mPEG-carboxymethyl astaxanthin monoester: a novel hydrophilic astaxanthin with increased water solubility and bioavailability

Abstract To develop hydrophilic astaxanthin with significantly enhanced water solubility, an optimized one-step synthesis method was developed by heating free astaxanthin (F-Asta) and mPEG-carboxymethyl (mPEG-CM) in dichloromethane (27 °C) with two catalysts, yielding 61.38 ± 2.16% of mPEG-carboxymethyl astaxanthin monoester (mPC-Asta) in 12 h. mPC-Asta showed a characteristic wavelength absorption at 441 nm with high dispersibility (206 mg·mL-1) in water. The particle size of mPC-Asta nanomicelles was in the range of 10–30 nm. Experiments on storage stability indicated best maintenance of mPC-Asta nanomicelles at 4 °C, pH 5, in the dark and in the presence of nitrogen. The AUC0-t of Asta in the serum of mice after gavage of mPC-Asta nanomicelles was 9.05±0.69 h·μg·mL-1, which was significantly higher (four-fold) than that of F-Asta. The results show that mPC-Asta greatly enhances water solubility and bioavailability of astaxanthin.