Retention Of Flavonoids Research Articles

Retention of Phytochemical Compounds and Antioxidative Activity in Traditional Baked Dish "proja" Made from Pigmented Maize.

Two genotypes of pigmented maize (black (BM) and red (RM)) were used as flour ingredients in several formulations of the traditional baked maize dish "proja". This study investigated the stability of phytochemical compounds and antioxidant activity in proja as affected by baking and different acidity degrees of dough formulations. Compared to RM proja, all BM proja formulations were significantly higher in antioxidant compounds and exhibited the highest inhibitory activity (73-85%) against DPPH. There was a strong significant correlation between DPPH inhibition and total phenolics (r2 = 0.95), flavonoids (r2 = 0.96), and anthocyanins (r2 = 0.97) in baked proja. After baking, 67-85% of total phenolics were retained. The fate of flavonoids and anthocyanins after baking was variable: from 70% degradation to liberation. Dough acidity significantly and positively affected the content of phenolics, flavonoids, and anthocyanins in BM proja (r2 = 0.70, 0.82, and 0.47, respectively). Baking increased antioxidant activity against DPPH, •OH, and O2•- radicals in proja, except for ≈10% decline of DPPH inhibition in BM proja. In RM proja, retention of inhibitory capacity against O2•- was highly correlated to flavonoid retention (r2 = 0.71). Using pigmented maize flour in proja baking resulted in proja with appreciable content of total phenolics, flavonoids, anthocyanins, and high antioxidant activity, confirming the significant improvement of the nutrient profile of this traditional food.

Effects of wall materials on the physicochemical properties of spray-dried bitter gourd (Momordica charantia L.) powders

Bitter gourd has numerous health-promoting effects on the human body. However, its use has been greatly limited due to its poor acceptance by consumers, resulting from its strong bitterness. This study investigated the effects of five wall materials, namely, soybean protein isolate, gum arabic, maltodextrin, resistant starch, and a soybean lecithin calcium caseinate mixture, on the physicochemical properties of spray-dried bitter gourd powders. The results showed that all five wall materials reduced the moisture content, water activity, browning degree, agglomeration, and bitterness of the spray-dried bitter gourd powder. Maltodextrin was found to be the most effective at reducing water activity, while soybean protein isolate was best at protecting the colour, and the soybean lecithin calcium caseinate mixture was best at reducing hygroscopicity and masking bitterness. Additionally, all five wall materials improved the preservation of flavonoids, saponins, and vitamin C, with soybean protein isolate being the most effective in improving the total flavonoid retention ratio and the soybean lecithin calcium caseinate mixture being the best in improving the retention ratios of total saponins and vitamin C. The spray-dried bitter gourd powder prepared with soybean protein isolate had the highest antioxidant activity and α-glucosidase inhibitory activity. These results are significant for understanding the relationship between wall materials and the physicochemical properties of spray-dried powder. Additionally, these materials provide bitter gourd product manufacturers with useful guidance for producing high-quality products. Furthermore, the results could provide useful insights for processing fruits with similar product characteristics, thus contributing to the enrichment of food processing knowledge.

Evaluation of green chili stored at the chilling condition: Effects of thermal and ultrasound pretreatments

The research was conducted to evaluate the effect of thermal (Hot Water) and non-thermal (Ultrasound) pretreatments on the changes of physical and nutritional quality attributes, and marketability of the green chili stored at chilling condition. Freshly harvested green chili was pretreated with hot water, ultrasound and Control (Untreated) respectively and the shelf life study was performed. The experiment was designed by Completely Randomized Design with three replications. There was a significant (p < 0.05) differences observed among the treatments. It was observed that physiological weight loss, firmness, and ascorbic acid decreased significantly where pH, total soluble solids and titrable acidity increased over the storage time. The samples treated with hot water revealed the least amount of lightness in the green chili among all the treatments. The highest retention of flavonoids and antioxidant activity was found in the ultrasound treated samples. However, the total phenolic content was found to be sunstentially greater in the untreated samples after storage. The obtained results indicated that average shelf life of green chili was increased up to 16 days at chilling condition compared to untreated sample. Green chili treated with ultrasound showed the highest marketability (82%) at the end of the storage while retaining the quality attributes.

