Seasonal Variability of the Biochemical Composition and Antioxidant Properties of Fucus spiralis at Two Azorean Islands

This study evaluates, for the first time, the seasonal (winter and summer) and geographical (São Miguel–SMG and Santa Maria–SMA Islands) variability of Fucus spiralis (Fs) biochemical composition (dry weight basis) and antioxidant properties. Protein and carbohydrates presented higher values in Fs-SMG(winter), lipids, total dietary fiber, and energy value in Fs-SMA(summer), and ash and soluble dietary fiber/insoluble dietary fiber ratio in Fs-SMA(winter). The fatty acid (FA) profiles showed a lower SFA in Fs-SMG(summer), whereas MUFA and PUFA presented higher values in Fs-SMG(summer) and Fs-SMG(winter), respectively. Excellent dietary ratios of n6/n3 PUFA and hypocholesterolemic/hypercholesterolemic FA were found, with lower values in Fs-SMA(winter) and higher in Fs-SMG(summer), respectively. The highest total phenolics was found in Fs-SMA(summer) acetone:water extract and total flavonoids showed the higher value in Fs-SMG(winter) methanol extract. The best free radical-scavenging activity was observed in the Fs-SMA(winter) methanol (EC(50) = 0.045 mg/mL) and acetone:water (EC(50) = 0.059 mg/mL) extracts. The ferric-reducing antioxidant power showed the best results in Fs-SMA(winter) methanol extract (EC(50) = 0.016 mg/mL) and Fs-SMA(summer) acetone:water extract (EC(50) = 0.017 mg/mL). The best ferrous ion-chelating activity was found in Fs-SMG(winter) acetone:water extract. Overall, results revealed that F. spiralis nutritional and functional bioactivity values have geographical and seasonal variations and that its regular consumption may add benefits to human health.