Thermal Isomerization Research Articles

Light-Induced and Thermal Isomerization of Azobenzenes on Immobilized Gold Nanoparticle Aggregates.

Morphologically different gold nanoparticle (AuNP) aggregates were prepared on macroscopic surfaces covered with a layer of polydopamine (PDA). The extent of particle aggregation and the particle size distribution could be controlled by the Au(III) reduction times, while the reduction process was triggered solely by the redox active polymer. Shorter reaction times led to smaller particles along with lower levels of aggregation, while longer reductions resulted in larger average particle diameter and heavier aggregation. The prepared surfaces were characterized by UV-Vis, AFM and KPFM techniques. These surfaces were used as solvent-free condensed phases to probe the photochemical and thermal isomerization processes of attached azobenzenes with different spacer lengths. Fast and reversible light-induced switching was observed in each case. The thermal cis-to-trans isomerization was found to be accelerated for particle-bound azobenzenes compared to those in solution.

Oral Supplementation with Z-Isomer-Rich Astaxanthin Inhibits Ultraviolet Light-Induced Skin Damage in Guinea Pigs

The effect of oral supplementation with astaxanthin of different Z-isomer ratios on ultraviolet (UV) light-induced skin damage in guinea pigs was investigated. Astaxanthin with a high Z-isomer content was prepared from the all-E-isomer via thermal isomerization. Intact (all-E)-astaxanthin and the prepared Z-isomer-rich astaxanthin were suspended in soybean oil and fed to guinea pigs for three weeks. The UV-light irradiation was applied to the dorsal skin on the seventh day after the start of the test diet supplementation, and skin parameters, such as elasticity, transepidermal water loss (TEWL), and pigmentation (melanin and erythema values), were evaluated. The accumulation of astaxanthin in the dorsal skin was almost the same after consumption of the all-E-isomer-rich astaxanthin diet (E-AST-D; total Z-isomer ratio = 3.2%) and the Z-isomer-rich astaxanthin diet (Z-AST-D; total Z-isomer ratio = 84.4%); however, the total Z-isomer ratio of astaxanthin in the skin was higher in the case of the Z-AST-D supplementation. Both diets inhibited UV light-induced skin-damaging effects, such as the reduction in elasticity and the increase in TEWL level. Between E-AST-D and Z-AST-D, Z-AST-D showed better skin-protective ability against UV-light exposure than E-AST-D, which might be because of the greater UV-light-shielding ability of astaxanthin Z-isomers than the all-E-isomer. Furthermore, supplementation with Z-AST-D resulted in a greater reduction in skin pigmentation caused by astaxanthin accumulation compared to that of E-AST-D. This study indicates that dietary astaxanthin accumulates in the skin and appears to prevent UV light-induced skin damage, and the Z-isomers are more potent oral sunscreen agents than the all-E-isomer.

Cover Image

The cover image is based on the Research Article Experimental and theoretical investigation on the thermal isomerization reaction of tristriazolotriazines by Matthias Jochem, Daniel Limbach, Stefan Glang, Tobias Haspel, and Heiner Detert, https://doi.org/10.1002/poc.4346.

Preparation of Highly Stable Z‐Isomer‐Rich Lycopene Nanodispersions via a Continuous‐Flow System with Selected Emulsifiers

AbstractAs a potent antioxidant with numerous health benefits, lycopene finds multiple applications. Among the geometric isomers of lycopene, the Z‐isomers have greater bioavailability than the all‐E‐isomer but are less stable and hence, less suitable for practical applications. Herein, highly stable Z‐isomer‐rich lycopene nanodispersions are produced through the thermal isomerization of (all‐E)‐lycopene in a flow reactor followed by continuous dispersion in an aqueous emulsifier (Tween 20, sucrose fatty acid ester, or polyglycerol fatty acid ester [PFAE]) solution upon agitation with an in‐line swirl mixer. The effects of emulsifier type and other processing conditions (flow rate, pressure, temperature, lycopene Z‐isomer ratio) on dispersion efficiency and properties are examined in detail, and finally, Z‐isomer‐rich lycopene nanodispersions (>60% of total Z‐isomer ratio and <10 nm of mean particle size) are successfully obtained. Moreover, it is found that lycopene Z‐isomers have greater encapsulation efficiency for dispersions with emulsifiers than that of the all‐E‐isomer. The storage test of the resulting dispersions clearly shows that the highest storage stability is achieved in the case of using PFAE, which effectively inhibits lycopene degradation and reverse (Z‐ to all‐E) isomerization.Practical applications: To practical use of lycopene Z‐isomers, it is essential to improve their storage stability as well as usability (i.e., dispersibility in water). The present study reveals that when producing the lycopene dispersions, the use of PFAE as an emulsifier allows to improve the stability of lycopene isomers and inhibit the Z‐ to all‐E‐isomerization during storage. Given the high demand for stable Z‐isomer‐rich lycopene formulations, the obtained results promote the practical use of lycopene Z‐isomers in diverse (e.g., food and cosmetic) industries.

