Astaxanthin Esters Research Articles

Complex formation and stabilization of Z‐isomer‐enriched astaxanthin esters derived from Haematococcus lacustris with water‐soluble carriers via spray drying

AbstractTo enhance the water solubility and bioavailability of astaxanthin esters, inclusion complexes of Z‐isomer‐enriched astaxanthin esters with water‐soluble carriers were prepared using a spray drying technique. A food‐grade Haematococcus alga extract was used as the source of astaxanthin esters, and the Z‐isomerization was performed via direct heating of the extract. Polyvinylpyrrolidone (PVP) and hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) were used as water‐soluble carriers. The effects of spray drying conditions on the encapsulation efficiency of astaxanthin esters in the carriers and the total Z‐isomer ratio of encapsulated astaxanthin esters were investigated, and the physical properties and storage stability of the resulting composites were evaluated. Under optimum spray drying conditions, efficient production of highly water‐soluble Z‐isomer‐rich astaxanthin esters was achieved in both carriers: >95% encapsulation efficiency and >55% total Z‐isomer ratio. The physical properties, such as surface morphology and particle size distributions, of the resulting particles differed significantly between PVP and HP‐β‐CD. Storage tests demonstrated that the formulated Z‐isomer‐rich astaxanthin esters were highly stable. Our findings will contribute to the practical applications of Z‐isomer‐rich astaxanthin materials.Practical Applications: The formulation technology developed in this study has the potential to address the industrial challenges of using astaxanthin, that is, low water solubility and low bioavailability. Furthermore, the low storage stability of astaxanthin Z‐isomers, which hinders their industrial use, can be solved simultaneously. The resulting Z‐isomer‐rich astaxanthin powders are expected to be used in a wide range of applications, including nutraceuticals, cosmetics, and animal feeds.

Structural characteristics of phenylboronic acid-modified astaxanthin ester and its effect on DSS-induced ulcerative colitis by blocking reactive oxygen species and maintaining intestinal homeostasis

A novel and reactive oxygen species (ROS) responsive astaxanthin phenylboronic acid derivative (AstaD-PBA) was constructed by grafting phenylboronic acid (PBA) onto astaxanthin succinate diester (AstaD), and its chemical structure and physicochemical property were identified. AstaD-PBA could effectively improve the ROS quenching ability in the lipopolysaccharide (LPS)-induced RAW264.7 cell inflammation model. Then, the bioactivity of AstaD-PBA was studied by 4 zebrafish ROS-responsive inflammatory models induced by LPS, copper (Cu2+), high-fat diet, and dextran sodium sulfate (DSS). The results suggest that AstaD-PBA might have high biosafety and the best effect on ulcerative colitis (UC) induced by DSS. Furtherly, AstaD-PBA significantly alleviated and treated weight loss and colonic shrinkage, inhibited inflammatory cytokines, and maintained microbiota homeostasis to improve UC in C57BL/6J mice. Alistipes and Oscillibacter were expected to be considered UC marker flora according to the Metastats analysis and Pearson correlation Mantel test (P < 0.01) of 16S rRNA gene sequencing data. In conclusion, AstaD-PBA has been promised to be a functional compound to improve UC and maintain intestinal microbiota homeostasis.

The impact of Neoporphyra haitanensis dietary supplement on astaxanthin esters and fatty acids accumulation associated with immune promotion in Pacific white shrimp (Litopenaeus vannamei)

