# Antioxidant and Antimicrobial Properties of Selected Red Seaweeds from Central Portugal
## 4 Discussion
### Species-Specific Notes
rubens_ required the same concentration of the aqueous extract to inhibit growth, while _E. elongata_ showed no antimicrobial activity at all. None of these algae presented activity against _E. coli or S. cerevisiae_. Coralline seaweeds have shown potential as a dietary calcium supplement to promote bone health [60; 61; 62]. Other authors have unveiled the antimicrobial potential of dichloromethane extracts of _C. officinalis_ against _E. coli_[96], the antioxidant [97; 98], anti-inflammatory and anticancer potential of methanolic extracts of _J. rubens_ and _E. elongata_ (formerly _C. elongata_) [98], and the insecticidal [99], anti-tumour [100] and anti-bacterial [101] potential of the methanolic, organic and ethanolic extracts, respectively, of _J. rubens_. _M. lichenoides_ is a seaweed that, although scarcely studied, showed promise in most analyses performed in the present study. Specifically, the ABTS results show its potential as an antioxidant comparable to that found for coralline algae, which, as previously mentioned, presented the most promising results. However, in the TPC assay it shows a lower phenolic content when compared to the other species analyzed. Hence, compounds other than phenols are responsible for this bioactivity. As for its antibacterial potential, _M. lichenoides_ is one of the few three seaweed species whose aqueous extracts can severely inhibit the growth of both _B. subtilis_ and _S. cerevisiae. M. lichenoides_ shows quite interesting results, further worth researching, especially given that this seaweed has not yet been given attention or focus regarding its bioactive potential, as far as we are aware. The few studies available seem to mostly focus on the distribution and systematics of the entire genus _Mesophyllum_[102; 103]. _L. viscida_ is the seaweed that presented the lowest antioxidant potential of all the species studied, showing the highest EC\({}_{50}\) values, and the lowest polyphenol content, when compared to the overall results presently obtained. Similarly to most species studied, _L. viscida_ aqueous extracts inhibit _B. subtilis_ growth; however, _L. viscida_ is one of the three species that inhibit _S. cerevisiae_ growth as well. These results may indicate that _L. viscida_ is worth further study within the scope of microbiology, as this seaweed has previously shown antimicrobial activity against bacteria and fungi [104]. To this day, and considering the currently studied species, _L. viscida_ remains one of the seaweed species severely lacking research focused on its biotechnological potential. The results obtained in the present work can be summarized by noting the species that stood out in each assay: _Corallina officinalis_ and _Porphyna umbilicalis_ for the highest antioxidant potential, measured by the ABTS and the TPC assay, respectively, and _Sphaerococcus coronopifolius_ and _Mesophyllum lichenoides_ for the highest antibacterial potential against, respectively, _Bacillus subtilis_ and _Saccharomyces cerevisiae_. All of the species showed quite noticeable antioxidant or antimicrobial activities, but generally performed far better in either the antioxidant or the antimicrobial assessment, but not both at once. There are questions that remain unanswered, namely the nature of the metabolite(s) accountable for the measured activities, and whether changing the extraction method or solvent would yield different results.