# Antioxidant and Antimicrobial Properties of Selected Red Seaweeds from Central Portugal
## 4 Discussion
### Species-Specific Notes
One of the major constituints of the genus _Porphyra_ is porphyrin, which is a linear sulphated polyssacharide that can be extracted with water [75], beneficial to human health and with a diverse array of bioactivities, namely antioxidant [29]. It was also reported by [PERSON] et al. [76] that _P. umbilicalis_ had comparatively higher concentrations of polyphenols and Micosporin-like Aminoacids (MAAs) (from a selected pool of species analyzed), which were not only better extracted with water, but also showed antioxidant activity. Therefore, it remains to be seen which component(s) of our aqueous extracts of _P. umbilicalis_ is (are) responsible for the bioactivities observed in the ABTS and the MIC assay, although phenols stand as the leading hypothesis, considering they are present in large amounts in this seaweed when compared to all other species analyzed. In addition to the environmental fluctuations previously discussed that may have possibly played a role in shaping the bioactivity potential of _P. umbilicalis_, we must also consider the relevance of taxonomic position, which perhaps may have influenced the significant difference between _P. umbilicalis_ and all other species analyzed regarding the polyphenol content. While all the other red seaweed species presently considered belong to class Florideophyceae, _P. umbilicalis_ is a Bangeophyceae, meaning it is an ancient algae shaped by the environment through the ages, and, thus, stands perfectly adapted today. Florideophyceae and Bangeiophyceae are, thus, highly divergent [77], a fact that may have implications on their bioactivity potential. _C. ciliatum_ has shown bioactive potential, although not outstanding when regarding all the other species studied, presenting one of the highest EC\({}_{50}\) values and being one of the species with the lowest polyphenol content. Regarding antimicrobial activity, the extracts of this seaweed inhibit the growth of _B. subtilis_, similarly to most other seaweed species. A previous study assessed the antimicrobial activity of ethanolic extracts of _C. ciliatum_, which also showed modest potential as an antibacterial and antifungal agent, when compared to a large pool of green, brown and red seaweeds [78]. Methanol, dichloromethane and _n_-hexane extracts of _C. ciliatum_ also failed to inhibit _E. coli_, but the dichloromethane extract showed activity against _B. subtilis_[39], which was still of little import when compared to the greater results obtained for other algal species by the authors. _C. ciliatum_ stands as an example of one seaweed species that is far from being explored or acknowledged in academic settings regarding the current topic, which may produce an opportunity to study it further. _O. pinnatifida_ is an edible species, widely common in central Portugal, and studies have unveiled its biological properties, namely antioxidant, antidiabetic and prebiotic. _O. pinnatifida_ did not stand out regarding antioxidant activity reported in the ABTS assay; however, it showed an appreciable amount of polyphenols and was one of the few seaweeds that showed inhibitory ability against _B. subtilis_ and _S.cerevisiae_. This is especially relevant in the MIC respective to _B. subtilis_, the growth of which was inhibited by a lower concentration than what was generally required to produce the same effect, when taking into consideration the concentrations of all the other seaweed extracts currently analyzed. It remains to be assessed which specific compounds are responsible for this activity. [PERSON] et al. [79] shed light on the chemistry and structure of enzymatic extracts obtained from this Rhodophyta, finding the presence of agarans within this algae. _O. pinnatifida_ has a reportedly high concentration of MAA, extracted with water, with a positive correlation with antioxidant activity [76]. These compounds, agarans or MAA, perhaps play a role in the activities found in the present study, although it is equally likely that this activity is caused by other groups of compounds, such as pigments. The seaweed _C.