To explore and develop effective feed additives for enhancing shrimp cultivation, an 8-week feeding experiment was conducted in Litopenaeus vannamei with dietary supplementation ranging from 0% to 5% Neoporphyra haitanensis. The results indicated that a diet containing 2% N. haitanensis enhanced trypsin activity, as well as the height and width of intestinal villi, leading to improved growth performance of L. vannamei. The specific growth rate (SGR), weight gain rate (WGR) and the ratio of flesh content were increased by 1.1 to 2.0 times, while the hepatosomatic index (HSI) and condition factor (CF) values were 85.6% and 91.5% of those in the control group, respectively. Additionally, the inclusion of 2% N. haitanensis in the diet led to a 1.1-fold increase in the accumulation of fatty acids, particularly DHA and EPA. The diet also exhibited elevated levels of β-carotene, zeaxanthin, α-cryptoxanthin, and β-cryptoxanthin, which correlated with the increased content of carotenoids in the shrimp. The exoskeleton was identified as the primary site for assimilating α−/β-carotenes, free astaxanthin, and its diesters (mainly EPA and DHA chains), accompanied by heightened redness (a*) value. Meanwhile, the muscle tended to accumulate astaxanthin and its monoesters (mainly C16:0 and C18:0 chains) and hepatopancreas had lowest contents of astaxanthin and its diesters (mainly DHA chain). Furthermore, the Toll and IMD immune signal pathways in L. vannamei were activated with 2% N. haitanensis in the die, up-regulating the expression of immune-related genes dorsal, relish and imd, and antibacterial peptides genes crustin, lysozyme, and penaeidin3a. Concurrently, the activities of immune-related enzymes ACP and AKP, as well as antioxidant enzymes CAT, SOD, and GPH-Px, were enhanced, while AST and ALT activities were decreased. In terms of intestinal health, the addition of 2% N haitanensis contributed to the preservation of the intestinal tissue structure and promoted the abundance of beneficial bacteria, while reducing the abundance of Vibrio in L. vannamei. The enhanced immune and antioxidant performance of L. vannamei was demonstrated to prevent intestinal structure damage and increase survival rates, as evidenced by WSSV infection experiments. These results offer valuable insights into the dose-dependent effects of dietary seaweeds in promoting shrimp cultivation.

Thermal isomerization of astaxanthin esters in the green alga Haematococcus lacustris without any chemicals

Recent evidence indicates that carotenoid Z-isomers have higher oral bioavailability and biological activity than the all-E-isomers. Therefore, many researchers have investigated the development of efficient carotenoid isomerization techniques, primarily thermal treatment. However, most of them studied the free form of carotenoids. In this study, the thermal isomerization characteristics of astaxanthin esters derived from the food-grade Haematococcus alga were investigated. For practical applications, edible oils were used as the medium in the isomerization process, and organic solvents or other chemicals were not used. Furthermore, a continuous heated flow isomerization system was installed. The optimal heating conditions increased the total Z-isomer ratio of astaxanthin esters to approximately 60% while inhibiting astaxanthin decomposition. The resulting Z-isomer-rich astaxanthin esters displayed excellent storage stability. The stability was shown to be potentially higher than that of the free form. This superior stability of the Z-structure of ester forms was demonstrated by density-functional theory. The observations of this study would contribute to the practical applications of Z-isomer-rich astaxanthin materials.

The Biosynthesis of Astaxanthin Esters in Schizochytrium sp. is Mediated by a Bifunctional Diacylglycerol Acyltransferase.

Astaxanthin esters are a major form of astaxanthin found in nature. However, the exact mechanisms of the biosynthesis and storage of astaxanthin esters were previously unknown. We found that Schizochytrium sp. synthesized both astaxanthin and docosahexaenoic acid (DHA)-enriched lipids. The major type of astaxanthin produced was free astaxanthin along with astaxanthin-DHA monoester and other esterified forms. DHA accounted for 41.0% of the total fatty acids from astaxanthin monoesters. These compounds were deposited mainly in lipid droplets. The biosynthesis of the astaxanthin esters was mainly carried out by a novel diacylglycerol acyltransferase ScDGAT2-1, while ScDGAT2-2 was involved only in the production of triacylglycerol. We also identified astaxanthin ester synthases from the astaxanthin-producing algae Haematococcus pluvialis and Chromochloris zofingiensis, as well as a thraustochytrid Hondaea fermentalgiana with an unknown carotenoid profile. This investigation enlightens the application of thraustochytrids for the production of both DHA and astaxanthin and provides enzyme resources for the biosynthesis of astaxanthin esters in the engineered microbes.

