Insight into carotenoid structure in a single microalgae cell

Astaxanthin (AXT), a superpotent antioxidant, is a cancer-protective carotenoid occurring in some orange and red fruits, vegetables and leaves, but is also produced by microalgae Haematococcus pluvialis [1,2], yeast, salmon, trout, krill, shrimp etc.

The changes of AXT structure upon thermal stress were investigated for unicellular microalgae Haematococcus pluvialis by means of in situ Raman spectroscopy and rationalized based on DFT computations. Although no visual changes are observed in the Haematococcus cells upon heating from -150°C, the distinct changes in Raman spectra occurs from -100°C systematically up to 150°C. The exponential increase of the Raman shift of the ν C=C band at ca. 1520cm^-1 along with the change of 1190:1160cm^-1 ratio is observed that correlates with changes observed in theoretical spectra of conformers ordered by decreasing energy. It is assumed that AXT molecules, initially in the form of H-aggregates with the TT conformations of the end-rings, interconvert toward more stable gauche forms upon thermal stress.

Figure 1: The molecular structure of astaxanthin

Acknowledgement: This research was supported by the Polish Ministry of Science and High Education (grants no. N204311037 and N204013635). Computational center „Cyfronet“ (Krakow, Poland) is acknowledged for CPU time.

References: 1. Hussein G, Sankawa U, Goto H, Matsumoto K and Watanabe H (2006)J Nat Prod 69: 443–449

2. Higuera-Ciapara I, Félix-Valenzuela L and Goycoolea F M (2006) Crit Rev Food Sci 46: 185–196