|Searching for bioactive compounds from macroalgae with interest in aquaculture as immunostimulants|
Lomotey, I. (2011). Searching for bioactive compounds from macroalgae with interest in aquaculture as immunostimulants. MSc Thesis. University of Algarve, Centre of Marine Science: Faro. 33 pp.
Drugs > Immunomodulators > Immunostimulants
The occurrence of antibiotic resistant bacteria associated with fish diseases is a worldwide problem in aquaculture, which has received considerable attention in the last years and continues to increase due to the absence of a more effective and safer use of antibiotics. Phagocytosis is one of the main mediators of non-specific immunity to pathogens including bacteria, viruses, and parasites in fish. In mammals phagocyte activation is usually associated with an abrupt rise in oxygen consumption, leading to the production of reactive oxygen species, which have potent microbicidal activities and play an important role in the host defence against microorganisms. Macro- and microalgae contain several bioactive compounds. In fish, it has been shown that seaweed-derived chemicals can modify the activity of some components of the immune system and increase protection against disease. In this context, the objectives of this work are to compare the effects of extracts from selected species of Cystoseira on the respiratory burst of Sparus aurata phagocytes, evaluate the antibacterial activities of the extracts on common bacteria pathogens in aquaculture and the antioxidant and metal chelating properties of selected Cystoseira species. Methodologies employed included extraction of natural compounds; isolation of head kidney phagocytes, determination of reactive oxygen species production; evaluation of the extracts toxicity and determination of their antioxidant and antibiotic potential. The stimulatory effects of the extracts varied within species, with the best response for NO production obtained with C. humilis at the concentration of 10 mg/mL. Extracts from C. humilis, C. compressa, C. nodicaulis and C. usneoides had stimulatory effect on superoxide anion (O2-), except for C. tamariscifolia, which did not induce any stimulatory effects on the cells at all concentrations tested. Water extract of C. compressa, C, nodicaulis, C. tamariscifolia and C. usneoides showed antioxidant activity and the highest antioxidant activity was obtained with C. compressa with an IC50 value of 1.42 mg/mL. C compressa was the only species showing chelating activity against copper with an IC50 of 4.64 mg/mL. The species C. tamariscifolia and C. humilis also showed chelating activity against iron and the best result was the one obtained with C. tamariscifolia with an IC50 of 5.45 mg/mL. However, extracts from the five species of Cystoseira did not show antibiotic properties. Results suggest that water soluble extracts of selected Cystoseira species do have interests as immunostimulants and are therefore promising candidates for more detailed in vitro and in vivo studies.