Effect of different extraction conditions on phlorotannin content and antioxidant activity of extract from brown algae ( Sargassum angustifolium (

Brown algae are a valuable source of natural antioxidant compounds, especially phlorotannins. In this study, the extraction was performed from brown alga Sargassum angustifolium by three methods: solvent, ultrasound- assisted and microwave-assisted. Then the amount of phlorotannin content and antioxidant properties of the extracts were evaluated. The solvent extraction was performed at room temperature (26-28 °C) with ethanol/ water solvent in three ratios (30:70), (50:50), and (70:30). Also, the extraction was performed by ultrasound- assisted and microwave-assisted with ethanol solvent in three durations of 10, 25, and 40 minutes. Ultrasound- assisted conditions included 24 kHz frequency, 400 w power level and 50% amplitude. The power level of microwave-assisted was 450 w. The amount of phlorotannin content, total phenolic content, ferric reducing antioxidant power, DPPH radical scavenging activity, and total antioxidant capacity in different extracts were evaluated. The results showed that the yield of phlorotannin content was dependent on the solvent concentration, and its amount increased with increasing polarity of the solvent. According to this, the maximum amount of phlorotannin was obtained from ethanol/ water treatment (30:70) at the rate of 3.40± 0.00 mg phloroglucinol per gram dry weight that was significantly higher than the other two treatments (P< 0.05). The highest total phenol content was obtained in ethanol/ water treatment (30:70) and the highest total antioxidant capacity was obtained in ethanol/ water treatment (70:30). According to all factors and variables considered, the best treatment was microwave assisted- extraction in the duration of 25 and 40 minutes. Finally, it was found that the extract of brown alga S. angustifolium was a perfect choice for the extraction of antioxidant compounds, especially phlorotannins for dietary and medicinal purposes.