Abstract
Astaxanthin can be derived from various sources, including petrochemical synthesis, natural sourcing from green algae, or microbial fermentation. As one of the strongest antioxidants known by nature, astaxanthin is attracting attention as an active ingredient in cosmetic products designed to protect the skin against oxidative stress. In contrast to widely performed chemical antioxidant activity assays, this study compares synthetic, algal, and corynebacterial astaxanthin in a physiologically relevant test setting: the intracellular antioxidant activity in cultured human skin cells (keratinocytes). The astaxanthin-rich corynebacterial oleoresin demonstrated superior antioxidant properties in the assay with an EC(50) of 2.7 µM, whereas the synthetic and algal-based variants showed no significant effect. Given the potential application of such raw materials, it is therefore tempting to speculate that astaxanthin-containing corynebacterial oleoresins could serve as a natural, superior active ingredient for skin health applications in the future.