Content Of Flavonol Glycosides Research Articles

Assesment of quality of Ginkgo biloba extract and dietary supplements in Vietnam market based on flavonol glycoside content and flavonoid ratio

Ginkgo biloba is one of the oldest medicinal herbs in the world. It is commonly used as a dietary supplement to protect against blood circulation disorders, improve memory, and prevent cognitive decline. Currently, Vietnam and other countries have regulations in place to ensure the quality of Ginkgo biloba extract in their pharmacopoeia. In this study, the quality of 11 raw materials and 120 dietary supplement products containing ginkgo extract was evaluated based on flavonol glycoside content and the ratio of component flavonoids. The results revealed a significant number of unsatisfactory samples, highlighting the need for closer monitoring of quality products to protect consumer rights.

Four glycosyltransferase genes are responsible for synthesis and accumulation of different flavonol glycosides in apple tissues.

Flavonols are widely synthesized throughout the plant kingdom, playing essential roles in plant physiology and providing unique health benefits for humans. Their glycosylation plays significant role in improving their stability and solubility, thus their accumulation and function. However, the genes encoding the enzymes catalyze this glycosylation remain largely unknown in apple. This study utilized a combination of methods to identify genes encoding such enzymes. Initially, candidate genes were selected based on their potential to encode UDP-dependent glycosyltransferases (UGTs) and their expression patterns in response to light induction. Subsequently, through testing the in vitro enzyme activity of the proteins produced in Escherichia coli cells, four candidates were confirmed to encode a flavonol 3-O-galactosyltransferase (UGT78T6), flavonol 3-O-glucosyltransferase (UGT78S1), flavonol 3-O-xylosyltransferase/arabinosyltransferase (UGT78T5), and flavonol 3-O-rhamnosyltransferase (UGT76AE22), respectively. Further validation of these genes' functions was conducted by modulating their expression levels in stably transformed apple plants. As anticipated, a positive correlation was observed between the expression levels of these genes and the content of specific flavonol glycosides corresponding to each gene. Moreover, overexpression of a flavonol synthase gene, MdFLS, resulted in increased flavonol glycoside content in apple roots and leaves. These findings provide valuable insights for breeding programs aimed at enriching apple flesh with flavonols and for identifying flavonol 3-O-glycosyltransferases of other plant species.

Effects of UVA on Flavonol Accumulation in Ginkgo biloba

Ginkgo is an economic tree species with high medicinal value, and flavonols are its main medicinal components. This research was conducted to investigate the molecular mechanism underlying the influence of Ultraviolet A (UVA) treatment on the synthesis of ginkgo flavonols with the aim of increasing their content. Ginkgo full-sib hybrid offspring were used as test materials. The phenylalanine ammonialyase (PAL), cinnamate 4-hydroxylase (C4H), and 4-coumarate: CoA ligase (4CL) enzyme activities, as well as flavonol contents, were measured under the same intensity of white light (300 μmol·m−2·s−1) with the addition of 20, 40, and 60 μmol·m−2·s−1 UVA separately after 20 days of treatment. The control check (CK) and treatment with the highest flavonol content were chosen for transcriptome sequencing analysis. The results showed that the PAL, C4H, and 4CL enzyme activities, as well as the flavonol and totalflavonol glycoside contents, of ginkgo hybrid progeny differed significantly under different UVA treatments. They showed a tendency to increase and then decrease, reaching a maximum value under UVA-4 (40 μmol·m−2·s−1 ultraviolet UVA light intensity) treatment. Ribonucleic acid (RNA) sequencing revealed the presence of 4165 genes with differential expression, and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that the metabolic pathways commonly enriched across all four comparison groups included ‘phenylpropanoid biosynthesis’, while the pathways commonly enriched in green-leaf ginkgo UVA-4 treatment (TL), yellow-leaf ginkgo mutant CK treatment (CKY), and green-leaf ginkgo CK treatment (CKL) were related to ‘flavonoid biosynthesis’. Treatment with UVA light led to the increased expression of PAL and 4CL enzymes in the phenylpropanoid biosynthesis pathway, as well as increased expression of chalcone synthase (CHS), Flavanone 3-hydroxylase (F3H), and flavonol synthase (FLS) enzymes in the flavonoid biosynthesis pathway, thereby promoting the synthesis of ginkgo flavonols. In summary, the use of 40 μmol·m−2·s−1 UVA treatment for 20 days significantly increased the flavonol content and the expression of related enzyme genes in ginkgo hybrid offspring, enhancing ginkgo flavonoids and increasing the medicinal value of ginkgo.