Novel Azocoumarin Derivatives-Synthesis and Characterization.

The paper presents synthesis and characterization of nine new thiazolyl-(phenyldiazenyl)-2H-chromen-2-one dyes. The impact of substituent structure in thiazole ring in the synthesized azocoumarin derivatives on electrochemical properties, photoisomerization process and photovoltaic response was examined. The dyes were electrochemically active and undergo reduction and oxidation processes. They showed low electrochemically estimated energy band gap in the range of 1.71–2.13 eV. Photoisomerization process of the synthesized molecules was studied in various solvents such as ethanol, chloroform and N,N-dimethylformamide (DMF) upon the UV illumination. It was found that novel azodyes showed reversible trans-cis-trans isomerization and exhibited long thermal back to the trans form, that was even 7 days in DMF. Selected azocoumarin were molecularly dispersed in polystyrene for preparation of guest-host azopolymer systems to study the cis-trans thermal isomerization of obtained dyes in solid state. The photovoltaic activity of the azochromophores was tested in bulk-heterojunction solar cells. They acting as weak donors in device with structure ITO/PEDOT:PSS/dye:PC70BM/Al. No photovoltaic response of cells with azocoumarin derivatives bearing 4-fluorobenzene, 3,4-dichlorobenzene, or 4-(1-adamantyl) unit was found. Additionally, dye which showed the best activity was examined in three-component solar cells ITO/PEDOT:PSS/PTB7:PC70BM:dye/PFN/Al.

Open-Form Configurational Isomers of a Tricyanofuran-Type Metastable-State Photoacid.

We determine the presence of four open-form configurational isomers for an unsubstituted metastable-state photoacid (mPAH) of the tricyanofuran (TCF) type in solution, at room temperature, via 2D NMR experiments. Electronic structure calculations are carried out to predict the relative stability of the isomers found experimentally and their isomerization barriers. According to the calculated rate constants for isomerization, the molecule can freely interconvert between the open-form isomers, thereby providing a thermal pathway between the isomers that might be better suited to access the cyclized closed-form configuration and those that are not. In establishing the open form isomeric makeup of the TCF mPAH under study, this work establishes the need to consider the four isomers in further studies on the thermal and excited-state isomerization processes and substituent effect thereon.

Cavity-altered thermal isomerization rates and dynamical resonant localization in vibro-polaritonic chemistry

It has been experimentally demonstrated that reaction rates for molecules embedded in microfluidic optical cavities are altered when compared to rates observed under "ordinary" reaction conditions. However, precise mechanisms of how strong coupling of an optical cavity mode to molecular vibrations affects the reactivity and how resonance behavior emerges are still under dispute. In the present work, we approach these mechanistic issues from the perspective of a thermal model reaction, the inversion of ammonia along the umbrella mode, in the presence of a single-cavity mode of varying frequency and coupling strength. A topological analysis of the related cavity Born-Oppenheimer potential energy surface in combination with quantum mechanical and transition state theory rate calculations reveals two quantum effects, leading to decelerated reaction rates in qualitative agreement with experiments: the stiffening of quantized modes perpendicular to the reaction path at the transition state, which reduces the number of thermally accessible reaction channels, and the broadening of the barrier region, which attenuates tunneling. We find these two effects to be very robust in a fluctuating environment, causing statistical variations of potential parameters, such as the barrier height. Furthermore, by solving the time-dependent Schrödinger equation in the vibrational strong coupling regime, we identify a resonance behavior, in qualitative agreement with experimental and earlier theoretical work. The latter manifests as reduced reaction probability when the cavity frequency ωc is tuned resonant to a molecular reactant frequency. We find this effect to be based on the dynamical localization of the vibro-polaritonic wavepacket in the reactant well.

