Study of RP HPLC Retention Behaviours in Analysis of Carotenoids

Optimising microalgal dyes extraction design for stable dye-sensitized solar cells: Chromatographic insights on bio-deterioration and longevity

BACKGROUND

The demand for sustainable energy solutions has increased interest in natural microalgal dyes as photosensitizers in dye-sensitized solar cells (DSSCs). This study addresses the critical issue of maximizing dye integrity and yield during extraction, particularly the degradation that occurs at temperatures above 60 °C. Our investigation of dye extraction from Asterarcys quadricellulare and Scenedesmus sp. using hot solvent methods revealed significant findings. High-Performance Liquid Chromatography (HPLC) analysis identified essential pigments, including Chlorophyllide a and β-carotene.

RESULTS

Our research found that temperatures above 60 °C reduce chlorophyll (Chl) stability and extraction efficiency. Using multiple wavelengths in a photodiode array (PDA) detector improves Chl identification by targeting distinct absorption peaks, resolving overlap with other compounds, and confirming purity. This approach also helps validate extraction methods and ensures accurate quantification. Since high temperatures are detrimental to Chl stability, this method is crucial for reliable analysis and longer dye storage. Ethanol outperformed methanol in extraction efficiency, while the stability of the dyes was tied to specific derivatives. Notably, Scenedesmus sp. showed better preservation of chlorophyll compounds, influenced by extraction temperature and solvent characteristics.

SIGNIFICANCE

This research underscores the potential for optimising natural dye extraction methods, offering a pathway to enhance the sustainability and cost-effectiveness of DSSC production, thus contributing to greener energy technologies.

Effects of fermentation on the structures of yellow compounds in citrus pomace

To enhance the stability and light resistance of the yellow compounds in citrus pomace, our study successfully isolated and purified five compounds using ultrasonic-assisted extraction and column chromatography. The identified compounds include methyl linoleate, (2-ethyl)hexyl phthalate, 1,3-distearoyl-2-oleoylglycerol, 6,6-ditetradecyl-6,7-dihydroxazepin-2(3H)-one, and n-octadeca-17-enoic acid. The monomers extracted from fresh pomace, compounds 1 and 2, exhibit structural similarities to flavonoids and carotenoids. In contrast, the polymers isolated from fermented pomace, compounds 3, 4, and 5, share structural units with the fresh pomace compounds, indicating the transformation to stable polymeric forms. This suggests that the microbial fermentation process not only enhances the value of citrus pomace, but also provides a promising pathway for the synthesis of natural antioxidant yellow pigments with far-reaching theoretical and practical significance.

Development and validation of extraction and clean-up procedures for UPLC-MS/MS analysis of aflatoxins in spices

UPLC-MS/MS analytical conditions for the analysis of aflatoxins in spices were optimized and validated in this study. Liquid-liquid partition-based protocols for the cleaning up of extracts using common organic solvents such as acetonitrile, hexane, and ethyl acetate were developed and validated. The developed liquid-liquid partition methods were compared with immuno-affinity column and QuEChERS clean-up methods for the UPLC-MS/MS analysis of aflatoxins in 8 spices. The reduction of lipophilic components using the partition with hexane is particularly useful in spices like red pepper that have higher levels of fatty acids, carotenoids, sterols, triterpenoids, etc. The subsequent partitioning with ethyl acetate considerably reduced the matrix interference from the polar components and increased the sensitivity. The cleaning up of spice extracts using liquid-liquid partition techniques resulted in limits of quantification (LOQ) of 2-5 µgL-1 in UPLC-MS/MS analysis. Trueness, repeatability, and reproducibility of the methods were in acceptable ranges. The accuracy of the developed methods was further verified by analyzing aflatoxins in naturally incurred samples of spices and comparing the results with those obtained from the immuno-affinity column cleanup-HPLC-FD method.

