On the Health Benefits vs. Risks of Seaweeds and Their Constituents: The Curious Case of the Polymer Paradigm

Abstract

To exploit the nutraceutical and biomedical potential of selected seaweed-derived polymers in an economically viable way, it is necessary to analyze and understand their quality and yield fluctuations throughout the seasons. In this study, the seasonal polysaccharide yield and respective quality were evaluated in three selected seaweeds, namely the agarophyte Gracilaria gracilis, the carrageenophyte Calliblepharis jubata (both red seaweeds) and the alginophyte Sargassum muticum (brown seaweed). It was found that the agar synthesis of G. gracilis did not significantly differ with the seasons (27.04% seaweed dry weight (DW)). In contrast, the carrageenan content in C. jubata varied seasonally, being synthesized in higher concentrations during the summer (18.73% DW). Meanwhile, the alginate synthesis of S. muticum exhibited a higher concentration (36.88% DW) during the winter. Therefore, there is a need to assess the threshold at which seaweed-derived polymers may have positive effects or negative impacts on human nutrition. Furthermore, this study highlights the three polymers, along with their known thresholds, at which they can have positive and/or negative health impacts. Such knowledge is key to recognizing the paradigm governing their successful deployment and related beneficial applications in humans.

Keywords: biomedical; health benefits; health risks; polymer seasonal variation; polysaccharides.

Figure 1

Three seaweeds studied at the collection site (Figueira da Foz, Portugal): (a) Calliblepharis jubata (Rhodophyta—carrageenan-bearing); (b) Gracilaria gracilis (Rhodophyta—agar bearing); (c) Sargassum muticum (Phaeophyta—alginate-bearing).

Figure 2

Carrageenan content analyzed seasonally. The extraction yields are expressed as mean ± standard deviation (n = 3). ^a,b The same letters indicate no significant differences at the p-value < 0.05 level.

Figure 3

FTIR-ATR spectrum of the carrageenan extracted from Calliblepharis jubata.

Figure 4

Agar content analyzed seasonally. The extraction yield results are expressed as mean ± standard deviation (n = 3). ^a The letters indicate no significant differences at the p-value < 0.05 level.

Figure 5

FTIR-ATR spectrum of the agar extracted from Gracilaria gracilis.

Figure 6

Alginate content analyzed seasonally. The extraction yields are expressed as mean ± standard deviation (n = 3). ^a,b Similar letters indicate no significant differences at the p-value < 0.05 level.

Figure 7

FTIR-ATR spectrum of the alginate extracted from Sargassum muticum.