Quercetin Glycosides Research Articles

LC-HRMS for the Identification of Quercetin and Its Derivatives in Spiraea hypericifolia (Rosaceae) and Anatomical Features of Its Leaves.

Spiraea hypericifolia L. is affiliated with the section Chamaedryon Ser. of the genus Spiraea L. (Rosaceae). Similar to many other Spiraea species, S. hypericifolia most often accumulates flavonols among other flavonoids, in particular quercetin and its derivatives. An ethanol-water extract from the aerial part of S. hypericifolia collected in the vicinity of the Ilyichovo settlement (Krasnoyarsk Krai, Russia) was analyzed by liquid chromatography with high-resolution mass spectrometry. Primary and secondary metabolites were found in the extract; structural interpretation consistent with quercetin and its derivatives was proposed for 10 of them. Major compounds were various glycosides of quercetin containing glucose (four compounds), galactose (one compound), xylose (two compounds), arabinose (one compound), or rutinose (one compound) as a carbohydrate residue. Isorhamnetin and 3-O-methylquercetin-3'-O-β-D-glucopyranoside were identified among methyl-containing compounds. The latter compound and reynoutrin, rhamnetin-3-O-β-D-xylopyranosyl-β-D-glucopyranoside, and quercetin-3-O-(6″-O-malonyl)-β-D-glucoside have not been previously found in S. hypericifolia. Data on the presence of quercetin and its derivatives in the extract of S. hypericifolia expand the understanding of the possible practical use of this plant. In addition, the microscopic features of S. hypericifolia leaves were studied. The diagnostic features of the leaf blade necessary for the authentication of raw materials were revealed: straight-walled epidermis cells, stomata located on both sides of the leaf blade (amphistomatic type), two types of trichomes, and wrinkled cuticula with nodi. The main anatomical diagnostic features of the leaves of S. hypericifolia were determined, which makes it possible to assess the authenticity of the raw material.

Endoplasmic reticulum as a target in cardiovascular diseases: Is there a role for flavonoids?

Flavonoids are found in natural health products and plant-based foods. The flavonoid molecules contain a 15-carbon skeleton with the particular structural construction of subclasses. The most flavonoid's critical subclasses with improved health properties are the catechins or flavonols (e.g., epigallocatechin 3-gallate from green tea), the flavones (e.g., apigenin from celery), the flavanones (e.g., naringenin from citrus), the flavanols (e.g., quercetin glycosides from berries, onion, and apples), the isoflavones (e.g., genistein from soya beans) and the anthocyanins (e.g., cyanidin-3-O-glucoside from berries). Scientific data conclusively demonstrates that frequent intake of efficient amounts of dietary flavonoids decreases chronic inflammation and the chance of oxidative stress expressing the pathogenesis of human diseases like cardiovascular diseases (CVDs). The endoplasmic reticulum (ER) is a critical organelle that plays a role in protein folding, post-transcriptional conversion, and transportation, which plays a critical part in maintaining cell homeostasis. Various stimuli can lead to the creation of unfolded or misfolded proteins in the endoplasmic reticulum and then arise in endoplasmic reticulum stress. Constant endoplasmic reticulum stress triggers unfolded protein response (UPR), which ultimately causes apoptosis. Research has shown that endoplasmic reticulum stress plays a critical part in the pathogenesis of several cardiovascular diseases, including diabetic cardiomyopathy, ischemic heart disease, heart failure, aortic aneurysm, and hypertension. Endoplasmic reticulum stress could be one of the crucial points in treating multiple cardiovascular diseases. In this review, we summarized findings on flavonoids' effects on the endoplasmic reticulum and their role in the prevention and treatment of cardiovascular diseases.

