MitoQ

The positive charge drives the molecule across the mitochondrial inner membrane, where it concentrates several-hundred-fold relative to ordinary CoQ10 and is recycled by the respiratory chain back to its active ubiquinol form.

The rationale is that excess mitochondrial reactive-oxygen-species (ROS) production drives age-related vascular dysfunction, so a mitochondria-targeted antioxidant should improve function where untargeted antioxidants fail.

The honest read of the human evidence: the single best signal is a small crossover RCT in healthy older adults (Rossman 2018, Hypertension) where 6 weeks of 20 mg/day raised brachial-artery flow-mediated dilation (a surrogate marker of endothelial function) by ~42%.

Smaller pilot RCTs echo acute or short-term vascular improvements in peripheral artery disease and chronic kidney disease, and a phase-II hepatitis-C trial lowered liver aminotransferases (ALT) without changing viral load.

Against that, the largest and most rigorous clinical trial — the PROTECT study in newly-diagnosed Parkinson's disease (128 patients) — found NO effect on disease progression, and a controlled exercise-training study found MitoQ neither helped nor hurt aerobic adaptations.

So the evidence is genuinely mixed: a plausible, well-characterized mechanism and a few positive surrogate-marker RCTs in vascular function, set against null disease-modifying trials and an absence of any hard clinical-outcome or lifespan data in humans.

It is generally well tolerated at studied doses (10-20 mg/day), making it a reasonable, modest-evidence option for those targeting vascular/mitochondrial support rather than a proven therapy.