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Abstract
Astaxanthin when esterified with ferulic acid is better singlet oxygen quencher with k2 = (1.58 ± 0.1) 1010 L mol− 1s− 1 in ethanol at 25°C compared with astaxanthin with k2 = (1.12 ± 0.01) 109 L mol− 1s− 1. The ferulate moiety in the astaxanthin diester is a better radical scavenger than free ferulic acid as seen from the rate constant of scavenging of 1-hydroxyethyl radicals in ethanol at 25°C with a second-order rate constant of (1.68 ± 0.1) 108 L mol− 1s− 1 compared with (1.60 ± 0.03) 107 L mol− 1s− 1 for the astaxanthin:ferulic acid mixture, 1:2 equivalents. The mutual enhancement of antioxidant activity for the newly synthetized astaxanthin diferulate becoming a bifunctional antioxidant is rationalized according to a two-dimensional classification plot for electron donation and electron acceptance capability.
Acknowledgement
DRC thanks CNPq for the research fellowship. Prof. Mauricio da Silva Baptista (Chemistry Institute, University of São Paulo) is knowledge for grant the access to the time resolved NIR spectrofluorimeter.
Declaration of interest
The authors report no declarations of interest. The authors alone are responsible for the content and writing of the paper.
This research is part of the bilateral Brazilian/Danish Food Science Research Program “BEAM - Bread and Meat for the Future” supported by FAPESP (Grant No. 2011/51555-7 and 2009/54040) to DRC and by the Danish Research Council for Strategic Research (Grant No. 11-116064) to LHS.