E/Z isomerization of astaxanthin and its monoesters in vitro under the exposure to light or heat and in overilluminated Haematococcus pluvialis cells

Improved Flesh Pigmentation of Rainbow Trout (Oncorhynchus mykiss) by Feeding Z-Isomer-Rich Astaxanthin Derived from Natural Origin

The use of Paracoccus carotinifaciens-derived natural astaxanthin as an alternative to synthetic astaxanthin has attracted considerable attention from the aquaculture industry. Furthermore, to enhance the bioavailability of astaxanthin, its "Z-isomerization" has been actively studied in recent years. This study investigated the effects of feeding a diet containing astaxanthin rich in the all-E- or Z-isomers derived from P. carotinifaciens on the pigmentation and astaxanthin concentration in rainbow trout (Oncorhynchus mykiss) flesh. Z-Isomer-rich astaxanthin was prepared from the P. carotinifaciens-derived all-E-isomer by thermal treatment in fish oil, and the prepared all-E-isomer-rich astaxanthin diet (E-AST-D; total Z-isomerratio = 9.1%) and Z-isomer-rich astaxanthin diet (Z-AST-D; total Z-isomer ratio of astaxanthin = 56.6%) were fed to rainbow trout for 8 weeks. The feeding of Z-AST-D resulted in greater pigmentation and astaxanthin accumulation efficiency in the flesh than those fed E-AST-D. Specifically, when E-AST-D was fed to rainbow trout, the SalmoFan score and astaxanthin concentration of the flesh were 22.1±1.4 and 1.36±0.71 μg/g wet weight, respectively, whereas when Z-AST-D was fed, their values were 26.0±2.5 and 5.33±1.82 μg/g wet weight, respectively. These results suggest that P. carotinifaciens-derived astaxanthin Z- isomers prepared by thermal isomerization are more bioavailable to rainbow trout than the all-E-isomer.

Astaxanthin Isomers: A Comprehensive Review of Isomerization Methods and Analytic Techniques

The presence of multiple conjugated double bonds and chiral carbon atoms endows astaxanthin with geometric and optical isomers, and these isomers widely exist in biological sources, food processing, and in vivo absorption. However, there remains no systematic summary of astaxanthin isomers regarding isomerization methods and analytic techniques. To address this need, this Review focuses on a comprehensive analysis of Z-isomerization methods of astaxanthin, including solvent system, catalyst, and heat treatment. Comparatively, high-efficiency and health-friendly methods are more conducive to put into practical use, such as food-grade solvents and food-component catalysts. In addition, we outline the recent advances in analysis techniques of astaxanthin isomers, as well as the structural characteristics reflected by various methods (e.g., HPLC, NMR, FTIR, and RS). Furthermore, we summarized the related research on the safety evaluation of astaxanthin isomers. Finally, future trends and barriers in Z-transformation and analysis of astaxanthin isomers are also discussed.

Characteristics of LED light-induced geometrical isomerization and degradation of astaxanthin and improvement of the color value and crystallinity of astaxanthin utilizing the photoisomerization

The effects of light-emitting diode (LED) irradiation characterized by different emission wavelengths on the E/Z-isomerization and degradation of astaxanthin were investigated. LED irradiation slightly promoted Z-isomerization of astaxanthin, whereas the all-E-isomerization was highly efficiently promoted at specific wavelengths, especially at 365 nm. Astaxanthin isomers did not degrade significantly when dissolved in ethanol and subjected to LED irradiation conditions for 300 min. However, significant degradation was achieved when ethyl acetate was used for dissolution, and the samples were irradiated at the wavelength of 405 nm. The addition of α-tocopherol suppressed the photodegradation of astaxanthin. LED irradiation significantly affected the physical properties of astaxanthin Z-isomers. Irradiation with 365, 405, and 470 nm LEDs enhanced the color value (redness) and crystallinity of the Z-isomers via an all-E-isomerization reaction. These findings can contribute to the development of technologies that can arbitrarily control the E/Z-isomer ratio and physical properties of astaxanthin.

Safety of a change in specifications of the novel food oleoresin from Haematococcus pluvialis containing astaxanthin pursuant to Regulation (EU) 2015/2283

