Elsevier

Food Chemistry

Volume 109, Issue 2, 15 July 2008, Pages 439-446
Food Chemistry

Analytical Methods
Determination of carotenoids in Dunaliella salina cultivated in Taiwan and antioxidant capacity of the algal carotenoid extract

https://doi.org/10.1016/j.foodchem.2007.12.043Get rights and content

Abstract

A simple HPLC method with good separation efficiency was developed to determine all-trans and cis forms of carotenoids in Dunaliella salina cultivated in Taiwan. The analysis used a C30 column (250 × 4.6 mm, 5 μm) and an isocratic solvent system (flow rate = 1 mL/min) mixing methanol–acetonitrile–water (84/14/2, v/v/v) and methylene chloride, (75/25, v/v). Carotenoids were detected at 450 nm. Moreover, the antioxidant capacities of the algal carotenoid extract were also evaluated with Trolox equivalent antioxidant capacity (TEAC) assay, reducing power and 2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH) radical scavenging assay. Results showed that 7 carotenoids in the algal extract could be separated simultaneously within 30 min and the total amount of them was 290.77 mg/g algae. The contents of all-trans-β-carotene and 9- or 9′-cis-β-carotene, the major carotenoids in the algae, were 138.25 and 124.65 mg/g algae, respectively. The contents of all-trans-lutein, all-trans-zeaxanthin, 13- or 13′-cis-β-carotene, all-trans-α-carotene and 9- or 9′-cis-α-carotene were 6.55, 11.27, 4.95, 2.69, and 2.41 mg/g algae, respectively. The algal carotenoid extract had significantly higher antioxidant activity than all-trans forms of α-carotene, β-carotene, lutein and zeaxanthin in all antioxidant assays. The cis forms of carotenoids, especially 9- or 9′-cis-β-carotene, might play crucial roles for the antioxidant capacities of the algal extract.

Introduction

Dunaliella salina is a type of unicellular and halophilic green biflagellate microalga without a rigid cell wall structure (Ben-Amotz and Avron, 1992, Denery et al., 2004, García-González et al., 2005, Raja et al., 2007). Because D. salina contains abundant β-carotene, the algae has been used as a food coloring agent, a pro-vitamin A supplement for food and animal feed, an additive to food and cosmetics, a health food product (antioxidant claim) and so on (Edge et al., 1997, Johnson and Schroeder, 1995).

Carotenoids are recognized as efficient antioxidants against oxidative damage (Jimenéz, & Pick, 1993). They could quench singlet oxygen (1O2), resulting in the suppression of lipid peroxidation (Burton and Ingold, 1984, Foote and Denny, 1968). Ben-Amotz (1999) indicated that humans could lower incidence of certain cancers, coronary heart disease and other degenerative diseases through eating carotenoid-rich vegetables and fruits (Ben-Amotz, 1999, Gester, 1993, Ziegler, 1989). For the determination of carotenoids, the reversed-phase high performance liquid chromatography (RP-HPLC) has been used routinely because of its excellent separation efficiency (Chen et al., 2004, Inbaraj et al., 2006, Liu et al., 2004, Tai and Chen, 2000). There are, however, no thorough reports on the composition and content of carotenoids in D. salina cultivated in Taiwan.

In the present study, we developed an isocratic RP-HPLC method to determine carotenoids including their isomers in D. salina; the amounts of these compounds in the algae were also quantified. The antioxidant activities of the algal carotenoid extract for Trolox equivalent antioxidant capacity (TEAC) assay, reducing power and scavenging ability on 2,2-diphenyl-2-picrylhydrazyl hydrate (DPPH) radicals were also investigated in this work.

Section snippets

Materials

Spray dried powder of D. salina (Dunal) Teod. cultivated in Taiwan was obtained from Gong Bih Enterprise Co., Ltd. (Wunlin, Taiwan).

Chemicals and standards

All-trans forms of α-carotene, β-carotene, lutein and zeaxanthin standards were purchased from Sigma Co. (St. Louis, MO, USA). Solvents used for the extraction and determination of carotenoids, such as acetonitrile (ACN), methanol (MeOH), methylene chloride (CH2Cl2), ethanol (EtOH), acetone and n-hexane were purchased from Merck Co. (Darmstadt, Germany). Deionized

HPLC analysis of carotenoids in D. salina

Fig. 1 is the HPLC chromatogram of carotenoid extract from D. salina. Seven carotenoids (the spectral characteristics and Q-ratios of the seven resolved peaks corresponded to carotenoids) in the extract could be separated simultaneously within 30 min. Table 1 shows the assignment data for all-trans and cis forms of carotenoids in D. salina. Peaks 1, 2, 4 and 6 were certainly assigned as all-trans forms of lutein, zeaxanthin, α-carotene and β-carotene, respectively based on the criteria expounded

Conclusion

In this investigation, seven carotenoids were determined in D. salina cultivated in Taiwan using a HPLC method with isocratic solvent system. The algal carotenoid extract had remarkably higher antioxidant activity than all-trans forms of α-carotene, β-carotene, lutein and zeaxanthin. The cis forms of carotenoids in the extract, especially 9- or 9′-cis-β-carotene, might play crucial roles in the antioxidant activity. Therefore, our work provides the necessary information to exploit D. salina as

Acknowledgment

This work was supported by Chun Shan Medical University, Taichung, Taiwan (Project No. CSMU-82-B-013 and CSMU 94-OM-A-163).

References (38)

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