Adsorption Chromatography Research Articles

Foreign experience in determining the group hydrocarbon composition of petroleum feedstock and petroleum products

Determination of the group hydrocarbon composition (saturated and aromatic hydrocarbons, resins, asphaltenes) of petroleum dispersed systems is predominantly carried out using chromatographic analysis methods: liquid adsorption chromatography, high-performance liquid chromatography, thin-layer chromatography with flame ionization detection. The specificity of standard methods developed for the analysis of petroleum feedstock and petroleum products using a particular method often results in the incompatibility of results both in terms of the nomenclature of the identified hydrocarbon groups and the determined concentration values. This review provides a comparative assessment of chromatographic methods for analyzing the group hydrocarbon composition of petroleum feedstock and petroleum products, their features, advantages, and disadvantages. The main options for modifying standard methods aimed at achieving correlation between the results obtained by different analysis methods are described.

Thermolytic Synthesis of Asphaltene-like Nitrogenous Bases and Study of Their Aggregative Stability

The work is devoted to the study of the influence of nitrogenous bases on the composition of oil and the structure of asphaltenes on their colloidal stability in solution. Model petroleum systems with a basic nitrogen content of 1, 2, and 3% wt. were used as objects of study. Asphaltene-like nitrogenous bases were obtained by thermolysis of model petroleum systems with different nitrogen contents. The results were obtained using elemental analysis, non-aqueous potentiometric titration, spectrophotometry, 1H NMR spectroscopy, and liquid adsorption chromatography. It was established that the content of Nbas in asphaltenes increases by 0.3–1.3% wt. with the increase in quinoline content in petroleum components. Quinoline is incorporated into the supramolecular structure of asphaltenes and increases their average molecular weight by 650 amu. and aromaticity by 2%. The aggregative stability of asphaltenes decreases by 1.5–6 times with an increase in their average molecular weight and an increase in Nbas in their composition as a component of a dispersion medium. The colloidal stability of synthetic asphaltene-like substances, on the contrary, is due to the appearance of their molecular sequence of fragments containing Nbas in aromatic rings.

Nickel-ion substituted hydroxyapatite matrices for metal-affinity chromatographic purification of recombinant proteins.

Hydroxyapatite (HAp) is a calcium phosphate ceramic, widely used as a matrix for protein chromatography. The crystal structure of HAp is amenable to a wide range of substitutions, thus allowing for the alteration of its properties. In this study, nickel-ion substituted HAp (NiSHAp) was synthesized using a wet-precipitation method, followed by spray drying. This resulted in the structural incorporation of nickel ions within well-defined microspheres, which were suitable for chromatographic applications. The chromatographic experiments were conducted with NiSHAp and compared with spray-dried hydroxyapatite (SHAp) matrices. Protein purification experiments were conducted using refolded recombinant L-asparaginase (L-Asp), which was produced as inclusion bodies in Escherichia coli. The results showed that NiSHAp effectively adsorbed L-Asp, which was selectively eluted using a phosphate buffer, surpassing the efficiency of imidazole-based elution. In contrast, SHAp showed weaker binding and lower selectivity. The significance of this study lies in developing a scalable NiSHAp matrix for protein purification, especially for large-scale applications. The NiSHAp matrix offers a cost-effective alternative to commercial immobilized metal affinity chromatography (IMAC) adsorbents, especially for purifying His-tagged proteins. This innovative approach exhibits the advantages of mixed-mode chromatography by combining the properties of hydroxyapatite and IMAC in a single matrix, with the potential of improved industrial-scale protein purification.

