## 1 Introduction  
Marine seaweeds are renewable natural resources that have high potential for application in the pharmaceutical, food and nutritional, nutraceutical, animal feed, packaging, and cosmetic industries, among others [1; 2; 3; 4]. These organisms are generally rich in proteins, minerals, vitamins, and fibers, and also reveal the presence of highly diverse bioactive compounds [5; 6; 7; 8; 9; 10; 11]. Red seaweeds (Rhodophyta) are macroscopic, benthic, and multicellular organisms that are commonly used in human nutrition, mainly in Asian countries. They are also important sources of thickening and gelling food additives due to their richness in phycocolloids such as agar or carrageenan [4; 8; 12; 13]. These organisms often thrive in environments where light, salinity, and temperatures can reach extremes [13; 14; 15]. To adapt to such extreme conditions, seaweeds produce a wide variety of secondary metabolites that exhibit powerful biological activities and are therefore highly valued as active and functional ingredients not only for the food and feedstock industry, but also in health care and cosme [10; 11; 16; 17; 18]. The production of active compounds in algae can be adjustedby manipulating the appropriate growing conditions; thus, they are natural bioreactors [19]. Seaweed extracts commonly present different bioactivities related to the presence of compounds such as polysaccharides, pigments, compounds with antioxidant activity, and substances similar to plant growth regulators [6; 7; 20]. The antibacterial activity present in macroalgae extracts is usually attributed to compounds such as proteins but also to polyphenols, polysaccharides, pigments, and PUFAs [6; 21; 22]. Antioxidant activity, conversely, seems to be frequently associated with glutathione, mycosporine-like amino acids, ascorbate, pigments, and polyphenols, among other compounds, and is widely reported in red seaweeds [6; 23; 24]. In this sense, it is also interesting to establish adequate, profitable, and ecologically acceptable extraction procedures that allow not only the meeting of the legal requirements regarding the use of solvents on food and feed production processes but also to ensure of all the properties of interest that seaweeds possess [24; 25]. Traditional extraction techniques such as Soxhlet, solid-liquid extraction (SLE), or liquid-liquid extraction (LLE) can be adjusted, minimizing the cost of solvents and the times involved [26]. The use of new extraction techniques such as extraction by supercritical fluids (SFE), ultrasound, and microwave assisted extraction (MAE), among others, provide an effective alternative [5; 27; 28] but require high investment in equipment. When the intention is to incorporate algae extracts in food or animal feed, the objectives go beyond obtaining a product with nutritional value. These goals are usually related to the bioactive properties of these extracts and the potential to obtain food/feed with desirable functional properties; therefore, extraction procedures must be carefully evaluated. _Gracilaria gracilis_ (Stackhouse) [PERSON], [PERSON] & [PERSON] 1995, is a red seaweed (Rhodophyta) considered an agaophyte due to its high agar content [12; 14]. It is widely distributed throughout the world and lives in temperate waters up to a maximum of 30 \({}^{\circ}\)C and tolerating a wide range of salinity values. This highly valuable seaweed can also be a source of different organic compounds such as R-phycoerythrin, arachidonic acid, proteins, and phenols in addition to their antioxidant and radical scavenging potential [8; 29]. Antimicrobial activity has also been reported in this genus [30; 31; 32; 33] related to the presence of compounds such as polyphenols and fatty acids [30]. In these seaweeds, as in many other living organisms, reactive oxygen species (ROS) are commonly produced during metabolism but there are enzymatic and non-enzymatic cellular defense mechanisms [34] that allow their elimination.