Changes in antioxidant activity of fresh marine macroalgae from the Canary Islands during air-drying process

Marine macroalgae develop structurally distinct molecules that have been long recognized as an important source of natural products, e.g., bioactive compounds and antioxidants, such as carotenoids, amino acids, proteins, lipids, vitamins and polyphenols, with promising properties as anticoagulant, anti-proliferative and antimicrobial. In this study we analyzed the antioxidant activity of 24 fresh methanolic extracts from marine macroalgae from the Canary Islands. Additionally, the effects of air-drying process in the antioxidant activity were also evaluated. Plant material was collected in three locations on the island of Tenerife. Total antioxidant activity methods included DPPH-free radical scavenging activity and ferrous iron chelating activity. Phytoconstituents evaluated were total carotenoids, proline, phenols, flavonoids and condensed tannins content. Our results indicated that from fresh material, species Cladophora liebetruthii, Dasycladus vermicularis and Dictyopteris polypodioides presented the highest scavenging activity, supported by high correlation with phenolics and flavonoids content, however, in air-dry extracts, Anadyomene saldanhae and D. polypodioides showed the highest antioxidant potential, correlated with a high phenolic compounds content. Asteronema breviarticulatum and D. polypodioides presented a high content of carotenoids in fresh and air-dry state. The highest ferrous iron chelating activity (>60 %) was recorded in extracts from fresh material in Grateloupia imbricata and Lophocladia trichoclados. However, only L. trichoclados was able to maintain this high activity after air-drying supported by a high proline content. A. breviarticulatum was the species that showed the highest condensed tannins content both in fresh and dried extracts. The study revealed that fresh extracts of D. vermicularis, D. polypodioides and L. trichoclados possess promising properties as raw materials to obtain biologically active substances in alimentary and pharmaceutical industry. Besides, these properties were maintained after the air-drying period in the last two species, which makes them species of great interest to be used under drying preservation methods.