GC–MS and LC-MS/MS metabolomics revealed dynamic changes of volatile and non-volatile compounds during withering process of black tea

High-performance liquid chromatography (HPLC), headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC–MS) and ultra-high performance liquid chromatography–Q-Exactive HF-X mass spectrometer (UHPLC–Q-Exactive HF/MS) were carried out to reveal dynamic changes of volatile and non-volatile compounds during the withering process of black tea. A total of 118 volatile organic compounds (VOCs) and 648 metabolites were identified in fresh and withered tea-leaves, respectively. Among them, 47 VOCs (OAV > 1.0) for the aroma formation, and 46 characteristic metabolites (VIP > 1.50, p < 0.01) selected through orthonormal partial least squares-discriminant analysis, indicated the withering contribution during black tea processing. Overall, the withering promoted alcohols, aldehydes, phenols, heterocyclic oxygen, hydrocarbons and halogenated hydrocarbons through relevant hydrolyzation, decomposition, terpene synthesis, and O-methylation. The hydrolyzation, O-methylation, condensation and N-acylation of kaempferol glycosides, quercetin glycosides, ester catechins, and gallic acid generated the accumulation of methoxyl flavonoids and flavonoid glucosides, dihydrokaempferol, syringic acid, theaflavins, and N-acylated amino acids, respectively.

Mechanistic Insights of Rutin against Metabolic Disorders

Rutin, a quercetin glycoside comes under the class flavonol. The aglycone part of rutin is known as quercetin. It is found in numerous fruits and plants, especially apricots, buckwheat, cherries, grapefruit, grapes, oranges, and plums. Rutin shows cardioprotective, neuroprotective, and nephroprotective effects mediated via its antioxidant mechanism. The neuroprotective effect of rutin is utilized in the treatment of Parkinson’s disease. It has been documented in the scientific literature that rutin improves obesity through brown fat activation, modulates DNA damage signaling in cancer cells, reduces inflammation by inhibiting eicosanoid biosynthesis, lipoxygenase, cyclooxygenase, and phospholipase A2 activities, enhances insulin release as well as decreases the expression of resistin along with increases the expression of PPAR γ in diabetic patients, increases total cholesterol, high-density lipoprotein and very low-density lipoprotein levels, whereas low-density lipoprotein level decreases resulting into antilipidemic activity, inhibits diabetic liver injury and diabetic cardiomyopathy. Repurposing of rutin was also done against SARS-CoV-2. Our study aims to survey the most recent progress with emphasis on how rutin adapts intracellular signaling cascades to treat different metabolic disorders. However, the precise cellular and molecular mechanisms of rutin are known and more clinical studies are required to provide a novel therapeutic approach for the treatment of metabolic disorders.

In Vitro and in Silico Insights on the Biological Activities, Phenolic Compounds Composition of Hypericum perforatum L. Hairy Root Cultures

Three Hypericum perforatum hairy root lines (HR B, HR F and HR H) along with non-transformed roots were analyzed for phenolic compounds composition and in vitro enzyme inhibitory properties. In silico molecular modeling was performed to predict the interactions of the most representative phenolic compounds in HR clones with enzymes related to depression, neurodegeneration and diabetes. Chromatographic analyses revealed that HR clones represent an efficient source of quinic acid and hydroxybenzoic acids, epicatechin and procyanidin derivatives, quercetin and kaempferol glycosides, as well numerous xanthones. In vitro antidepressant activity of HR extracts through monoamine oxidase A (MAO-A) inhibition was attributed to the production of oxygenated and prenylated xanthones. The neuroprotective potential of HR extracts was related to the accumulation of quercetin 6-C-glucoside, epicatechin, procyanidins and γ-mangostin isomers as potential inhibitors of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). Vanillic acid and prenylated xanthones in HR clones as promising inhibitors of tyrosinase additionally contributed to the neuroprotective activity. Five preeminent xanthones in HR (γ-mangostin, mangiferin, garcinone C, garcinone E and 1,3,7-trihydroxy-6-metoxy-8-prenyl xanthone) along with the flavonol quercetin 6-C-glucoside effectively inhibited α-amylase and α-glucosidase indicating the antidiabetic properties of HR extracts. Transgenic roots of H. perforatum can be exploited for the preparation of novel phytoproducts with multi-biological activities.

