Table 2.
Representative lipophilic cations compounds: chemical features and neurodegenerative-disease fit.
| Compound (TPP+ conjugate) | Cargo class/core chemistry | Primary mitochondrial action | Chemical advantages | Chemical liabilities | Best-fit NDD context (conceptual) | Key translational bottlenecks |
|---|---|---|---|---|---|---|
| MitoQ (Murphy and Smith, 2007; Smith et al., 2012) | Quinone (ubiquinone/ubiquinol cycling) | Redox cycling; lipid peroxidation suppression | Sustained activity via ETC-mediated reduction; strong IMM association | Context-dependent pro-oxidant risk at high accumulation; ΔΨm dependence | AD/PD where ROS and ETC stress are early features | BBB exposure; chronic dosing safety; stage dependence |
| SkQ1 (Jiang et al., 2018; Skulachev et al., 2009) | Plastoquinone derivative | Cardiolipin-associated antioxidant protection | High membrane/lipid targeting; cristae stabilization potential | High lipophilicity may increase nonspecific membrane perturbation | AD/aging-related synaptic mitochondrial fragility; inflammation-linked injury | Long-term safety; distribution control (Zielonka et al., 2017) |
| MitoTEMPO/MitoTEMPOL (Dikalov and Harrison, 2014; Trnka et al., 2008) | Nitroxide radical (SOD mimetic) | Catalytic ROS scavenging; oxidative stress attenuation | Catalytic-like ROS handling; strong fit for dopaminergic oxidative stress | Radical chemistry can have off-target reactivity; PK variability | PD (dopamine/iron-driven ROS burden) | Exposure/retention in brain; dose-limited toxicity |
| MitoVitE (McCormick et al., 2016; Plecitá-Hlavatá et al., 2009; Smith et al., 2003) | α-Tocopherol (lipid antioxidant) | Inhibits lipid peroxidation in membranes | Strong membrane protection; synergy with ROS reduction | Very lipophilic → nonspecific membrane binding; accumulation toxicity risk | AD where lipid peroxidation/cardiolipin damage contributes to synapse loss | Safety window; formulation challenges |
| MitoGSH (Kezic et al., 2016; Liu Y. et al., 2023; Marí et al., 2020) | Glutathione-linked thiol system | Enhances endogenous redox buffering | Aligns with native antioxidant networks; complements catalytic scavengers | Thiol instability/metabolism; limited persistence | Broad NDDs with redox imbalance (AD/PD/ALS) | Bioavailability; stability; sustained efficacy |
| MitoNAC (Cheng et al., 2023; Vilas-Boas et al., 2023) | N-acetylcysteine-linked thiol | Supports GSH synthesis; redox buffering | Simple chemistry; boosts endogenous defense | Similar thiol limitations; dosing may be high | Broad NDDs; potentially ALS where oxidative stress is prominent | BBB penetration; chronic regimen practicality |
| Mito-metformin (Ay et al., 2024; Loan et al., 2024) | Biguanide (metabolic modulator) | Bioenergetics/biogenesis signalling modulation | Repurposing logic; targets metabolic component of NDDs | Risk of mitochondrial over-inhibition if excessive; ΔΨm dependence | PD/aging-related mitochondrial biogenesis deficits | Mechanism complexity; tolerability and dose optimization |
| Rhodamine derivatives (Chauhan et al., 2022; Silachev et al., 2015) | Delocalized aromatic cation dye | Mitochondrial imaging; carrier-assisted antioxidant delivery | Strong membrane permeability; intrinsic fluorescence; tunable chemistry | Phototoxicity risk; limited therapeutic potency alone | AD/PD mitochondrial dysfunction mapping; theranostics | Stability; toxicity; limited drug payload capacity |
| Dequalinium (DQA)/DQAsomes (Mursaleen et al., 2023; Yue Zhang et al., 2021) | Dicationic amphiphile vesicle-forming system | Gene and small-molecule mitochondrial delivery | Self-assembly; macromolecule delivery potential; dual targeting | Complex PK; cellular toxicity at high dose | Emerging for neurodegeneration gene modulation; mitochondrial repair | Scale-up; BBB delivery; safety profile |
| Pyridinium-based cations (Xu et al., 2022; Zielonka et al., 2017) | Aromatic heterocycle cation | ROS sensing; mitochondrial phototherapy; cargo conjugation | Electronic tunability; optical activity; modular synthesis | Potential off-target reactivity; limited clinical experience | AD imaging; anti-aggregation strategies | Translational validation; pharmacokinetics |
| Cyanine dyes (mitochondria-targeted) (Kim J. et al., 2023; Yan et al., 2024) | Extended conjugated cationic dye | Imaging; photothermal/photodynamic modulation | Strong mitochondrial accumulation; BBB penetration; theranostics | Phototoxicity; metabolic instability | Neuroinflammation imaging; mitochondrial dysfunction monitoring | Safety; light-based therapy limitations |
| Berberine derivatives (cationic alkaloids)(Aryal et al., 2022; Yuan et al., 2019) | Planar bioactive cation scaffold | Modulation of mitochondrial metabolism and ROS | Natural product origin; BBB penetration; multi-target activity | Off-target signaling; variable mitochondrial specificity | AD/PD metabolic dysfunction; neuroinflammation | Dose optimization; specificity |