Egyptian Artbrospira phytosterols: Production, identification, antioxidant and antiproliferative activities

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Cultivation of microalgae as a source of phytosterol and other lipid compounds has gained more attention for commercial applications in pharmaceutical, cosmetic and food function industries. In this research, native Spirulina maxima SM from Egypt was grown in individual cultures containing various concentrations of nitrogen (N), phosphorus (P) and sulfur (S) elements in order to elucidate the effect of its elements on lipid and phytosterols production and to evaluate its antioxidant and antiproliferative activities. The results revealed that the SM was able to grow in different concentrations of testing elements S (from 0.3 to 2.4 mM), P (from 0.3 to 2.4 mM) and N (0.3 to 3.2 mM) with significant differences. A high potential for production of MS biomass, total lipid and phytosterol contents were obtained in individual cultures containing 0.6 mM N, 0.6 mM P and 0.80 mM, respectively. Therefore, these concentrations (combination of S+P+N element) were selected for cultivation of SM at large scale in a column photobioreactor (PBR 300 L) to induce sufficient SM biomass so that, we can obtain an adequate amount of total lipid and phytosterol contents. Phytosterols (PS) of native SM grown in the 300 L PBR were partially purified from unsaponified extracts of SM total lipid followed by its purification by crystallization process. The identification and quantification of PS profile were performed by GC-FID analysis. The results revealed high levels of campsterol, D7-Avena sterol, β-sitosterol, stigmasterol and other compounds. These PS compounds showed marked in vitro superoxide, DPPH and OH radical scavenging activity, which was comparable with the results obtained with standard antioxidants BHA or α-tocopherol. Moreover, SM phytosterols exhibited anti-proliferative activity against three human cancer cell lines (MCF-7, Hep-G2 and HCT-116) with IC50 values less than 11.62 fig/mL as assessed by in vitro MTT colorimetric method. Thus, SM phytosterol may be considered as a potential natural source of promising ingredient in the future for a range of health applications for human, cosmetic industries and in functional food.