Continuous production of Z-isomer-rich astaxanthin nanodispersions with stabilized Z-structures using selected ester-based nonionic emulsifiers

The multiple beneficial biological activities of astaxanthin show promise for the application of ​nutritional supplements and cosmetics, but the industrial use of this carotenoid is hindered by its high crystallinity and poor solubility, which result in low oral bioavailability and percutaneous absorbability. These drawbacks are inherent to many carotenoids and are typically addressed through their formulation as aqueous dispersions. Given that carotenoid Z-isomers have greater bioavailability than the corresponding all-E-isomers, we herein realized the continuous production of Z-isomer-rich astaxanthin nanodispersions and determined the optimal conditions for Z-isomer stabilization. The thermal isomerization of (all-E)-astaxanthin was performed in a flow reactor using subcritical ethyl acetate as a solvent, and a total Z-isomer ratio of >60% was achieved in only 15 s. The mixture of isomers was dispersed in an aqueous solution of an ester-based nonionic emulsifier using an in-line swirl mixer, and the properties of these dispersions were investigated as functions of emulsifier type. The best performance was observed for sucrose fatty acid ester, which promoted the formation of fine dispersions (average particle size of <10 nm) and stabilized astaxanthin Z-isomers. Thus, the Z-isomer-rich fine dispersions are expected to increase the bioavailability of astaxanthin and hold great promise for its industrial applications.

Pitfalls of Using Biomarker Maturity Parameters for Organic Matter Maturity Assessment Suggested by Coal Hydrous Pyrolysis

Crude oil maturity assessment is a vital goal for petroleum geochemistry, and equally important is the exploration of maturity indicators of sufficient credibility. While most molecular proxy parameters have been extensively used and have provided some useful insights; the component ratios approach is somewhat limited in validity regarding oil maturity characterization for variable reasons. Novel thermal trends of hopanes and steranes were observed in a series of hydrous pyrolysates of an immature coal (0.49 %Ro) generated at eight target temperatures ranging from 250–375 °C (measured vitrinite reflectance of 0.71–0.91 %Rm), which–further substantiated this idea. Expelled oil and extractable bitumen were combined as the total soluble organic material (tSOM) for each pyrolysis experiment to mitigate the effects of primary expulsion fractionation. While bitumen extracted from the original coal—the 250 °C tSOM—the 275 °C tSOM (0.49–0.73 %Rm) sequence recorded normal increases in C31 αβ-hopane 22S/(22S + 22R) and decreases in C29–C30 βα-moretane/αβ-hopane ratios, low values and continuous decreases in C29 5α-sterane 20S/(20S + 20R) and ββ/(αα + ββ), Ts/(Ts + Tm) and C29Ts/(C29Ts + C29 αβ-hopane) suggested no biomarker thermal isomerization but predominant control from precursor-to-biomarker transformation. Continuous increases in 22S/(22S + 22R) until 1.43 %Rm accorded with thermal isomerization, but a delayed ratio equilibration at 1.43 %Rm again suggested biomarker precursor interference, which also played a role in the reductions in 20S/(20S + 20R) and ββ/(αα + ββ) to 0.9 %Rm, whereas increasing and high values of C29–C30 βα-moretane/αβ-hopane ratios occurring during 0.73–1.43 %Rm. Reversals in 22S/(22S + 22R) and fluctuations in 20S/(20S + 20R) and ββ/(αα + ββ) at elevated maturity levels with minimum yields of biomarker precursors were predominantly controlled by differential isomer degradative rates. These rarely reported thermal distribution patterns of biomarkers illustrated very complicated biomarker generation–destruction processes during maturation and suggested that the release of bond biomarker to the free status may govern the biomarker maturity ratios rather than thermal isomerization. While the rapid heating conditions and high temperatures in pyrolysis differ inevitably from natural evolution under geological conditions, our study unveiled that unusual biomarker ratios in geological samples could be the norm, contradictory to common beliefs. Accordingly, we propose that isomer concentration is an essential tool to validate maturity estimation of organic matter by isomer ratios, especially for highly mature oils and sediment extracts.

