This says it's new, but it seems old. Published: 24 February 2021
nature.com/articles/s41392-... berberine improves brain dopa/dopamine levels to ameliorate Parkinson’s disease by regulating gut microbiota
Yan Wang, Qian Tong, Shu-Rong Ma, Zhen-Xiong Zhao, Li-Bin Pan, Lin Cong, Pei Han, Ran Peng, Hang Yu, Yuan Lin, Tian-Le Gao, Jia-Wen Shou, Xiao-Yang Li, Xian-Feng Zhang, Zheng-Wei Zhang, Jie Fu, Bao-Ying Wen, Jin-Bo Yu, Xuetao Cao & Jian-Dong Jiang