Following a request from the European Commission, the EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA) was asked to deliver an opinion on the safety of a change of specifications of the novel food (NF) oleoresin from Haematococcus pluvialis containing astaxanthin (ATX) pursuant to Regulation (EU) 2015/2283. The NF is already authorised as ingredient for the use in food supplements as defined in Directive 2002/46EC in accordance to Regulation (EU) 2017/2470. The NF concerns an oleoresin which contains ~ 10% ATX, obtained by supercritical CO2 extraction of the homogenised and dried biomass of cultivated H. pluvialis. This NF has been assessed by the Panel in 2014. With the present dossier, the applicant proposed to lower the minimum specification limits for protein and ATX monoesters for the NF, and to increase the maximum specification limit for the relative amount of ATX diesters in total ATX. An increase of the maximum specification limit for the 9-cis isomer is also applied for. Although the data are limited regarding bioavailability and distribution in humans of these three naturally occurring ATX isomers, the available in vitro and in vivo data suggest that the 13-cis rather than the 9-cis ATX is selectively absorbed, i.e. has a higher bioavailability and/or possibly emerges from isomerisation of all-trans ATX. The Panel notes that the toxicity of the individual ATX isomers has not been studied individually. However, the ADI of 0.2 mg/kg, which was established for synthetic ATX and ATX from H. pluvialis, applies also for ATX in the oleoresin from H. pluvialis with the proposed changes of specifications. The Panel concludes that the NF, oleoresin from H. pluvialis containing ATX, is safe with the proposed specification limits.

Light Increases Astaxanthin Absorbance in Acetone Solution through Isomerization Reactions

Astaxanthin quantitative analysis is prone to high variability between laboratories. This study aimed to assess the effect of light on the spectrometric and high-performance liquid chromatography (HPLC) measurements of astaxanthin. The experiment was performed on four Haematococcus pluvialis-derived astaxanthin-rich oleoresin samples with different carotenoid matrices that were analyzed by UV/Vis spectrometry and HPLC according to the United States Pharmacopoeia (USP) monograph. Each sample was dissolved in acetone in three types of flasks: amber glass wrapped with aluminium foil, uncovered amber glass, and transparent glass. Thus, the acetone solutions were either in light-proof flasks or exposed to ambient light. The measurements were taken within four hours (spectrometry) or three hours (HPLC) from the moment of oleoresin dissolution in acetone to investigate the dynamics of changes in the recorded values. The results confirm the logarithmic growth of astaxanthin absorbance by 8-11% (UV/Vis) and 7-17% (HPLC) after 3 h of light exposure. The changes were different in the samples with different carotenoid matrices; for instance, light had the least effect on the USP reference standard sample. The increase in absorbance was accompanied with the change of isomeric distribution, namely a reduction of 13Z and an increase of All-E and 9Z astaxanthin. The greater HPLC values' elevation was related not only to the increase of astaxanthin absorbance, but also to light-dependent degradation of internal standard apocarotenal. The findings confirm a poor robustness of the conventional analytical procedure for astaxanthin quantitation and a necessity for method revision and harmonization to improve its reproducibility.

Nanotechnology-Abetted Astaxanthin Formulations in Multimodel Therapeutic and Biomedical Applications

Astaxanthin (AXT) is one of the most important fat-soluble carotenoids that have abundant and diverse therapeutic applications namely in liver disease, cardiovascular disease, cancer treatment, protection of the nervous system, protection of the skin and eyes against UV radiation, and boosting the immune system. However, due to its intrinsic reactivity, it is chemically unstable, and therefore, the design and production processes for this compound need to be precisely formulated. Nanoencapsulation is widely applied to protect AXT against degradation during digestion and storage, thus improving its physicochemical properties and therapeutic effects. Nanocarriers are delivery systems with many advantages─ease of surface modification, biocompatibility, and targeted drug delivery and release. This review discusses the technological advancement in nanocarriers for the delivery of AXT through the brain, eyes, and skin, with emphasis on the benefits, limitations, and efficiency in practice.

Identification and Content of Astaxanthin and Its Esters from Microalgae Haematococcus pluvialis by HPLC-DAD and LC-QTOF-MS after Extraction with Various Solvents

Haematococcus pluvialis, a unicellular green microalga that produces a secondary metabolite under stress conditions, bears one of the most potent antioxidants, namely xanthophyll astaxanthin. The aim of our study was to determine the content of astaxanthin and its esterified forms using three different solvents-methyl tert-butyl ether (MTBE), hexane isopropanol (HEX -IPA) and acetone (ACE)-and to identify them by using high performance liquid chromatography coupled with diode array detection and the quadrupole time-of-flight mass spectrometry (HPLC-DAD and LC-QTOF-MS) technique. We identified eleven astaxanthin monoesters, which accounted for 78.8% of the total astaxanthin pool, six astaxanthin diesters (20.5% of total), while free astaxanthin represented the smallest fraction (0.7%). Astaxanthin monoesters (C16:2, C16:1, C16:0), which were the major bioactive compounds in the H. pluvialis samples studied, ranged from 10.2 to 11.8 mg g-1 DW. Astaxanthin diesters (C18:4/C18:3, C18:1/C18:3) were detected in the range between 2.3 and 2.6 mg g-1 DW. All three solvents were found to be effective for extraction, but MTBE and hexane-isopropanol extracted the greatest amount of free bioactive astaxanthin. Furthermore, MTBE extracted more low-chain astaxanthin monoesters (C16), and hexane-isopropanol extracted more long-chain monoesters (C18 and above) and more diesters. We can conclude that MTBE is the solvent of choice for the extraction of monoesters and hexane-isopropanol for diesters.