Antibacterial properties of extracts of Solidago canadensis and their potential use as dietary supplements in red swamp crayfish (Procambarus clarkii)

Abstract

Canadian goldenrod (Solidago canadensis) is one of the most destructive invasive weeds in Southeastern China. To evaluate its potential application as dietary supplement in red swamp crayfish (Procambarus clarkii), the antibacterial properties of aqueous and ethanol extracts of this plant against three major pathogenic bacteria in crayfish aquaculture were examined. Inhibition zone tests and determination of minimum inhibitory concentration revealed that the extracts had lower antibacterial activity than extracts from two traditional medicinal plants that possess antibacterial properties, garlic (Allium sativum) and cortex phellodendri (Phellodendron chinense). However, they did exhibit greater antibacterial effects than extracts from another widely used medicinal plant, Sophora flavescens, and an aquatic weed, Alternanthera philoxeroides. Aqueous extracts of Canadian goldenrod gave greater inhibition than the ethanol extracts. Crayfish fed a diet with 2% these aqueous extracts exhibited significantly higher enzyme activity of alkaline phosphatase, catalase and phenoloxidase (P < 0.05). Based on the results of this study, we conclude that aqueous extracts of Canadian goldenrod are highly promising for the development of new dietary supplement for use in crayfish aquaculture.