Effect of quercetin glycosides on cognitive functions and cerebral blood flow: a randomized, double-blind, and placebo-controlled study.

This study aimed to examine the effects of quercetin glycoside-containing beverages on cognitive function and cerebral blood flow (CBF) in adult men and women aged between 60 and 75 years. Eighty healthy men and women with no cognitive impairment and aware of ageing-related forgetfulness underwent a placebo-controlled, randomized, double-blind, and parallel-group trial. They regularly consumed 500 mL of beverage containing 110 mg of quercetin glycoside as isoquercitrin for 40 weeks. Cognitive function assessment by Cognitrax was the endpoint of the study. The participants were assessed for CBF, health-related quality of life, as well as physical, biological, and hematological parameters, and lateral index. Cognitrax demonstrated that the reaction time significantly improved in the quercetin glycoside intake group. The CBF measurement suggested that quercetin glycoside intake could likely suppress the decrease in cerebral blood volume, CBF, and cerebral activity owing to stress alleviation and inhibition of the accumulation of amyloid β (Aβ), a waste product in the brain, although there were no significant differences between the groups. Quercetin glycoside intake as a beverage could improve reaction time and may potentially inhibit the decrease in CBF and suppress Aβ accumulation.

Salicylic acid elicitation improves antioxidant activity of spinach leaves by increasing phenolic content and enzyme levels

Elicitation is used in agriculture as a method of crop protection or a means to enhance nutraceutically or pharmaceutically important metabolites with the help of chemical stimuli known as elicitors. In the present experiment elicitor potential of Salicylic acid has been exploited to induce metabolic changes in spinach plant. Salicylic acid of various concentrations (1–0.01 mg/ml) were applied on spinach leaves through foliar spray and observed for biochemical changes. A multifold increase in the amount of total phenolic and total flavonoid as well as enzyme activity of peroxidase, catalase and superoxide dismutase was observed in a dose dependent manner. An increase in the antioxidant activity was observed and was shown to be correlated with the phenolic compounds. Growth parameters measured in the form of total biomass and total chlorophyll were decreased by high concentrations. Metabolite profile of the control and treated leaves was generated through ESI-MS in the positive and negative ion modes. The results showed an increase in the ion intensity peak of phenolic acids, such as gentisic acid, hydroxycinnamic acid, coumaric acid, ferulic acid and caffeic acid as well as major flavonoids of spinach plant, like kaempferol, quercetin, isorhamnetin and patulitin glycosides. Ferulic and caeffic acids were quantified by HPLC and showed an increase in their amount after elicitor treatment.

Does phenotyping of Hypericum secondary metabolism reveal a tolerance to biotic/abiotic stressors?

In this review we summarize the current knowledge about the changes in Hypericum secondary metabolism induced by biotic/abiotic stressors. It is known that the extreme environmental conditions activate signaling pathways leading to triggering of enzymatic and non-enzymatic defense systems, which stimulate production of secondary metabolites with antioxidant and protective effects. Due to several groups of bioactive compounds including naphthodianthrones, acylphloroglucinols, flavonoids, and phenylpropanes, the world-wide Hypericum perforatum represents a high-value medicinal crop of Hypericum genus, which belongs to the most diverse genera within flowering plants. The summary of the up-to-date knowledge reveals a relationship between the level of defense-related phenolic compounds and interspecific differences in the stress tolerance. The chlorogenic acid, and flavonoids, namely the amentoflavone, quercetin or kaempferol glycosides have been reported as the most defense-related metabolites associated with plant tolerance against stressful environment including temperature, light, and drought, in association with the biotic stimuli resulting from plant-microbe interactions. As an example, the species-specific cold-induced phenolics profiles of 10 Hypericum representatives of different provenances cultured in vitro are illustrated in the case-study. Principal component analysis revealed a relationship between the level of defense-related phenolic compounds and interspecific differences in the stress tolerance indicating a link between the provenance of Hypericum species and inherent mechanisms of cold tolerance. The underlying metabolome alterations along with the changes in the activities of ROS-scavenging enzymes, and non-enzymatic physiological markers are discussed. Given these data it can be anticipated that some Hypericum species native to divergent habitats, with interesting high-value secondary metabolite composition and predicted high tolerance to biotic/abiotic stresses would attract the attention as valuable sources of bioactive compounds for many medicinal purposes.

