Comparison and evaluation of extraction efficiency and antioxidant activity of astaxanthin extracted from Haematococcus microalgae (Haematococcus pluvialis) using acetone solvent and acid-acetone combined technique

The aim of the present study was to extract, saponify and purify astaxanthin pigment from Haematococcus microalgae (Haematococcus pluvialis) and evaluate its antioxidant activity (DPPH free radical scavenging activity and reduction of ferric ions). For extraction, two single (extraction using acetone solvent or ACE) and combined (extraction by pretreatment with hydrochloric acid and then extraction with acetone or HCl-ACE) methods were used. According to the results, amount of extracted astaxanthin (mg/g) by two methods of acetone (ACE) and hydrochloric acid pretreatment (HCl-ACE), in the extraction, saponification and final purification stages were 4.09 (13.65%), 8.49 (28.30%), 14.59 (48.65%) and 9.49 (31.65%), 13.59 (45.30%) and 25.09 (83.65%), respectively. DPPH free radical inhibition activity of extracted astaxanthin with two ACE and HCl-ACE methods (50 to 300 μg/ml) ranged from 66.25 to 76.26% and 85.39 to 94.06%, respectively. These values for ferric ion reduction power were in the absorption range of 0.61 to 0.75 and 0.78 to 0.92 at the wavelength of 700 nm, respectively. The pigment extracted using the combined method (compared to the single method) had significantly more antioxidant activity (p<0.05). In addition, in both tests, increasing the concentration of astaxanthin up to 100 μg/ml, the trend of antioxidant activity was recorded as increasing and then constant (no significant difference between the concentrations of 200 and 300 μg/ml). Comparison of the antioxidant activity of astaxanthin with synthetic antioxidants showed that the pigment extracted by combination method (at high concentrations) had the activity closer or even more than BHA and BHT. According to the findings, the combined method (acid-acetone) compared to the single method (acetone) can improve the extraction efficiency and antioxidant activity of this pigment. Therefore, the method used for the extraction and purification of astaxanthin potentially affects its extraction efficiency and antioxidant activity, and by choosing the extraction optimum method, the mentioned two indicators can be improved in the pigment.