In Vitro Evaluation of the Antibacterial and Antioxidant Activities of Extracts of Gracilaria gracilis with a View into Its Potential Use as an Additive in Fish Feed

Abstract

Fish in aquaculture systems are subject to several stressors that inhibit the immune response and potentiate the development of disease and increased mortality. The inclusion of additives in the fish diet, namely seaweeds or their extracts, that are natural sources of bioactive compounds can be an important tool for promoting the health and well-being of these animals. The present study aims at the development of sustainable and effective methodologies for the extraction of bioactive compounds of the red seaweed Gracilaria gracilis, exploring its antibacterial and antioxidant potential and considering its potential use as an additive for functional fish feeds. The yield of the extraction methods was evaluated upon the use of sequential solid–liquid extraction techniques with ethanol and water as solvents, different extraction temperatures (room temperature: 40 °C and 70 °C), and extraction time. The results demonstrated that the adoption extraction times of 30 min at 40 °C provided higher yields. We also evaluated the antioxidant capacity and the antibacterial properties of the obtained extracts against different strains that cause fish diseases by disk diffusion and broth microdilution methods. The antioxidant activity was determined by the DPPH reducing capacity method and quantification of total polyphenols content (TPC). With these results, we can establish extraction procedures that allow the future use of G. gracilis extracts, with antibacterial and antioxidant effects in a safe and effective way.

Inhibitory Potentials of Kappaphycus Alvarezii on Bacteria Isolated from Clinical Samples

“…Patni et al, [42], Masika and Afolayan [43] and Karou et al, [44] were stated the susceptibility pattern of gram-positive bacteria than gram negative bacteria. Antimicrobial property of a seaweed extracts were directly proposed to the active constituents.…”

In Vitro Fermentation Characteristics of Pine Needles (Pinus densiflora) as Feed Additive

“…As a feed additive of natural products and useful microorganisms, the evaluation of antibacterial activity against livestock pathogens in functional evaluation is an important indicator and has been widely analyzed [25,39,40]. There are antibacterial substances such as polyphenols, flavonoids, and sulfur compounds in natural products [41,42], and pine needles have also been reported to have antimicrobial activity against various pathogenic microorganisms [43,44].…”

“…Antioxidants in natural products play a role in maintaining physical health from high temperatures and oxidative stress in livestock, preventing quality deterioration of livestock products, and improving productivity [39,[46][47][48]. In general, the antioxidant capacity of natural products is verified by assays using TPC, TFC, DPPH, ABTS, and various stress-induced cells [40,[49][50][51].…”

<i>Gracilaria Gracilis</i> – A Review of Ecological Knowledge, Chemical Composition, Cultivation, and Applications

“…Gracilaria species are exploited and employed in a variety of sectors, including direct consumption as human food [Jensen, 2004;Dillehay et al, 2008;Gordon, 2017], in medicine to treat intestinal constipation, dysentery, enteritis, thyroid diseases, urinary disorders, respiratory disease, and diarrhea [Khare, 2007;Costa et al, 2016;Fu et al, 2016;Leódido et al, 2017]. These species contain many bioactive chemicals with various biological characteristics, such as anti-cancer [Zandi et al, 2010;Sakthivel et al, 2016;Yi et al, 2022], anti-inflammatory [Chaves et al, 2013;Chen et al, 2013;da Costa et al, 2017], anti-diabetic [Makkar and Chakraborty, 2017], anti-oxidant and anti-bacterial [Widowati et al, 2014;Afonso et al, 2021]. The extracts of Gracilaria are also used in agriculture as biostimulants for lettuce [Torres et al, 2018] and against pathogens like the root-rot fungus, Phytophthora cinnamomi [Jiménez et al, 2011], in aquaculture as an immunity booster for shrimp [Lin et al, 2011;Chen et al, 2016], as a feed [Valente et al, 2006 Gracilaria gracilis is a benthic, intertidal red macroalga (Rhodophyta) that belongs to the commercially valuable Gracilaria genus, to the order Gracilariales and Family Gracilariaceae.…”