Evaluation of Croton bonplandianum Leaf Extract for the Control of Bacterial Pathogens and Growth Enhancement in Labeo rohita

Abstract

The rapid expansion of aquaculture has been accompanied by an increased incidence of bacterial diseases, resulting in significant economic losses and reduced fish productivity. The present study investigated the antimicrobial potential of Croton bonplandianum leaf extracts against fish pathogenic bacteria and evaluated their effects on the growth performance of Labeo rohita (Rohu). Pathogenic bacteria were isolated from infected fish samples and identified using morphological and biochemical characterization. Leaves of C. bonplandianum were collected, processed, and extracted using ethanol, acetone, and petroleum ether solvents. Preliminary phytochemical screening revealed the presence of biologically active compounds including alkaloids, flavonoids, tannins, phenols, terpenoids, glycosides, and saponins. The bioactive constituents were further characterized using Thin Layer Chromatography (TLC), UV–Visible spectroscopy, and Fourier Transform Infrared (FTIR) spectroscopy. Antimicrobial activity of the crude extracts was assessed against selected fish pathogens using the agar well diffusion method. The extracts exhibited varying degrees of inhibitory activity against Aeromonas hydrophila, Vibrio campbellii, Vibrio parahaemolyticus, Staphylococcus aureus, Escherichia coli, and other bacterial isolates. A feeding trial was conducted using juvenile Labeo rohita supplemented with different concentrations of C. bonplandianum extract. Fish receiving the supplemented diets demonstrated improved growth performance, feed utilization efficiency, survival rate, and disease resistance compared with the control group. The findings suggest that C. bonplandianum possesses significant antimicrobial and growth-promoting properties and may serve as a sustainable phytotherapeutic alternative to conventional antibiotics in freshwater aquaculture. The study highlights the potential application of medicinal plant-based feed additives for enhancing fish health and promoting environmentally friendly aquaculture practices