amyloid formation, the prevention and treatment of a majority of amyloid-related disorders are still challenging. In this study, we investigated the effects of various plant extracts on amyloid formation of α-synuclein. We found that the extracts from Eucalyptus gunnii are able to inhibit amyloid formation, and to disaggregate preformed fibrils, in vitro. The extract itself did not lead cell damage. In the extract, miquelianin, which is a glycosylated form of quercetin and has been detected in the plasma and the brain, was identified and assessed to have a moderate inhibitory activity, compared to the effects of ellagic acid and quercetin, which are strong inhibitors for amyloid formation. The properties of miquelianin provide insights into the mechanisms controlling the assembly of α-synuclein in the brain.

Biosci Biotechnol Biochem