Antioxidant contents of Fucus vesiculosus L., in response to environmental parameters

• Autor(a) principal: Mendes, Madalena Caria
• Data de Publicação: 2017
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.1/10605
• topic: Algas; Compostos fenólicos; HPLC; Variação sazonal; Ensaios antioxidantes

Seaweed are a diverse group of algae with great value and vast application possibilities. The seaweed Fucus vesiculosus, stands out for having elevated concentrations of polyphenols and antioxidant activities. Polyphenols possess many biological properties including antioxidant, antimicrobial, anti-inflammatory, and free radical scavenging activities. Therefore, this species is a possible candidate as natural source of bioactive compounds for the development of novel products to be applied in the nutraceutical, pharmaceutical, and cosmetic industries, in the future. This project aimed to investigate the effects of seasonality, and culture conditions such as salinity and ultraviolet radiation (UV) on the antioxidant contents and in vitro properties of F. vesiculosus. This was carried out through spectrophotometric analysis, namely total phenolic contents (TPC), high performance liquid chromatography (HPLC), α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging activity and iron chelating capacity. Furthermore, the epiphytic algae coverage was determined and physodes (structures containing phenolics) were investigated microscopically through vanillin-HCL staining. This information was used to identify the best harvest time targeting the highest concentration of antioxidants, which was hypothesized to be in late summer-early autumn, due to the protection against UV-irradiation over summer by phenolic accumulation. Significant differences supporting seasonality in antioxidants were found. Late Spring to early Fall had the highest extraction yields (P»0.0045) and concentrations (P< 0.0010) in contrast to the lowest winter concentrations. A total of 13 monophenolic acids were detected through RP-HPLC, with September samples being the most diverse in compounds and March samples the least. Gallic acid was identified in all analyzed months. Furthermore, antioxidant contents and activity was linked to environmental parameters, namely positive correlations between temperature, TPC (P= 0.0391) and DPPH (P= 0.0016); likewise, between sunlight hours per day, TPC (P= 0.0458) and DPPH (P=0.0060). During experimental growth trials, three salinity concentrations and presence of UV light were tested, to verify or reject the second hypothesis: increasing salinity and exposure to UV light would yield higher polyphenolic concentrations. No significant differences were observed between the TPC and salinity (P=0.0525), and light (P=0.2443), under the experimental conditions tested. Regarding growth rate there were significant differences between different salinities (P=0.0216). Lastly, physodes were observed to test a third hypothesis inquiring on their location within tissues. Microscopic images revealed that physodes were distributed mainly in the outer layers of the blades, epidermis and outer cortical layers, serving as a shield effect.