Investigation of antiviral activity of four microalgae and two cyanobacteria extracts on infectious bronchitis virus

Many studies indicate that microalgae and cyanobacteria, widely used in cosmetics, medicine, various industrial areas, and as food sources for humans and animals, have potential applications in alternative treatments. These species have high nutritional value due to their high protein, carbohydrate, and fatty acid content. Microalgae display diverse morphological and physiological features, and their biological properties vary according to the metabolites they produce. The therapeutic properties of microalgae have been investigated in numerous scientific studies. The literature reports that microalgae possess anticancer, cholesterol-lowering, anti-inflammatory, antioxidant, and antiviral activities, as well as the ability to stimulate the immune system. Interest in compounds with antiviral activity against SARS-CoV-2, which emerged in China and spread worldwide, is currently at its peak. The discovery and isolation of bioactive compounds with antiviral effects is of great importance. In this study, the antiviral effects of Arthrospira platensis, Prasinococcus sp., Nanofrustulum shiloi, Phaeodactylum tricornutum, Scenedesmus sp., and Pseudanabaena sp. were investigated. The antiviral effects of extracts from these microalgae/cyanobacteria species were assessed by in ovo experiments in the embryonated chicken egg system using the Infectious Bronchitis Virus (IBV) D274 strain, which agglutinates erythrocytes. Among the microalgae/cyanobacteria species, Pseudanabaena sp., which exhibits the lowest hemagglutination activity (log2HA=4 at 5 mg/kg and log2HA=5 at 10 mg/kg), shows the strongest and most potent antiviral activity and is more effective at 5 mg/kg than at 10 mg/kg.