Determination of quercetins in onion (Allium cepa) using infrared spectroscopy

Quality analysis and geographical origin identification of Rosa roxburghii Tratt from three regions based on Fourier transform infrared spectroscopy

The study aimed to provide new information of Rosa roxburghii Tratt (RRT) for the production of functional foods and distinguish the geographical origins of RRT. The nutritional components of RRT from three regions in China, such as vitamin C, polysaccharides, total flavonoids, and total phenolics, and their antioxidant activities were analyzed by one-way ANOVA. The results of Fourier transform infrared spectroscopy (FT-IR) combined with principal component analysis (PCA), stepwise linear discriminant analysis (SLDA), k-nearest neighbor (k-NN), and support vector machine (SVM) were used to establish discriminant models to identify the geographical origin of RRT. The results of one-way ANOVA showed that the contents of some nutrients and antioxidant activity were significantly different among RRT from different regions and their FT-IR spectra also showed significant differences. The characteristic fingerprint bands of FT-IR (1679-1618 cm^-1and 1520-900 cm^-1) closely related to the geographical origins of RRT were screened out. Based on SLDA, a discriminant model was established to realize the classification and identification of RRT from different regions and the correct discrimination rate of the testing sample set obtained with the established model reached 100 %. Geographical factors caused the obvious differences in nutritional components and antioxidant activity in RRT. The characteristic fingerprint bands of RRT obtained with FT-IR could be used to identify the geographical origins of RRT more quickly and accurately.

Effects of supplemental dried wild leek (Allium scorodoprasum L. subsp. rotundum) leaves on laying performance, egg quality characteristics, and oxidative stability in laying hens

This study aimed to examine the effect of dietary supplementation of dried wild leek (Allium scorodoprasum L. subsp. rotundum) leaves on laying performance, egg traits, antioxidant status, and oxidative stability in laying hens. For this purpose, a total of 96 Lohmann White laying hens aged 22 weeks allocated into four treatment groups each containing 24 hens. Hens were fed a diet supplemented with 0 (control), 1 (WL1), 2 (WL2), and 3 (WL3) g/kg dried wild leek (DWL) leaves. During the 10-week trial, egg weight was increased and feed efficiency was improved with 2 and 3 g/kg DWL leaves. No significant differences were observed among groups for egg production, feed intake, internal and external egg quality characteristics, and egg yolk cholesterol concentration. Levels of malondialdehyde and total antioxidant-oxidant status of egg yolk were not affected from DWL supplementation. However, 2,2-diphenyl-1-picrylhydrazyl radical scavenging activity was increased and oxidative stress index was decreased in egg yolk. Superoxide dismutase enzyme activity was increased in the group of WL3, and total antioxidant status levels were increased in the groups of WL2 and WL3 in serum. DWL supplementation reduced serum cholesterol concentration significantly. No marked changes were observed in other blood parameters. In conclusion, DWL is considered to be high antioxidant supplement due to having high antioxidant capacity and important bioactive compounds. Dietary supplementation of DWL leaves at 3 g/kg could be a viable and beneficial feed additive to improve egg weight and feed efficiency, increase DPPH radical scavenging activity in egg yolk and antioxidant status of hen. Therefore, the usage of DWL leaves in the laying hen diets will be beneficial for egg producers and poultry nutritionists to produce functional eggs having low cholesterol and high antioxidants.

Three Glycosyltransferase Mutants in a One-Pot Multi-enzyme System with Enhanced Efficiency for Biosynthesis of Quercetin-3,4'-O-diglucoside

Quercetin-3,4'-O-diglucoside (Q3,4'G), among the major dietary flavonoids, is superior to quercetin aglycone or quercetin monoglucoside in solubility. However, its low content in nature makes it hard to be prepared in large quantities by traditional extraction methods. In the present study, the F378S mutant of UGT78D2 (78D2_F378S) derived from Arabidopsis thaliana with improved regioselectivity and the V371A mutant of UGT73G1 (73G1_V371A) derived from Allium cepa were adopted to realize a two-step continuous glycosylation of quercetin to produce Q3,4'G. The mutation S31D was introduced to the sucrose synthase from Micractinium conductrix with enhanced activity, which was responsible for regenerating UDP-glucose by coupling with 78D2_F378S and 73G1_V371A. Using the aforementioned enzymes, prepared from the three-enzyme co-expression strain, 4.4 ± 0.03 g/L (7.0 ± 0.05 mM, yield 21.2%) Q3,4'G was produced from 10 g/L quercetin after reaction for 24 h at 45 °C.