Effects of pre-processing on the active compounds before drying Eucommia ulmoides leaves

Aiming to provide a new way that preserves more active components in Eucommia ulmoides (EU) leaves, this paper utilizes 4 methods, i.e., microwave, steam, air heating, and frying, to process EU leaves before drying, and their respective effects on the leaves were evaluated. The antioxidant activity of EU leaves in vitro was measured by the DPPH free radical method; the contents of total flavonoids (TFC) and total phenols (TPC) were analyzed by spectrophotometry; and the contents of main active components were determined by high-performance liquid chromatography (HPLC). The results showed the pre-process improved the quality of the EU leaves. As a simple and fast process, the microwave process is the most effective technique in the retention of flavonoids and four active ingredients except aucubin. High power (800 W) and short time (2.5 min) are more conducive to the retention of active ingredients, with high antioxidant activity. Appropriate steam and frying processes also exhibited benefits for the active components. In particular, the samples treated with steam for 10 minutes showed great potential for industrial application with the highest antioxidant activity and polyphenol content. Therefore, proper pre-processing before drying should be conducted to effectively protect the active components of EU leaves.

Evaluation of the uniformity, quality and energy cost of four types of vegetables and fruits after pilot-scale pulse-spouted bed microwave (915 MHz) freeze-drying

The homogeneity of dried products produced via pilot-scale pulse-spouted bed microwave (915 MHz) freeze-drying (pilot-scale PSBMFD) was investigated using sweet corn, potato, banana and hawthorn as experimental materials. The quality and energy cost of the dried products were also investigated. Regarding the moisture content, color difference and shrinkage ratio, pilot-scale PSBMFD achieved high drying uniformity (⩾90%, d.b.). Compared with the conventional freeze-drying (CFD) method used in industries, pilot-scale PSBMFD effectively increased the nutrient retention (d.b.) in dried samples. It increased the retention of flavonoids in sweet corn, potato cube, banana slice and hawthorn by approximately 11.68%, 15.82%, 5.76%, and 15.94% and the total phenolic content by 11.85%, 23.58%, 28.34%, and 24.17%, respectively. Further, pilot-scale PSBMFD resulted in a larger honeycomb porous structure, greater hardness and brittleness as well as shrinkage and lower apparent density than CFD. Regarding the energy cost, pilot-scale PSBMFD can save more energy than CFD (⩾39%, d.b.). This pilot-scale experimental study provides a theoretical basis and technical support for the commercial application of the PSBMFD technology.

Effects of five extraction methods on total content, composition, and stability of flavonoids in jujube

The present study investigated the effects of different extraction methods including water-water bath (W-WB), ethanol-water bath (E-WB), deep eutectic solvent (DES) combined with ultrasound-assisted extraction (DES-UAE), microwave-assisted extraction (DES-MAE), and enzyme-assisted extraction (DES-EAE) on flavonoids (total flavonoid content, flavonoid composition, and stability) in jujube. The highest total flavonoid content of 8.03mg/g was obtained by the DES-MAE extraction. Fifteen types of flavonoids were identified from jujube. The amount of rutin produced by the E-WB and DES-UAE methods was 66.88±1.58μg/g and 45.23±3.22μg/g, respectively. The retention of flavonoids in DES-UAE extracts were 98.15±0.51%, 64.25±2.21% after 2h of high temperature treatment at 90°C and 21days of dark storage, respectively. The flavonoids extracted by different methods were suitable for dark storage under different light contrasts, where the retention of flavonoids extracted by DES-UAE method was 86.44±2.45%. In conclusion, DES-UAE would be an efficient method for flavonoid extraction from jujube.