Recent Advances in the Therapeutic Potential of Carotenoids in Preventing and Managing Metabolic Disorders

Carotenoids constitute compounds of significant biological interest due to their multiple biological activities, such as antimicrobial, anticancer, antiadipogenic, antidiabetic, and antioxidant properties. Metabolic syndrome (MetS) comprehends a series of metabolic abnormalities (e.g., hypertension, obesity, and atherogenic dyslipidemia) that can affect children, adolescents, and the elderly. The treatment of MetS involves numerous medications, which, despite their efficacy, pose challenges due to prolonged use, high costs, and various side effects. Carotenoids and their derivatives have been proposed as alternative treatments to MetS because they reduce serum triglyceride concentrations, promote insulin response, inhibit adipogenesis, and downregulate angiotensin-converting enzyme activity. However, carotenoids are notably sensitive to pH, light exposure, and temperature. This review addresses the activity of carotenoids such as lycopene, lutein, fucoxanthin, astaxanthin, crocin, and β-carotene towards MetS. It includes a discussion of sources, extraction methods, and characterization techniques for analyzing carotenoids. Encapsulation approaches are critically reviewed as alternatives to prevent degradation and improve the biological performance of carotenoids. A brief overview of the physiopathology and epidemiology of the diseases, including MetS, is also provided.

A Scoping Review on Carotenoid Profiling in Passiflora spp.: A Vast Avenue for Expanding the Knowledge on the Species

The Passiflora genus is recognised for its ethnopharmacological, sensorial, and nutritional significance. Yet, the screening of its dietary and bioactive molecules has mainly targeted hydrophilic metabolites. Following the PRISMA-P protocol, this review assessed the current knowledge on carotenoid composition and analysis within Passiflora, examining 968 records from seven databases and including 17 studies focusing on carotenoid separation and identification in plant parts. Those publications originated in America and Asia. P. edulis was the most frequently examined species of a total of ten, while pulp was the most studied plant part (16 studies). Carotenoid analysis involved primarily high-performance liquid chromatography separation on C18 columns and detection using diode array detectors (64.71%). Most studies identified the provitamin A β-carotene and xanthophylls lutein and zeaxanthin, with their geometric configuration often neglected. Only one study described carotenoid esters. Besides the methodology's insufficient description, the lack of use of more accurate techniques and practices led to a high risk of bias in the carotenoid assignment in 17.65% of the articles. This review highlights the opportunity to broaden carotenoid studies to other species and parts within the diverse Passiflora genus, especially to wild, locally available fruits, which may have a strategic role in enhancing food diversity and security amidst climatic changes. Additionally, it urges the use of more accurate and efficient analytical methods based on green chemistry to better identify Passiflora carotenoids.

Preparation, characterization, and separation mechanism of a dehydroabietic-acid-based shape-selective chromatographic stationary phase1

Chromatographic stationary phases with molecular-shape selectivity are advantageous for the separation and analysis of geometric isomers. Herein, dehydroabietic acid is bonded on the surface of silica microspheres via 3-glycidoxypropyltrimethoxysilane to form a monolayer dehydroabietic-acid stationary phase (Si-DOMM) with a racket-shaped structure. Various characterization techniques indicate that Si-DOMM is successfully prepared, and the separation performance of a Si-DOMM column is evaluated. The stationary phase has a low silanol activity and metal contamination and a high hydrophobicity and shape selectivity. The resolutions of lycopene, lutein, and capsaicin on the Si-DOMM column confirm that the stationary phase exhibits high shape selectivity. The elution order of n-alkyl benzene on the Si-DOMM column indicates its high hydrophobic selectivity and suggests that the separation is an enthalpy-driven process. Repeatability experiments reveal highly stable preparation processes of the stationary phase and column and indicate that the relative standard deviations of retention time, peak height, and peak area are less than 0.26%, 3.54%, and 3.48%, respectively. Density functional theory calculations using n-alkylbenzenes, polycyclic aromatic hydrocarbons, amines, and phenols as model solutes provide an intuitive and quantitative description of the multiple retention mechanisms. The Si-DOMM stationary phase exhibits superior retention and high selectivity for these compounds via multiple interactions. The bonding phase of the monolayer dehydroabietic acid stationary phase with a racket-shaped structure has a unique affinity for benzene, strong shape selectivity, and good separation performance for geometrical isomers with different molecular shapes.