Insights into the remarkable attenuation of hen egg white lysozyme amyloid fibril formation mediated by biogenic gold nanoparticles stabilized by quercetin-functionalized tara gum

Aberrant protein misfolding and/or aggregation and fibrillation has been linked to the pathogenesis of several debilitating chronic diseases including Alzheimer's and Parkinson's disease. Inhibiting protein amyloidogenesis has been proposed as a viable strategy to prevent or ameliorate associated disorders. Herein, we investigated the anti-amyloidogenic properties of biogenic gold nanoparticles (QTG-GNP) prepared via a simple green chemistry route and stabilized by quercetin-functionalized tara gum (QTG). The synthesized QTG-GNP was extensively characterized for its physicochemical attributes via UV-visible spectroscopy, TEM, FESEM, EDX, DLS/Zeta potential, FTIR, RAMAN, XRD, XPS, and TGA analyses, as well as for its biological properties. The results revealed that small-sized (5.01 ± 1.17 nm), well-dispersed, highly stable and round-shaped biogenic gold nanoparticles were successfully synthesized at room temperature with QTG as the sole reductant /stabilizer. Importantly, QTG-GNP demonstrated potent anti-aggregation and fibrillation inhibitory effects against amyloidogenic hen egg white lysozyme (HEWL). Also, QTG-GNP was able to dissociate pre-formed HEWL amyloid fibrils. Furthermore, the constructed nanoparticles exhibited potent anti-radical activities against DPPH and ABTS⁺ and were cytocompatible with mouse L929 fibroblast cells. On the basis of these findings, it was established that QTG-GNP holds strong prospects for further development as an agent for countering protein aggregation and associated disease conditions.

Effects of Allium cepa and Its Constituents on Respiratory and Allergic Disorders: A Comprehensive Review of Experimental and Clinical Evidence

The health benefits of Allium cepa (A. cepa) have been proclaimed for centuries. Various pharmacological and therapeutic effects on respiratory, allergic, and immunologic disorders are shown by A. cepa and its constituents. Flavonoids such as quercetin and kaempferol, alk(en)yl cysteine sulfoxides including S-methyl cysteine sulfoxide and S-propyl cysteine sulfoxide, cycloalliin, thiosulfinates, and sulfides are the main compounds of the plant. A. cepa displays broad-spectrum pharmacological activities including antioxidant, anti-inflammatory, antihypertensive, and antidiabetic effects. Our objective in this review is to present the effects of A. cepa and its constituents on respiratory, allergic, and immunologic disorders. Different online databases were searched to find articles related to the effect of A. cepa extracts and its constituents on respiratory, allergic, and immunologic disorders until the end of December 2020 using keywords such as onion, A. cepa, constituents of A. cepa, therapeutic effects and pharmacological effects, and respiratory, allergic, and immunologic disorders. Extracts and constituents of A. cepa showed tracheal smooth muscle relaxant effects, indicating possible bronchodilator activities or relieving effects on obstructive respiratory diseases. In experimental animal models of different respiratory diseases, the preventive effect of various extracts and constituents of A. cepa was induced by their antioxidant, immunomodulatory, and anti-inflammatory effects. The preventive effects of the plant and its components on lung disorders induced by exposure to noxious agents as well as lung cancer, lung infection, and allergic and immunologic disorders were also indicated in the experimental and clinical studies. Therefore, this review may be considered a scientific basis for development of therapies using this plant, to improve respiratory, allergic, and immunologic disorders.

