Background: Ethanolic, aqueous and lipidic extracts of Spirulina platensis were evaluated for their bioactive substances (polyphenols and fatty acids) and antioxidant activities using two different assays diphenyl-1-picrylhydrazyl (DPPH) and azino-bis (ethylbenzthiazoline-6- sulfonicacid (ABTS)). Methods: The phenolic compounds amounts were determined by colorimetric assays and were analyzed by high-performance and liquid chromatography (HPLC) method. The identification of phenolic compounds in the extract was accomplished by comparison of their retention times with those of pure standards. The chemical composition of fatty acids in lipidic extract was determined by GC/FIDs and GC/MS method. Results: The obtained results revealed that using DPPH, the ethanolic extract recorded the highest activity with (IC50=449 μg/mL ± 83). It was characterized with a high levels of phenolic and flavonoid content 0.33 ± 0.01 mg GAE/g dw and 0.21 ± 0.01 mg quercetin/g dw, respectively. The ethanolic extract showed the presence of caffeic acid, syringic acid, ferulic acid, p-coumaric acid, chlorogenic acid, kaempferol, quercetin and apigenin. Those entire phenolic compounds seem participle synergistically to the pronounced higher activity. To the best of our knowledge, the apigenin (4′, 5, 7,-trihydroxyflavone), a natural compound which is famously known by its potent antiradical activity, was identified for the first time in Moroccan S. platensis only in the ethanolic extract. A high positive correlation (r=0.895) between the antioxidant activity and the chemical composition of ethanolic extract was observed. For ABTS, lipidic extract showed the highest activity with (IC50=740 μg/mL ± 12). A total of 15 fatty acids compounds, amounting 89.73% of the extract were identified. γ-linolenic acid (GLA) (39.02%) and α-linolenic acid (ALA) (13.85%) were the major component and contribute greatly to the antioxidant activity observed. The lipidic extract has a high content of unsaturated fatty acids (70.95%) which are often exhibited very high antioxidant activity since they have two or more double bonds and chain lengths. The aqueous extract either with DPPH or ABTS methods, recorded low antioxidant activity. Its correlation was r=0.499, lower than found in the ethanolic extract. Conclusions: These results showed that Spirulina platensis could be considered as a valuable source of fatty acids and phenolics with potent antioxidant activity. It may be employed in the manufacture of pharmaceutical drugs as an alternative source of natural antioxidants.

The samples of Spirulina platensis were collected from Lake Foum Elouad, Laayoune (South of Morocco) and cultivated using Zarrouk’s synthetic medium in the laboratory. The essential oil was isolated by hydrodistillation and analysed by GC/FID and GC/MS. The average yield oil obtained was 0.9%. A total of 66 compounds, amounting 96.7 % of the essential oils, were identified. The major components of S. platensis essential oils were heptadecane (41.7 %), tetradecane (25.3 %), ethyl benzene (5.5 %) and 6-methyl-5-hepten-2-one (3.7 %). Interestingly, it has been reported for the first time in the Moroccan Spirulina, the presence of geosmin, which is a very important component of odour in cyanobacteria. To our knowledge, the geosmin was not found in any S. platensis essential oils before. The antibacterial activity of the essential oil was evaluated against six strains. The most potent effect of the essential oil was obtained against two Gram (+) bacteria: B. antharcis, S. epidermidis and the Gram (-) bacteria E. coli (with the higher inhibition zone as 28 mm). The MICs were respectively 16.37, 19.13 and 17.81 μL/mL. A total inhibition was shown for S. aureus. Thus the essential oil of S. platensis possess effective antimicrobial properties.

The cyanobacterium Arthrospira platensis (A. platensis)a genus of nonheterocystous filamentous cyanobacteriais used in industrial applications and as a food supply. The current research work aims to study the physicochemical characteristics of A. platensis indigenous to the Moroccan Atlantic coast at Laayoune (Foum El Oued lagoon). The contents of proteins, carbohydrates, vitamins, lipids, minerals, heavy metals, energy value, humidity, ash, pigments, and tannins in A. platensis were investigated using protocols as described in the earlier literature. The values of protein, carbohydrate, and lipid contents in A. platensis were 58.9±0.07, 14.67, and 45.54 respectively. The values of vitamins B₂ and B₃ dosed in A. platensis were 1.31±0.19 and 30.8±0.001mg/kg, respectively. The values of heavy metals including lead and chromium were 70±4.5 and 5±0.5 PPB (parts-per-billion), respectively; however, no trace concerning cadmium was detected. The values of energy value, humidity, and ash content were 346.48±0.21, 11.6±0.17, and 9.1±0.21kcal/100g, respectively. The results of pigment content showed the presence of chlorophyll b, chlorophyll a, and carotenoids of 37.506±3.38, 26.066±3.08, and 9.52±0.22mg/g, respectively. The results obtained revealed that A. platensis indigenous to the Moroccan Atlantic coast at Laayoune was found to be very rich in proteins, carbohydrates, vitamins, minerals, ash, and pigments and lower in heavy metals and saturated fats when compared with species investigated in the literature. Thus, A. platensis indigenous to the Moroccan Atlantic coast at Laayoune fulfills the requirements for being used as dietary supplements.