Methanolic leaf extract of Annona glabra enhances antioxidant defense and promotes histological recovery of damaged tissues in bacteria-challenged Basa fish (Pangasius bocourti)

Abstract

Intensive culture of Basa fish ( Pangasius bocourti ) in the Mekong Delta is increasingly constrained by bacterial diseases caused by Edwardsiella ictaluri , Aeromonas veronii and Vibrio parahaemolyticus , while extensive antibiotic use raises concerns regarding antimicrobial resistance and residues in aquaculture products. This study provides an integrated assessment of the in vitro antibacterial and antioxidant activities of Annona glabra methanolic leaf extract (AgME) together with its in vivo effects on survival, growth, hematology and spleen histopathology in P. bocourti challenged with all three pathogens over a 20-day feeding trial. AgME inhibited E. ictaluri , A. veronii and V. parahaemolyticus , and exhibited a DPPH free-radical scavenging IC50 of 39.521 µg/mL, indicating biologically relevant antioxidant capacity in addition to its bacteriostatic effects. In experimentally challenged fish, dietary supplementation with 2% AgME reduced cumulative mortality, preserved growth performance, improved hematological recovery and promoted partial restoration of splenic white-pulp architecture compared with untreated infected controls, and generally outperformed doxycycline across the three bacterial challenges. In unchallenged fish, AgME-fed controls also showed higher survival than doxycycline-fed controls under the same husbandry conditions. Together, these findings identify AgME as a promising plant-derived feed-additive candidate that combines broad-spectrum antibacterial activity with antioxidant and host-supportive properties in Basa culture and motivate further work to define its phytochemical profile, refine dose–response relationships and clarify the mechanisms underlying the observed protection.