Pore-blocking steric mass-action model for adsorption of bioparticles

The steric mass-action (SMA) model has been widely reported to describe the adsorption of proteins in different types of chromatographic adsorbents. Here in the present work, a pore-blocking steric mass-action model (PB-SMA) was developed for the adsorption of large-size bioparticles, which usually exhibit the unique pore-blocking characteristic on the adsorbent and thus lead to a fraction of ligands in the deep channels physically inaccessible to bioparticles adsorption, instead of being shielded due to steric hindrance by adsorbed bioparticles. This unique phenomenon was taken into account by introducing an additional parameter, Lin, which is defined as the inaccessible ligand densities in the physically blocked pore area, into the PB-SMA model. This fraction of ligand densities (Lin) will be deducted from the total ligand (Lt) for model development, thus the steric factor (σ) in the proposed PB-SMA will reflect the steric shielding effect on binding sites by adsorbed bioparticles more accurately than the conventional SMA model, which assumes that all ligands on the adsorbent have the same accessibility to the bioparticles. Based on a series of model assumptions, a PB-SMA model was firstly developed for inactivated foot-and-mouth disease virus (iFMDV) adsorption on immobilized metal affinity chromatography (IMAC) adsorbents. Model parameters for static adsorption including equilibrium constant (K), characteristic number of binding sites (n), and steric factor (σ) were determined. Compared with those derived from the conventional SMA model, the σ values derived from the PB-SMA model were dozens of times smaller and much closer to the theoretical maximum number of ligands shielded by a single adsorbed iFMDV, indicating the modified model was more accurate for bioparticles adsorption. The applicability of the PB-SMA model was further validated by the adsorption of hepatitis B surface antigen virus-like particles (HBsAg VLPs) on an ion exchange adsorbent with reasonably improved accuracy. Thus, it is considered that the PB-SMA model would be more accurate in describing the adsorption of bioparticles on different types of chromatographic adsorbents.

Optically active components of oil from the deepwater Gunashli field

The article presents the results of study of deep-water Gunashli oil’s optically active components. Oil is separated into 50 oC fractions, after studying the physicochemical properties of the resulting fractions, they are dearomatized by liquid chromatographic adsorption, as well as polar and non-polar solvents. The physicochemical properties, optical activity and chiroptic properties were studied, as well as the structural composition of the obtained naphthene-paraffin hydrocarbons was studied by IR spectroscopic analysis. The highest properties of optical activity are observed in naphthene-paraffin hydrocarbons, which boil away in the temperature range of 400–450 oC. The obtained results are very important in the selection of petroleum components, obtaining their narrow fractions, as well as the identification or isolation of optically active substances.

Continuously Tunable MOFs Enable Precise Mass Transfer for High-Performance Isomer Separation.

Modulating mass transfer is crucial for optimizing the catalytic and separation performances of porous materials. Here, we systematically developed a series of continuously tunable MOFs (CTMOFs) that exhibit incessantly increased mass transfer. This was achieved through the strategic blending of ligands with different lengths and ratios in MOFs featuring the fcu topology. By employing a proportional mixture of two ligands in the synthesis of UiO-66, the micropores expanded, facilitating faster mass transfer. The mass transfer rate was evaluated by dye adsorption, dark-field microscopy, and gas chromatography (GC). The GC performance proved that both too-fast and too-slow mass transfer led to low separation performance. The optimized mass transfer in CTMOFs resulted in an exceptionally high separation resolution (5.96) in separating p-xylene and o-xylene. Moreover, this study represents the first successful use of MOFs for high-performance separation of propylene and propane by GC. This strategy provides new inspiration in regulating mass transfer in porous materials.

Cu(II)-Loaded Polydopamine-Coated Urchin-like Titanate Microspheres as a High-Performance IMAC Adsorbent for Hemoglobin Separation.

Immobilized metal ion affinity chromatography (IMAC) adsorbents generally have excellent affinity for histidine-rich proteins. However, the leaching of metal ions from the adsorbent usually affects its adsorption performance, which greatly affects the reusable performance of the adsorbent, resulting in many limitations in practical applications. Herein, a novel IMAC adsorbent, i.e., Cu(II)-loaded polydopamine-coated urchin-like titanate microspheres (Cu-PDA-UTMS), was prepared via metal coordination to make Cu ions uniformly decorate polydopamine-coated titanate microspheres. The as-synthesized microspheres exhibit an urchin-like structure, providing more binding sites for hemoglobin. Cu-PDA-UTMS exhibit favorable selectivity for hemoglobin adsorption and have a desirable adsorption capacity towards hemoglobin up to 2704.6 mg g-1. Using 0.1% CTAB as eluent, the adsorbed hemoglobin was easily eluted with a recovery rate of 86.8%. In addition, Cu-PDA-UTMS shows good reusability up to six cycles. In the end, the adsorption properties by Cu-PDA-UTMS towards hemoglobin from human blood samples were analyzed by SDS-PAGE. The results showed that Cu-PDA-UTMS are a high-performance IMAC adsorbent for hemoglobin separation, which provides a new method for the effective separation and purification of hemoglobin from complex biological samples.