Experimental and theoretical investigation on the thermal isomerization reaction of tristriazolotriazines

AbstractThe isomerization of tristriazolotriazione with tangential substituents to radial isomers occurs in a cascade of three ring opening/rotation/ring closure steps of the central triazine. Donor substitution accelerates the isomerization which can be catalyzed by Brønsted acids. The velocity of the rearrangements drops with each step by a factor of 4, whereas the gain in heat of formation increases. Density functional theory (DFT) calculations led to transition states; their energies correspond to the experimental data. Threefold isomerization strongly affects the mesomorphic properties.

The influence of temperature, light, and storage period on the colour and chemical profile of kunzea essential oil (Kunzea ambigua (Sm.) Druce)

Essential oil distilled from the leaves and twigs of Kunzea ambigua is in high demand for its ‘soft, medicinal and soothing aroma’ and claimed muscle relaxant properties. This study investigated the changes in oil colour and chemical composition of kunzea essential oil over eight months of storage in a freezer (−20 °C), a refrigerator (4 °C) and at room temperature (20 °C), with and without ambient light. The oil colour was measured by a colourimeter, and chemical compositions were analysed using Gas Chromatography (GC) Mass Spectrometry (MS) and Flame Ionisation Detection (FID). Samples were analysed at one-, three-, five- and eight-month intervals. The colour difference (Δ E * ) was highest in oils stored in the light at room temperature for eight months (5.60 ± 0.03%), whilst samples kept in the dark were more stable with ΔE * at room temperature of 1.97 ± 0.00%, refrigeration at 1.55 ± 0.02%, and freezing temperatures at 1.08 ± 0.17%. Stored kunzea essential oil became darker in colour, becoming less yellow and decreasing in greenness, with extended storage periods.The monoterpenes, sesquiterpenes and total volatile compounds in oil stored for eight months in the freezer, refrigerator, and room temperature without light were overall generally stable compared to fresh oil. Significant interactions between storage period and temperature/light treatments were recorded for bicyclogermacrene, α-humulene, α-campholenal and linalool, showing a decrease in all oils under all conditions during extended storage periods, though changes were minimal in frozen oil. However, the oils exposed to the light showed a significant decrease in these components, particularly for germacrene D, β-caryophyllene and α-humulene, likely due to thermal isomerization, relative to fresh oil.Overall, kunzea essential oil stored in a freezer or refrigerator was the most stable and consistent in colour and chemical profile whereas there is evidence that some components may be when exposed to light with negative consequences for oil colour and quality.

Synthesis of novel silica encapsulated spiropyran-based thermochromic materials.

A series of novel spiropyrans were synthesized through the condensation of substituted 3,3-dimethyl-2-methyleneindoline with different nitro-substituted o-hydroxy aromatic aldehydes. Indoles were initially substituted with a variety of alkanes and esters moieties. The substituted 3,3-dimethyl-2-methyleneindoline was then reacted with nitro-substituted o-hydroxy aromatic aldehydes to yield the respective spiropyrans. The synthesized novel spiropyrans were encapsulated in silica nano-shells to protect them from the effect of moisture and pH. The thermochromic behaviour of novel spiropyrans was studied by UV-visible spectroscopy. The thermally induced isomerization of spiropyran derivatives was carried out in a water/ethanol mixture. The thermal isomerization of spiro-heterocyclic (colourless form) to merocyanine (MC) (coloured form) was a discontinuous process and was observed in a temperature range of 5–60°C via UV-visible spectrometer. The absorption process occurs reversibly regardless of the heating/cooling sequence. The spiropyran derivatives, therefore, have a potential application for colorimetric temperature indication.

Potassium Aluminyl Promoted Carbonylation of Ethene

AbstractThe potassium aluminyl [K{Al(NONDipp)}]2([NONDipp]2−=[O{SiMe2NDipp}2]2−, Dipp=2,6‐iPr2C6H3) activates ethene towards carbonylation with CO under mild conditions. An isolated bis‐aluminacyclopropane compound reacted with CO via carbonylation of an Al−C bond, followed by an intramolecular hydrogen shift to form K2[Al(NONDipp)(μ‐CH2CH=CO‐1κ2C1,3‐2κO)Al(NONDipp)Et]. Restricting the chemistry to a mono‐aluminium system allowed isolation of [Al(NONDipp)(CH2CH2CO‐κ2C1,3)]−, which undergoes thermal isomerisation to form the [Al(NONDipp)(CH2CH=CHO‐κ2C,O)]−anion. DFT calculations highlight the stabilising influence of incorporated benzene at multiple steps in the reaction pathways.

