Enhancing the Antioxidant Activity of Alginic Acid Extracted from Sargassum Angustifolium Brown Algae Based on Optimizing the Extraction

Abstract

Background: Researchers are always searching for chemicals with antioxidant properties. The cell wall polysaccharide of Sargassum angustifolium consists of alginic acid. To use this polysaccharide and investigate on its various effects, it must first be isolated from brown algae and the operational parameters of extraction need to be optimized to reach the maximum antioxidant effect. Materials and Methods: The effects of changing the parameters (temperature, time, and power of ultrasonic waves) used in the extraction of alginic acid were discussed based on changes in the antioxidant effect. After that, M/G (β-D-mannuronic acid to α-L-guluronic acid ratio) was measured using 1H NMR spectra, and the antioxidant activity of the extracted alginic acid was examined using the DPPH method. Results: The highest antioxidant effect was observed in sample No. 4 with an extraction temperature of 65°C, extraction duration of 25 min, and 640 W of ultrasonication power, whereas the lowest antioxidant effect was observed in sample No. 7 at 45°C, 20 min, and 480 W. Conclusion: Structural changes due to increasing temperature may cause less activity, whereas the optimum temperature was 65°C. There was no direct relationship between M/G and IC50, and it should be examined along with molecular weight. Increasing the intensity of the waves increased the antioxidant activity. The extraction yield can be increased by increasing A/W (Gram of algal sample per mL of solvent). It appears that the extraction under optimum conditions enhances the MM block epimer, which may lead to an increase in the antioxidant activity.