Brick sand particles as an adsorbent in column chromatography to remove heavy metals from solution

The column chromatography method was used with brick sand particles as an adsorbent for the removal of heavy metals (Cr, Fe, and Pb) from the aqueous solution. These metals can pollute water, and soil and also come in contact with the food chain, causing life-threatening health issues in the human body. The pore volume and the specific surface area of the brick sand particles were determined using the standard method which was 44.41% and 29.4 m2/g respectively. The different concentrations of toxic metals in the water solution were considered to determine the adsorption capacity of the adsorbent. The adsorption methods were able to remove about 94% of Cr, 24% Pb, and 69% Fe from the aqueous solution. From the investigation results, we may conclude that raw brick sand particles can play a vital role as an adsorbent in the treatment of heavy metal-contaminated wastewater. Moreover, the saturated adsorbent can be used as an element of construction materials to prevent further pollution. Bangladesh J. Sci. Ind. Res. 59(1), 47-54, 2024

Purification of Anti-Mycobacterium tuberculosis MPT64 Immunoglobulin-Y from Egg-Yolk Supernatant Using Thiophilic Adsorption Chromatography

The significance of immunoglobulin Y (IgY) as a particular antibody equal to mammalian IgG is well understood. However, due to a lack of reliable purification procedures, producing highly pure IgY remains problematic. In this study, we aimed to optimize the recovery of pure IgY anti-MPT64 using thiophilic adsorption chromatography. The purification of IgY anti-MPT64 was achieved by initial PEG lipid precipitation, then an optimized purification by varying the gradient concentration of elution buffer into five steps gradient (0-20, 20-40, 40-60, 60-80, and 80-100%v/v) for three injection column volume (CV) each and two steps gradient (0-50 and 50-100%v/v) in eight CV for each concentration. The obtained IgY was characterized by SDS-PAGE and dot-blot then determined its content levels using the Lowry method. The results showed that the five steps gradient purification was found to provide a better purity level of IgY than the two steps gradient. However, the IgY content obtained in the two steps gradient purification (2.2632± 0.011 mg/mL) was higher than the five steps gradient purification (1.35482 ± 0.023 mg/mL). Nevertheless, both purified IgY results can recognize MPT64 protein through a dot blot test. Therefore, it can be summarized that thiophilic adsorption chromatography with five steps gradient of purification was an efficient process to obtain a higher purity of IgY anti-MPT64, especially to be targeted as a diagnostic kit component for MPT64 detection.

Mixed-mode size-exclusion silica resin for polishing human antibodies in flow-through mode

The polishing step in the downstream processing of therapeutic antibodies removes residual impurities from Protein A eluates. Among the various classes of impurities, antibody fragments are especially challenging to remove due to the broad biomolecular diversity generated by a multitude of fragmentation patterns. The current approach to fragment removal relies on ion exchange or mixed-mode adsorbents operated in bind-and-gradient-elution mode. However, fragments that bear strong similarity to the intact product or whose biophysical features deviate from the ensemble average can elude these adsorbents, and the lack of a chromatographic technology enabling robust antibody polishing is recognized as a major gap in downstream bioprocessing. Responding to this challenge, this study introduces size-exclusion mixed-mode (SEMM) silica resins as a novel chromatographic adsorbent for the capture of antibody fragments irrespective of their biomolecular features. The pore diameter of the silica beads features a narrow distribution and is selected to exclude monomeric antibodies, while allowing their fragments to access the pores where they are captured by the mixed-mode ligands. The static and dynamic binding capacity of the adsorbent ranged respectively between 30-45 and 25–33 gs of antibody fragments per liter of resin. Selected SEMM-silica resins also demonstrated the ability to capture antibody aggregates, which adsorb on the outer layer of the beads. Optimization of the SEMM-silica design and operation conditions – namely, pore size (10 nm) and ligand composition (quaternary amine and alkyl chain) as well as the linear velocity (100 cm/h), ionic strength (5.7 mS/cm), and pH (7) of the mobile phase – afforded a significant reduction of both fragments and aggregates, resulting into a final antibody yield up to 80% and monomeric purity above 97%.

Online coupling of liquid chromatography and two-dimensional diffusion ordered spectroscopy for the analysis of oligostyrenes