Transcriptome Analysis on the Quality of Epimedium koreanum in Different Soil Moisture Conditions at Harvesting Stage.

Epimedium koreanum is a traditional Chinese tonic herb. Its main medicinal components are secondary metabolites such as flavonoids and flavonol glycosides, but the biosynthetic mechanism is still unclear. Moisture conditions are a key environmental factor affecting E. koreanum medicinal components during harvesting. Different stages of E. koreanum under natural conditions after rainfall were selected to study changes in physiological properties, herb quality, and transcriptome. Malondialdehyde (MDA) content increased significantly in the D3 stage after rainfall, and protective enzyme levels also rose. Additionally, the flavonol glycoside content was relatively high. We sequenced the transcriptomes of D1, D3, and D9 (R) and identified differentially expressed genes (DEGs) related to flavonoid synthesis. This analysis allowed us to predict the roadmap and key genes involved in flavonoid biosynthesis for E. koreanum. These results suggest that the E. koreanum quality can be enhanced by natural drought conditions in the soil after precipitation during harvest. The harvesting period of E. koreanum is optimal when soil moisture naturally dries to a relative water content of 26% after precipitation. These conditions help E. koreanum tolerate a certain level of water scarcity, resulting in increased expression of flavonoid-related genes and ultimately enhancing the quality of the herb.

Holistic quality evaluation method of Epimedii Folium based on NIR spectroscopy and chemometrics.

There are some problems in the quality control of Epimedii Folium (leaves of Epimedium brevicornum Maxim.), such as the mixed use of Epimedii Folium from different harvesting periods and regions, incomplete quality evaluation, and time-consuming analysis methods. Near-infrared (NIR) spectroscopy was conducted to establish a rapid overall quality evaluation method for Epimedii Folium. Quantitative models of the total solid, moisture, total flavonoid, and flavonol glycoside (Epimedin A, Epimedin B, Epimedin C, Icariin) contents of Epimedii Folium were established by partial least squares regression (PLSR). The root mean square error (RMSE) and correlation coefficient (R) were used to evaluate the performance of models. The qualitative models of Epimedii Folium from different geographic origins and harvest periods were established based on K-nearest neighbor (KNN), back-propagation neural network (BPNN), and random forest (RF). Accuracy and Kappa values were used to evaluate the performance of models. A new multivariable signal conversion strategy was proposed, which combines NIR spectroscopy with the PLSR model to predict the absorbance values of retention time points in the high-performance liquid chromatography (HPLC) fingerprint to obtain the predicted HPLC fingerprint. The Pearson correlation coefficient and cosine coefficient were used to evaluate the similarity between real and predicted HPLC fingerprints. Qualitative models, quantitative models, and the similarity between real and predicted HPLC fingerprints are satisfactory. The method serves as a fast and green analytical quality evaluation method of Epimedii Folium and can replace traditional methods to achieve the overall quality evaluation of Epimedii Folium.

Effects of yellowing and drying treatment temperatures on the taste of autumn green tea

This study aimed to reduce the bitterness and astringency properties of autumn green tea using different yellowing and drying treatments. The results showed that as the yellowing temperature increased, the contents of tea polyphenols, gallated catechins, flavonol glycosides, and bitter amino acids decreased, while the content of soluble sugar and flavonols increased. The tea sample (YEL35 °C) subjected to yellowing treatment at 35 °C exhibited weak bitterness and astringency intensities and a relatively low content of flavonol glycosides. As the drying temperature increased, the content of gallated catechins decreased. In addition, the tea sample (DRY75 °C) subjected to drying treatment at 75 °C exhibited weak bitterness and astringency intensities, the highest contents of umami amino acids and Thea, and a relatively low content of gallated catechins. Multivariate statistical analysis revealed that vitexin-2-O-rhamnoside, pferol-3-O-rutinoside, myricetin-3-O-galactoside, and quercetin-3-O-glucoside played an important role in the astringency property of the tea. In addition, Asn, Thr, Pro, and Met were positively correlated with umami. Hence, the quality of autumn green tea was improved under optimal yellowing and drying temperatures of 35 and 75 °C, respectively.

