The copper(II) complex of dantron showed therapeutic effect on bacterial gill-rot disease in tilapia infected by Flavobacterium columnar

Abstract

Dantron (DA), a kind of polyhydric anthraquinone and one of the bio-active ingredient in Rheum officinale was chosen as the ligand to coordinate with the bio-active copper(II) ion to achieve its antibacterial copper(II) complex, DA-Cu. The coordination structure of DA-Cu, both in the crystal state and solution state, was studied by spectroscopy and X-ray single-crystal diffraction analysis. The inhibition zone, MIC (minimum inhibitory concentration) and MBC (minimum bactericidal concentration) values regarding the in vitro antibacterial activity of DA-Cu towards Flavobacterium columnar, which causes the bacterial gill-rot disease on fish, were significant and specific. DA-Cu in vivo acute toxicity on zebrafish and tilapia was evaluated, suggesting that the higher dose of DA-Cu than 0.1 mg/mL might give potential toxicity. The further therapeutic effect of DA-Cu on the tested tilapia challenged by Flavobacterium columnar was also studied, which showed its clear advantage (including the survival rate, relative weight gain rate, and feed conversion ratio) over DA and the positive control, Sanhuang San, at a much lower dosage of 0.025 mg/mL.