The effect of Allium cepa extract on the chitosan/PLGA scaffolds bioactivity

Allium cepa extracts (AC) allow the fabrication of a biomaterial that, together with chitosan and PLGA, could be osteoconductive and promote a better and faster regeneration of bone tissue, with biocompatibility and biomineralization properties. In this work, scaffolds were developed by the thermally induced phase separation (TIPS) technique. An in vitro bioactivity analysis was performed using simulated body fluid (SBF). Scanning electron microscopy (SEM), energy dispersion spectroscopy, and infrared spectroscopy were used for the scaffolds characterization. The results showed a structure with a pore size distribution between 50 and 100 μm, which allowed the uniform formation of biological apatite crystals on the surface of the scaffolds. The chitosan/policaprolactone/Allium cepa scaffold (ChPAC) showed the most promising results with a ratio of P/Ca between 1.6 and 1.7, a value very close to that of hydroxyapatite.

Subcritical Water Extraction of Phenolic Compounds from Onion Skin Wastes (Allium cepa cv. Horcal): Effect of Temperature and Solvent Properties

The valorization of onion skin wastes (OSW) through the extraction, identification, and quantification of phenolic compounds was studied in this work, using subcritical water in a semicontinuous extractor (2.5 mL/min; 105-180 °C; 5 MPa). The extraction of flavonoids resulted to be fast (<30 min) and temperature sensitive (maximum at 145 °C; total flavonoids, 27.4 ± 0.9 mg/g dry OSW (DOSW)). The experimental results were fitted to the Weibull model. The influence of the solvent properties on the flavonoids quantification was found to be critical. A precipitate was formed once the extracts cooled down. If removed, a significant fraction of the high temperature extracted flavonoids (as much as 71%, at 180 °C) was lost. Such a condition affected especially those compounds that show extremely low solubility in water at room temperature, whereas quercetin glycosylated derivatives were less affected by the polarity change of the medium induced by the temperature change. It was demonstrated that it is necessary to re-dissolve the subcritical water extracts by the addition of ethanol, which led to a medium with a polarity equivalent to that obtained with water at high temperature. At 145 °C, quercetin (15.4 ± 0.4 mg/g DOSW) and quercetin-4'-glucoside (8.4 ± 0.1 mg/g DOSW) accounted for the 90% of the total flavonoids identified. By recovering high added value bioactive compounds from OSW the principles of circular economy were fulfilled, providing a new use for this agricultural waste.

Modulation of Chronic Inflammation by Quercetin: The Beneficial Effects on Obesity

Obesity has become a major risk factor for the development of chronic diseases such as insulin resistance, type 2 diabetes mellitus, and cardiovascular disease. Moreover, obesity induces chronic inflammation in adipose tissue, liver, skeletal muscle, and the vascular system. Quercetin is the major representative of the flavonoid subclass of flavonols, which is ubiquitously contained within natural plants such as green tea, and vegetables, including onions and apples. Researchers have focused greater attention to the beneficial physiological roles of quercetin, which has anti-oxidative, anti-inflammatory, and anti-fibrotic effects on insulin resistance and atherosclerosis in obesity-related diseases. Also, the anti-inflammatory effects of quercetin on intestinal microbiota have been demonstrated in obesity. In addition, there is increasing evidence that quercetin is associated with epigenetic activities in cancer, and in maternal undernutrition during gestation and lactation. In this review, we focus on the chemical properties of quercetin, its dietary sources in obesity, and its anti-inflammatory effects on insulin resistance, atherosclerosis, intestinal microbiota, and maternal under-nutrition with epigenetic activity.

Dietary Quercetin and Kaempferol: Bioavailability and Potential Cardiovascular-Related Bioactivity in Humans