Phytochemical Analysis of &lt;i&gt;Lysimachia vulgaris&lt;/i&gt; L. Aerial Part: Isolation and Structure Elucidation of Secondary Metabolites

Introduction. Natural sources, especially plants, have been used in folk medicine of various countries for many centuries and appears as rich sources of natural compounds. One of the interesting plants for study is the yellow loosestrife (Lysimachia vulgaris L.), the information on the chemical composition of which is scarce.Aim. Carry out a phytochemical research of the L. vulgaris aerial part, by isolation of individual secondary metabolites and elucidation of their structure.Material and methods. Aerial part of L. vulgaris, was collected in the Leningrad region (Vsevolozhsk district, Morozov village, the shore of Lake Ladoga) in July 2021. Fraction analysis was performed through analytical high-performance liquid chromatography (HPLC) using a LC-20 Prominence (Shimadzu corp., Japan) equipped with a SPD-M20A diode-array detector. The isolation of compounds was carried out by open column chromatography using sorbent Dianion HP-20, as well as by preparative HPLC using a Smartline system (Knauer, Germany) equipped with a spectrophotometric detector. The structures of the isolated compounds were established by NMR experiments (Bruker Avance III 400 MHz, Germany).Results and discussion. As a result of L. vulgaris aerial part phytochemical research, the structures of seven individual compounds (1–7) were elucidated. Compounds 1 and 2 are luteolin and quercetin, respectively, while compounds 3–7 are glycosides of quercetin, myricitin and kaempferol, namely myricetin-3-O-β-D-rutinoside (3), myricetin-3-O-β-D-glucopyranoside (4), quercetin-3-O-β-D-rutinoside (rutin) (5), quercetin-3-O-β-D-glucopyranoside (6), kaempferol-3-O-β-D-rutinoside (7).Conclusion. As a result of L. vulgaris aerial part phytochemical research, seven individual compounds were isolated. Compounds 1 and 4 have been found in the aerial part of L. vulgaris for the first time, and all compounds (1–7) have been isolated for the first time from the yellow loosestrife herb.

AKTIVITAS ANTIOKSIDAN DARI EKSTRAK DAUN TELANG (Clitoria ternatea L)

Telang (Clitoria ternatea) has long been used as a traditional medicine for the cure of various diseases. Commonly used parts of Clitoria ternatea are flowers and leaves. The leaves of telang flowers contain flavonoids, flavanol glycosides, kaempferol glycosides, quercetin glycosides and glycoside mirisetin.Telang leaves (Clitoria ternatea L.) contain flavonoid compounds that can act as antioxidants by donating hydrogen so as to stabilize electron deficiency in free radicals. The purpose of this study was to determine the antioxidant activity of telang leaf extract by looking at the IC50 value. Telang leaves were extracted by the maceration method using ethanol solvent.The antioxidant activity test was determined by the DPPH method (1,1-diphenyl-2-picrylhydrazyl) with a vitamin C comparator that has been proven to have a very effective free radical potential. The results showed that the IC50 value of telang leaf extract was 1175 μg / mL, based on this value telang leaf extract is included in the very weak category so that it can be developed as one of the sources antioxidants from natural ingredients.

