Astaxanthin: A comprehensive review of synthesis, biological activities and applications.

The extraction and application of highly bioactive natural compounds have recently become a major focus of research, with astaxanthin attracting particular interest due to its exceptional antioxidant activity and diverse biological functions. Herein, we provide a comprehensive and systematic summary of the latest advances in astaxanthin research. Various synthetic pathways and extraction techniques are critically evaluated, with emphasis on their respective advantages, limitations, and industrial applicability. The physicochemical instability of astaxanthin, including its sensitivity to light, heat, and oxygen, is thoroughly analyzed, and recent strategies to enhance its stability, are discussed. Furthermore, the recent progress in astaxanthin applications across the food industry, cosmetic formulations, biomedical therapies, and animal nutrition is systematically reviewed, highlighting both commercial achievements and remaining technical challenges. By integrating and critically analyzing the existing literature, this review aims to provide valuable insights and a forward-looking perspective to support the expanded industrial utilization of astaxanthin across multiple fields.