Roger Casado,1 Filipa R. Pinto,1 Sónia Barroso,1 Maria M. Gil2
1 MARE – Marine and Environmental Sciences Centre / ARNET – Aquatic Research Network, Polytechnic of Leiria, 2520–614 Peniche, Portugal
2 MARE – Marine and Environmental Sciences Centre / ARNET – Aquatic Research Network, ESTM, Polytechnic of Leiria, 2520-641 Peniche, Portugal
Macroalgae are relatively easy to cultivate/produce at industrial scale making them relevant natural resources of bioactive compounds. Wild macroalgae are more exposed to stress factors and are expected to be richer in bioactive compounds than the cultivated ones. The aim of this work was to compare the phenolic content and the antioxidant activity between wild algae (Ulva sp.) collected off the Portuguese coast and cultivated algae (Ulva rigida). Differences between fresh and freeze-dried/air-dried samples were also assessed. Higher antioxidant activity is generally observed in wild seaweed collected in summer and spring. Wild samples of both seasons were also analysed for comparison. The samples studied were LWU-Su (Lyophilized Wild Ulva sp. from Summer), FWU-Sp (Fresh Wild Ulva sp. from Spring), WUL-Sp (Lyophilized Wild Ulva sp. from Spring), FCU (Fresh Cultivated Ulva Rigida), LCU (Lyophilized Cultivated Ulva rigida), DCU (Dried Cultivated Ulva rigida).
The extraction of bioactive compounds was performed using an ethanol:water mixture (75:25), and the extracts obtained were screened for total phenolic content (TPC) and the antioxidant activity (Ferric Reducing Antioxidant Power – FRAP) (Table 1).
Higher phenolic contents and antioxidant activities were obtained for cultivated samples when compared to the wild ones. Regarding fresh vs. dried samples, fresh samples presented both higher content in phenolic compounds and antioxidant activities. It was also observed that freeze-drying was the drying process that best preserved the bioactive compounds. Regarding the samples collected in spring vs. samples collected in summer, no statistically significant differences were observed.
Table 1. Total phenolic compounds (TPC) and antioxidant activity (FRAP) of Ulva sp. extracts.
| TPC (mg GAE/g algae) | FRAP (µmol AAE/g algae) | |
| FWU- Sp | 0,29 ± 0,09 a | 0,43 ± 0,26 a |
| LWU- Sp | 0,16 ± 0,04 b | 0,25 ± 0,06 b |
| LWU- Su | 0,13 ± 0,03 a | 0,30 ± 0,06 a |
| DCU | 0,09 ± 0,03 bc | 0,18 ± 0,04 bc |
| FCU | 0,32 ± 0,06 cd | 0,85 ± 0,12 b |
| LCU | 0,22 ± 0,03 d | 0,29 ± 0,11 c |
Different low case letters in the same row indicate significant statistical differences (p<0.05).
GAE, gallic acid equivalents; EAA – ascorbic acid equivalents.
Acknowledgements: This work was financially supported by LA/P/0045/2020 (ALiCE), UIDB/50020/2020 and UIDP/50020/2020 (LSRE-LCM), funded by national funds through FCT/MCTES (PIDDAC), by FCT – Fundação para a Ciência e a Tecnologia, I.P., within the scope of the project MARE (UIDB/04292/2020 and UIDP/04292/2020). This study also had the support of national funds through Fundação para a Ciência e Tecnologia (FCT), under the project LA/P/0069/2020 granted to the Associate Laboratory ARNET.