Biochemical Assessment of Some Red Sea Brown Algae with Potential of Antioxidant and Antimicrobial Agents

The nutritional compositions of fatty acids (FAs), amino acids (AAs), polysaccharides, and phenolic compounds from brown seaweeds Cystoseira trinodis, Dictyota cervicornis, Padina gymnospora, and Turbinaria oranata were studied, and their antioxidant and antimicrobial activities were evaluated. For the assessment of phytocompounds, gas chromatography-mass spectrometry (GCMS) and high-resolution liquid chromatography (HPLC) were employed. D. cervicornis and T. oranata showed high levels of saturated FA in their lipophilic profiles (48.13 and 42.41%, respectively), mainly palmitic acid (16:0) with 38.4 and 33.79%, respectively. In contrast, C. trinodis and P. gymnospora contained the highest amounts of unsaturated FAs (51.5 and 38.15%, respectively), composed predominantly of oleic acid (18:1, n9) with proportions of 18.29 and 33.79%. Unsaponifiable lipids consist primarily of phytol, cholest-5-en-3-ol, stigmasterol, and 9Z-octadecenamide. The major phenolic compounds were gallic acid in D. cervicornis, catechin in T. oranata and C. trinodis, and kaempferol in P. gymnospora with values of 227.54, 209.63, 167.18 and 85.82 µg/g, respectively. The backbone of the polysaccharides in P. gymnospora was galactose (26.5%), ribose (38.9%) in C. trinode, mannose (49.7%) in D. cervicornis, and rhamnose (30.7%) in T. oranata. In all species, leucine and phenylalanine were the primary essential AAs, whereas proline was the main non-essential AA. The MeOH extracts of T. oranata and C. trinodis displayed mild antioxidant activity with IC₅₀ values of 26.1 and 30.5 μg/ml. FAs contents of C. trinodis and D. cervicornis possessed antibacterial properties against Staphylococcus aureus and Bacillus cereus, while FAs contents of T. oranata and P. gymnospora exhibited potent antifungal activities against Penicillium expansum and Syncephalastrum racemosum with the inhibition MIC value for both = 0.312mg/ml.

Graphical Abstract