The aim of the present study was to isolate and evaluate the antioxidant and antimicrobial activity of astaxanthin pigment. Astaxanthin was isolated from Portunus sanguinolentus (Three Spotted Crab), Callinectes sapidus (Blue Crab) and Paralithodes brevipes (Spiny King Crab) using DMSO: Acetone solvent mixture. The yield of astaxanthin from Portunus sanguinolentus (Three Spotted Crab), Callinectes sapidus (Blue Crab) and Paralithodes brevipes (Spiny King Crab) was found to be 29.01 µg/g, 38.98 µg/g and 18.06 µg/g. The isolated astaxanthin along with the astaxanthin standard was tested for antioxidant activity viz., Total Antioxidant, Reducing Power, Hydrogen Per Oxide Radicals Scavenging Assay, DPPH Free Radicals Scavenging Activity, Ferrous Metal Ion Chelating Activity. Total antioxidant activity of astaxanthin (three crabs) ranged from 50 % to 83 % and the maximum of 58 % was found in astaxanthin standard. The increase in O.D was seen, which reflected a good reducing activity in both the astaxanthin standard and test samples. A good hydrogen peroxide radicals scavenging property was gained which ranged from 33 % to 91 %. Also, it is found that all the samples of astaxanthin possessed a good DPPH activity. A good chelating activity of 40 % to 64 % was gained by both isolated and standard astaxanthin. The antimicrobial activity of isolated and standard astaxanthin was also studied against the isolated organism (E.coli) from spoiled milk and rotten meat. The astaxanthin pigment was found to be more effective against isolated strains at concentration of 50 µg where the zone of inhibition was found to be in the range of 10.05 ± 0.53 mm to 12.11 ± 0.95 mm. The study indicate that the astaxanthin isolated from three crab varieties have promising antioxidant and antimicrobial activities which can be used in food and pharmaceutical industries.
