engleski

Potential of sage extracts to inhibit Aphanomyces astaci, a causative agent of crayfish plague

Aphanomyces astaci (Oomycetes) is the causative agent of crayfish plague disease. It exerts significant negative impacts on European crayfish species, both in natural settings and in freshwater aquaculture. However, there are no specific anti-oomycete treatments, and current therapies use harmful chemicals such as formaldehyde and malachite green. Research of specific anti-oomycetal treatments using plant extracts present a new trend in aquaculture. Thus, the aim of this study was to test the anti-Aphanomyces activity of the sage leaves extracts. Sage (Salvia officinalis, Lamiaceae) is an aromatic Mediterranean plant rich in bioactive secondary metabolites. Such substances, including polyphenols and simple phenolic acids (i.e. phenolic acids, flavonoids, lignans, stilbenes), have known antimicrobial and antifungal properties, but their activity against freshwater Oomycetes wasn’t tested to date. In this study, the extraction of polyphenols from sage leaves was performed using extracting solvent under magnetic stirring at boiling temperature for 1 h under reflux in a condensation system. In order to investigate the effect of different solvents on the extraction efficiency of polyphenols, ethanol (ethanol-water), acetone (acetone-water), methanol (methanol-water), ethanol-acetone-methanol (ethanol-acetone-methanol-water) and water were used. While all sage extracts exhibited high content of polyphenols, extraction yields nevertheless varied considerably as function of solvent nature. The antiAphanomyces activity of sage extracts was assessed using modified well diffusion method and the results were quantified by measuring the retardation of oomycete radial growth. As will be presented, both organic and hydro-organic solvent extracts of sage leaves exhibited good anti–Aphanomyces activity. In conclusion, this research demonstrates the potential of Mediterranean plant extracts in control/treatment of oomycete-caused diseases in freshwater aquaculture.

Aphanomyces astaci, crayfish plague, polyphenols, sage extracts, Salvia offici

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