The aim of this study was to introduce a powerful coupling of Liquid Adsorption Chromatography (LAC) and Diffusion-Ordered Spectroscopy (DOSY) for comprehensive structure analysis. This new hyphenation approach facilitated the simultaneous separation of a polymer mixture and the determination of molar masses within a single 3D experiment. The online coupling of High-Performance Liquid Chromatography (HPLC) and two-dimensional DOSY-NMR will be called 3D-LAC-NMR-DOSY experiment. Our methodology enabled the chromatographic separation of analytes based on their chemical heterogeneity, and provided accurate molar masses of the analytes through 2D-DOSY. This new method was demonstrated on a polystyrene oligomer mixture. In this case, the oligostyrenes could be separated with LAC according to their tacticity and chain length in protonated acetonitrile as eluent and DOSY measurements provided the molar masses of each oligomer. In order to show the power of the 3D-LAC-NMR-DOSY method, the comparison to 2D-DOSY, 3D-DOSY and LAC-NMR was separately evaluated. Furthermore, the recently published solvent-independent molar mass calibration of diffusion coefficients was also successfully applied in our LAC-DOSY studies for molar mass predictions of the oligomers in acetonitrile. The predicted molar masses were in good agreement with the LAC-DOSY measurements and were verified by calibrations of diffusion coefficients and mass spectrometry. Finally, this pioneering 3D technique offers a powerful new tool for advancing structure analysis and enhancing our understanding of complex systems such as oligostyrenes.

Isolation of Polyphenols from Aqueous Extract of the Halophyte Salicornia ramosissima.

Polyphenols from residual non-food grade Salicornia ramosissima have health-promoting effects in feed, food, or nutraceutical applications. Therefore, the isolation of polyphenols is of interest from a series of environmentally friendly isolation methods with recyclable solvents. The isolation of polyphenols from non-food grade S. ramosissima was investigated using sequential membrane filtration with and without acid pretreatment, liquid-liquid extraction, resin adsorption, and centrifugal partition chromatography (CPC); analyzed by the Folin-Ciocalteu assay for total polyphenols; and finally analyzed using UPLC-TQMS in negative ion-spray mode for detection of 14 polyphenols. Sequential membrane filtration and acid hydrolysis indicated the polyphenols forming complexes with other compounds, retaining the polyphenols in the retentate fraction of large molecular weight cut-off membrane sizes. Conventional liquid-liquid extraction using sequential ethyl acetate and n-butanol showed most polyphenols were extracted, apart from chlorogenic acids, indicating a low isolation efficiency of higher polarity polyphenols. Analysis of the extract after resin adsorption by Amberlite XAD-4 resin showed high efficiency for separation, with 100% of polyphenols adsorbed to the resin after 13 bed volumes and 96.7% eluted from the resin using ethanol. CPC fractionations were performed to fractionate the concentrated extract after resin adsorption. CPC fractionations of the 14 polyphenols were performed using an organic or aqueous phase as a mobile phase. Depending on the mobile phase, different compounds were isolated in a high concentration. Using these easily scalable methods, it was possible to comprehensively study the polyphenols of interest from S. ramosissima and their isolation mechanics. This study will potentially lead the way for the large-scale isolation of polyphenols from S. ramosissima and other complex halophytes. The compounds of the highest concentration after CPC fractionation were isoquercitrin and hyperoside (155.27 mg/g), chlorogenic acid (85.54 mg/g), cryptochlorogenic acid (101.50 mg/g), and protocatechuic acid (398.67 mg/g), and further isolation using CPC could potentially yield novel polyphenol nutraceuticals.

Changes in composition and structure of nitrogenous bases of resin components of heavy oil from the Nurlatskoe oilfield in the course of thermal decomposition

The relevance. The need to obtain information on heat treatment effect on composition and structure of nitrogenous bases of resin components of heavy oil from the Nurlatskoe field (Republic of Tatarstan) to solve the problems associated with their negative impact on oil refining. The aim. To characterize the composition of nitrogenous organic bases, isolated from the resins of bituminous oil of the Nurlatskoe field, and the products of their thermal cracking. Methods. Complex formation, extraction, liquid adsorption chromatography, potentiometric titration, 1H NMR spectroscopy, structural group analysis, combined gas chromatography-mass spectrometry. Results. Based on a comparative study of the composition and structure of nitrogenous bases of the initial and thermally treated resins of the bituminous oil from the Nurlatskoe field, the authors found out that they both contain high- and low-molecular nitrogenous bases with predominance of high-molecular compounds precipitated by hydrogen chloride. As a result of thermal exposure, the number of such bases increases due to an increase in the proportion of compounds with shorter alkyl substituents in their composition. The method of structural group analysis was used to show that the main directions of thermal transformations of high- and low-molecular bases of resins in Nurlatskoe oil are destruction of alkyl substituents and cyclization of shortened alkyl chains with formation of naphthenic rings. Among the lowest molecular weight bases of the initial resins and thermolysate the authors have identified alkyl-substituted quinolines, benzoquinolines, azapyrenes, thiophenoquinolines, and benzothiophenoquinolines with similar molecular weight distributions. During the thermolysis of resins, the relative content of low molecular weight homologues in the identified nitrogenous bases increases. The share of structures with reduced chromatographic mobility caused by a decrease in the degree of spatial screening of a nitrogen atom increases among similar homologues.

