Protective Properties of Astaxanthin and its Esters Isolated from the Haematococcus pluvialis Alga during the Photodegradation of Chlorophyll a

Abstract

The effect of the natural carotenoid astaxanthin (AST) and its esters as inhibitors of chlorophyll (Chl) a photodegradation in the Haematococcus pluvialis unicellular alga has been studied. It was shown that the presence of AST or its esters in low concentrations ((0.67 μM)) suppressed by 15-17% the Chl a destruction as a result of irradiation of a Chl a solution in acetone with white light (250 μmol photons∙m-2∙s-1 for 2 h 20 min). When Chl a solutions were irradiated with blue light (500 μmol∙photons∙m-2∙s-1 for 5 h) in the presence of AST or its esters at high concentrations (AST : Chl a = 5 : 1 mol/mol), the Chl a degradation was suppressed by 40-50%. In a highly polar medium (methanol), the rate of Chl a photodegradation was much higher than in an apolar medium (hexane : acetone = 94 : 6). Esterified AST forms are better protectors of Chl a than unsubstituted AST, which is consistent with the general idea of the predominance of AST esters in the microalga H. pluvialis cells in vivo. The results indicate a possible protective role of AST against Chl a photooxidation in H. pluvialis cells. astaxanthin, chlorophyll, singlet oxygen, photodegradation, Haematococcus pluvialis This work was supported by the Belarusian Republican Foundation for Basic Research (project no. B19РМ-010) and Russian Foundation for Basic Research (project no. 19-54-04003).