## 4 Discussion
Extraction yields were higher with water as reported in other studies with red seaweeds including _Agaropython vermiculophyll_ (formerly _Gracilaria vermiculophyll_) [69, 70, 71]. However, the results obtained in the ethanolic fractions in terms of average yield are lower than those obtained by [PERSON] et al. [36] regarding _Crassiphycus changii_ (formerly _Gracilaria changii_, 13.06 \(\pm\) 1.14%). In A. vermiculophyll, the average yield for the ethanolic and aqueous extract were 6.5 \(\pm\) 0.1% and 33.4 \(\pm\) 1.5%, respectively [71], higher than the values we found. Extraction efficiency is a highly variable parameter depending on cell rupture efficiency, solvent, pH, temperature, and extraction time, among other factors. The antioxidant activity present in several macroalgal extracts indicates a correlation with the total phenolic content [43, 72], justifying why many studies focus on the quantification of these compounds. Often, extracts that have a lower content of pigments and phenolic compounds demonstrate reduced antioxidant activity. The use of effective and rigorous methods of measuring TPC is essential as they allow us to better understand the effect that these compounds can have on animal health and well-being, considering they are one of the most important natural bioactive compounds. The quantification of TPC is considered an indicator of antioxidant capacity; however, it is a parameter that can be assessed with slightly different methodologies (with different reference substances, extract concentrations, reaction times, and temperatures, among other factors) and the comparison of results is somehow complex. In the red seaweeds _Percoladiella capillacea_ and _Osmundaria obtusiloba_, the use of 70% ethanol was effective as a solvent for the extraction of phenolic compounds [22] especially those that were of a polar nature such as the polyphenols bond to proteins or sugars, saponins, phlorotannin's, and organic acids, among others [73]. In these two species, the authors found a TPC of 15.23 and 30.54 mg GAE g\({}^{-1}\) extract, respectively [22]. Also, the studies of [PERSON] and [PERSON] [71] that studied the TPC in six red seaweed species found high values in _Polysiphonia ticoides_ (19.2 \(\pm\) 0.61 mg GAE g\({}^{-1}\) dw) and _Porphyna purpurea_ (2.99 \(\pm\) 0.05 mg GAE g\({}^{-1}\) dw). In the red algae _Hypnea musiformis_, _Hypnea valentiae_, and _Jania rubens_, the TPC reached values of 9.84, 6.91, and 4.95 mg GAE g\({}^{-1}\) dw in methanolic extracts [74]. In this study, the fractioning of crude extracts demonstrated that the fractions of the polar solvent (specially ethyl acetate) had greater antioxidant potential, particularly in _H. musciformis_. In _Porphyna tenera_, the TPC varied from 10.81 to 32.14 mg GAE g\({}^{-1}\) in the extract depending on the temperature and the solvent used in the extraction [75]. Additionally, in _Kappaphycus alvarezii_, some compounds that exhibited remarkable antioxidant activity were already identified and characterized [76, 77, 78]. In _Chondracanthus chamissoi_ and _Laurencia chilensis_, the estimation of TPC indicated a relatively low level with the higher concentrations obtained with dichloromethane and ethyl acetate extracts of _L. chilensis_ (2.15 \(\pm\) 0.14 and 2.27 \(\pm\) 0.35 mg GAE g\({}^{-1}\) dw, respectively) [79]. In _Crassiphucus birdiae_ (formerly _Gracilaria birdiae_), the hydrocolloid fraction obtained with water at 90 \({}^{\circ}\)C exhibited interesting antioxidant properties (IC50 = 1.62 mg mL\({}^{-1}\)) in addition to a high extraction yield (27.2 % dw) [80], demonstrating it to be an interesting source of antioxidant compounds. The TPC obtained by these authors in the ethanol extracts of _C. birdiae_ and _Crassiphucys corneus_ (formerly _G. cornea_) were 1.13 and 0.88 mg GAE g\({}^{-1}\) extract, respectively. Furthermore, in these species, the ethanol extracts have a high antioxidant performance although lower than the commercial antioxidant BHT. The IC50 values for the ethanolic extracts on _C. birdiae_ and _C.