Characterization of glucose Oxidase from Penicillium chrysogenum MDC 8358: Prospects for application in food industry

Backgrounds: Food enzymes play a crucial role in enhancing specific food attributes, such as improving texture, eliminating toxins and allergens, producing carbohydrates, and enhancing flavor and appearance characteristics. Glucose oxidase (GOX) catalyzes the oxidation of glucose to produce gluconic acid and hydrogen peroxide, making it applicable in various practical scenarios. This enzyme could be utilized to eliminate glucose, thereby facilitating the creation of functional food suitable for individuals with diabetes and glucose intolerance.Our main goal was to characterize GOX from a Penicillium chrysogenum strain isolated from Armenian ecosystems.Methods:GOX of P. chrysogenum MDC 8358 was obtained by surface fermentation using glucose as a carbon source. The enzyme was purified 230-fold to homogeneity using a three-step purification scheme consisting of ion exchange, adsorption, and gel filtration chromatography. Results:The specific activity of the purified enzyme reached 271.2 U/mg. GOX from P. chrysogenum MDC 8358 has shown to be dimeric with a molecular weight of 135.5 kDa, consisting of two equal subunits with a molecular weight of 70 kDa. Isoelectric focusing has revealed a pH of 4.6. The enzyme has displayed a temperature optimum of 40 °C, and a pH optimum of 6.8, being more thermostable at acidic pH. Characterized GOX was highly specific for β-D-glucose and has shown only minor activities to mannose, xylose, and galactose. Keywords:Penicillium chrysogenum MDC 8358, surface fermentation, glucose oxidase, purification, characterization, functional food preservation

ACE inhibitory peptides from enzymatic hydrolysate of fermented black sesame seed: Random forest-based optimization, screening, and molecular docking analysis

In this study, black sesame seeds were fermented by Lactobacillus Plantarum NCU116 and then hydrolyzed using acid protease to improve Angiotensin-I-converting enzyme (ACE) inhibitory activity. The random forest-particle swarm optimization (RF-PSO) model was applied to predict the ACE inhibitory activity during the hydrolysis process based on the experimental data. After separating by adsorption chromatography, gel filtration chromatography, and reversed phased-high performance liquid chromatography and then screening in silico method, eight peptides were identified from fermented black sesame seed hydrolysates as ITAPHW, SLPNYHPSPR, QYLPR, IRPNGL, YHNAPIL, LSYPR, GFAGDDAPRA, and LDPNPRSF with IC50 values of 51.69 μM, 146.67 μM, 655.02 μM, 752.60 μM, 1.02 mM, 2.01 mM, 1.97 mM, and 3.43 mM, respectively. ITAPHW and SLPNYHPSPR exhibited high antioxidant activity and inhibited the ACE activity in a non-competitive pattern. Molecular docking revealed that the strong ACE inhibition of ITAPHW and SLPNYHPSPR is probably attributed to the interaction with Zn2+ of ACE.

Observation of a volatile astatine hydroxide species in online gas-adsorption thermochromatography experiments

During recent online gas-phase experiments with the transactinide elements copernicium (Cn, Z = 112) and flerovium (Fl, Z = 114), the transport of a volatile astatine species was observed. Comprehensive Monte Carlo simulations of the deposition pattern of 211At on the given quartz, selenium, and gold chromatographic surfaces were carried out, and the corresponding adsorption enthalpies were estimated. Based on the astatine speciation from previous model experiments, the compound observed in this work was ascribed to AtOH/HAtO. The herein presented results assist in paving the way toward a future chemical characterization of tennessine (Ts, Z = 117) with similar gas adsorption chromatography techniques.