Comparative metabolite profiling of four polyphenol rich Morus leaves extracts in relation to their antibiofilm activity against Enterococcus faecalis

Enterococci are a common cause of urinary tract infections. The severity of enterococcal infections is associated with their ability to form biofilms. Morus leaves are known as a natural antibacterial, however, their antibiofilm activity against Enterococcus remains unveiled. This study aimed to evaluate the ability of four polyphenol-rich Morus leaves extracts (Morus nigra, M. rubra, M. macroura, and M. alba) to inhibit biofilm formed by enterococcal clinical isolates in relation to their metabolic profiling. Results revealed that 48% of the isolates formed strong biofilm, 28% formed moderate biofilm, 20% formed weak biofilm, and only 4% did not form a biofilm. The strong biofilm-forming isolates were E. faecalis, and hence were chosen for this study. The antibiofilm activity of the four polyphenol-rich Morus leaves extracts revealed that the M. nigra extract exhibited the highest percentage of biofilm inhibition followed by M. rubra then M. macroura and the least inhibition was detected in M. alba, and these results were in accordance with the phenolic and flavonoid contents of each extract. UPLC-ESI-MS/MS identified 61 polyphenolic compounds in the four extracts. Further, multivariate analysis confirmed clear segregation of M. nigra from the other species suggesting disparity in its metabolome, with accumulation of flavonoids, anthocyanidins, phenolic acids and coumarin derivatives. Quercetin and kaempferol glycosides were found to be positively and significantly correlated to the antibiofilm activity. In conclusion, M. nigra ethanolic extracts showed the highest phenolic content and antibiofilm activity and they could be developed as a complementary treatment for the development of antimicrobial agents.

Phenylalanine induces mango fruit resistance against chilling injuries during storage at suboptimal temperature

Cold is the best means of prolonging fruit storage. However, tropical fruit are susceptible to cold storage. The mode of action of mango fruit tolerance to suboptimal cold temperature of 7 or 10 °C after postharvest application of 8 mM phenylalanine was investigated using transcriptomic and metabolomic analyses of mango fruit during suboptimal cold storage. Phenylalanine-treated fruit had less chilling injuries—black spot and pitting electrolyte leakage,—and reduced decay after suboptimal cold storage. Phenylalanine treatment induced genes related to plant–pathogen interactions, plant hormone signal transduction, and the phenylpropanoid pathway, increasing the levels of the flavonoids quercetin and kaempferol glycosides and anthocyanins, and antioxidant content. Reduced oxidation led to lower lipid peroxidation, and a reduction in fatty acid-degradation products, e.g., volatile aldehydes. Treatment with phenylalanine, therefore, enhances chilling tolerance of mango fruit through regulation of metabolic and defense-related pathways, maintaining high levels of flavonoids, and antioxidants enzyme activity, and reducing H2O2 content, lipid peroxidation, and volatile aldehydes.

Total phenolics, quercetin glycosides and antioxidant activity in organic and conventional orchards in three apple cultivars during fruit growth

Aim of study: To evaluate whether organic and conventional management practices, cultivar and fruit growth stage affect total phenolic content, antioxidant activity and quercetin glycosides in apples of three cultivars. Area of study: The trials were conducted in commercial orchards located in Chimbarongo, O’Higgins Region, Chile. Material and methods: Two types of orchard management (organic and conventional) were studied in three apple cultivars: Gala 'Brookfield', Granny Smith and Fuji 'Raku Raku'. Total phenolic content, antioxidant activity and quercetin glycosides were evaluated according to management practices, fruit growth stage, cultivar, fruit weight and skin surface. Data were analyzed statistically using a truncated multiple regression model. Main results: No differences were found between organic and conventional management regarding polyphenol concentration and antioxidant activity, except for specific quercetin glycosides. However, significant differences were observed between cultivars in both variables, as well as in fruit development throughout the season, which showed a significant dilution of polyphenols and antioxidant activity as the fruit grew. Research highlights: Cultivar and fruit growth stage were decisive in total phenolic content, glycosidic quercetins and apples antioxidant activity. Conventional and organic management practices were significant for quercetin glycoside concentration, which is the main polyphenol in apples.