Fruit and vegetable intake has been associated with a reduced risk of cardiovascular disease. Quercetin and kaempferol are among the most ubiquitous polyphenols in fruit and vegetables. Most of the quercetin and kaempferol in plants is attached to sugar moieties rather than in the free form. The types and attachments of sugars impact bioavailability, and thus bioactivity. This article aims to review the current literature on the bioavailability of quercetin and kaempferol from food sources and evaluate the potential cardiovascular effects in humans. Foods with the highest concentrations of quercetin and kaempferol in plants are not necessarily the most bioavailable sources. Glucoside conjugates which are found in onions appear to have the highest bioavailability in humans. The absorbed quercetin and kaempferol are rapidly metabolized in the liver and circulate as methyl, glucuronide, and sulfate metabolites. These metabolites can be measured in the blood and urine to assess bioactivity in human trials. The optimal effective dose of quercetin reported to have beneficial effect of lowering blood pressure and inflammation is 500 mg of the aglycone form. Few clinical studies have examined the potential cardiovascular effects of high intakes of quercetin- and kaempferol-rich plants. However, it is possible that a lower dosage from plant sources could be effective due to of its higher bioavailability compared to the aglycone form. Studies are needed to evaluate the potential cardiovascular benefits of plants rich in quercetin and kaempferol glycoside conjugates.

Characterization and Quantification of Major Flavonol Glycosides in Ramps (Allium tricoccum)

The ramp (Allium tricoccum) is a traditional plant in the eastern Appalachian Mountains. Ramps have been used in traditional medicine for their health-promoting roles in lowering blood pressure and cholesterol. Information on the chemical composition of the potentially bioactive components in ramps is limited. Therefore, the aim of this work was to characterize and quantify major flavonols in ramps. Flavonoids were extracted in 50% methanol and 3% acetic acid. Characterization was conducted using UHPLC-PDA-MS and MS/MS, and quantification was performed using UHPLC-PDA detection. The major flavonol glycosides were kaempferol sophoroside glucuronide, quercetin sophoroside glucuronide, kaempferol rutinoside glucuronide, quercetin hexoside glucuronide, quercetin sophoroside, and kaempferol sophoroside. All conjugates were detected in leaves. Quercetin and kaempferol sophoroside glucuronide conjugates were detected in the stem, but no flavonol glycosides were detected in the bulb. The total amounts of the identified quercetin and kaempferol conjugates in whole ramps were 0.5972 ± 0.235 and 0.3792 ± 0.130 mg/g dry weight, respectively. Flavonol conjugates were concentrated in the leaves. To our knowledge, this work is the first to identify and quantify the major flavonol glycosides in ramps. Our findings suggest that specifically the leaves may harbor the potentially bioactive flavonols components of the plant.

A neutral Cu-based MOF for effective quercetin extraction and conversion from natural onion juice

A new neutral metal–organic framework can efficiently extract natural product quercetin (QT) from fresh QT-rich onion juice and rapidly convert it into Cu–QT with a relatively high conversion rate.

New robust sensitive fluorescence spectroscopy coupled with PLSR for estimation of quercetin in Ziziphus mucronata and Ziziphus sativa

Flavonoids are natural antioxidants derived from plants and commonly found in a variety of foods to sequester free radicals. Quercetin, belonging to flavonol subclass of flavonoids, has received considerable attention because of its wide uses as a nutritional supplement as well as a phytochemical remedy for a number of diseases. In the current study, quantification of quercetin was carried out in two medicinally important flavonoid rich plant Ziziphus mucronata and Ziziphus sativa. Emission spectroscopy was utilized as a new method coupled with Partial Least Squares Regression (PLSR) and the cross validation was done by UV-Visible spectroscopy. The results indicated the higher quercetin content in Z. mucronata (1.50±0.034%) than Z. sativa (1.21±0.052%), and were further verified through Folin-Ciocalteu Colorimetric method (Z. mucronata; 1.41±0.26% and Z. sativa; 1.13±0.136%). In this study the sensitivity was explained in term of slope i.e. Slope=0.9973.