Application of different drying methods for evaluation of phytochemical content and physical properties of broccoli, kale, and spinach

In this study, quality characteristics of broccoli, kale, and spinach dried with hot air drying (AD), freeze drying (FD) and Refractance Window drying (RWD) were investigated, including phenolics, flavonoids, vitamins, glucosinolates, color, Tg and microstructure. Broccoli, kale and spinach samples dried using RWD had the highest total phenolics content (8.50, 18.77 and 12.40 mg/g, respectively). The highest retention of flavonoids was found in FD broccoli (8.98 mg/g), RWD kale (19.51 mg/g), and RWD spinach (9.31 mg/g). The FD-samples had the highest glucosinolates, followed by RWD. The FD and RWD samples also showed less color changes compared to the AD samples, which had darker color indicating chlorophyll degradation. Tg was in the range of 55–60 °C for all RWD, AD and FD vegetable samples, apart from AD broccoli which showed a slightly higher Tg. Among the 3 drying methods, the AD vegetables had a rough surface while that of the FD and RWD samples were relatively smooth. Overall, this study concludes that the quality retention in the dried vegetables is product and drying method specific and, therefore, selection of the best drying method for a product needs to be done considering both, the quality retention and energy consumption.

Drying Techniques and Storage: Do They Affect the Nutritional Value of Bee-Collected Pollen?

In this study, the effect of different drying processes (freeze-drying (FD), microwave-assisted drying (MWD) and classic hot air drying (HAD)) on the polyphenols, flavonoids, and amino acids content was investigated on bee-collected chestnut, willow and ivy pollen for human consumption. Furthermore, the pollen chemical properties were monitored after three and six months of storage, and then analyzed using a multivariate approach. Chestnut pollen was the richest source of polyphenols, flavonoids, and rutin, while ivy pollen contained the highest amount of total and free amino acids, and total and free proline. Drying and storage affected pollen chemical composition with species-dependent effects. MWD allowed the best retention of flavonoids in chestnut pollen for up to six months of storage. All drying techniques led to a depletion of flavonoids in willow pollen; however, MWD ensured the highest flavonoids content after six months. FD and MWD did not lead to flavonoids depletion in ivy pollen during storage. Additionally, storage did not affect the rutin content, which was highest in FD willow samples after six months. Notably, both FD and MWD techniques are efficient in preserving amino acids-related quality of bee pollen up to six months of storage.

Establishment of concentration process and physical property parameter model of Carthami Flos extract based on quality by design

To explore the potential of &quot;physical property model&quot; based on the concept of quality by design(QbD),during the application of process analysis technology(PAT) in the concentration process. The Carthami Flos was used as a model drug. Firstly, the total flavonoid retention rate and the hydroxysafflor yellow A(HSYA) retention rate of the concentrated solution were used as indicators to determine the concentration temperature range of the Carthami Flos extract. Then different concentrations were prepared at the optimal concentration temperature, and the corresponding viscosity(η) and electrical conductivity(σ) at different concentrations and temperatures were measured. Data processing software such as Excel, 1 stOpt, SPSS, and MATLAB were used to establish Carthami Flos extract's mathematical model of physical parameters: ρ-C, η-C, η-T, η-C-T, σ-T, σ-C-T. The results showed that the best concentration temperature of the Carthami Flos extract should not exceed 60 ℃, and the R~2 of the exponential equation and Arrhenius equation established based on physical parameters was all greater than 0.9, indicating that such model had better predictive ability. The mathematical model:η=14.465 1 exp(-0.019 8T+ 0.771 1C-0.058 3C~2), σ=4.061 0 + 0.004 3T +(-1.104 1 +0.950 9T)C-0.556 9TC~2 can be used to reflect the comprehensive effect of concentration and temperature on viscosity or conductance, laying foundation for the establishment of an online monitoring system for the viscosity or conductivity of the extraction liquid in the concentration step, rapid prediction of the concentration status, and control of the concentration endpoint. This study has initially proved the feasibility of using the physical property model as the core of the research idea in application of PAT for intelligent quality control of traditional Chinese medicine concentration links, providing a reference for the online intelligent monitoring of concentration steps of traditional Chinese medicine extracts.