Accurate varietal classification and quantification of key quality compounds of grape extracts using the absorbance-transmittance fluorescence excitation emission matrix (A-TEEM) method and machine learning

Rapid and accurate quantification of grape berry phenolics, anthocyanins and tannins and identification of grape varieties are both important for effective quality control of harvesting and initial processing for winemaking. Current reference technologies, including High-Performance Liquid Chromatography (HPLC), can be rate-limiting and too complex and expensive for effective field operations. In this paper, we analyse robotically prepared grape extracts from several key varieties (n = Calibration/n = Prediction samples), including Cabernet-Sauvignon (64/10), Grenache (16/4), Malbec (14/4), Merlot (56/10), Petite Sirah (52/10), Pinot noir (54/8), Syrah (20/2), Teroldego (14/2) and Zinfandel (62/12). Key phenolic and anthocyanin parameters measured by HPLC included Catechin, Epicatechin, Quercetin Glycosides, Malvidin 3-glucoside, Total Anthocyanins and Polymeric Tannins. Split samples diluted 50-fold in 50 % EtOH pH 2 were analysed in parallel using the A-TEEM method following Multi-block Data Fusion of the absorbance and unfolded EEM data. A-TEEM chemical data were calibrated (n = 390) using Extreme Gradient Boosting (XGB) Regression and evaluated based on the Root Mean Square Error of the Prediction (RMSEP), the Relative Error of Prediction (REP) and Coefficient of Variation (R2P) of the Prediction data (n = 62). The regression results yielded an average Relative Error of Prediction (REP) of 5.89 ± 2.47 % and an R2P of 0.941 ± 0.025. While we consider the REP values to be in the acceptable range at significantly &lt; 10 %, we acknowledge that both the grape extraction method repeatability and HPLC reference method sample repeatability (5-8 % RSD) likely constituted the major sources of variation compared to the A-TEEM instrumental sample repeatability (&lt; 2 % RSD). The varietal classification was analysed using Agglomerative Hierarchical Cluster Analysis (HCA) and XGB discrimination analysis of the multi-block data. The classification results yielded 100 % True Positive and True Negative responses for the Calibration and Prediction Data for all tested varieties. We conclude that the A-TEEM method requires a minimum of sample preparation and rapid acquisition times (&lt; 1 min) and can serve as an accurate secondary method for both grape varietal identification and phenolic quantification. Importantly, the software application of the regression and classification models can be effectively automated for operators.

New 8-prenylated quercetin glycosides from the flowers of Epimedium acuminatum and their testosterone production-promoting activities.

Phytochemical investigation was carried out for the flowers of Epimedium acuminatum Franchet. by first conducting LC-MS analysis, leading to the identification of 32 compounds. Furthermore, guided by LC-MS profiling, three new 8-prenylated quercetin glycosides (3′-hydroxylikarisoside C, 3′-hydroxylepimedoside E, 3′-hydroxyldiphylloside B), one new anthocyanin (delphinidin-3-O-p-coumaroyl-sophoroside) and six known compounds were isolated from the flowers of E. acuminatum for the first time, and their structures were characterized based on spectroscopic methods including 1D and 2D NMR, and HRESIMS. Combining our discoveries and literature survey, a revised classification of Epimedium flavonols was proposed as Type A (8-prenylated kaempferol based), which was further subdivided into subtype icaritin and subtype demethylicaritin, and Type B (8-prenylated quercetin based), which was further subdivided into subtype 3′-hydroxylicaritin and subtype 3′-hydroxyldemethylicaritin. The structure-activity relationship (SAR) study was carried out by comparing testosterone production-promoting activities of all the new compounds along with nine related Epimedium flavonols, revealing that the new 8-prenylated quercetin glycosides (subtype 3′-hydroxyldemethylicaritin in Type B) exhibited lower testosterone production-promoting activities in rat primary Leydig cells than Epimedium flavonols of subtype demethylicaritin in Type A, but possessed higher activities than the Epimedium flavonols of subtype icaritin in Type A. These results suggested that either methylation at C-4′ position or hydroxylation at C-3′ position of ring B could significantly reduce the testosterone production-promoting activities of Epimedium flavonols.