The difference of flavonol glycosides in cultivated and wild sea buckthorn berries in China

Sea buckthorn (Hippophaë rhamnoides L.) is well-known for its high content of flavonol glycosides (FGs), yet accurately determining the quantity of these nutrients present in the berries remains a challenge due to the significant variability of these nutrients and lack of reference standards. In this study, flavonol glycosides in sea buckthorn berries were identified and quantified using ultra-performance liquid chromatography Q-exactive high resolution mass spectrometry (UPLC-QE HRMS). The results showed that the total content of flavonol glycosides ranged from 39.5 to 240.2 mg/100 g fresh berries. The wild berries from Sichuan had remarkably high contents and unique profiles of flavonol glycosides. The main flavonol glycosides in all of the samples were isorhamnetin glycosides and quercetin glycosides, the predominant flavonol glycosides were different between different samples. The sPLS-DA statistical analysis indicated that cultivated and wild sea buckthorn can be distinguished based on their distinct composition and content of flavonol glycosides. The HCA clustered 16 high expression levels of FGs, which were revealed in a wild sample obtained from Sichuan.

Comprehensive analysis of environmental factors on the quality of tea (Camellia sinensis var. sinensis) fresh leaves

“High mountain, cloud and mist produce high-quality tea”; however, the specific mechanism has not been fully understood. To explore the influence of environmental factors on the quality of tea fresh leaves, we firstly selected the same variety of tea plant growing at different altitudes in Xuan'en County, China. And then, based on the analyses of the physical and chemical properties of the soil where they grew, we comprehensively analyzed the composition and content of volatile and non-volatile substances in these tea fresh leaves harvested from 27 sampling sites. The relative contents of linalool and its oxides I and II, phenylethanol and nerol in paddy soil were higher than those in red soil and yellow soil, but the contents of acids and esters were significantly lower than those in other soils (P < 0.05). Benzoic acid content and palmitic acid content are relatively high in red soil and yellow soil, respectively. The amino acid content of tea fresh leaves produced in paddy soil is significantly lower than that in red soil and yellow soil, while the contents of catechins and flavonol glycosides were significantly higher than that in other soils (P < 0.05). The relative contents of EGCG, ECG and C in paddy soil were significantly higher than those in yellow soil and red soil. The content of alkaloids in red soil is high. With the increase of altitude, the content of amino acids gradually increased, and the catechins content showed a trend of first decreasing and then increasing; the phenolic acid content changes in accordance with catechins with the elevation; the flavonoids content (alcohols) glycosides did not change obviously in each altitude range. These results are helpful for us to fully understand the influence of environmental factors on the quality of fresh tea leaves.

Metabolite Profiling and Transcriptome Analysis Explain the Difference in Accumulation of Bioactive Constituents in Taxilli Herba from Two Hosts.

Taxilli Herba (TH) is a semi-parasitic herb and the host is a key factor affecting its quality. Flavonoids are the main bioactive constituents in TH. However, studies on the difference in accumulation of flavonoids in TH from different hosts are vacant. In this study, integrated transcriptomic and metabolomic analyses were performed on TH from Morus alba L. (SS) and Liquidambar formosana Hance (FXS) to investigate the relationship between the regulation of gene expression and the accumulation of bioactive constituents. The results showed that a total of 3319 differentially expressed genes (DEGs) were screened in transcriptomic analysis, including 1726 up-regulated genes and 1547 down-regulated genes. In addition, 81 compounds were identified using ultra-fast performance liquid chromatography coupled with triple quadrupole-time of flight ion trap tandem mass spectrometry (UFLC-Triple TOF-MS/MS) analysis, and the relative contents of flavonol aglycones and glycosides were higher in TH from SS group than those from the FXS group. A putative biosynthesis network of flavonoids was created, combined with structural genes, and the expression patterns of genes were mostly consistent with the variation of bioactive constituents. It was noteworthy that the UDP-glycosyltransferase genes might participate in downstream flavonoid glycosides synthesis. The findings of this work will provide a new way to understand the quality formation of TH from the aspects of metabolite changes and molecular mechanism.