Potassium Aluminyl Promoted Carbonylation of Ethene.

The potassium aluminyl [K{Al(NONDipp)}]2 ([NONDipp]2−=[O{SiMe2NDipp}2]2−, Dipp=2,6‐iPr2C6H3) activates ethene towards carbonylation with CO under mild conditions. An isolated bis‐aluminacyclopropane compound reacted with CO via carbonylation of an Al−C bond, followed by an intramolecular hydrogen shift to form K2[Al(NONDipp)(μ‐CH2CH=CO‐1κ2 C 1,3‐2κO)Al(NONDipp)Et]. Restricting the chemistry to a mono‐aluminium system allowed isolation of [Al(NONDipp)(CH2CH2CO‐κ2 C 1,3)]−, which undergoes thermal isomerisation to form the [Al(NONDipp)(CH2CH=CHO‐κ2 C,O)]− anion. DFT calculations highlight the stabilising influence of incorporated benzene at multiple steps in the reaction pathways.

New aspects of acid-assisted nucleophilic substitution reactions of 11-vertex nido-carboranes

Reactions of the nido-carborane salts Me4N[7,8-R,R-7,8-nido-C2B9H10] (R,R = Me2; R,R = o-C6H4(CH2)2) with Me2S in the presence of triflic acid give a mixture of isomeric carboranes 9-Me2S-7,8-R,R-7,8-nido-C2B9H9 and 10-Me2S-7,8-R,R-7,8-nido-C2B9H9. In contrast, Me4N[7,8-(CH2)3–7,8-nido-C2B9H10] affords the only isomer 10-Me2S-7,8-(CH2)3–7,8-nido-C2B9H9. Interaction of Me4N[7,8-(CH2)3–7,8-nido-C2B9H10] and dimethyl sulfoxide in acidic conditions leads to the formation of a product 10-Me2SO-7,8-(CH2)3–7,8-nido-C2B9H9 in which, according to the SC-XRD, dimethyl sulfoxide molecule attaches to nido-carborane cage through an oxygen atom. The half-peak potential of the first oxidation wave of nido-carboranes correlates well with their ability to undergo acid-assisted nucleophilic substitution reactions. Thermal isomerization of 10-Me2S substituted nido-carboranes to 9-Me2S isomers was observed at higher temperatures than acid-assisted nucleophilic substitution and could proceed with the formation of 11-vertex closo-carboranes as intermediates according to the DFT study.

The thermal isomerization of benzvalyne to benzyne.

The isomerization of the highly strained benzvalyne structure to o-benzyne has been investigated using MCSCF and CCSD(T) levels of theory. Two reaction channels were modeled: the disrotatory one which leads directly to the benzyne product, and the conrotatory one which leads to an intermediate which can subsequently lead to the benzyne product. Energies at the MRMP2 level give 22.9 kcal mol-1 for the disrotatory channel and 21.7 and 1.4 kcal mol-1 for the two steps in the conrotatory one. However, the CCSD(T) energies give 19.3 and 14.2 kcal mol-1 for the two conrotatory steps. The first step of the conrotatory channel is significantly higher than the second so is rate determining for this channel. Comparison of the two separate channels shows that the conrotatory has just a slight energetic edge of 1.2 kcal mol-1 at the MRMP2 level. We did not compute the disrotatory channel at the CCSD(T) level due to the significant biradical nature of the wavefunction with natural orbital occupation numbers of 1.2 and 0.8 in the active space.

Fast relaxing red and near-IR switchable azobenzenes with chalcogen and halogen substituents: periodic trends, tuneable thermal half-lives and chalcogen bonding.

Molecular photoswitches operating in the red to near-IR region with controllable thermal relaxation rates are attractive components for photo-regulating biological processes. Herein, we report the synthesis of red-shifted azobenzenes functionalised with the heavier chalcogens and halogens that meet these requirements for biological application; namely fatigue-resistant photo-switching with red and near IR light and functional handles for further functionalisation for application. We report robust periodic trends for the chalcogen and halogen azobenzene series, and exploit intramolecular chalcogen bonding to tune and redshift the absorption maxima, supported by photo-physical measurements and solid-state structural analysis. Remarkably, the rate of the Z → E thermal isomerisation can be tuned over timescales spanning 107 s by judicious choice of chalcogen and halogen substituents.