The microbiota catabolites of quercetin glycosides concertedly enhance the resistance against acetaldehyde-induced oxidative stress

3,4-Dihydroxyphenylacetic acid (DOPAC) and 3-hydroxyphenylacetic acid (OPAC) are the predominant catabolites of quercetin glycosides, such as quercetin 4′-O-β-glucoside from the onion, produced by intestinal microbiota. Although each catabolite has been reported to protect the cells from acetaldehyde-induced cytotoxicity, the effect of their combination remains to be clarified. The purpose of this study was to determine whether the combination of DOPAC and OPAC enhances the resistance against the acetaldehyde-induced oxidative stress in the cultured hepatocytes. The pretreatment of the combination of DOPAC (5 μM) and OPAC (5 μM) showed significant protection against the acetaldehyde- and hydrogen peroxide-induced cytotoxicity, even though each compound at the same concentration did not. This combination also significantly inhibited the intracellular dichlorofluorescin diacetate-detectable reactive oxygen species (ROS) level, whereas the solo treatment did slightly, suggesting that reducing mechanisms of ROS or compounds that enhance ROS production are involved in the cytoprotective effect. The combinatory treatment significantly enhanced the gene expression of not only the aldehyde dehydrogenases (ALDHs), but also glutamate-cysteine ligase, catalytic subunit, the first rate-limiting enzyme of glutathione (GSH) synthesis. Accordingly, both the intracellular GSH level and the total ALDH activity were enhanced by DOPAC plus OPAC. Involvement of GSH in the cytoprotection as well as ALDH up-regulation by the combination was confirmed by the experiments using a GSH biosynthesis inhibitor, buthionine sulfoximine. Taken together, the present results suggested that the quercetin microbiota catabolites concertedly protect the cells from acetaldehyde through a pre-enhanced resistance against oxidative stress by the GSH-dependent up-regulation of ALDHs.

Different Effects of Quercetin Glycosides and Quercetin on Kidney Mitochondrial Function-Uncoupling, Cytochrome C Reducing and Antioxidant Activity.

Flavonols are found in plants as aglycones and as glycosides. Antioxidant activity of flavonols may occur via several mechanisms within the cell, and mitochondria as a target may play an important role. There is a lack of information about the influence of the sugar moiety on biological activity of flavonoid glycosides. The aims of study were to investigate the effects of quercetin and its glycosides on mitochondrial respiration rates at various metabolic states, and to evaluate their antioxidant potential using chemical and biological approaches. Mitochondrial function was measured using an oxygraphic method, cytochrome c reduction spectrophotometrically, H2O2 generation in mitochondria fluorimetrically, and antioxidant activity of flavonoids using an HPLC-post column system. Our data revealed that quercetin and its glycosides isoquercitrin, rutin, and hyperoside uncouple kidney mitochondrial respiration (increasing the State 2 respiration rate) and significantly reduce cytochrome c. Moreover, quercetin, and its glycosides decrease the production of mitochondrial H2O2 and possess radical scavenging and ferric reducing capacities. The highest activity was characteristic for quercetin, showing that the sugar moiety significantly diminishes its activity. In conclusion, our results show the efficient radical scavenging, ferric and cytochrome c reducing capacities, and uncoupling properties of quercetin and its glycosides, as well as the importance of the sugar residue and its structure in the regulation of kidney mitochondrial function.