Simultaneous extraction and purification of natural astaxanthin from Haematococcus pluvialis using adsorptive chromatography

The Haematococcus pluvialis is a recognized source of natural astaxanthin. The realm of astaxanthin bioprocessing is emerging with advanced techniques of cultivation and astaxanthin extraction. The present study addresses constraint of H. pluvialis cultivation under the Indian tropical environment for improved astaxanthin production, followed by purification of extracted astaxanthin. The chemical-based extraction using DMSO, yielded 163 mg g−1 of astaxanthin. Further, alkaline saponification was performed with 0.015 M NaOH at 25 °C to de-esterify astaxanthin esters. Considering the prerequisite of food and feed applications, a process was developed for the removal of non-GRAS solvent (DMSO) using adsorptive chromatography. Based on static adsorption and desorption studies of the resins, Amberlite XAD 1180 N was selected for column chromatography. Purification by column chromatographic study yielded DMSO-free 97.3 mg g−1 of astaxanthin, resulting in 80.8 % recovery. Stability studies confirmed 92 % retention of purified astaxanthin with 85 % antioxidant activity at 4 °C over 90 days.

건강기능식품 공전 내 HPLC-UV 기반 아스타잔틴 분석법 개선 및 평가

The HFF (Health Functional Foods) Code provides protocols for the quantitative analysis of 68 types of HFF ingredients. Astaxanthin is one of the HFF with antioxidant properties, preventing cell damage and reducing eye fatigue, becoming popular in the HFF market. To improve the astaxanthin assay protocol, we changed the LC condition from a tertiary pump to a binary pump and optimized the mobile phase and gradient accordingly. Based on the differences in the enzymes, we also observed the efficiency of the conversion of astaxanthin ester to free astaxanthin. We validated our modified method based on AOAC guidelines, including linearity (R20.99), selectivity, accuracy (recovery 92~105%), and precision (%RSD 2). An applicability was evaluated on 15 health functional food products, and the recovery values were satisfied within the range of 80-120%. In this study, we modernized the analytical method of astaxanthin by modifying the LC conditions, and standardized the cholesterol esterase with the highest efficiency.

Selectively extraction of astaxanthin from Haematococcus pluvialis by aqueous biphasic systems composed of ionic liquids and deep eutectic solutions

Haematococcus pluvialis is rich in astaxanthin ester (Ast1) and free astaxanthin (Ast2). The astaxanthin is natural antioxidant, and shows higher biodegradability and eco-friendly characteristics than commercial astaxanthin. However, the existing extraction technology is difficult to achieve selectively separation of Ast1 and Ast2. Novel aqueous biphasic systems (ABSs) composed of ionic liquids (ILs) and deep eutectic solvents (DESs) were developed to selectively extract Ast1 and Ast2. The results showed that the ABS composed of tributyloctylphosphine chloride ([P4448]Cl) and choline chloride:d-fructose ([ChCl][Fru]) performed best. The yield and partition coefficient of astaxanthin was 2.35 mg·g−1 and 103.59, respectively. Moreover, Ast1 and Ast2 could be selectively separately with the highest coefficient of specificity of 48.31. Furthermore, the ABS maintained an excellent extraction capacity after three cycles of recycling. As compared with organic solvent extraction and prior methods, the IL-DES ABS is more efficient, recyclable, and environmentally friendly for selectively extraction of astaxanthin.

Determination of astaxanthin and astaxanthin esters in three samples of shrimp waste (Parapenaeus longirostris) by high performance liquid chromatography coupled photo-diode array and mass spectrometry detection

The present study aimed to identify the content of astaxanthin and its esterified forms using high-performance liquid chromatography coupled with diode array and atmospheric pressure chemical ionisation mass spectrometry detection in three samples of shrimp waste. The analyses revealed twenty-one astaxanthin derivatives, including astaxanthin in free form, across all three extracts with the highest number of derivatives observed in the head extract. The shell extract had a lower content of astaxanthin and its esterified forms, with monoesterified astaxanthins being the major components, with contents ranging from 0.5–1 mg g−1. On the other hand, in both global waste and head extracts, astaxanthin diesters were found to be the dominant bioactive compounds, with contents ranging from 0.7–5.2 mg g−1 and 10.2–18.2 mg g−1, respectively. Notably, the astaxanthin content extracted from head was significantly higher compared to other extracts, indicating its potential as a valuable source of bioactive compounds.