Quality evaluation of ginkgo biloba leaves based on non-targeted metabolomics and representative ingredient quantification

Ultra-performance liquid chromatography coupled with time-of-flight mass spectrometry (UPLC-Q-TOF-MS/MS) combined with multivariate statistical analysis was applied to the study of plant metabolomics to reveal the factors affecting the content of ginkgo leaf compounds. As a follow-up analysis, the terpene lactones and ginkgolic acids were quantified simultaneously using ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC-QqQ-MS/MS), and subsequently total flavonol glycosides were quantified by high-performance liquid chromatography (HPLC). The results revealed that a total of 52 compounds were potentially identified by establishing a database, and 10 compounds were verified by reference standards; terpene lactones, ginkgolic acids, and flavonoids were the differential compounds; and ginkgolide A was identified as an important indicator compound for tree age. In addition, quantitative analysis showed that the contents of total flavonol glycosides and terpene lactones were highest during April and August in young ginkgo leaves, and differed based on origin. In summary, numerous compounds were rapidly detected by liquid chromatography coupled with MS, the ginkgo leaf samples were compared, and the differential metabolites were screened out. The content changing rules of the target compounds in ginkgo leaves from different regions with different tree ages and harvesting periods were clarified.

Characterization and potential bioactivity of polyphenols of Rosa rugosa

Rosa rugosa is widely cultivated in China, and the blossom of R. rugosa is used to extract rose essential oil or directly make into various foods, such as mei gui hua cake, mei gui hua sauce. Rose dregs are mostly used as fertilizer after extracting essential oil and the polar part has not been fully utilized. There is still much to be done in the products and deep processing of rose. In this study the content of total flavonol glycosides, the extractable polyphenols, the non-extractable polyphenols, the total phenolic and the total anthocyanins in R. rugosa from five major production areas in China was analyzed; the biological activities of the total extract, the polyphenols fraction, the flavonol glycosides fraction and the isolated compounds of R. rugosa were evaluated, including antioxidant, anti-ultraviolet, inhibitory activities of α-glucosidase, lipase, alveolar epithelial cell senescence and tyrosinase, together with regulating activities on intestinal flora. The components content of R. rugosa in different producing areas was significantly different. The total flavonol glycosides in Yunnan, the extractable polyphenols and the total phenolics in Shandong, the non-extractable polyphenols in Xinjiang, the total anthocyanins in Gansu was the higher than other areas. The polyphenols fraction showed antioxidant and anti-ultraviolet properties, inhibition of alveolar epithelial cell senescence, lipase and tyrosinase activities, and regulation of intestinal flora. The flavonol glycosides fraction showed α-glucosidase inhibitory activity. The results showed the polyphenols fraction and the flavonol glycosides fraction of R. rugosa could be used as skin care products and healthy food ingredient.

Effect of origin, tree age, and harvesting time on content of flavonoids and terpene lactones in Ginkgo Folium

The content of total flavonol glycosides in Ginkgo Folium in the planting bases was determined by high performance liquid chromatography(HPLC).The samples were extracted by reflux with methanol-25% hydrochloric acid.The HPLC conditions were as follows: Agilent ZORBAX SB-C_(18) column(4.6 mm×250 mm, 5 μm), isocratic elution with mobile phase of 0.4% phosphoric acid solution-methanol(45∶55), flow rate of 1 mL·min~(-1), column temperature of 30 ℃, detection wavelength of 360 nm, and injection vo-lume of 10 μL.A method for the determination of terpene lactones in Ginkgo Folium was established based on ultra-high performance liquid chromatograph-triple-quadrupole/linear ion-trap tandem mass spectrometry(UPLC-QTRAP-MS/MS).The UPLC conditions were as below: gradient elution with acetonitrile-0.1% formic acid, flow rate of 0.2 mL·min~(-1), column temperature of 30 ℃, sample chamber temperature of 10 ℃, and injection volume of 10 μL.The ESI~+and multiple reaction monitoring(MRM) were adopted for the MS.The above methods were used to determine the content of total flavonol glycosides and terpene lactones in 99 batches of Ginkgo Folium from 6 planting bases, and the results were statistically analyzed.The content of flavonoids and terpene lactones in Ginkgo Folium from different origins, from trees of different ages, harvested at different time, from trees of different genders, and processed with different methods was compared.The results showed that the content of total flavonol glucosides in 99 Ginkgo Folium samples ranged from 0.38% to 2.08%, and the total content of the four terpene lactones was in the range of 0.03%-0.87%.The method established in this study is simple and reliable, which can be used for the quantitative analysis of Ginkgo Folium.The research results lay a basis for the quality control of Ginkgo Folium.