High-temperature Supercritical CO2 Extraction of Lycopene from Tomato Powder for Enhancing Z-Isomerization and Recovery of Lycopene.

This study aimed to investigate the effect of extraction conditions (temperature, pressure, and entrainer content) on the total Z-isomer ratio and recovery of lycopene in the extracts obtained after supercritical CO2 (SC-CO2) extraction of lycopene from tomato powder, with a particular focus on high-temperature conditions (≥ 80°C). The results showed that high-temperature SC-CO2 extraction promoted the thermal isomerization of lycopene in a temperature-dependent manner up to 120℃. For example, when lycopene extraction was carried out at 80, 100, 120, and 140°C and a pressure of 30 MPa with an entrainer, ethanol, for 180 min, the total Z-isomer ratios obtained were 25.0, 57.2, 67.2, and 67.0%, respectively. The entrainer content also affected the Z-isomer ratio of lycopene, but the pressure had little effect. Interestingly, when SC-CO2 extraction was performed under high-temperature conditions (≥ 100°C), the extraction efficiency of lycopene was dramatically improved, e.g., when lycopene was extracted at 80, 100, 120, and 140°C under the same other conditions as above, the recovery rates of lycopene were 4.6, 28.5, 79.9, 84.8%, respectively. In general, SC-CO2 extraction of fat-soluble components is performed at temperatures in the range of 40-80°C because the SC-CO2 density decreases with increasing temperature, and thus, their solubility (extraction efficiency) decreases. However, our results showed that the lycopene recovery increased in a temperature-dependent manner, which might be due to the solubility enhancement associated with thermal Z-isomerization of lycopene (i.e., lycopene Z-isomers have greater solubility than the naturally occurring all-E-isomer). The high-temperature SC-CO2 extraction of lycopene from tomato materials not only enhances the Z-isomer ratio of lycopene in the resulting extracts but also improves lycopene recovery. This new finding will greatly contribute to the value addition and cost reduction of natural lycopene sources obtained by SC-CO2 extraction.

Nickel-catalysed cycloaddition oligomerisation of 1,6-diynes to medium-size cyclic polyenes

A nickel-catalysed reaction of 1,6-diynes produced cyclic polyene oligomers with a narrow PDI. Their thermal isomerization gave the regio-isomeric cyclic polyenes consisting of trans-disubstituted alkenes.

Extraction of Fucoxanthin Isomers from the Edible Brown Seaweed Undaria pinnatifida Using Supercritical CO2: Effects of Extraction Conditions on Isomerization and Recovery of Fucoxanthin.

Fucoxanthin, a characteristic carotenoid found in brown seaweeds, has been reported to exert beneficial biological activities, including antiobesity and anticancer activities Moreover, the Z-isomers of this compound potentially have greater bioavailability and biological activities than the naturally predominant all-E-isomer. Therefore, the consumption of Z-isomer-rich fucoxanthin through daily meals and dietary supplements may have beneficial effects. In this study, we aimed to investigate the effects of different extraction conditions on the Z-isomer ratio and recovery of fucoxanthin obtained from Undaria pinnatifida using supercritical CO2 (SC-CO2), particularly focusing on the high-temperature conditions that enhance thermal Z-isomerization. High-temperature SC-CO2 extraction at ≥ 120°C was found to enhance the thermal isomerization of fucoxanthin. For example, when the extraction was performed at 40, 80, 120, and 160°C and 30 MPa for 30 min with a co-solvent (ethanol), the total Z-isomer ratios were 11.7, 11.5, 18.7, and 26.5%, respectively. Furthermore, the high-temperature extraction significantly improved fucoxanthin recovery under high-pressure (≥ 30 MPa) conditions in the presence of the co-solvent. For example, when fucoxanthin was extracted at 40, 80, 120, and 160°C under the same conditions as above, the recoveries were 17.5, 20.6, 30.7, and 29.5%, respectively. Hence, the high-temperature SC-CO2 extraction of fucoxanthin from U. pinnatifida would not only enhance health benefits of fucoxanthin via the Z-isomerization but also improve the productivity. Moreover, the use of non-toxic CO2 and a low-toxicity organic solvent (ethanol) ensures that the final fucoxanthin product is safe for consumption. The Z-isomer-rich fucoxanthin obtained using this method is accordingly considered to have potential for use as a dietary supplement.