<![CDATA[Spirulina platensis is a spiral-shaped filamentous microalga classified as a cyanobacterium, known for its diverse bioactive properties, including antioxidant, antimalarial, antidiabetic, anticancer, and antibacterial activities. This study aimed to determine the best extraction method based on the total phenolic content and antioxidant activity of S. platensis and identify antioxidant-related phytochemicals. The biomass of S. platensis was obtained after 14 days of cultivation in the laboratory. Two extraction methods were evaluated: maceration and ultrasound-assisted extraction (UAE), using ethanol as the solvent at a 1:20 (b/v) ratio. The results showed that the UAE method produced significantly higher extract yield, total phenolic content, and antioxidant activity (IC₅₀) than maceration (p < 0.05). The values obtained using UAE were 14.70 ± 1.97%, 128.657 ± 2.67 mg GAE/g, and 148.652 ± 7.78 ppm, respectively. Thin-layer chromatography (TLC) revealed six spots in the extracts. Two of these, with Rf values of 0.78 and 0.98 (exhibited antioxidant activity, as indicated by the yellow color development). Further phytochemical analysis using FeCl₃ confirmed that the spots contained polyphenols. In conclusion, UAE is an effective method for extracting phenolic compounds from S. platensis, enhancing both the phenolic yield and antioxidant activity. These findings support the potential use of S. platensis extracts as natural antioxidants in functional foods and pharmaceutical applications.]]>
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