Phycocyanin in Spirulina (currently named Arthrospira platensis) acts as an antioxidant in various biological systems. The antioxidant, anti-inflammatory, antibacterial, and UV protective activity of unadulterated Arthrospira (UAP) and the product of Arthrospira fermented with lactic acid bacteria (FAP) were assayed in skin-care models. The results showed that both UAP and FAP had skin-care activities in all tested models, except for anti-bacterial activity. FAP scavenged DPPH (1,1-diphenyl-2-picrylhydrazyl) radical and nitric oxide, along with anti-inflammatory and UV protective activities, all of which varied with the dose used, but nevertheless, were significantly higher than those found in UAP. The UV protective activity of FAP was also significantly higher (p<0.05) than that of UAP. The total phenol content increased up to 1.73 fold, which suggested the cell walls of the algae were subjected to biodegradation during fermentation, resulting in the release of smaller molecules with higher antioxidant activities. Moreover, the level of phycocyanobilin in FAP was higher than in UAP. These results suggest that Arthrospira fermented by symbiotic lactic acid bacteria released unidentified polyphenols and converted phycocyanin to phycocyanobilin, providing these activities. Therefore, FAP has a greater potential for use in skin-care products than UAP. (C) 0 2011 Elsevier Ltd. All rights reserved.