Towards real time release testing of Shuxuening injection based on near infrared spectroscopy and accuracy profile

Real time release testing (RTRT) has been applied in the pharmaceutical process to ensure the high quality of finished products. Near infrared (NIR) spectroscopy is one of the primary analytical methods to implement RTRT. In this study, an NIR quantitative method was developed to determine the content of total flavonol glycosides in Shuxuening injection and validated by the accuracy profile approach. Combining the NIR validation with quality specification limits, a reliable RTRT method was constructed. Shuxuening injection samples of different concentrations were prepared and characterized by NIR spectroscopy. A first-order Savitzky–Golay derivative was used to pretreat the NIR spectra, and the competitive adaptive reweighted sampling method was used to select the feature variables. Partial least squares (PLS) regression was used to build the NIR quantitative model. The trueness, precision, and accuracy of the developed NIR models were validated by accuracy profile, and the measurement uncertainty was also estimated. Finally, the unreliability graph as a decision tool was established to avoid risk, enabling correct decision making to release of Shuxuening injection. The root mean square error of calibration, root mean square error of cross validation, root mean square error of prediction, and the ratio of prediction to deviation of the PLS model were 19.6 μg·mL−1, 20.9 μg·mL−1, 29.9 μg·mL−1, and 12.2, respectively, indicating the NIR quantitative model had good predictive performance. The validation results prove that the precision, trueness, and accuracy of the NIR quantitative model were within the acceptable limits. Based on the unreliability graph, the decision to release Shuxuening injection was satisfied, if the prediction of total flavonol glycosides fell into the range from 783 μg·mL−1 to 900 μg·mL−1. The RTRT method for Shuxuening injection based on NIR spectroscopy and accuracy profile can improve the efficiency and accuracy of quality control.

CsHCT-Mediated Lignin Synthesis Pathway Involved in the Response of Tea Plants to Biotic and Abiotic Stresses.

Many studies have shown that phenolic compounds such as lignin and flavonoids enhance plant resistance. Tea plants are rich in flavonoid compounds. Whether these compounds are related to tea plant resistance is unclear. In this study, an interesting conclusion was drawn on the basis of experimental results: in response to abiotic stress (except for sucrose treatment), gene expression was increased in the phenylpropanoid and lignin pathways and was reduced in the flavonoid pathway in tea plants. CsHCTs, the genes located at the branch point of the lignin and flavonoid pathways, are most suitable for regulating the ratio of carbon flow in the lignin pathway and flavonoid synthesis. Enzymatic and genetic modification experiments proved that CsHCTs encode hydroxycinnamoyl-coenzyme A:shikimate/quinate hydroxycinnamoyl transferase in vitro and in vivo. Furthermore, the genetic modification results showed that the contents of phenolic acids and lignin were increased in tobacco and Arabidopsis plants overexpressing CsHCTs, whereas the content of flavonol glycosides was decreased. Both types of transgenic plants showed resistance to many abiotic stresses and bacterial infections. We speculate that CsHCTs participate in regulation of the metabolic flow of carbon from the flavonoid pathway to the chlorogenic acid, caffeoylshikimic acid, and lignin pathways to increase resistance to biotic and abiotic stresses.

Differences in Leaf Chemistry and Glandular Trichome Density between Wild Southwestern American Hop (Humulus neomexicanus) and Commercial Hop Cultivars.

The female flowers ("cones") of the hop plant (Humulus L.) produce compounds that contribute to the flavor and other properties of beer. Hop leaves and cones produce many of the same compounds, which also confer agronomic traits such as insect and disease resistance. Targeted and untargeted ultraperformance liquid chromatography-quadrupole time-of-flight-mass spectrometry with Waters MSE technology (UPLC-QTof-MSE) metabolomics were used to compare leaf phytochemical compositions of greenhouse-grown southwestern American wild Humulus neomexicanus (A. Nelson and Cockerell) Rydb. against a group of commercial hop cultivars consisting of both pure European Humulus lupulus L. and European-North American hybrids. Principal component analysis showed a clear distinction in chemical profiles between the two groups. H. neomexicanus leaves had a significantly higher content of total α acids (p = 4.4 × 10-9), total bitter acids (p = 2.6 × 10-6), cohumulone (p = 1.0 × 10-13), humulone + adhumulone (p = 9.1 × 10-4), and the prenylflavonoids xanthohumol (p = 0.013) and desmethylxanthohumol (p = 0.029) as well as significantly higher densities of glandular trichomes (p = 1.3 × 10-6), the biosynthetic site of those compounds. Most flavonol glycosides measured were also significantly more abundant in H. neomexicanus (p = 1.5 × 10-22 to 0.0027), whereas phenolic acids were consistently, but generally nonsignificantly (p > 0.05), more abundant in the cultivars. The higher bitter acid, prenylflavonoid, and flavonol glycoside content of H. neomexicanus leaves may help to confer more favorable insect and disease-resistance properties.