Optimization and identification of astaxanthin esters from shrimp waste using microbial fermentation method

Optimization and identification of astaxanthin esters from shrimp waste using microbial fermentation method

OPTIMIZATION OF THE ASTAXANTHINE ETER SYNTHESIS BY THE METHOD OF MATHEMATICAL PLANNING

Relevance. Astaxanthin occurs naturally in free and esterified form. An important distinguishing property of astaxanthin esters is their great stability during storage, heating and oxidation. It is possible to obtain a substance with an optimal set of physical, chemical and biological characteristics by improving the method of synthesis of the active molecule, which is rationally carried out by mathematical methods. The purpose of the study is to optimize the method for the synthesis of astaxanthin ester and benzoic acid by the method of mathematical planning of the experiment. Material and methods. The influence of the synthesis parameters on the yield of the ester of astaxanthin and benzoic acid, β,β-carotene-4,4'-dione-3,3'-dibenzoate, was evaluated by the method of mathematical planning of the experiment, using the construction of a mathematical model based on the first-order regression equation. Results. The steep ascent method was used to determine the optimal parameters for the synthesis of β,β-carotene-4,4'-dione-3,3'-dibenzoate. The maximum yield of the target product – β,β-carotene-4,4'-dione-3,3'-dibenzoate was achieved at a synthesis temperature of 60°C, a reaction time of 4.5 hours, a biocatalyst amount of 0.5 g, and a stirring speed of 55 rpm. Conclusions. Using the construction of a mathematical model and the search for optimal conditions using the steep climb method, we managed to increase the yield of the target synthesis product – β,β-carotene-4,4'-dione-3,3'-dibenzoate from 50% in the initial conditions to 65%, and also to reveal the influence of all considered factors on the synthesis process. The data obtained on the basis of the conducted studies by the method of mathematical planning of the experiment suggest that the optimal yield of β,β-carotene-4,4'-dione-3,3'-dibenzoate is achieved if the synthesis is carried out at 60°C for 4.5 hours, with a stirring speed of 55 rpm and in the presence of 0.5 g of the Novozyme 435 biocatalyst. During the experiment, it was found that an additional optimization parameter to be introduced into the model could be the “number of biocatalyst use cycles”. However, at the moment it cannot be taken into account in the mathematical model, because this property of the enzyme refers to uncontrolled optimization factors.

Expression of fatty acid related gene promotes astaxanthin heterologous production in Chlamydomonas reinhardtii.

Natural astaxanthin is a high-value ketone carotenoid mainly derived from Haematococcus pluvialis, which is an excellent antioxidant for human consumption. To study the role of lipids in accumulation of astaxanthin, the H. pluvialis-derived astaxanthin synthesis pathway genes (β-carotene ketolase gene, BKT and β-carotene hydroxylase gene, BCH) and fatty acid elongation gene (mitochondrial trans-2-enoyl-coa reductase gene, MECR) were heterologously co-expressed in C. reinhardtii. Zeaxanthin, the precursor of astaxanthin synthesis, was significantly increased after BKT and BCH were expressed. In contrast, the α-carotene that competes with astaxanthin synthesis for lycopene decreased significantly. This redistribution of carbon flow was conducive to the synthesis of astaxanthin. In addition, the transformant only expressed astaxanthin metabolism related genes (BKT, BCH) would lead to an increase in total lipid, a decrease in monounsaturated fatty acids and an increase in polyunsaturated fatty acids. On this basis, the expression of MECR gene further increased the total lipid, and the relative content of different fatty acids also changed. The astaxanthin content of algal strains transformed with BKT and BCH genes was nearly 50% higher than that of the wild type. On this basis, the astaxanthin content of transformants expressing MECR gene related to long-chain fatty acid synthesis was increased by 227.5%. In this study, an astaxanthin production model similar to H. pluvialis by combining carotenoid metabolism and fatty acid metabolism was constructed in C. reinhardtii. The results suggest that the increase in astaxanthin is indeed linked to the regulation of fatty acid metabolism, and this link may involve the type of fatty acids and the dynamics of astaxanthin ester in cells. The strategy of promoting the synthesis of fatty acids has potential to achieve efficient production of astaxanthin in C. reinhardtii.

