In vitro bioactive potential of several macroalgae species

Algae are described as a source of bioactive compounds, with nutritional and therapeutic benefits for the human health [1]. In general, dried macroalgae are foods with a low-caloric content, being rich in non-digestible polysaccharides, proteins and essential aminoacids, vitamins, interesting minerals and phenolic compounds. Although the lipid content is low, this matrix is rich in polyunsaturated fatty acids, essential for the correct functioning of the organism [2]. This study aimed to evaluate the bioactive potential of the hydroethanolic extract of several macroalgae species, namely Laminaria ochroleuca Bachelot de la Pylaie, Saccharina latissila Linnaeus, Ulva lactuca Linnaeus, Palmaria palmata L., Porphyra sp., Codium tomentosum Stackhouse, Undaria pinnafitida (Harvey) Suringar and Himantalia elongate (Linnaeus) SF Grey. The antioxidant activity was evaluated through the OxHLIA method; the antimicrobial activity was determined using the microdilution method using Gram-positive and Gram-negative bacteria, and fungi; and the toxicity was evaluated in a non-tumour primary cell culture (PLP2), by applying the sulforhodamine B assay. The results showed bioactive activity in all the in vitro assays performed. In the antioxidant activity, L. ochroleuca was the species that stood out with an EC50 value of 1.7±0.3 mg/mL. Otherwise, for the antibacterial activity all macroalgae revealed inhibitory capacity against the studied strains, especially S. latissila and H. elongata with MIC values of 0.5 mg/mL for the Salmonella Typhimurium and Bacillus cereus strains, respectively. H. elongata also presented the most promising values for the bactericidal capacity (MBC=1 mg/mL) for Bacillus cereus. Regarding the antifungal activity, inhibitory and fungicidal capacity was also verified in all the studied species, particularly in S. latissila with MIC values of 0.5 mg/mL and MFC values of 1 mg/mL for Aspergillus fumigatus, Aspergillus niger and Aspergillus versicolor strains. Moreover, all the studied macroalgae samples did not present toxicity in the non-tumour primary cell culture evaluated. This work allowed to verify the in vitro bioactive effects of several macroalgae species, namely regarding its antioxidant, antibacterial and antifungal potential.The authors are grateful to the Foundation for Science and Technology (FCT, Portugal) for financial support by national funds FCT/MCTES to CIMO (UIDB/00690/2020); L. Barros, C. Pereira and R. Calhelha thank the national funds through the FCT, I.P., through the institutional scientific employment program-contract for their contracts; and for financial support to Ministry of Education, Science and Technological Development of Republic of Serbia. The authors are also grateful to FEDER-Interreg España-Portugal programme for financial support through the project 0377_Iberphenol_6_E.