Flavonoid glycosides from Hylotelephium sieboldii var. sieboldii and var. ettyuense endemic to Japan

Twenty-one flavonoids were isolated from the leaves and stems of Hylotelephium sieboldii var. sieboldii and var. ettyuense (Crassulaceae) endemic to Japan. They were characterized as kaempferol and quercetin glycosides such as 3-O-sophorosides, 3-O-neohesperidosides, 3,7-di-O-rhamnosides, 3-O-neohesperidoside-7-O-rhamnosides, 3-O-glucoside-7-O-rhamnosides, 3-O-sophoroside-7-O-rhamnosides, 3-O-glucosides and 3-O-rhamnosides by UV, LC-MS, acid hydrolysis, and NMR and/or HPLC comparisons with authentic samples. Flavonoids of H. sieboldii var. sieboldii are 3,7-O-glycosides of kaempferol and quercetin. On the other hand, those of H. sieboldii var. ettyuense were flavonol 3-O-diglycosides, together with a few 3,7-O-glyosides. Flavonol 3-O-monoglycosides were found in both varieties. Flavonoids were reported from Hylotelephium sieboldii in this survey for the first time.

Enzyme inhibitory activity of Dioscorea nipponica Makito hydroethanolic extracts of leaves and tubers in relation to their major secondary metabolites

Different anatomical parts of Dioscorea nipponica Makito have been used in foods and folk medicines for their nutritional and pharmacological properties; however, the scientific data on enzyme inhibitory activities and phytochemicals in plant extracts remain rather scarce. Such information is important for expanding possible uses of plant origin preparations in nutrition. This study, using commonly applied assays, evaluated inhibitory activity of 70% ethanol extract of D. nipponica leaves and tubers against such physiologically important enzymes as α-amylase, α-glucosidase, acethylcholinesterase, and angiotensin-converting enzyme (ACE). Inhibition of α-glucosidase and acethylcholinesterase required lower leaf extract concentrations as compared with other two enzymes. The IC50 values of α-glucosidase and α-amylase inhibition were 66.08 and 438 μg/mL, respectively, while the inhibition of ACE at 250–1250 μg/mL was from 28.02 ± 1.17% to 77.13 ± 0.78%. The mode of inhibition of α-glucosidase and acethylcholinesterase was evaluated by the kinetic studies. Leaf and tuber extracts displayed a mixed-type non-competitive mode of α-glucosidase inhibition. Phytochemical composition of extracts was determined by UPLC-QTOF/MS and HPLC-UV methods. Leaf extract was remarkably stronger enzyme inhibitor than tuber extract and it may be explained by the differences in the secondary metabolite composition. Quinic, chlorogenic acids and quercetin glycosides, which are well-known enzyme inhibitors, were the main phytochemicals in the leaf extract, while steroidal glycosides, peptides and oligomeric sugars were the major constituents in the tuber extract. It is expected that new knowledge on D. nipponica will serve for its valorisation in developing new health beneficial ingredients for functional foods and nutraceuticals.

Discovery of possible hepatoprotective components from lychee pulp phenolic extract by online knockout methods

Lychee pulp phenolic extract (LPPE) possessed protective effects against nonalcoholic fatty liver disease (NAFLD), while the specific components concerned were unclear. In this study, twelve major components in LPPE were identified by LC-MS and prepared by on line knockout methods. Two antioxidant methods companied with hepatocyte steatosis assay were used to evaluate the contribution of twelve components to the hepatoprotective effects of LPPE. The identified components include four procyanidins and eight flavonoids, they all play active roles in the oxygen radical absorbance capacity of LPPE, while only B-type procyanidin trimer and quercetin 3-O-rutinoside-7-O-rhamnoside exert positive effects on cellular antioxidant activity of LPPE. Six components including procyanidin B2, epicatechin, two quercetin glycosides, and two procyanidin trimers are considered as contributors to lipid accumulation inhibitory effects of LPPE with B-type procyanidin trimer being identified as the main contributor. All the twelve components were recognized as hepatoprotective components against NAFLD in LPPE.