Cloning and functional characterization of three flavonoid O-glucosyltransferase genes from the liverworts Marchantia emarginata and Marchantia paleacea

Flavonoid glycosides are important plant secondary metabolites with broad pharmacological activities. Flavonoid glycosides are generated from aglycones, in reactions catalyzed by typical uridine diphosphate-dependent glycosyltransferases (UGTs). Liverworts produce various types of flavonoid glycosides; however, only two UGTs have been characterized from liverworts to date. Here, we isolated three genes encoding UGTs (MeUGT1, MeUGT2, and MpalUGT1) from the liverwort species Marchantia emarginata and Marchantia paleacea through transcriptome sequencing. Recombinant MeUGT1, MeUGT2, and MpalUGT1 proteins heterologously produced in Escherichia coli exhibited catalytic activity towards multiple flavonoids. MeUGT1 and MpalUGT1 catalyzed the glycosylation of flavonols into the corresponding 3-O-glucosides with UDP-glucose as the sugar donor, while MeUGT2 exhibited a wider substrate specificity that included flavonols, flavones, and flavanones. When MeUGT2 was expressed in E. coli, the yield of flavonol 3-O-glucosides reached to 40–60% with feeding of the substrates kaempferol or quercetin under optimal conditions. Furthermore, heterologous expression of MeUGT1 in Arabidopsis thaliana increased the flavonol glycoside contents in the plants. Therefore, the UGTs characterized in this study could provide new data that will be useful for examining flavonoid biosynthesis in liverworts.

Phenolic profiles of the endemic species Astragalus palibinii Polozhij

For the first time, the composition and content of phenolic compounds (PC) of plant leaves of an endemic rare species of the Xiphidium Bunge section of the genus Astragalus L. of Siberia – Astragalus palibinii Polozhij was studied by HPLC. 11 compounds of phenolic nature were identified in water-ethanol extracts of A. palibinii leaves: gallic, p-hydroxybenzoic, chlorogenic, caffeic, ferulic, trans-ferulic, cinnamic acids, isoquercitrin, rutin, isoramnetin-3-O-rutinoside and L-epicatechin. The composition of PC in the leaves of plants of three cenopopulations A. palibinii from Khakassia is the same, with the exception of one hydroxycinnamic acid in trace amounts. The content (mg per 100 g DW) of flavonol glycosides in the leaves of A. palibinii plants varies in the range of 0.442–0.907, the content of hydroxycinnamic and hydroxybenzoic acids in the range of 98.5–109.7 and 32.5–83.9, respectively. The quantitative profiles of all the studied groups of PC are characterized by significant variability in the content of individual components. The variability of the content of hydroxycinnamic acids, flavonoids and hydroxybenzoic acids was determined as very low, medium and increased, respectively.

Utjecaj različitih metoda sušenja na sadržaj polifenolnih spojeva u kožicama crnih sorata grožđa

