Berberine and its more biologically available derivative, dihydroberberine, inhibit mitochondrial respiratory complex I: a mechanism for the action of berberine to activate AMP-activated protein kinase and improve insulin action. - Turner N; Li J; Gosby A; To SWC; Cheng Z; Miyoshi H; Taketo MM; Cooney GJ; Kraegen EW; James DE; Hu L; Ye J (Diabetes, 2008)