This study was conducted to isolate and identify the bioactive compounds from the ethanolic extract of Syzygium cumini leaf against Vibrio species through a bioassay-guided fractionation. The ethanol extract was exposed to silica gel chromatography followed by reversed phase HPLC to isolate the most effective fraction against V. parahaemolyticus. Using further UHPLC-orbitrap-ion trap mass spectrometry, five compounds were isolated with broad-spectrum potency against a range of Vibrio species viz. V. parahaemolyticus, V. alginolyticus, V. harveyi, V. vulnificus and V. anguillarum. The IC50 values for the compounds ranged from 8 to 48 µg/mL against the most sensitive species V. vulnificus and 58 to >400 µg/mL against V. alginolyticus. The results of the toxicity tests demonstrated that the compounds were not harmful for shrimp. The study's findings indicate that S. cumini leaf extract may contain bioactive molecules that are able to be substituted for antibiotics to treat vibriosis in shrimp farming.
Keywords: Syzygium cumini; antibiotics; bioassay-guided purification; isolated compounds; toxicity; vibriosis.