Identification, Quantification and Kinetic Study of Carotenoids and Lipids in Rhodotorula toruloides CBS 14 Cultivated on Wheat Straw Hydrolysate

Production of carotenoids and lipids by Rhodotorula toruloides CBS 14 cultivated on wheat straw hydrolysate was investigated. An ultra-high-performance liquid chromatography (UHPLC) method for carotenoid quantification was developed and validated. Saponification effects on individual carotenoid quantification were identified, and lipid and carotenoid kinetics during cultivation were determined. The carotenoids β-carotene, γ-carotene, torularhodin, and torulene were identified; β-carotene was the major carotenoid, reaching a maximum of 1.48 mg/100 g dry weight. Recoveries of the carotenoids were between 66 and 76%, except torulene and torularhodin, which had lower recoveries due to saponification effects. Total carotenoid content in saponified and unsaponified yeast extract, respectively, determined by UHPLC or photometer, respectively, was 1.99 mg/100 g and 4.02 mg β-EQ/100 g dry weight. Growth kinetics showed a positive correlation between carotenoid content and lipid accumulation. β-carotene was the major carotenoid at all time points. At the end of the cultivation, triacylglycerols (TAGs) were the major lipid class, with 58.1 ± 3.32% of total lipids. There was also a high proportion of free fatty acids, reaching from 20.5 to 41.8% of total lipids. Oleic acid (C18:1) was the major fatty acid. The lipid yield at the end of the cultivation was 0.13 g/g of sugar consumed.

Titanium industrial residues surface modification towards its reuse as antimicrobial surfaces

In this study, a new material obtained from titanium ingots residue was coated with natural carotenoids having antibacterial properties. The waste is a no recycling titanium scrap from technological production process which was pressed and transformed into disks titanium samples. Through anodization and annealing procedures of the titanium disk, a nanostructured titanium dioxide surface with photocatalytic and antibacterial properties was successfully obtained. The titanium scrap impurities (V, Al, and N), unwanted for production process, have shown to improve electrochemical and semiconductor properties of the residue surfaces. The nanostructured titanium scrap surface was modified with two different carotenoids, torularhodin and β-carotene, to potentiate the antibacterial properties. The bactericidal tests were performed against Salmonella typhimurium and Escherichia coli, both Gram-negative. The best bactericidal effect is obtained for nanostructured titanium scrap disks immersed in torularhodin, with a percentage of growth inhibition around 60% against both tested bacteria. The results suggest that this low-cost waste material is suitable for efficient reuse as antibacterial surface after a few simple and inexpensive treatments.

Presence of Cholesterol in Non-Animal Organisms: Identification and Quantification of Cholesterol in Crude Seed Oil from Perilla frutescens and Dehydrated Pyropia tenera

Studies have reported that cholesterol, a molecule found mainly in animals, is also present in some plants and algae. This study aimed to determine whether cholesterol exists in three dehydrated algae species, namely, Pyropia tenera, Saccharina japonica, and Undaria pinnatifida, and in one plant species, namely, Perilla frutescens (four perilla seed oil samples were analyzed). These species were chosen for investigation because they are common ingredients in East Asian cuisine. Gas chromatography-flame ionization detection (GC-FID) analysis found that cholesterol was present in P. tenera (14.6 mg/100 g) and in all four perilla seed oil samples (0.3–0.5 mg/100 g). High-performance liquid chromatography with evaporative light-scattering detection (HPLC-ELSD) also demonstrated that cholesterol was present in P. tenera (14.2 mg/100 g) and allowed the separation of cholesterol from its isomer lathosterol. However, cholesterol could not be detected by HPLC-ELSD in the perilla seed oil samples, most likely because it is only present in trace amounts. Moreover, liquid chromatography-tandem mass spectrometry (LC-MS/MS) confirmed the presence of cholesterol in both P. tenera and perilla seed oil. MRM results further suggested that lathosterol (a precursor of cholesterol) was present in P. tenera.