Effect of quercetin glucosides from Allium extracts on HepG2, PC-3 and HT-29 cancer cell lines

The present study investigated the effects of quercetin glucosides, which were isolated from the Chinese onion (Allium chinense), garlic (Allium sativum), onion (Allium cepa L.) and the Welsh onion (Allium fistulosum L.) in HepG2, HT-29 and PC-3 cancer cell lines. Quercetin-3,4'-di-O-glucoside (3,4'-Qdg) and quercetin-4'-O-glucoside (4'-Qmg) comprise ~98% of the flavonoids in the methanol extract of onion. A small amount of 3,4'-Qdg is present in the Welsh onion and Chinese onion, whereas 4'-Qmg is also present in the Welsh onion. In HepG2 cells, 4'-Qmg was demonstrated to exhibit more significant growth inhibition compared with 3,4'-Qdg and quercetin 3-β-D-glucoside, but exhibited less inhibitory effects in PC-3 and HT-29 cells. These results suggest the anti-proliferative potential of 4'-Qmg in various cancer cell lines and the health benefits of the genus Allium. The findings indicate the potential of 4'-Qmg as an anticancer agent for further development.

FT-IR-based method for rutin, quercetin and quercitrin quantification in different buckwheat (Fagopyrum) species

The present study explores an alternative method for antioxidants determination in buckwheat (Fagopyrum) samples. Buckwheat contains different amounts of the antioxidants rutin, quercetin and quercitrin in different plant parts. Buckwheat seeds are most commonly used as food; however, preparations from the herb can also be used as a rich source of rutin. Infrared spectroscopy was used for individual and sum quantification of rutin, quercetin and quercitrin in whole and ground flowers and leaves of seven different buckwheat species. Correlation coefficients R of calibration and independent validation set for rutin, quercetin and quercitrin were 1.00 and 0.98, 0.94 and 0.99, 0.99 and 0.95, respectively. Some of the developed models had accuracy comparable to the reference HPLC method. Additionally many different parameters that give an important insight into the FTIR technique are discussed (different plant parts, whole and ground untreated samples, 3 different resolutions, 7 spectra pre-treatments, using individual or averaged spectra, reducing spectral data input, considering additional non-spectral data). The implemented technique used no sample preparation, is non-destructive and uses very little amounts of sample. Result show that infrared spectroscopy can be a fast and environmentally friendly alternative technique for routine analysis of main flavonoids in aerial parts of buckwheat.

Onion derived carbon nanodots for live cell imaging and accelerated skin wound healing

Nitrogen, sulfur, and phosphorous co-doped water-soluble carbon nanodots are synthesized from culinary waste onion peel powder (OPP) by a short microwave treatment. Onion Derived Carbon Nano Dots (OCND) that comprised hydrophilic group-decorated amorphous nano-dots exhibited bright, stable fluorescence at an excitation of 450 nm and emission wavelength at 520 nm along with a free radical scavenging property. The OCND exhibited excellent stability at different pH and UV exposure. Although extracted polyphenols degraded in the extract, interestingly it was shown to be cytocompatible and blood compatible as observed during cytotoxicity, fluorescence imaging of the cell and a hemolysis study. The present work not only focuses on the synthesis of OCND from the OPP extract but also provides an interesting fact that, even after the degradation of polyphenols in the extract, they are non-toxic to human cells (HFF & MG63) and RBCs. Moreover, OCND had no adverse effect on the migration rate of Human Foreskin-derived Fibroblasts (HFFs) as observed from a scratch assay. In addition to accelerating the migration rate of fibroblasts, the OCND altered intra- and extracellular reactive oxygen species (ROS) by enhancing the antioxidant mechanism of a fibroblast under oxidative stress. Further, OCND was observed to accelerate wound healing in a full thickness (FT) wound in a rat model for topical application, which can be attributed to its radical scavenging potential. In summary, this study leads to a new type of OCND synthesis route, which is inherently co-doped with phosphorous, sulfur and nitrogen and holds a great promise for a myriad of biological applications, including bio-imaging, free radical scavenging and wound healing.

