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Article

Membrane Permeabilities of Ascorbic Acid and Ascorbate

Institute of Biophysics, Johannes Kepler University Linz, Gruberstr. 40, 4020 Linz, Austria
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Biomolecules 2018, 8(3), 73; https://doi.org/10.3390/biom8030073
Received: 31 July 2018 / Revised: 10 August 2018 / Accepted: 13 August 2018 / Published: 17 August 2018
Vitamin C (VC)—a collective term for the different oxidation and protonation forms of ascorbic acid (AscH)—is an essential micronutrient that serves as (i) a potent antioxidant and (ii) a cofactor of a manifold of enzymatic processes. Its role in health is related to redox balance maintenance, which is altered in diseases such as obesity, cancer, neurodegenerative diseases, hypertension, and autoimmune diseases. Despite its importance, VC uptake has been poorly investigated. Available literature values for the passive membrane permeability P of lipid bilayers for AscH scatter by about 10 orders of magnitude. Here, we show by voltage clamp that P of AscH’s anionic form (ascorbate Asc ) is negligible. To cross the membrane, Asc picks up a proton in the membrane vicinity and releases it on the other side of the membrane. This leads to a near-membrane pH drop that was visualized by scanning pH microelectrodes. The AscH concentration dependent pH profiles indicated P   =   1.1   ±   0.1   ×   10 8   cm / s . Thus, AscH’s P is comparable to that of sorbitol and much lower than that of other weak acids like acetic acid or salicylic acid. The observation suggests that the capacity of the passive transcellular transport pathway across the lipid matrix does not suffice to ensure the required VC intake from the gastrointestinal tract. View Full-Text
Keywords: scorbic acid; ascorbate; passive membrane permeability; vitamin C; membrane permeation; weak acid permeation scorbic acid; ascorbate; passive membrane permeability; vitamin C; membrane permeation; weak acid permeation
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MDPI and ACS Style

Hannesschlaeger, C.; Pohl, P. Membrane Permeabilities of Ascorbic Acid and Ascorbate. Biomolecules 2018, 8, 73. https://doi.org/10.3390/biom8030073

AMA Style

Hannesschlaeger C, Pohl P. Membrane Permeabilities of Ascorbic Acid and Ascorbate. Biomolecules. 2018; 8(3):73. https://doi.org/10.3390/biom8030073

Chicago/Turabian Style

Hannesschlaeger, Christof, and Peter Pohl. 2018. "Membrane Permeabilities of Ascorbic Acid and Ascorbate" Biomolecules 8, no. 3: 73. https://doi.org/10.3390/biom8030073

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