Development and validation of a novel approach based on ultrasonic-assisted enzymatic extraction and RP-UHPLC for simultaneous determination of astaxanthin isomers and alpha-tocopherol in Haematococcuspluvialis derived supplements

A rapid, effective andgreenmethod was developed for simultaneous determination of total (free and esterified) astaxanthin (AX) isomers (all-E, 9Z and 13Z) and alpha-tocopherol(AT) in Haematococcuspluvialis derived supplements. The new method employed a highly efficient ultrasonic-assisted enzymatic extraction (UAEE) techniqueto perform deesterificationwith Cholesterol esterase from Pseudomonas fluorescenspermitting the concurrent detection. The subsequent RP-UHPLC method for separating and measuring was performed on a simple C18 column within 10.5 min by using methanol and ammonium acetate as mobile phase with a gradient elution. The proposed method was validated according to international guidelines and itproved to be highly accurate and robust. The optimized UHPLC method allowed easy transfer to HPLC, and allowed rapid analysis of active ingredients profiling in H. derived supplements.To our knowledge, this is the first quantification approach describing the rapid simultaneous analysis of the functional lipophilic substances including AX isomers in H. derived supplements using UAEE technique combined with RP-UHPLC.Moreover, this holistic approachcan be used to identify whether AX products are of natural origin or chemical synthesis, and may find more applications in new forms of H. derived productswith complexbiological matrix for more research on the bioavailability of AXisomersfrom natural source.

Suitability of stationary phase for LC analysis of biomolecules

Biologically active compounds such as carotenoids/isoprenoids, vitamins, steroids, saponins, sugars, long chain fatty acids, and amino acids play a very important role in coordinating functions in living organisms. Determination of those substances is indispensable in advanced biological sciences. Engineered stationary phase in LC for the analysis of biomolecules has become easier with the development of chromatographic science. In general, C₁₈ column is being used for routine analysis but specific columns are being used for specific molecule. Monolithic columns are found to have higher efficiency than normal column. Among recent introduction, triacontyl stationary phases, designed for the separation of carotenoid isomers, are widely used for the estimation of carotenoids. In comparison to conventional C₁₈ phases, C₃₀ phases exhibited superior shape selectivity for the separation of isomers of carotenoids. It is also found useful for better elution and analysis of tocopherols, vitamin K, sterols, and fatty acids. Vitamin K, E, and their isomers are also successfully resoluted and analyzed by using C₃₀ column. Amino bonded phase column is specifically used for better elution of sugars, whereas phenyl columns are suitable for the separation and analysis of curcuminoids and taxol. Like triacontyl stationary phase, pentafluorophenyl columns are also used for the separation and analysis of carotenoids. Similarly, HILIC column are best suited for sugar analysis. All the stationary phases are made possible to resolute and analyze the target biomolecules better, which are the future of liquid chromatography. The present article focuses on the differential interaction between stationary phase and target biomolecules. The applicability of these stationary phases are reported in different matrices.

Liquid Chromatography Analysis of Common Nutritional Components, in Feed and Food

Food and feed laboratories share several similarities when facing the implementation of liquid-chromatographic analysis. Using the experience acquired over the years, through application chemistry in food and feed research, selected analytes of relevance for both areas were discussed. This review focused on the common obstacles and peculiarities that each analyte offers (during the sample treatment or the chromatographic separation) throughout the implementation of said methods. A brief description of the techniques which we considered to be more pertinent, commonly used to assay such analytes is provided, including approaches using commonly available detectors (especially in starter labs) as well as mass detection. This manuscript consists of three sections: feed analysis (as the start of the food chain); food destined for human consumption determinations (the end of the food chain); and finally, assays shared by either matrices or laboratories. Analytes discussed consist of both those considered undesirable substances, contaminants, additives, and those related to nutritional quality. Our review is comprised of the examination of polyphenols, capsaicinoids, theobromine and caffeine, cholesterol, mycotoxins, antibiotics, amino acids, triphenylmethane dyes, nitrates/nitrites, ethanol soluble carbohydrates/sugars, organic acids, carotenoids, hydro and liposoluble vitamins. All analytes are currently assayed in our laboratories.