Aquatic microalgae “Anabaena oryzae”: phenolic compounds, antioxidant activity and antibacterial activity against Streptococcus mutans oral bacteria

Natural antioxidant replacements have been a common subject in recent decades for the substitution of artificial antioxidants. Microalgae have been reported to exhibit interesting bioactive properties especially their antioxidant capacity and antibacterial activity. The goal of the present work is to investigate the possibility of using the blue-green microalgae 'Anabeanae orayzae' for extract preparation and to determine the phenolic compounds that make up this extract and its possible antioxidant and antibacterial capacities by emphasizing the role of the extract in oral disease prevention. The results showed that Anabaena extract possesses a notable antioxidant capacity and also good phenolic compounds content. Algae and cyanobacteria have been demonstrated to produce secondary metabolites with diverse bioactivities. The DPPH scavenging activity of different concentrations of Anabaena extract. As for the DPPH scavenging activity of different concentrations of Anabaena extract, the results show that a concentration of Anabaena extract equal to 2.98 mg/ml was capable of inhibiting 50% of the free radicals (IC₅₀). Anabaena extract can be thus considered as an excellent antioxidant since its IC₅₀ is a small concentration value and it is agreed that a low IC₅₀ value represents high antioxidant activity. Concerning the phenolic compounds detected in Anabaena extract, they were salicylic acid, gallic acid, tannic acid, caffeic acid, and benzoic acid. The highest concentrations determined in Anabaena extract were for salicylic and tannic acids. In regard to Anabaena extract antibacterial activity against S. mutans, the ability of Anabaena extract to inhibit S. mutans was tested and the results showed that the extract has an inhibitory effect against S. mutans with an inhibition zone diameter equal to 13 (mm). It can be concluded that Anabaena extract possesses the potential antibacterial substances that can be used against oral pathogens and for dental caries prevention.