Mitochondria-targeted astaxanthin prevents oxidative stress in intestinal crypt epithelial cells by regulating redox balance and mitophagy

Astaxanthin (AXT) with mitochondria-targeted ability is desired for effectively preventing oxidative stress in various intestinal diseases. However, it is challenging to prepare mitochondria-targeted AXT (Mito-AXT) using traditional covalent bond methods due to the fragile structure of AXT and harsh reaction conditions, which result in low production yields and poor biocompatibility. Herein, we proposed a strategy to enhance the mitochondria-targeted efficiency of AXT by combining it with lipophilic cationic compounds through a non-covalent approach. Mito-AXT was synthesized through electrostatic coupling between anionic sulfonate-modified AXT (AXT-SO 3 ) and cationic (3-carboxypropyl) triphenylphosphonium bromide (TPP). The synthetic strategy successfully preserved the inherent DPPH and hydroxyl radical trapping capacity of AXT and achieved the efficient preparation of Mito-AXT with a yield of 86.17%. The accumulation of cationic TPP in mitochondria after the disassembly of Mito-AXT surprisingly facilitated the enrichment of anionic AXT-SO 3 in mitochondria. Notably, Mito-AXT regulated the redox balance, mitochondrial membrane potential, and mitophagy in IEC-6 cells under oxidative stress, thereby preventing apoptosis, compared to TPP-modified AXT molecules formed by covalent bonds. Furthermore, biosecurity analysis confirmed that Mito-AXT exhibited excellent biocompatibility. The results provided a simple, effective, and safe way to enhance the mitochondria-targeted efficiency of AXT through Mito-AXT, thereby effectively regulating the mitochondrial homeostasis in intestinal cells under oxidative stress.