Application of Attenuated Total Reflectance-Fourier Transformed Infrared (ATR-FTIR) Spectroscopy To Determine the Chlorogenic Acid Isomer Profile and Antioxidant Capacity of Coffee Beans

The chlorogenic acid isomer profile and antioxidant activity of both green and roasted coffee beans are reported herein using ATR-FTIR spectroscopy combined with chemometric analyses. High-performance liquid chromatography (HPLC) quantified different chlorogenic acid isomer contents for reference, whereas ORAC, ABTS, and DPPH were used to determine the antioxidant activity of the same coffee bean extracts. FTIR spectral data and reference data of 42 coffee bean samples were processed to build optimized PLSR models, and 18 samples were used for external validation of constructed PLSR models. In total, six PLSR models were constructed for six chlorogenic acid isomers to predict content, with three PLSR models constructed to forecast the free radical scavenging activities, obtained using different chemical assays. In conclusion, FTIR spectroscopy, coupled with PLSR, serves as a reliable, nondestructive, and rapid analytical method to quantify chlorogenic acids and to assess different free radical-scavenging capacities in coffee beans.

Production of organic acids by probiotic lactobacilli can be used to reduce pathogen load in poultry

Probiotic Lactobacillus can be used to reduce the colonization of pathogenic bacteria in food animals, and therefore reduce the risk of foodborne illness to consumers. As a model system, we examined the mechanism of protection conferred by Lactobacillus species to inhibit C. jejuni growth in vitro and reduce colonization in broiler chickens. Possible mechanisms for the reduction of pathogens by lactobacilli include: 1) stimulation of adaptive immunity; 2) alteration of the cecal microbiome; and, 3) production of inhibitory metabolites, such as organic acids. The Lactobacillus species produced lactic acid at concentrations sufficient to kill C. jejuni in vitro. We determined that lactic acid produced by Lactobacillus disrupted the membrane of C. jejuni, as judged by biophotonics. The spectral features obtained using Fourier-transform infrared (FT-IR) and Raman spectroscopy techniques were used to accurately predict bacterial viability and differentiate C. jejuni samples according to lactic acid treatment. FT-IR spectral features of C. jejuni and Lactobacillus grown in co-culture revealed that the metabolism was dominated by Lactobacillus prior to the killing of C. jejuni. Based on our results, the development of future competitive exclusion strategies should include the evaluation of organic acid production.

Evolution of phenolic compounds from color and flavor problems to health benefits

Early studies focused on the negative effects on color and flavor of foods, followed by exploration of the antioxidant properties and the associated health benefits. The growing body of evidence suggests that plant-based polyphenols may help prevent or delay the onset of a multiplicity of diseases. Newer work suggests that a variety of polyphenols can alter the expression of genes in the inflammatory pathway. Data also show that the absorption of the polyphenols is very limited. Insulin resistance and endothelial and mitochondrial dysfunction are hallmarks of the metabolic syndrome and aging and occur at the early stages of the disease. There is limited clinical evidence that certain polyphenolic metabolites by virtue of their anti-inflammatory activities can improve insulin sensitivity and endothelial and mitochondrial function, suggesting that polyphenols are good for disease prevention. The goal of this review is to summarize the evolution and emphasize the potential benefits of polyphenols.

Multielement fingerprinting as a tool in origin authentication of PGI food products: Tropea red onion

Tropea red onion ( Allium cepa L. var. Tropea) is among the most highly appreciated Italian products. It is cultivated in specific areas of Calabria and, due to its characteristics, was recently awarded with the protected geographical indications (PGI) certification from the European Union. A reliable classification of onion samples in groups corresponding to "Tropea" and "non-Tropea" categories is now available to the producers. This important goal has been achieved through the evaluation of three supervised chemometric approaches. Onion samples with PGI brand (120) and onion samples not cultivated following the production regulations (80) were digested by a closed-vessel microwave oven system. ICP-MS equipped with a dynamic reaction cell was used to determine the concentrations of 25 elements (Al, Ba, Ca, Cd, Ce, Cr, Dy, Eu, Fe, Ga, Gd, Ho, La, Mg, Mn, Na, Nd, Ni, Pr, Rb, Sm, Sr, Tl, Y, and Zn). The multielement fingerprint was processed using linear discriminant analysis (LDA) (standard and stepwise), soft independent modeling of class analogy (SIMCA), and back-propagation artificial neural network (BP-ANN). The cross-validation procedure has shown good results in terms of the prediction ability for all of the chemometric models: standard LDA, 94.0%; stepwise LDA, 94.5%; SIMCA, 95.5%; and BP-ANN, 91.5%.