| Summary: | 碩士 === 國立宜蘭大學 === 生物資源學院碩士在職專班 === 104 === Astaxanthin is one kind of carotenoid and it is the strongest antioxidant activity among the natural materials. Haematococcus pluvialis has the highest astaxanthin content. However, H. pluvialis has a thick cell wall, which causes resistance of solvent extraction of astaxanthin. The objectives of this study were to establish extraction and analysis methods for astaxanthin from H. pluvialis, and to analyze the antioxidant activity and stability of extract. Finally, the kinetics model for astaxanthin retention during storage could be established. Astaxanthin extract from the H. pluvialis was analyzed by HPLC and it was added 0.1N NaOH under 6℃ nitrogen saponification 24 hr at dark. HPLC condition was C18 reverse phase HPLC column chromatography with acetonitrile: methanol (15:85) as the mobile phase, 1 mL/min of flow rate, and detection at 476 nm wavelength. Astaxanthin in extract from H. pluvialis powder by acid pretreatment and ultrasonic extraction by ethanol after 0.1 N NaOH saponification 24 hours for HPLC analysis was 76.38% of total carotenoid by colorimetric analysis. The colorimetric method for total carotenoid analysis could be instead of HPLC method to fast and convenient analysis extracts from H. pluvialis, and the astaxanthin content could be calculated by the relationship formula.
There were several extraction methods such as DMSO and acetone, homogenization, ultrasonic extraction and acid pretreatment with ultrasonic extraction by ethanol for extracting astaxanthin from H. pluvialis and their total carotenoid contents were analyzed by colorimetric methods. The results showed that H. pluvialis powder by acid pretreatment of 4N HCl at 70℃ 10 min, and 20 min ultrasonic extraction by 95% ethanol had the highest values of total carotenoid in 24.61 mg/g and 62.43% scavenging ability of DPPH by colorimetric analysis. Total carotenoids in the extracts by DMSO or acetone were 16.76 mg/g, 0.9 mg/g. Moreover, total carotenoids in the extracts by homogeneous and ultrasonic extraction were only 0.58 mg/g and 0.41 mg/g, respectively. Except the acid pretreatment and ethanol ultrasonic extraction, other extracts had very low DPPH scavenging ability.
The stabilities of astaxanthin (ASX) and β-cyclodextrin encapsulated astaxanthin (CD-ASX) were analyzed at four different storage temperature (25, 40, 45, and 50oC) in a sealed tube and an uncovered tube, respectively. The kinetics of ASX and CD-ASX retentions were the zeroth reaction order and the reaction rate constant k values were increased with higher storage temperature. There were significant difference between uncover and sealed conditions. Therefore, temperature and air significantly affected the stabilities of ASX. The ASX retention rates were plotted with inverse of different absolute storage temperatures, then the activation energy (Ea) could be obtained according to Arrhenius’ equation. The results showed that the activation energy (Ea) of ASX after encapsulation in the seal condition increased from 56.82 kJ/mol to 113.08 kJ/mol. The activation energy (Ea) of ASX after encapsulation in the uncover condition increased from 51.72 kJ/mol to 106.02 kJ/mol; therefore, the encapsulation of ASX could improve its stability.
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