## 4 Discussion
Second, GSH functions as a cofactor for other antioxidant systems, including Glyoxalase 1 and Glyoxalase 2, glutathione-dependent peroxideroxins, and glutathione-dependent thiol: disulfide oxidoreductase (glutaredoxins) [75; 76; 77]. In addition, the significant reduction in lipid peroxidation can be explained by the consumption of GSH, but also by a direct effect of the phenolic components of the EO, as they can act as reducing agents, hydrogen atom donors, and singlet oxygen scavengers. The radical-scavenging activity of phenolics depends on structural features that favor phenolic hydrogen donation and the stability of the resulting phenoxyl radicals. For example, eugenol (4-allyl-2-methoxyphenyl) (the major constituent of EO-OG in this study) is a phenolic compound of the phenylpropanol class that has a hydroxyl group attached to an aromatic ring in its structure [78; 79]. The phenolic hydroxyl and allylic moiety present in eugenol effectively contribute to the antioxidant activity of this natural product. In particular, the unsaturation is very valuable for eugenol's activity concerning free radicals, since the molecule can stabilize after scavenging the radical on this aromatic ring [80; 81]. The antioxidant properties of EO-OG here observed may be attributed to its major and minor compounds. Eugenol was the major compound identified in the EO-OG used in the present study. Eugenol's free-radical-scavenging, anti-lipoperoxidation, and antioxidant activities have been assigned to its high polyphenic contents [79; 80; 82]. Different EOs rich in eugenol exhibit these biological activities and are beneficial in the aquaculture setting. They include EO-OG, _Cinnamomum zeylanicum_ (cinnamon), _Eugenia carophyllus_ (clove), _Rosmarinus officinalis_ (rosemary), _Origanum vulgare_ (oregano), and _Thymus vulgaris_ (thyme), among others [13; 83; 84; 85]. Likewise, minor constituents of EO-OG may have synergically contributed to the bioactivities of this EO. The sesquiterpene \(\beta\)-caryophyllene has presented properties such as antioxidant, antineoplastic, and antimicrobial ones in human cells and pathogens [86], and antioxidant, anti-inflammatory and wound re-epithelialization activities in rats [87]. In rats, \(\beta\)-caryophyllene showed a cardioprotective effect by reducing the heart lipid content [88] and displayed hypolipidemic effects similar to those of the simvastatin drug [89; 90]. Similarly, the tricyclic sesquiterpene copaene displayed antioxidant properties in human lymphocytes [91]. Lastly, the use of EO-OG as a dietary supplement, regardless of the inclusion level, did not affect the carcass proximate composition of _M. rosenbergii_ juveniles. The bromatological composition of aquatic animals such as fish and decapods varies according to the species, sex, age, water parameters, and diet profile [92; 93; 94]. The results of the current study suggest that EO-OG can be used as a dietary antioxidant without influencing the bromatologicalcomposition of prawn carcasses. Notably, one may observe a positive effect on the protein content of prawn biomass, although this was not statistically significant in this study. Forthcoming studies may perform a meta-analysis to show combined effects. Similarly, further research may test higher inclusion levels of EO-OG (i.e., >3.0 g kg \({}^{-1}\)) to determine the precise optimum dose as well as analyze the activity of digestive enzymes. Likewise, future studies may assess the organoleptic properties of prawns fed a diet supplemented with EO-OG and the potential antioxidant effect of isolated compounds (e.g., eugenol) on _M. rosenbergii_ juveniles.