The aim of this work was to determine the effect of different drying treatments: freeze-drying, room-drying, and oven-drying on the grape phenolic composition of the 'Regent' and 'Cabernet Sauvignon' varieties. After drying, the samples were grounded, submerged to ultrasound-assisted extraction, and analyzed with high-performance liquid chromatography (HPLC). This study demonstrated that the use of different drying methods significantly affects the content of polyphenols in grape skins extracts. The greatest content of anthocyanins-diglucoside was preserved using freeze-drying, i.e. 15706.86 mg/kg for 'Regent', while the content of anthocyanins-monoglucoside was best preserved by room-drying, i.e. 216778.68 and 9220.30 mg/kg for 'Regent' and 'Cabernet Sauvignon', respectively. The highest content of flavonol glycosides (2583.04 and 1429.64 mg/kg for 'Regent' and 'Cabernet Sauvignon', respectively), hydroxycinnamic acids (1303.31 and 544.88 mg/kg for 'Regent' and 'Cabernet Sauvignon', respectively), and stilbene (2321.52 and 79.36 mg/kg for 'Regent' and 'Cabernet Sauvignon', respectively) was observed in the oven-dried samples. By applying freeze-drying the most optimal content of flavan-3-ol was preserved. Contents of polyphenolic compounds in oven-dried samples after 6 months of storage were almost identical to those in the samples analyzed immediately after drying. The greatest rate of degradation was observed in the room-dried samples while it was moderate in the freeze-dried ones. The results of this experiment demonstrate that it is necessary to dry samples in different ways to obtain the highest content of a certain polyphenolic group of compounds. The application of a drying method is determined by the goal of the final dried product in terms of content and composition of different polyphenolic compounds; thus, the obtained results could have an application in scientific research and for commercial purposes as well.

Flavonol Glycosides: In Vitro Inhibition of DPPIV, Aldose Reductase and Combating Oxidative Stress are Potential Mechanisms for Mediating the Antidiabetic Activity of Cleome droserifolia.

Diabetes is a major health problem that is associated with high risk of various complications. Medicinal plants hold great promise against diabetes. The traditional use of Cleome droserifolia as an antidiabetic agent was correlated to its flavonol glycosides content. In the current study, five major flavonol glycosides appeared on the RP-HPLC chromatogram of the aqueous extract namely; quercetin-3-O-β-d-glucosyl-7-O-α-rhamnoside (1), isorhamnetin-7-O-β-neohesperidoside (2), isorhamnetin-3-O-β-d-glucoside (3) kaempferol-4′-methoxy-3,7-O-α-dirhamnoside (4), and isorhamnetin-3-O-α-(4″-acetylrhamnoside)-7-O-α-rhamnoside (5). The inhibitory activities of these compounds were tested in vitro against several enzymes involved in diabetes management. Only the relatively less polar methoxylated flavonol glycosides (4, 5) showed mild to moderate α-amylase and α-glucosidase inhibitory activities. Compounds 1–4 displayed remarkable inhibition of dipeptidyl peptidase IV (DPPIV) enzyme (IC50 0.194 ± 0.06, 0.573 ± 0.03, 0.345 ± 0.02 and 0.281 ± 0.05 µg/mL, respectively) comparable to vildagliptin (IC50 0.154 ± 0.02 µg/mL). Moreover, these compounds showed high potential in preventing diabetes complications through inhibiting aldose reductase enzyme and combating oxidative stress. Both isorhamnetin glycoside derivatives (2, 3) exhibited the highest activities in aldose reductase inhibition and compound 2 (IC50 5.45 ± 0.26 µg/mL) was even more potent than standard quercetin (IC50 7.77 ± 0.43 µg/mL). Additionally, these flavonols exerted excellent antioxidant capacities through 2, 2-diphenyl-1-picrylhydrazil (DPPH) and ferric reducing antioxidant (FRAP) assays.

Phenolics profiling by HPLC-DAD-ESI-MSn aided by principal component analysis to classify Rabbiteye and Highbush blueberries

Although blueberries are widely studied, little information exists on their composition and content of flavonol glycosides. Most studies identify only a few flavonols in blueberries due to separation and identification issues. In the present study, we identified 44 flavonols and chlorogenic acid in 30 samples of Highbush and Rabbiteye blueberry, using HPLC-DAD-ESI-MSn. Highbush group fruits presented mainly quercetin-3-galactoside in their composition, while Rabbiteye group fruits exhibited higher levels of quercetin-3-rhamnoside and quercetin-3-glucuronide. Among the identified flavonols, 8 acylates (acetyl and hydroxymethylglutaroyl) were found, of which quercetin-3-O-[4″-(3-hydroxy-3-methylglutaroyl)]-α-rhamnoside was found for the first time in blueberries. This compound is exclusive to the cultivars Florida and Powderblue, where it is present in high quantities. Glucuronides of syringetin and laricitrin, and rhamnosyl-galactosides of myricetin, quercetin and isorhamnetin were also found for the first time in blueberries. The Principal Component Analysis showed that blueberry groups can be distinguished based on their phenolic compound profile.