Abstract
In the search for antibiotic alternatives from safe and effective medicinal plants against fish pathogenic bacteria, we found that a combined extract (CE) of 1:1 (w/w) ratio of Angelica gigas Nakai roots and aerial parts of Artemisia iwayomogi Kitamura showed antibacterial activity against the fish pathogenic bacteria. By antibacterial activity-guided fractionations and isolations, five com-pounds were isolated and identified as decursinol angelate (1), decursin (2), xanthotoxin (3), demethylsuberosin (4), and 2,4-di-hydroxy-6-methoxyacetophenone (5) through spectroscopic analyses, such as nuclear magnetic resonance (NMR) and mass spectrometry (MS). Among the compounds, 1 and 2 showed the highest antibacterial activities against Streptococcus iniae and Vibrio anguillarum, showing minimum inhibitory concentrations (MICs) of 62.5–250 μg/mL. Compounds 3, 4, and 5 were also found to be active, with MICs of 31.25–1,000 μg/mL for those strains. Furthermore, active compounds, 1 and 2 in CE were simul-taneously quantified using high-performance liquid chromatography-tandem MS (HPLC-MS/MS). The average contents of 1 and 2 in CE was 3.68% and 6.14%, respectively. The established method showed reliable linearity (r2 > 0.99), good precision, accuracy, and specificity with intra- and inter-day variations of < 2 % and recoveries of 90.13%–108.57%. These results may be helpful for establishing the chemical profile of CE for its commercialization as an antibiotic alternative in aquaculture.
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