Spirulina is a seaweed consumed worldwide and studies related to its biological properties have increased in recent years. However, comparative studies on the antioxidant activity of spirulina are currently scarce. For this reason, this study compared the antioxidant activity of aqueous, hydroalcoholic, and ethanolic extracts of four brands of spirulina (B1, B2, B3, and B4), which are frequently consumed in the city of Arequipa, Peru. For this purpose, fluid extracts of spirulina were prepared using ultrasound. All four brands of spirulina studied were found to exhibit significant antioxidant activity. The aqueous extracts obtained antioxidant activity values of 51.70 ± 0.52, 48.24 ± 0.52, 36.82 ± 0.46, and 13.52 ± 0.61 μmol TE/mL for brands B1, B2, B3 and B4, respectively. In the hydroalcoholic extracts, the antioxidant capacity was 6.66 ± 0.53, 6.48 ± 0.95, 3.25 ± 0.17, and 2.8...