Anti-bacterial mechanism of the P-3 against Aeromonas hydrophila NJ-35 extracted from the Potentilla chinensis Ser. (Wei Ling Cai)

Abstract

Potentilla chinesis Ser. (Wei Ling Cai) was a food for humans and animals in China, as well as a traditional Chinese herb recorded in “ZhonghuaBencao”. Aeromonas hydrophila NJ-35 (NJ-35) was a bacterial pathogen associated with high mortality rate in aquaculture. The purpose of the present work was to isolate and identify the anti-bacterial components against the NJ-35 from the extract of Wei Ling Cai, as well as explore the underlying anti-bacterial mechanism. The peak 3 was the most efficient anti-bacterial component in all collected peaks, and it was identified as (1R,2S,5R,6S)-2,6-bis(3-ethyl-4-hydroxy-5-methoxyphenyl)-3,7-dioxabicyclo[3.3.0]octane (P-3) by high-resolution mass spectrometry (HRMS) and nuclear magnetic resonance (NMR). The minimum inhibition concentration (MIC) of P-3 against NJ-35 was 0.125 mg/mL. The results of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) combined with NanoLC-ESI-MS/MS showed that, in the P-3-treated group, the proteins of phosphoglucomutase (PGM), pyruvate dehydrogenase E1 and alkyl hydroperoxide reductase subunit C (AhpC) were up-regulated, whereas, the porin and 30S ribosomal S3 were down-regulated. In addition, after the treatment of P-3, the activity of alkaline phosphatase (AKP) and the membrane permeability were increased (P < 0.01). The results of scanning electron microscope (SEM) showed that P-3 made the NJ-35 shriveled, sunken, and wrinkled. Taken together, these results suggested the P-3 might be a promising anti-bacterial agent for pharmacological research, and Wei Ling Cai could be a food-borne treatment for the A. hydrophila infection in aquaculture.