Rapid and Efficient Conversion of All-E-astaxanthin to 9Z- and 13Z-Isomers and Assessment of Their Stability and Antioxidant Activities

Euro J Lipid Sci & Tech

Sowa

Kawashima

2020

The effects of heating and photo-irradiation on the stability of all-E-isomer-rich and Z-isomer-rich xanthophylls, astaxanthin and its structurally related xanthophylls, adonirubin, and adonixanthin, are investigated. The xanthophylls with high Z-isomer content are prepared from their high-purity all-E-isomers by thermal isomerization and filtering techniques, that is, total Z-isomer ratios of adonirubin, astaxanthin, and adonixanthin are 80.9%, 89.5%, and 72.5%, respectively. The all-E-and Z-isomer-rich xanthophylls dissolved in ethanol are stored at 4, 30, and 50°C in the dark and at 30°C under photo-irradiation using a fluorescent light for 21 days. In the all-E-isomer-rich xanthophylls, as the storage temperature increases, the total Z-isomer ratio becomes higher, whereas in the Z-isomer-rich xanthophylls, the all-E-isomer ratio becomes higher. Photo-irradiation slightly promotes Z-isomerization in (all-E)-xanthophylls, but highly promotes all-E-isomerization in Z-isomer-rich xanthophylls. In addition, photo-irradiation prevents thermal Z-isomerization of (all-E)-xanthophylls. Moreover, it is found that some xanthophyll Z-isomers such as (9Z)-astaxanthin are more stable than that of the other Z-isomers against heating and photo-irradiation. These findings can contribute not only to establishing suitable storage conditions for Z-isomer-rich xanthophylls, but also to developing control techniques for the E/Z-isomer ratio of the xanthophylls. Practical Applications: The fundamental data on the stability of xanthophyll isomers against heating and photo-irradiation and finding stable xanthophyll Z-isomers are very important to develop xanthophyll materials rich in the Z-isomers. Moreover, this study clearly shows that the heat treatment enhances the Z-isomerization of xanthophylls, whereas the photo-irradiation enhances the all-E-isomerization and prevents thermal Z-isomerization of them. This information can be utilized in technology for arbitrarily controlling E/Z-isomerization of xanthophylls.

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Thermal‐ and Photo‐Induced Isomerization of All‐E‐ and Z‐Isomer‐Rich Xanthophylls: Astaxanthin and Its Structurally‐Related Xanthophylls, Adonirubin, and Adonixanthin

Euro J Lipid Sci & Tech

Sowa

Kawashima

2020

“…They carried out the isomerization tests in ethyl acetate, while our study showed that Z ‐isomerization of lycopene proceeds efficiently without using such organic solvents. Furthermore, other Z ‐isomerization methods for carotenoids such as light irradiation and catalysis use chemical reagents. Thus, since the microwave irradiation for Z ‐isomerization of lycopene has high efficiency and safety, it is considered to be an extremely suitable method for practical applications in the food, drink, and dietary supplement manufacturing industries.…”

Section: Resultsmentioning

confidence: 99%

Microwave‐Accelerated Z‐Isomerization of (all‐E)‐Lycopene in Tomato Oleoresin and Enhancement of the Conversion by Vegetable Oils Containing Disulfide Compounds

Euro J Lipid Sci & Tech

Sato

Takehara

et al. 2018

The effect of microwave irradiation on Z‐isomerization of (all‐E)‐lycopene contained in tomato oleoresin is investigated, and the Z‐isomerization efficiency is compared to that of the conventional oil‐bath heating method. With a 4‐min microwave treatment at 2450 MHz frequency and 500 W power, the total Z‐isomer content of lycopene increased to approximately 70%, almost without decomposition, and the efficiency, at the same temperature, is higher than that with conventional heating. In both treatments, the (9Z)‐ and (13Z)‐isomers are mainly formed. Moreover, the effect of addition of vegetable oils to the oleoresin on the Z‐isomerization by microwave irradiation is examined. When roasted seed oils and garlic oil are added, the production of (5Z)‐lycopene, an isomer having higher functionality and storage stability among the Z‐isomers, is significantly increased. This work reveals that the promoting effect is probably caused by the presence of disulfide compounds existing commonly in the above oils: Thiyl radicals, produced from disulfide compounds by microwave irradiation, would act as a catalyst for the Z‐isomerization reaction. Practical Applications: Z‐Isomers of lycopene, which are the predominant forms in the human body, have higher bioavailability and antioxidant capacity than the all‐E‐isomer, which is the major configuration form in raw tomatoes. Thus, appropriate methods are required to achieve the efficient Z‐isomerization of (all‐E)‐lycopene. This study has developed an efficient production method for lycopene Z‐isomers by microwave irradiation of (all‐E)‐lycopene in edible vegetable oils containing disulfide compounds, in which neither organic solvents nor food additives are used. It would be practically feasible to utilize this procedure not only for food, drink, and dietary supplement manufacturing, but also for daily cooking. (all‐E)‐Lycopene in tomato oleoresin is efficiently isomerized to the Z‐isomers by microwave irradiation and the Z‐isomerization is accelerated by adding vegetable oils containing disulfide compounds.

Enhanced solubility and reduced crystallinity of carotenoids, β-carotene and astaxanthin, by Z -isomerization

Eur. J. Lipid Sci. Technol.

Kodama

Kageyama

et al. 2018

The impact of the Z‐isomer content of carotenoids, β‐carotene and astaxanthin, on their solubility in organic solvents and crystallinity is investigated. Carotenoid samples containing different Z‐isomer contents are prepared from the high‐purity all‐E‐isomers by the thermal isomerization and filtering technique: β‐carotene, 27.4% and 89.8% Z‐isomer content; astaxanthin, 34.5% and 63.2% Z‐isomer content. As the Z‐isomer content of the carotenoids increases, their relative solubility markedly improves, e.g., the solubility in ethanol of β‐carotene containing 89.8% Z‐isomer is ≈250 times higher than that of the all‐E‐isomer. Moreover, differential scanning calorimetry (DSC), powder X‐ray diffraction (XRD), and scanning electron microscopy (SEM) analyses clearly indicate that the (all‐E)‐carotenoids are present in the crystal state, while the Z‐isomers are present in an amorphous state. A number of studies have reported that the Z‐isomerization of carotenoids induced changes in bioavailability and antioxidant activity. This may be due to the change in physicochemical properties such as solubility and crystallinity by Z‐isomerization. In addition, these changes are important information for improving carotenoid processing. Practical Applications: Carotenoids in plants occur predominantly in the all‐E‐configuration, whereas the Z‐isomers are present in the human body in considerable quantity. Since (all‐E)‐carotenoids have low solubility in solvents and high crystallinity, efficiencies of those processing such as solvent extraction, micronization, and emulsification are low. However, this study experimentally reveals that solubilities of carotenoids, β‐carotene and astaxanthin, are significantly improved and crystallinities of them are reduced by Z‐isomerization. These fundamental data should contribute to improvement of carotenoids processing efficiency. The effect of the Z‐isomer content of carotenoids, β‐carotene and astaxanthin, on their solubility in organic solvents and crystallinity is investigated. Increasing the Z‐isomer contents of the carotenoids, those solubility improved and those crystallinity reduced.