In the current work, carotenoids of the three microalgae [Spirulina platensis (S. platensis), Scenedesmus obliquus (S. obliquus) and Dunaliellasalina (D. salina)] were extracted, quantified and exposed to phytochemical and biological (cytotoxic, antiviral, antioxidant, and anticholinesterase) activities.Also, some stress conditions were applied to S. platensis and S. obliquus to raise their carote...