Abstract
BACKGROUND: The application of traditional vitamin C (VC) and sodium acetate (SA) in aquafeeds is hampered by significant limitations. VC suffers from poor stability during feed processing and storage, as well as low bioavailability. SA is highly hygroscopic, thermally unstable, and rapidly absorbed, leading to short duration of action. This study aimed to design, synthesize, and evaluate tetraacetyl vitamin C ester (TVCE), a novel VC-acetic acid conjugate, as a superior alternative. RESULTS: TVCE was successfully synthesized via a one-step acetylation reaction with high yield (90%) and purity (> 95%). By optimizing the distillation recovery process, the by-product acetic acid from the reaction was efficiently recovered and recycled. TVCE demonstrated excellent lipophilicity, remarkable thermal stability (withstanding 160 °C), and was efficiently hydrolyzed by pancreatic lipase in simulated intestinal fluid, indicating its function as a prodrug. In zebrafish, TVCE enhanced systemic antioxidant capacity (increasing superoxide dismutase activity and total antioxidant capacity, while decreasing malondialdehyde content) comparably or superiorly to sodium VC-2-phosphate, even at a lower VC-equivalent dosage. In tilapia, dietary inclusion of TVCE, particularly at 0.1%, significantly improved the weight gain rate and survival rate (P < 0.05). Notably, despite providing only 48% of the acetate equivalent found in the physical mixture (sodium VC-2-phosphate + SA) group, TVCE still demonstrated superior performance. Furthermore, TVCE supplementation ameliorated liver and intestinal health, as evidenced by reduced serum alanine aminotransferase, diamine oxidase levels, and liver total triglyceride levels, improved tissue morphology, and an optimized gut microbiota structure characterized by an increased abundance of Bacteroidota. CONCLUSIONS: TVCE is successfully synthesized through a simple, green, and environmentally friendly process, which has successfully achieved the co-production of TVCE and acetic acid. TVCE effectively overcomes the stability and bioavailability issues of conventional VC and SA. In vivo studies demonstrated that TVCE significantly enhances growth performance, antioxidant status, and liver-intestine health in fish. These benefits are attributed to the synergistic effects of VC and acetic acid released upon hydrolysis, which results in a higher biological titer and achieving a "1 + 1 > 2" outcome. These findings establish TVCE as a promising multi-functional nutritional precursor with significant application potential in aquatic feeds.