Separation and Purification of Plant Extracts by Removal of Chlorophyll, Xanthophylls and Pigments using Mineral Adsorbents in Liquid Chromatography (CLS)

This study focused on the purification of plant extracts, with the help of adsorption chromatography (liquid chromatography with a solid stationary phase - CLS) so that the purified plant extracts lead to obtaining bioactive compounds in a pure state or with advanced purity. The studied extracts can be divide into categories as follows: a) The purification of extracts from perilla frutescens b) The purification of extracts from rosmarinus officinalis c) The purification of extracts from artemisia annua (peliniță) For the perilla frutescens extract, dried leaves, the purification aimed at obtaining pure crystals of ursolic acid and the physico-chemical analysis of the plant extracts before and after extraction, to determine the loss of the important compounds of the plant, due to their retention in the adsorbent layer. For the rosemary and wormwood (artemisia annua) extracts, dry leaves, the purification aimed at obtaining pure crystals of bioactive compounds (ursolic acid, artemisinin) and their gravimetric dosing to determine the bioactive compound content of the original plant. Mineral adsorbents and combinations of mineral adsorbents in the form of adsorbent mixtures have been used. Glass liquid columns of various sizes were used. For each experiment, the working times (saturation-activation time, elution and column washing time) were noted. All experiments were performed with the adsorption chromatography procedure, with gravity flow column (in adsorption chromatography with gravity flow column), without using Sephadex LH-20 macroporous resins as a stationary phase.

Characterization of chemical composition distribution of ethylene-propylene-diene terpolymers by room temperature liquid adsorption chromatography and comparison to statistical approach

The chromatographic analysis of ethylene-propylene-diene (EPDM) terpolymers has hitherto been carried out only at high temperature, 120–160 °C. However, EPDM terpolymers are amorphous which could potentially allow to study their chromatographic behavior at room temperature (RT). To verify this hypothesis, cloud point measurements were realized to determine prospective solvent candidates. The identified solvents enabled injecting EPDM and model ethylene propylene norbornene terpolymers at RT.The retention of EPDM terpolymers on porous graphitic carbon (PGC) is a function at least two adsorbing comonomer components, ethylene and diene, in all tested chromatographic systems. This makes it difficult to characterize the chemical composition distribution (CCD) of terpolymers, which is of immense technical interest. Therefore, a modified form of LAC (LACm) was employed for determining the CCD of EPDM terpolymers using the identified solvents. Finally, the CCD obtained using different experimental methods was compared to the CCD determined using Monte Carlo simulations.

Chlorinated paraffins in food contact materials made of rubber from the German market

Chlorinated paraffins (CPs), also known as polychlorinated alkanes (PCA), are a very complex class of polyhalogenated compounds currently produced in unmatchable amounts for different industrial uses. Short-chain CPs (SCCPs; C10- to C13-CPs) are listed as POPs in the Stockholm Convention and medium-chain CPs (MCCPs; C14- to C17-CPs) are proposed for listing. Here, we investigated the presence of SCCPs and MCCPs in 21 rubber samples used as food contact materials from the German market. For this purpose, an analytical method was developed which consisted of (i) freezing and (ii) grounding of the material, (iii) removal of oligomers by adsorption chromatography, (iv) matrix destruction with sulfuric acid, and (v) GC/ECNI-MS screening and quantification. Three of the rubber samples were found to contain predominantly MCCPs at 69, 113,000 and 341,000 mg/kg. The highest amount (corresponding with 34 weight-% CPs) was determined in one rubber band sample used to bundle a bunch of spring onions. A very high CP content of >300,000 mg/kg in this rubber band sample was confirmed by quantitative 1H NMR (qNMR) analysis. This rubber material was in direct contact with the onions and leaching of CPs into the food cannot be excluded. Even more, micro-abrasions of rubber could be unintentionally swallowed by the consumer and this CP exposure could be higher than the current CP intake via food.

A Sustainable Approach for the Valorization of Underutilized Date Fruits.

Secondary varieties of date fruits are often discarded because they do not have commercial value. However, their phytochemicals are very similar to those of the primary ones and therefore, they can be valorized as a source of compounds of interest, mainly phenols and dietary fiber. Their chemical composition changes with ripening, so their characterization throughout this process is of great significance. Date fruit samples were harvested at Khalal, Rutab, and Tamer stages, and a mixture of fruits from ornamental date trees was also analyzed. Aqueous and ethanolic extracts were studied for their phenolic composition. In aqueous extracts, phenols decreased with ripening, while in the ethanolic ones having higher phenolic content. Chelidonic acid, a γ-pyrone, was the major compound found in all extracts, but in the ethanolic ones, flavonoids were also present in similar amounts. After purification by adsorption chromatography, all extracts were assayed for their antimicrobial activity. Those from the Tamer stage showed the highest activity, especially against Gram-positive bacteria. The fibrous residues after aqueous and ethanolic extractions were also characterized. Their chemical composition suggested that they can be considered as a good source of prebiotic arabinoxylans and antioxidant fiber, whose antiradical activity correlated with their phenolic content. Date fruits from secondary varieties are promising as a worthwhile starting point for obtaining new value-added products.