Bioassay-guided isolation of antibacterial compounds from the leaf extract of Terminalia arjuna against the Vibrio species in shrimp

Abstract

The present research was intended to identify the bioactive molecules from the ethanolic extract of T. arjuna leaf against a diverse array of Vibrio species by means of a bioassay-guided fractionation. The antibacterial efficacy of compounds was assessed by the microdilution technique, while the brine shrimp mortality assay was employed to determine their toxicity. Following an initial screening, the ethanol extract underwent silica gel chromatography, succeeded by reversed phase HPLC, to identify the most potent fraction towards V. parahaemolyticus. Through further UHPLC-orbitrap-ion trap mass spectrometry, three likely compounds were identified, demonstrating broad-spectrum efficiency against several Vibrio species, including V. parahaemolyticus, V. harveyi, V. alginolyticus, V. vulnificus, and V. anguillarum. Among the bacteria, V. vulnificus was the most sensitive species (IC₅₀ ranged from 17 to 25 µg/mL) while V. harveyi was the most resistant species (IC₅₀ > 200 µg/mL) for the compounds. The toxicity test findings indicated that the compounds tested were not detrimental to shrimp. This is one of the most important reports identifying these specific fatty acid derivatives with anti-Vibrio activity in shrimp. The findings of the current study suggest that the leaf extract of T. arjuna may include bioactive compounds that might serve as potential complementary or prophylactic agents for the treatment of pathogenic Vibrio species in shrimp aquaculture.