Characterisation of esterified secondary carotenoids and of their isomers in green algae: a HPLC approach
Remias, Daniel Lütz
Under certain environmental conditions, green algae can produce a variety of secondary, non-photosynthetic carotenoids which are predominantly esterified with fatty acids. Our HPLC method is designed to characterise such carotenoid ester patterns without the need of saponification, what may cause artefacts or losses. The individual chromatogram of a species can help to typify a green alga on a chemotaxonomical level. A demonstration of the performance is given with two species whose cyst stages are known for a large production of secondary carotenoids, Chlamydomonas nivalis and Haematococcus pluvialis. The separation of carotenoid isomers is shown with the example of astaxanthin. Both algae accumulate, besides the standard type all-trans astaxanthin, also significant amounts of a cis-isomer (13Z-astaxanthin). The latter has an additional spectral absorption in the near UV-region (about 375 nm) and thus may play a role in avoidance of UV-irradiance stress which frequently occurs in the natural habitats of these algae. A technique to ensure an optimum-yield, artefact-free opening of algal cysts is also presented.