Biochemical assessment of some Red Sea brown algae with potential of antioxidant and antimicrobial agents

Abstract

Abstract 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. The lipophilic profile of D. cervicornis and T. oranata showed richness in saturated FAs (48.13 and 42.41%, respectively) mainly comprised of palmitic acid (16:0) with the proportions 38.4 and 33.79%, respectively. In contrast, C. trinodis and P. gymnospora revealed the highest amounts of unsaturated FAs (51.5 and 38.15%, respectively), constituted mainly of oleic acid (18:1, n9) with proportions 18.29 and 33.79%, respectively. Phytol, cholest-5-en-3-ol, β-stigmasterol and 9Z-octadecenamide were recorded as major unsaponifiable-lipid constituents. 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 85.82µg/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. The major essential AAs were leucine and phenylalanine, while proline was the major non-essential AAs in all species. The MeOH extracts of T. oranata and C. trinodis displayed mild antioxidant activity with IC50 values of 26.1 and 30.5µg/ml. FAs contents of C. trinodis and D. cervicornis exhibited antibacterial activities 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 inhibition MIC value for both = 0.312mg/ml.