SIRT3 and cholangiocarcinoma: SIRT3 can increase the OCR, indicating increased mitochondrial oxidative phosphorylation, which also induced increases in ROS levels.31 The Honokiol derived from the bark of magnolia trees is a natural biphenolic compound, which is also a SIRT3 activator.32 We found that the relative ROS levels increased significantly in CCA cells treated with Honokiol (Figure 3C).