CHARACTERIZATION OF ANTIOXIDANT AND ANTI-ENZYMATIC ACTIVITIES OF ALGAL EXTRACTS FROM THE PORTUGUESE COAST – POSSIBLE VALUABLE INGREDIENTS FOR FISH DIET SUPPLEMENTATION

Introduction

Macroalgae are natural sources of functional proteins and carbohydrates, carotenoids, phenolic compounds and vitamins. The use of macroalgae in fish diets has improved trends in fish growth, physiology, stress resistance, immune system, and fillet muscle quality.  Nevertheless, very few macroalgae species have been investigated as potential components in finfish diets, reviewed in (Kamunde et al., 2019; Wan et al., 2019). Due to the variable nutritional content of macroalgae, a previous characterization of their properties is essential.

Methods

Here, we performed a characterization of biological activities in seven macroalgae species naturally occurring in the southwest region of the Portuguese coast: the brown algae: Cystoseira sp., Fucus vesiculosus, Sargassum vulgarae; the red algae: Asparagopsis armata, Sphaerococcus coronopifolius, Plocamium cartilagineum and the green algae: Codium vermilara. The algae were collected by diving and were dried in the shadow at room temperature. Ethanolic extracts were prepared (100mg/ml) and further characterized by evaluation of total phenolic content and in-vitro antioxidant activity, by determining superoxide, DPPH and NO scavenging activity. In-vitro evaluation of anti-diabetic, anti-inflammatory and antioxidant capacity was done by measuring inhibitory activities of the extracts on the enzymes: lipoxygenase, acetylcholinesterase, tyrosinase, xanthine oxidase, α-glucosidase and α-amylase.

Results

Brown algae, namely Fucus vesiculosus, and Sargassum vulgarae, demonstrated to have the highest phenolic content (Fig. 1A) and antioxidant capacity (Fig.1B).

Brown algae also revealed an enhanced enzyme inhibitory activity when compared with green and red algae, especially anti-diabetic effects, by inhibiting α-amylase and glucosidase enzymes as shown by the very low IC50 values (Fig 2). Anti-inflammatory activity  by inhibition of lipoxygenase and acetylcholinesterase was prevalent in all extracts although at higher concentrations.

Conclusions

Extracts of seven species of naturally occurring marine macroalgae of in the southwest coast of Portugal were characterized for the first time regarding their antioxidant capacity and anti-enzymatic activity. There was individual variability regarding antioxidant levels but the brown algae Fucus vesiculosus, Sargassum vulgarae and Cystoseira sp., presented the highest levels of phenolic content and antioxidant capacity. Fucus vesiculosus and Sargassum vulgarae showed also good levels of anti-enzymatic activity in all analysis performed especially anti-diabetic activity by inhibiting α-amylase and α-glucosidase. Supplementation of finfish diet with these algae or algae extracts may bring benefits for the aquaculture industry and constitute a valuable functional ingredient in fish feeds.

Acknowledgments

Financial support from the FCT (grant UID/Multi/04326/2020) and European Maritime and Fisheries Fund (EMFF/FEAMP) through the National Operational Program MAR2020 (grant ALGASOLE-16-02-01-FMP-0058).

References

Kamunde, C., Sappal, R., Melegy, T.M., 2019. Brown seaweed (AquaArom) supplementation increases food intake and improves growth,  antioxidant status and resistance to temperature stress in Atlantic salmon, Salmo salar. PLoS One 14, e0219792.

Wan, A.H.L., Davies, S.J., Soler-Vila, A., Fitzgerald, R., Johnson, M.P., 2019. Macroalgae as a sustainable aquafeed ingredient. Rev. Aquac. 11, 458–492.