Astaxanthin- Enriched Fraction from the Microalga Haematococcus pluvialis Mitigates Kidney Injury via Modulation of Nrf2/Keap1 and MAPK/ERK Pathways in Rats

Acute kidney injury is a complication of using gentamicin in high doses and is associated with severe morbidity and mortality. Astaxanthin, the red xanthophyll carotenoid pigment, has an antioxidant power higher than 100 times that of vitamin E and 10 times more than that of β-carotene, making it one of the strongest bioactive carotenoids. Haematococcus pluvialis, Haematococcaceae, microalga produces high amounts of astaxanthin in the form of astaxanthin esters besides adequate amounts of free astaxanthin. We attempted to explore the potential therapeutic effects of astaxanthin- and astaxanthin ester–enriched fractions from H. pluvialis against acute kidney injury induced by gentamicin and their mechanisms of action in rats. Adult male Wister albino rats were injected with gentamicin (100 mg/kg, i.p.) for seven consecutive days to induce acute kidney injury, and these rats were treated daily with astaxanthin ester–enriched fractions (30 mg/kg; p.o.) for 14 days. LC/ESI–MS analysis revealed the presence of different isomers of free astaxanthin, astaxanthin monoesters, and astaxanthin diesters in the astaxanthin- and astaxanthin ester–enriched fractions. Astaxanthin and its esters ameliorated kidney dysfunction, modulated nuclear factor erythroid 2 related factor 2/Kelch-like erythroid associated protein 1/hypoxia-inducible factor-alpha, and suppressed mitogen-activated protein kinases/extracellular signal-regulated kinases/renin-angiotensin system expression. Astaxanthin and its ester improved early acute kidney injury via modulation of the Nrf2/Keap1 antioxidant defense pathway and MAPK/ERK signaling cascade.Graphical

Pulsed Electric Fields (PEF) and Accelerated Solvent Extraction (ASE) for Valorization of Red (Aristeus antennatus) and Camarote (Melicertus kerathurus) Shrimp Side Streams: Antioxidant and HPLC Evaluation of the Carotenoid Astaxanthin Recovery.

Shrimp side streams represent an important natural source of astaxanthin. Optimization of the astaxanthin extraction process from shrimp side streams is of great importance for the valorization of crustacean side streams and the development of astaxanthin-related products. The combined and independent effects of two innovative extraction technologies (pulsed electric fields (PEFs) and accelerated solvent extraction (ASE)) alone and/or combined in a sequential step, using two different solvents on astaxanthin extraction from two shrimp species, were evaluated. Astaxanthin content in the extracts of shrimp side streams was determined by both spectrophotometric and HPLC assays, being the determination of the carotenoid profiles performed by HPLC analysis. Compared to a solvent extraction control procedure, the astaxanthin content was increased after ASE and PEF treatments, for both shrimp species, independently of the solvent used. The highest recovery (585.90 µg/g) was obtained for the species A. antennatus, with the solvent DMSO when PEF and ASE were combined, while the increase in antioxidant capacity varied depending on the solvent used. HPLC analysis of the samples revealed the presence of unesterified (all-E) astaxanthin, four unesterified Z isomers of astaxanthin and many unresolved astaxanthin esters. Both technologies are useful tools to recover antioxidant valuable carotenoids such as astaxanthin from shrimp side streams.

Metabolite analysis of soybean oil on promoting astaxanthin production of Phaffia rhodozyma.

