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A laser flash photolysis study of the free radical chemistry of lipoic acid and dihydrolipoic acid

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Abstract

The free radical chemistry of lipoic acid (LA) and dihydrolipoic acid (DHLA) intersect at the point where DHLA loses hydrogen to a good hydrogen abstracting radical, while LA reacts with strongly reducing ketyl radicals capable of donating a hydrogen atom. While aliphatic thiyl radicals have an absorbance at ~ 330 nm, the resulting radical, formally also a thiyl radical has distinct spectroscopic properties with a maximum at 385 nm, suggesting that the two sulphur centres interact strongly with each other as part of the chromophore. The reactions that form these radicals were studied by laser flash photolysis that revealed DHLA as an excellent hydrogen donor, while LA is an excellent hydrogen acceptor. The results support earlier evidence that the real antioxidant is DHLA, while LA is not; yet, the reported facile interconversion of the two molecules suggests that LA may be a better supplement, given its shelf stability, compared with a far more difficult-to-handle DHLA.

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Acknowledgements

Thanks are due to the Natural Sciences and Engineering Research Council of Canada, the Canada Foundation for Innovation, the Canada Research Chairs Program for funding this research.

Funding

Natural Sciences and Engineering Research Council of Canada, Grand number: Discovery, Canada Research Chairs, Grand number: CRC1, Canada Foundation for Innovation, Grand number: EF.

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Authors and Affiliations

  1. Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON, K1N 6N5, Canada

    Saba Didarataee, Neeraj Joshi & Juan C. Scaiano

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  1. Saba Didarataee
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  3. Juan C. Scaiano
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Correspondence to Juan C. Scaiano.

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Didarataee, S., Joshi, N. & Scaiano, J.C. A laser flash photolysis study of the free radical chemistry of lipoic acid and dihydrolipoic acid. Photochem Photobiol Sci 22, 2579–2585 (2023). https://doi.org/10.1007/s43630-023-00473-7

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