Use of carrageenan in the screening of natural anti-inflammatory molecules in fish: in vitro effects of Chiliadenus glutinosus extracts

Abstract

Carrageenan, a high molecular weight sulphated polysaccharide, has been used in the screening of anti-inflammatory molecules in mammals. In this sense, Chiliadenus glutinosus (L.) Fourr., an endemic species of plant has been reported in the Spanish popular medicine due to their anti-inflammatory properties in humans. However, their properties have poorly been studied in fish. In this assay, different concentrations (0, 0.001, 0.01, 0.125, 0.25, 0.5 and 1 mg mL-1) of aqueous, ethanolic and methanolic extracts of this plant were elaborated, and the antioxidant, bactericidal (against four marine fish pathogen) and cytotoxic activity, as well as several immunological parameters in head-kidney leucocytes (HKLs) of gilthead seabream (Sparus aurata) were evaluated in a first experiment to determinate the extract with the best properties. Our results showed a dose-dependent antioxidant activity of each plant extract increasing with the concentration, a species- and extract-specific bactericidal activity, as well as a cytotoxic activity against the PLHC1 tumour cell line by the ethanolic and methanolic extracts. However, taking into account the cytotoxic effects of these two extracts on HKLs and the strong immunosuppressive effects on the immunological parameters assayed (peroxidase, respiratory burst activity and phagocytic capacity), a second experiment was developed by using only adjusted doses of the aqueous extract (0, 0.25 and 0.5 mg mL-1), in which immune parameters, cell morphology and inflammatory-related genes were studied in HKLs stimulated with λ-carrageenan. The present results offer a detailed view of the biological effects of C. glutinosus extracts, which could be interesting to the aquaculture sector due to their possible anti-inflammatory effects.