A microalgae Picochlorum sp. AZL19 from Moroccan Mediterranean as a novel source of antioxidant compounds

Microalgae are a valuable new source of safe and inexpensive antioxidants. The main objective of this research was to evaluate the potential of a microalgae Picochlorum sp. AZL19, isolated from the Moroccan Mediterranean, as a novel source of antioxidant compounds. The antioxidant activity of four extracts (methanol, chloroform, ethyl acetate and water) of this strain was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydrogen peroxide (H₂O₂) scavenging, ferric reducing antioxidant power (FRAP) and total antioxidant capacity (TAC) assays. The results prove that the methanolic extract is a more powerful antioxidant compared to the other extracts in the four assays, with the lowest IC₅₀ values ranging from 0.21 to 0.71 mg mL⁻¹. The methanolic extract exhibited the highest contents of total phenolics, total flavonoids, and total carotenoids, with values of 23.52 mg GAE g⁻¹, 5.99 mg QE g⁻¹, and 4.49 mg g⁻¹, respectively. The analysis of the correlations revealed a very strong correlation between the phenolic content and the antioxidant activities of the microalgae Picochlorum sp. AZL19. The results of phenolic compounds analysis using liquid chromatography electrospray ionization high resolution mass spectrometry (LC-ESI-HRMS) revealed the presence of nine phenolic compounds. Most of the phenolic compounds identified were phenolic acids. Eight of the identified compounds are reported for the first time in Picochlorum genus. In addition, this study represents the first description of three novel compounds in microalgae: shikimic acid, vanillic acid 4-β-D-glucoside and 5-methoxysalicylic acid. All of these identified compounds are known to have antioxidant activity. The principal carotenoids identified using liquid chromatography/atmospheric pressure chemical ionization mass spectrometry (LC/APCI-MS) analysis were lutein (54.0 %) and zeaxanthin (18.23 %). These findings indicate that the isolated Picochlorum sp. AZL19 strain possesses a high antioxidant activity and thus could be used as a potential novel source of natural antioxidants.