Mechanistic Chromatographic Column Characterization for the Analysis of Flavonoids Using Quantitative Structure-Retention Relationships Based on Density Functional Theory.

This work aimed to unravel the retention mechanisms of 30 structurally different flavonoids separated on three chromatographic columns: conventional Kinetex C18 (K-C18), Kinetex F5 (K-F5), and IAM.PC.DD2. Interactions between analytes and chromatographic phases governing the retention were analyzed and mechanistically interpreted via quantum chemical descriptors as compared to the typical ‘black box’ approach. Statistically significant consensus genetic algorithm-partial least squares (GA-PLS) quantitative structure retention relationship (QSRR) models were built and comprehensively validated. Results showed that for the K-C18 column, hydrophobicity and solvent effects were dominating, whereas electrostatic interactions were less pronounced. Similarly, for the K-F5 column, hydrophobicity, dispersion effects, and electrostatic interactions were found to be governing the retention of flavonoids. Conversely, besides hydrophobic forces and dispersion effects, electrostatic interactions were found to be dominating the IAM.PC.DD2 retention mechanism. As such, the developed approach has a great potential for gaining insights into biological activity upon analysis of interactions between analytes and stationary phases imitating molecular targets, giving rise to an exceptional alternative to existing methods lacking exhaustive interpretations.

Effects of processing and storage conditions on the stability of sweet potato (Ipomoea batatas L.) leaf flavonoids

SummaryThe effect of heat, high hydrostatic pressure (HHP) treatment, pH, light, temperature and simulated digestion on sweet potato leaf flavonoids (SPLF) stability was studied. Results showed heat treatment at 75 °C for 90 min or HHP treatment at 600 MPa for 30 min did not cause significant effect on SPLF. Heat treatment at 100 °C for 60 min and 90 min led to decrease in antioxidant activity by 20% and 25%, respectively, while pH 7.0 and 8.0 significantly decreased amount of SPLF by approximately 75%, decreased antioxidant activity by about 30% and 47% separately. Light treated samples recorded a decrease in SPLF by 52% and antioxidant activity by 24%. No significant effect on SPLF was observed for samples stored at −18 °C, 4 °C or room temperature. The retention of flavonoids and antioxidant activity was 45.9 ± 3.6% and 56.2 ± 2.6%, individually in SPLF after simulated digestion.

Flavonoid-Enriched Plant-Extract-Loaded Emulsion: A Novel Phytocosmetic Sunscreen Formulation with Antioxidant Properties.

The aim of this study was to develop a phytocosmetic sunscreen emulsion with antioxidant effect, containing a blend of flavonoid-enriched plant extracts. In vitro sun protection factor, antioxidant activity, skin irritation, photostability, cutaneous permeation, and retention of flavonoids were evaluated. Thermodynamically stable emulsions were obtained and tested for sensorial analysis after loading the blend of extracts. The selected emulsion was stable when stored at low temperatures (5 °C), for which after 120 days the concentration of quercetin and rutin were above their limit of quantification, i.e., 2.8 ± 0.39 μg/mL and 30.39 ± 0.39 μg/mL, respectively. Spreadability, low rupture strength and adhesiveness were shown to be similar to a conventional topical product. Higher brittleness, pseudo-plastic, and viscoelastic behaviors were also recorded for the developed phytocosmetic sunscreen. The product presented a critical wavelength of 387.0 nm and ultraviolet rays A and B (UVA/UVB) rate of 0.78, confirming that the developed formulation shows capacity for UVA/UVB protection, protecting skin against damages caused by ultraviolet (UV) radiation. Rutin was shown to permeate the skin barrier and was also quantified in the stratum corneum (3.27 ± 1.92 μg/mL) by tape stripping and retention test (114.68 ± 8.70 μg/mL). The developed flavonoid-enriched phytocosmetic was shown to be non-irritant to skin by an in vitro assay. Our results confirm the antioxidant activity, sun protection, and physical properties of the developed phytocosmetic for topical application.