Astaxanthin is a carotenoid with strong antioxidant property. In addition, it has anti-cancer, anti-tumor, anti-inflammatory and many other functions. The micro-organisms that mainly produce astaxanthin are Haematococcus pluvialis and Phaffia rhodozyma. Compared with H.pluvialis, P.rhodozyma has shorter fermentation cycle and easier to control culture conditions, but the yield of astaxanthin in P.rhodozyma is low. This article studied how to improve the astaxanthin production of P.rhodozyma. The results showed that when 10mL L-1 soybean oil was added to the culture medium, astaxanthin production increased significantly, reaching 7.35 mg L-1 , which was 1.4 times that of the control group, and lycopene and β-carotene contents also increased significantly. Through targeted metabolite analysis, the fatty acids in P.rhodozyma significantly increased under the soybean oil stimulation, especially the fatty acids closely related to the formation of astaxanthin esters, included palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1n9), linoleic acid (C18:2n6), α-linolenic acid (C18:3n3) and γ-linolenic acid (C18:3n6), thereby increasing the astaxanthin esters content. It showed that the addition of soybean oil can promote the accumulation of astaxanthin by promoting the increase of astaxanthin ester content. © 2022 Society of Chemical Industry.

Development and validation of reliable astaxanthin quantification from natural sources.

Astaxanthin derived from natural sources occurs in the form of various esters and stereomers, which complicates its quantitative and qualitative analysis. To simplify and standardize astaxanthin measurement with high precision, an enzymolysis-based astaxanthin quantification method was developed to hydrolyze astaxanthin esters and determine free astaxanthin in all its diastereomeric forms. Astaxanthin standards and differently processed Haematococcus pluvialis biomass were investigated. Linear correlation of standards of all-E-astaxanthin was observed in a measurement range between extract concentrations of 1.0 μg/mL and 11.2 μg/mL with a coefficient of variation below 5%. The diastereomers 9Z-, and 13Z-astaxanthin, and two di-Z-forms were detected. In contrast to the measurement of standards, the observed measurement range was extended to 30 μg/mL in extracts from H. pluvialis. The nature of the sample had to be taken into account for measurement, as cell, respectively, sample composition altered the optimal concentration for astaxanthin determination. The measurement precision of all-E-astaxanthin quantification in dried H. pluvialis biomass (1.2-1.8 mg dried biomass per sample) was calculated with a coefficient of variation of maximum 1.1%, whereas it was below 10% regarding the diastereomers. Complete enzymolysis was performed with 1.0 to 2.0 units of cholesterol esterase in the presence of various solvents with up to 2.0 mg biomass (dry weight). The method was compared with other astaxanthin determination approaches in which astaxanthin is converted to acetone in a further step before measurement. The developed method resulted in a higher total astaxanthin recovery but lower selectivity of the diastereomers. The reliability of photometric astaxanthin estimations was assessed by comparing them with the developed chromatographic method. At later stages in the cell cycle of H. pluvialis, all methods yielded similar results (down to 0.1% deviation), but photometry lost precision at earlier stages (up to 31.5% deviation). To optimize sample storage, the shelf life of astaxanthin-containing samples was investigated. Temperatures below -20°C, excluding oxygen, and storing intact H. pluvialis cells instead of dried or disrupted biomass reduced astaxanthin degradation.

Pigment signatures of algal communities and their implications for glacier surface darkening

Blooms of pigmented algae darken the surface of glaciers and ice sheets, thereby enhancing solar energy absorption and amplifying ice and snow melt. The impacts of algal pigment and community composition on surface darkening are still poorly understood. Here, we characterise glacier ice and snow algal pigment signatures on snow and bare ice surfaces and study their role in photophysiology and energy absorption on three glaciers in Southeast Greenland. Purpurogallin and astaxanthin esters dominated the glacier ice and snow algal pigment pools (mass ratios to chlorophyll a of 32 and 56, respectively). Algal biomass and pigments impacted chromophoric dissolved organic matter concentrations. Despite the effective absorption of astaxanthin esters at wavelengths where incoming irradiance peaks, the cellular energy absorption of snow algae was 95% lower than anticipated from their pigmentation, due to pigment packaging. The energy absorption of glacier ice algae was consequently ~ 5 × higher. On bare ice, snow algae may have locally contributed up to 13% to total biological radiative forcing, despite contributing 44% to total biomass. Our results give new insights into the impact of algal community composition on bare ice energy absorption and biomass accumulation during snow melt.

