Synthesis, characterization, and direct aqueous superoxide anion scavenging of a highly water-dispersible astaxanthin-amino acid conjugate

Henry L. Jackson, Arturo J. Cardounel, Jay L. Zweier, Samuel F. Lockwood

Research output: Contribution to journalArticlepeer-review

46 Scopus citations


The aqueous solubility and/or dispersibility of synthetic carotenoid analogs can be improved by varying the chemical structure(s) of the esterified moieties. In the current study, a highly water-dispersible astaxanthin (3,3′-dihydroxy-β,β-carotene-4,4′-dione) derivative was synthesized by esterification to the amino acid L-lysine, and subsequently converted to the tetrahydrochloride salt. Deep violet, evenly colored aqueous suspensions were obtained with addition of the novel derivative to USP purified water up to a maximum of 181.6mg/mL. These aqueous suspensions were obtained without the addition of heat, detergents, co-solvents, or other additives. At higher concentrations (above 181.6mg/mL), the dispersion became turbid and viscous. There was no saturation point up to 181.6mg/mL. The direct superoxide scavenging ability of the tetrahydrochloride dilysine astaxanthin salt was also evaluated by electron paramagnetic resonance (EPR) spectroscopy in a well-characterized in vitro isolated human neutrophil assay. The novel derivative was an extremely potent (micromolar concentration) aqueous-phase scavenger, with near-complete suppression of the superoxide anion signal (as detected by spin-trap adducts of DEPMPO) achieved at 100μM. To the authors' knowledge, this novel carotenoid derivative exhibits the greatest aqueous dispersibility yet described for a natural and/or synthetic C40 carotenoid, and as such, will find utility in those applications for which aqueous-phase singlet oxygen quenching and direct radical scavenging are required.

Original languageEnglish (US)
Pages (from-to)3985-3991
Number of pages7
JournalBioorganic and Medicinal Chemistry Letters
Issue number15
StatePublished - Aug 2 2004
Externally publishedYes


  • Aqueous dispersibility
  • Astaxanthin
  • Carotenoid derivatives
  • Carotenoids
  • Electron paramagnetic resonance
  • EPR
  • Spin traps
  • Superoxide anion
  • Tetrahydrochloride dilysine astaxanthin salt

ASJC Scopus subject areas

  • Biochemistry
  • Molecular Biology
  • Organic Chemistry
  • Drug Discovery
  • Pharmaceutical Science


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