Application of gum Arabic, β-cyclodextrin, and hydroxypropyl-β-cyclodextrin to microencapsulation by molecular inclusion of grape skin extract (Vitis labrusca var. Isabel)

Gum Arabic (GA), β-cyclodextrin (β-CD), and hydroxypropyl-β-cyclodextrin were used in different proportions to microencapsulate polyphenols obtained by aqueous extraction from a grape skin. Phenol contents of the microcapsules were evaluated for anthocyanins, flavonoids and total flavanols, antioxidant activity, color, moisture, water activity (Aw), solubility, hygroscopicity, and glass transition temperature (Tg). The microcapsules prepared with either 5% GA or a mixture of 3% GA and 2% β-CD had the highest retention of phenolic (78.9 and 67.5%, respectively), anthocyanins (35.3 and 29%, respectively) and antioxidant activity greater than 50% measured by the DPPH and CUPRAC methods. Treatment with 3% GA and 2% β-CD showed the highest retention of flavonoids (67.2%) and total flavanols (51.1%), as well as physical properties suitable for this type of product, such as Aw of 0.175, solubility greater than 90%, hygroscopicity of 17.3%, and Tg of 32.8°C, which may contribute to a greater stability of the powder. Practical applications Grape processing by-products have a great feasible commercial, and this is due at high concentrations of phenolic compounds in grape skin. It was possible to obtain inclusion complexes powder of phenolic compounds from grape skin, using cyclodextrin and its derivates in mixture with Arabic gum as carriers. This way, the stability of bioactive compounds may be improved during food processing, storage and pass through the gastrointestinal tract. In addition, it is possible to enhance solubility of phenolics compounds in aqueous dispersions. Powders obtained have antioxidant properties and potential prebiotic activity.

Milling and thermal treatment induced changes on phenolic components and antioxidant activities of pigmented rice flours.

Processing methods involved in value addition to pigmented broken rice, a milling by-product may affect the nutraceutical qualities. Hence the effect of pulverisation and toasting on nutraceutical content in brown rice flours of red and black rice varieties were studied. Plate milling reduced soluble, bound and total polyphenols in red, but increased in black; increased insoluble polyphenols and oryzanol, and reduced anthocyanin in both varieties; antioxidant activity is reduced in red, but increased in black. Toasting caused reduction of soluble, insoluble and total polyphenol, anthocyanin and antioxidant activity in both varieties with an increase in bound polyphenols, and retention of flavonoids and oryzanol. HPLC characterization of phenolics showed changes on processing in content of catechin, caffeic, vanillic, protocatechuic and ferulic acid. It can be concluded that processing impacts the phenolic components of pigmented broken brown rice flour and this information is useful for functional food industry.

Can Cold Brew Coffee Be Convenient? A Pilot Study For Caffeine Content in Cold Brew Coffee Concentrate Using High Performance Liquid Chromatography

Cold brew coffee is a brewing method that is increasing in prevalence. While it has been anecdotally suggested that this method may provide a more aromatic and flavourful coffee product, there is little research published that looks at the concentration of caffeine or other coffee substituents in cold brew coffee. The potential alteration in chemical composition in cold brew provides a few interesting avenues for research. Can caffeine in cold brew be quantified by conventional methods? If so, how does the caffeine profile of cold brews relate to hot brew methods? Here we report the caffeine content and variability in small batch cold brew coffee and show that HPLC/UV-Vis, a standard method for quantitation of caffeine in other extraction methods, is useful for detection of caffeine in cold brew coffee. The mean concentration of caffeine in an average 355 mL serving was found to be 207.22 ± 39.17 mg over five distinct batches of cold brew coffee concentrate. Cold brew preparation methods produce similar quantities of caffeine as hot brew preparation, yet may have increased storage capabilities including improved retention of flavonoids and other secondary metabolites. Therefore, cold brew may provide utility in clinical trials examining caffeine and the effect of other components of coffee as it is commonly consumed.

