Antibacterial effects of chebulagic acid and chebulinic acid isolated from Terminalia chebula against Vibrio parahaemolyticus

Vibrio parahaemolyticus (VP) is a common pathogenic bacterium in marine animals, causing significant economic losses to the aquaculture industry annually. There is an urgent need to develop environmentally friendly, safe and effective antibacterial agents. In this study, two active compounds were isolated and purified from the ethanol extract of Terminalia chebula and identified as chebulagic acid (CAA) and chebulinic acid (CIA) using mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy. The antibacterial results showed that both CAA and CIA exhibited a minimum inhibitory concentration (MIC) of 25 mg/L and a minimum bactericidal concentration (MBC) of 1250 mg/L against VP. The two compounds significantly increased the extracellular levels of AKP, nucleic acids, soluble proteins, and glucose of VP. Scanning electron microscopy results indicated that both active compounds significantly altered the cell morphology of VP, causing cell shrinkage and deformtion. Additionally, the two compounds exhibited potent inhibitory effects against several other pathogenic bacteria, including Pseudomonas aeruginosa, Aeromonas versonii, A. hydrophila, V. alginolyticus, and V. vulnificus. The 96-h half-lethal concentrations of CAA and CIA on Ctenogobius giurinus were 561.653 mg/L and 525.011 mg/L respectively. These values were 22.5 and 21.0 times higher than their MIC against VP, respectively. Therefore, CAA and CIA, derived from T. chebula extract, represent promising candidate molecules for the prevention and control of vibriosis.