Protective role of astaxanthin against u.v.-B irradiation in the green alga Haematococcus pluvialis

Cyst cells of the green alga Haematococcus pluvialis accumulate astaxanthin with maturation of the resting stage. To study the protective role of astaxanthin against u.v. damage, both immature (astaxanthin-poor) and mature (astaxanthin-rich) cyst cells were exposed to u.v.-A or u.v.-B irradiation, and the residual cell viability and astaxanthin levels were determined. u.v.-B decreased both cell viability and astaxanthin level of cyst cells to a greater extent than u.v.-A. Tolerance of mature cyst cells to u.v.-B was 6-fold higher than that of immature cyst cells. These results indicated that astaxanthin in cyst cells functions as a protective agent against u.v.-B irradiation.