Search for mycosporine-like amino acids and fatty acids in Isochrysis galbana and Nannochloropsis gaditana

Furtado, Joana

http://hdl.handle.net/10400.8/603

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Authors

Furtado, Joana

Abstract(s)

In this work two unialgal cultures, one of Isochrysis galbana (I. galbana) and another of Nannochloropsis gaditana (N. gaditana), were exposed to photosynthetic active radiation (PAR) plus ultraviolet radiation (UVR-B) (supplemented with 4h daily) in a photoperiod 16h: 8h, light: dark cycle. The content on mycosporine-like amino acids (MAAs) was determined by reverse phase isocratic high performance liquid chromatography (HPLC) employing C18 phase, in methanolic and aqueous methanolic extracts. No MAAs were identified, with the five standards available, but a peak (unknown compound) with absorption maximum (ëmax) at 338 nm was detected. The content on fatty acids (only for N. gaditana) was determined by gas chromatography (GC), eight fatty acids were identified (in ten presented in N. gaditana) and the most abundant fatty acid was the palmitic acid with 26,86% of the total fatty acids. In order to identify new sources of safe and inexpensive antioxidants, the antioxidant activity of different fractions of N. gaditana was evaluated, by the á,á-diphenyl-â-picrylhydrazyl (DPPH) radical scavenging assay. The N. gaditana was extracted using nhexane, ethyl acetate and water by a three-step sequential extraction procedure. The results varied between 0,23±0,46% and 1,23±0,60%, for the three fractions, when compared with the commercial standard butylated hydroxytoluene (BHT) that obtained a 95,0±2,68% of capacity for reduction of DPPH. With this work was concluded that the extracting procedures used were not adequate for the extraction of this kind of compounds, not only for the finding of MAAs or another UVabsorbing compounds, but also for other compounds with antioxidant properties. The results obtained for the extraction procedure for fatty acids showed good results.

Description

Dissertação de Mestrado em Biotecnologia dos Recursos Marinhos apresentada à ESTM - Escola Superior de Turismo e Tecnologia do Mar do Instituto Politécnico de Leiria