Characterization and Evaluation of the Biological Activities of Ulvan Extracted from Ulva lactuca with a Focus on the Antiviral Activity Against Herpes Simplex Virus Type 1

Aims: Physicochemical characterization and evaluation of the cytotoxic, antioxidant, antibacterial and antiviral activities of the ulvan polysaccharide, extracted from Ulva lactuca, with emphasis on its action against herpesvirus type 1 (HSV-1).

Study Design: The study followed an experimental design focusing on the bioactive properties of ulvan, involving tests against the HSV-1 virus, in addition to the evaluation of its cytotoxic, antioxidant and antibacterial properties.

Place and Duration of Study: This research was conducted at the Laboratory of Biochemistry and Molecular Biology of Microorganisms and Plants (BIOMIC) in conjunction with the Center for Research in Biodiversity and Biotechnology (BIOTEC), located at the Federal University of Delta do Parnaíba, state of Piauí, Brazil.

Methodology: Ulvan was obtained from the macroalgae Ulva lactuca collected on Coqueiro beach, in the city of Luis Correia, state of Piauí. The polysaccharide was characterized and evaluated for its biological activities. The antioxidant capacity was evaluated by the ABTS (2,2'-azinobis(3-ethylbenzenethiazoline-6-sulfonic acid)) radical scavenging assay, the cytotoxicity was evaluated by the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) test, and the antibacterial activity was evaluated by the minimum inhibitory concentration (MIC) technique. The percentage of HSV-1 inhibition was verified by titrations of the pretreatment assays of cells (PTC) and viral particles (PTV) with ulvan. The atomic force microscopy (AFM) technique was used to observe possible changes that ulvan could cause in the structure of HSV-1, in addition to verifying the dimensions of the particles between the control and the viral treatment with ulvan.

Results: Ulvan did not show antibacterial activity against the tested strains. However, it showed ABTS radical scavenging and reducing activity, in addition to low cytotoxicity with CC50 above 8,805 µg/mL and viral inhibition percentages of 65% and 88%. Through AFM images, a decrease in HSV-1 particles was observed after treatment with ulvan, which decreased from 150 nm to 79 nm, indicating that there was possible damage to the viral envelope.

Conclusion: This study provided valuable information into the biological activities of ulvan, providing unique insights into the mechanism of action of the polysaccharide against HSV-1. These results help advance knowledge on the use of marine polysaccharides as biomaterials, while contributing to new advances in the discovery of antiviral materials.