SkQ1
SkQ1. A plastoquinone tethered by a decyl linker to a triphenylphosphonium cation, so membrane potential drives it to accumulate in the inner mitochondrial membrane…
A plastoquinone tethered by a decyl linker to a triphenylphosphonium cation, so membrane potential drives it to accumulate in the inner mitochondrial membrane, where the respiratory chain recycles it to the quinol and it quenches mitochondrial ROS. The accumulation is the whole mechanism and the authors quantify it: PMID:19120014 verbatim, "taking into account distribution coefficient of SkQ1 between lipid and water (about 13,000 : 1)" the "SkQ1 concentration in the inner leaflet of the inner mitochondrial membrane should be 1.3x10(8) times higher than in the extracellular space" — that figure is the paper's own declared calculation from an assumed membrane potential, not a measurement. At micromolar concentrations the same molecule is pro-oxidant and cytotoxic, giving the narrow window its authors contrast with MitoQ. IN HUMANS IT IS AN EYE DROP AND NOTHING ELSE.
THE STORED MASS INCLUDES A COUNTER-ION AND THAT IS DISCLOSED RATHER THAN HIDDEN. PubChem CID 16679091 for `SkQ1` is C36H42BrO2P at 617.6 (re-queried 2026-09-26) — read the formula: one Br and one P, i.e. the BROMIDE SALT of a permanently charged phosphonium cation. The active species is the cation. No separate cation CID was fetched and no cation mass was computed, because that would mean supplying an atomic mass from memory. Nothing in this record does molar arithmetic, so the salt mass corrupts no calculation today; a later author who needs the cation must fetch it (HYGIENE R10). ROUTE CONVENTION: eye drops are recorded as TD here, following `bimatoprost` and `brimonidine`. THE HUMAN TRIAL, verbatim (PMID:26660938, 240 subjects, 10 sites, SkQ1 the active ingredient and the subject): "Visomitin is the first registered (in Russia) drug with a mitochondria-targeted antioxidant (SkQ1) as the active ingredient"; "study drug (Visomitin or placebo) was self-administered three times daily (TID) for 6 weeks, followed by a 6-week follow-up period"; and the result, "a 6-week course of TID topical instillation of Visomitin significantly improved the functional state of the cornea". Regimen only — no strength, so doses stays empty. THE ONE IN-VITRO POTENCY IS NOT STORED AS AN EC50: PMID:19120014 reports for SkQ1 and SkQR1 that "C(1/2) values for inhibition of the H2O2-induced apoptosis in fibroblasts appear to be as low as 1x10(-11) and 8x10(-13) M" — human fibroblasts, in vitro, and "appear to be as low as" is a floor claim, not a fitted EC50. A RAT DOSE UNIT THAT WAS NOT REINTERPRETED: PMID:22117772 prints "dosages from 0.02 up to 20 moles/kg per os", which is almost certainly a typographical error for nmol/kg; it is quoted as printed and not silently corrected, and nothing is stored from it. Rejected as a source: PMID:39178922, where SkQ1 is a comparator to MitoTEMPO and the abstract carries no concentrations.
Sources: PMID:26660938, PMID:19120014, PMID:22117772