The effect of additives on release and in vitro skin retention of flavonoids from emulsion and gel semisolid formulations.

To assess the effect of two different additives (propylene glycol (PG) and polyethylene glycol 400 (PEG 400)) on release and in vitro skin retention of quercetin and chrysin from semisolid bases (amphiphilic creams and acidic carbomer gels). For obtaining semisolid formulations, flavonoids were pre-dissolved in the liquid (PG or PEG 400) or directly suspended in the semisolid base. Three chrysin formulations ('cream 0', 'PG-cream' and 'PEG 400-cream') and five quercetin formulations ('cream 0', 'PG cream', 'PEG 400 cream', 'gel 0' and 'PG gel') were prepared. The release studies were carried out in Franz diffusion cells by means of a cellulose membrane. The porcine ear skin was used in in vitro skin retention studies. The dissolution was a prerequisite to increase the release rates of tested flavonoids from obtained semisolid formulations. The cumulative amount of chrysin released after 6 h from 'PEG 400 cream' containing partly dissolved form of that flavonoid was higher than that from 'cream 0' or 'PG cream' containing its suspended form. The formulations containing quercetin dissolved in PG ('PG cream', 'PG gel') or PEG 400 ('PEG 400 cream') exhibited higher release rates of that flavonoid than corresponding semisolid suspensions ('cream 0' or 'gel 0'). The effects of both liquid additives (PG and PEG 400) on the cumulative amount of quercetin released after 6 h were comparable. However, there was no correlation between the release rate and the skin retention. The amounts of the flavonoids found in the skin were strongly affected by the type of the used solvent. While PG increased the skin retention of both flavonoids, PEG 400 had no effect on chrysin skin retention and delayed quercetin skin absorption. The proper choice of the solvent added to the semisolid base is crucial for enhanced skin delivery of the tested flavonoids. PG is more efficient absorption promoter than PEG 400 of both chrysin and quercetin.

Potential use of secondary products of the agri-food industry for topical formulations and comparative analysis of antioxidant activity of grape leaf polyphenols

The aim of the present study was to develop a phytocosmetic using Vitis waste by-products, for use as a topical formulation for skin protection against ultraviolet radiation damage. The study also evaluates the free radical scavenger activity of the crude extracts of dried leaves of Vitis vinifera and Vitis labrusca, as well as the anthocyanins, flavonoid fraction and isolated compounds. Next, release and permeation studies of hydrogels were performed using Franz-type diffusion cells. Flavonoid acted more intensively in TRAP and conjugated dienes antioxidant assays, whereas anthocyanins had higher antioxidant activity in hydroxyl and nitric oxide assay. Only quercetin-3-O-glucuronide (5) was released from hydrogels, and the flavonoid retention in porcine ear skin after eight hours of permeation was below of limit of quantification for this compound. The polyphenols present in Vitis are capable of absorbing UV and visible light, justifying their potential as sunscreens for the development of a phytocosmetic.

Study on Processing Technology and Quality of Moringa oleifera leaves with y - Aminobutyric Acid

