Nutraceutical potential of Terminalia arjuna bark powder in enhancing enzymatic antioxidant defenses and disease resistance in aquaculture: implications for sustainable food safety and quality

Abstract

The indiscriminate use of prophylactic antibiotics in aquaculture poses serious threats to food safety, environmental health, and antimicrobial resistance, necessitating sustainable plant-based alternatives. This study evaluated the nutraceutical potential of Terminalia arjuna bark powder (TABP) as a dietary immunostimulant in Labeo rohita . Bark, leaf, and fruit materials were extracted using seven solvents of increasing polarity and screened for phytochemicals and in vitro antioxidant capacity via TPC, flavonoid, DPPH, ABTS, FRAP, and NO-scavenging assays. Based on superior bioactivity, TABP was incorporated into four iso-nitrogenous (30.36% crude protein) and iso-caloric diets at 0% (control), 0.1%, 1.0%, and 1.5%, which were fed to juvenile L. rohita ( n = 540) for 90 days in a completely randomized design. Growth performance, serum biochemistry, digestive enzyme activities (amylase, protease, lipase), oxidative stress biomarkers (SOD, catalase, GST), acetylcholinesterase activity, and serum hormones (cortisol, T3, T4) were assessed, followed by a bacterial challenge with Aeromonas hydrophila and Edwardsiella tarda and computation of the Integrated Biomarker Response (IBR) index. Bark extracts demonstrated the highest antioxidant potential across all assays. Dietary TABP significantly improved weight gain, feed efficiency, and digestive enzyme activities, while dose-dependently enhancing enzymatic antioxidant defenses, reducing serum cortisol, and elevating thyroid hormone levels. Post-challenge survival was significantly higher in TABP-supplemented groups, with IBR analysis confirming the strongest integrated biological response at 1.5% inclusion due to stress-related biomarker elevation. And also, it is to mention that recommended inclusion range for sustainable green fish production is 1%–1.23% TABP, aligning our current findings with our prior published evidence. The LC-MS fingerprinting identified catechin, ellagic acid, gallic acid, and epigallocatechin as predominant bioactive constituents. These findings demonstrate that dietary TABP effectively enhances antioxidant capacity, mitigates physiological stress, and improves disease resistance in farmed carp, offering a practical strategy to reduce antibiotic dependence and ensure sustainable aquatic food safety and quality.