Stability, structure, and antioxidant activity of astaxanthin crystal from Haematococcus pluvialis

Crystallized anthaxanthin was prepared through the cleaning crystallization method and the stabilities during thermal, lighting, and pH treatment, and antioxidant activities in vitro were evaluated. The structural characterizations of astaxanthin crystal were verified by H-1, C-13 NMR, and XRD analysis. The stability data showed that the astaxanthin crystal was more sensitive to heat, light, and pH compared to oleoresin. The sucrose had no outstanding influence on the astaxanthin crystal, while the stability of astaxanthin oleoresin slightly increased with the increase of sugar concentration. The XRD and nuclear magnetic resonance spectra elucidated that the astaxanthin crystal was all trans structure. The astaxanthin crystal showed the dominant 1,1 '-diphenyl-2-picrylhydrazyl (IC50 18.65 mu mol L-1), 2,2 '-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt(+)(21.1 mu mol L-1), center dot OH (IC50 49.46 mu mol L-1) and ferric reducing antioxidant power (IC50 81.60 mu mol L-1) activities. The investigated results would be helpful for improving the development of astaxanthin crystal in food products.