In order to obtain the high level of γ-aminobutyric acid Moringa oleifera leaves, Use 7% sodium glutamate solution to soak the fresh Moringa oleifera leaves, study effect of different treatment times and three different drying methods( hot air drying, vacuum freeze drying, shadow drying) on the formation of y-aminobutyric acid and quality (total flavonoids, soluble sugar, amino acids, polyphenols, color)of dried Moringa oleifera leaves. The results indicated that shadow-dried Moringa oleifera leaves had the hightest retention of γ-aminobutyric acid, but its browning degree were not preferable, soluble sugar was damaged gravely, and its vulnerable to weather conditions. Vacuum freeze dried Moringa oleifera leaves had the hightest retention of flavonoids, polyphenols and amino acids. The y-aminobutyric acid content of Vacuum freeze dried and hot air dried Moringa oleifera leaves had no much difference. Hot air dried Moringa oleifera leaves browning degree were preferable, it’s had an moderate content of soluble sugar and amino acids, the short drying time is characteristics of this drying method.with the treatment time increased, the content of γ-aminobutyric acid and amino acids content first increased and then decreased. Flavonoids and polyphenols content first decreased and then increased. Soluble sugar content decreased. In summary, after soaking with 7% sodium glutamate solution for 10h, then dried by hot air drying(drying temperature of 60°C), was the most suitable way for industrial production of the high level of γ-aminobutyric acid Moringa oleifera leaves.

Protective effect of a hydrogel containing Achyrocline satureioides extract-loaded nanoemulsion against UV-induced skin damage

Achyrocline satureioides is a medicinal plant widely used in South America that exhibits a well-documented antioxidant activity. Such activity has been related to their main aglycone flavonoids quercetin, luteolin, and 3-O-methylquercetin (3MQ). This study addresses the development of antioxidant hydrogels containing an A. satureioides extract-loaded nanoemulsions aimed at topical application. The systems investigated were A. satureioides extract-loaded nanoemulsions (ASNE) obtained by spontaneous emulsification procedure formulated in semisolid hydrogels composed of Carbopol® Ultrez 20 (HASNE). Hydrogels exhibit a non-Newtonian pseudoplastic behavior. A higher release of 3MQ from ASNE (3.61μg/cm2/h) was observed when compared with HASNE (2.83μg/cm2/h). Different parameters that may have an influence on the retention of flavonoids into the skin were investigated by using a Franz-type diffusion cells. Indeed, the amount of formulation applied on donor compartment was found to play a crucial role. At the optimized conditions, retention of approximately 2μg/cm2 of flavonoids was detected into the skin. A higher retention of 3MQ was detected (approximately 1.0μg/cm2) in comparison with the other flavonoids. Finally, a protection the porcine ear skin by formulations, against oxidative stress generated by UVA/UVB light was demonstrated by means of TBARS, protein carbonylation, and protein thiol content assays. The overall results showed the potential of the formulations developed in this study for the prevention of oxidative stress on the skin.

Retention Study of Flavonoids Under Different Chromatographic Modes.

The goal of this study was to investigate the chromatographic behavior of selected flavonoids from their different subgroups (flavonols, flavanones, flavones and isoflavones) in hydrophilic interaction liquid chromatography (HILIC). Chromatographic measurements were made on two different HILIC columns: cross-linked DIOL (Luna HILIC) and zwitterionic sulfoalkylbetaine (SeQuant ZIC-HILIC). Separation parameters such as the content of acetonitrile and pH of an eluent were studied. On the ZIC column, the retention factors of flavonoids increased with decreasing water content in the mobile phase. The increase in pH of the aqueous component mainly affects the polarity of the analytes. DIOL stationary phase shows more or less apparent dual retention mechanism, HILIC at the acetonitrile (ACN) content ≥75% and reversed phase (RP) with lower content of organic modifier. In the presence of ammonium acetate in the mobile phase, the retention of flavonoids onto the DIOL column increases without change in the selectivity of the separations. The similar effect, but considerably smaller was observed for aglycones on the ZIC column. The retention of studied glycosides (hesperidin, rutin) decreases in the presence of salt in the mobile phase. The significantly higher mass spectrometry sensitivity was observed under HILIC conditions in comparison with the most often used RP LC due to much higher content of ACN in the mobile phase. Finally, under optimal chromatographic conditions, the method was validated and applied for the determination of flavonoids in chamomile (Matricaria chamomilla L.) infusion.