Improvement of solubility, stability and antioxidant activity of carotenoids using deep eutectic solvent-based microemulsions

Natural carotenoids have been widely used as colorants and antioxidants in process of food, medicine, and cosmetic. However, the carotenoids have low bioactivity in vivo due to poor water-solubility. To enhance the solubility, stability and antioxidant activity of carotenoids, novel microemulsions (MEs) composed with deep eutectic solvents (DESs), tween 80 and water were developed as alternatives to organic solvents. The phase diagrams and physicochemical properties (viscosity, pH, and diameter) of the DES-based MEs were investigated at different temperatures. Then the solubility distribution, storage stability and DPPH free radical-scavenging activity of three carotenoids (astaxanthin, astaxanthin ester and lutein) in the MEs were evaluated. Compared with ethanol, methanol, and acetone, all the DES-based MEs studied significantly enhanced the solubility of the carotenoids due to the stronger hydrogen bonding and Van der Waals interactions. The highest solubilities of 0.27, 473.63, and 12.50 mg/mL for astaxanthin, astaxanthin ester and lutein, respectively, were observed in the MEs containing DES (DL-menthol:acetic acid = 1:2) at 35 ℃. Moreover, astaxanthin ester can be well preserved in the MEs containing DES (DL-menthol:octanoic acid = 1:2) with a half-life of more than 69 days. In addition, the DPPH scavenging capacities of the three carotenoids in all the MEs were higher than the organic solvents. The results revealed that the DES-based MEs with low viscosity (<0.2 Pa•s) and mild acidic pH (4−5) are potential solvents for natural carotenoids in food processing and storage, medicine making, as well as biomaterials processing.

Type I diacylglycerol acyltransferase (DGAT1) from the unicellular green alga Haematococcus pluvialis is a xanthophyll acyltransferase

Xanthophyll esters are present in a large number of plants and microalgae, but its biosynthesis process is poorly understood. We demonstrated that acylation of xanthophylls is catalyzed by type I diacylglycerol acyltransferase (DGAT) from the unicellular green alga Haematococcus pluvialis. Expression of HpDGAT1, and three of the four HpDGAT2 genes showed significant up-regulation under all the three adverse environmental conditions to trigger astaxanthin esters biosynthesis, respectively. Addition of recombinant HpDGAT1 into the enzymatic assay system with the endoplasmic reticulum membranes of H. pluvialis as the enzyme sources further significantly increased net xanthophyll esters formation. Overexpressing HpDGAT1 in an engineered Escherichia coli strain capable of producing free astaxanthin led to enhanced accumulation of both free astaxanthin and xanthophyll esters with maximum UV absorption at 480 nm, the typical feature of astaxanthin esters. Application of DGAT1 specific inhibitor A922500 decreased the content of astaxanthin esters up to 36% in H. pluvialis under high light stress. These data suggested that HpDGAT1 act as xanthophyll acyltransferase in H. pluvialis. Our findings broaden the understanding of xanthophylls acylation in microalgae.

Effect of Nanoemulsions Containing Astaxanthin or Its Esters on the Spatial Behavior of 5XFAD Mice

The effect of nanoemulsions (NE) of phospholipids containing astaxanthin (AST) or its esters on the spatial behavior of transgenic mice with Alzheimer’s disease 5XFAD at the age of 4–6 months is studied in an elevated plus maze and via an “open field” test. The nanoemulsions obtained by injection have a diameter of 70–100 nm and a polydispersity index of <0.3. The animals receive the preparations with food 5 times a week for two months. The dose of AST and esters is 2 mg/kg of body weight. Once a week, the animals receive a double dose of drugs. The control animals receive NE that do not contain carotenoids. Behavioral tests show that AST-treated mice spend significantly less time in the open arms of the elevated plus maze compared to the control mice. In the case of esters, no reliable significance is found. In the “open field” test, AST esters have a positive effect on the animals, slowing down thigmotaxis disorders in 5XFAD mice. At the same time, the introduction of any NE does not affect a decrease in motor activity. Hence, in Alzheimer’s mice treated with both AST and esters, the behavioral parameters in the elevated plus maze and the “open field” test tend to improve.