Total Flavonol Glycosides Research Articles

Effect of combined application of organic and chemical fertilizers on yield and quality of Epimedium pubescens

To investigate the effects of different ratios of organic and chemical fertilizers on the yield and quality of Epimedium pubescens,so as to provide a scientific basis for the fertilization of high-yield and high-quality E. pubescens cultivation. In this experiment,a field plot test was conducted,and CK(without fertilizer) was set as the control group,with five treatment groups with different ratios of organic fertilizers and chemical fertilizers set up,namely OF0(100% chemical fertilizers),OF25(25% organic fertilizers),OF50(50% organic fertilizers),OF75(75% organic fertilizers),and OF100(100% organic fertilizers). The effects of different fertilization patterns on the agronomic traits,yield,effective component content,nutrient accumulation,and soil physicochemical properties of E. pubescens were determined,and the yield and quality of the medicinal herb were comprehensively evaluated by using the CRITIC weights method. It was found that the herb yield of each treatment group was significantly increased compared with the CK group,although the yield of the groups with both organic fertilizer and chemical fertilizer was slightly lower than that of OF0. However,there was no significant difference,which indicated that the organic fertilizer combined with chemical fertilizer could ensure the herb yield. With the increase in organic fertilizer ratios,the medicinal components epimedin A,epimedin B,and epimedin C showed a tendency of first increasing and then decreasing,with the highest content in the OF25,while icariin showed a rising trend,with the best in the OF100. However,overall,the total flavonol glycosides ABCI accumulated the most in the OF25. The results of the CRITIC method showed that the top three fertilization treatments in terms of the comprehensive scores of the medicinal herb were OF25,OF50,and OF75. Organic fertilizer combined with chemical fertilizer is conducive to improving the soil's fertilizer holding and supply capacity,and the soil indexes are optimal in OF100. The soil enzyme activity is the highest in OF75. Meanwhile,organic fertilizer combined with chemical fertilizer can help the plant's uptake and accumulation of nutrients,and OF25 shows the most obvious effect.By comprehensively considering the influence of different ratios of organic and chemical fertilizers on the yield,effective component content,nutrient accumulation,and other indexes of E. pubescens,it is recommended that a 25% ratio(7 500 kg·hm~(-2)) of organic fertilizers and chemical fertilizers should be used in E. pubescens production in the first year,so as to promote the E. pubescens industry to increase yield and improve quality.

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.

Portable paper-based probe for on-site ratiometric fluorescence determination of total flavonol glycosides in plant extract using smartphone imaging.

A smartphone-assisted, paper-based ratio fluorescence probe is presented for the rapid, low-cost and on-site quantification of total flavonol glycosides in Ginkgo biloba extracts (GBE). The Al3+/Eu-MOF/paper-based probe utilizes lanthanide metal-organic framework (Ln-MOF) nanoparticles immobilized on Whatman filter paper along with Al3+ for detecting flavonols, which are the hydrolyzed products of flavonol glycosides. The color change of the paper-based fluorescence image from red to orange depends on the concentration of the target analyte in the sample solution. The smartphone equipped with a red, green, blue (RGB) color detector measured the fluorescence signal intensity on the paper substrate after adding flavonol. The analytical variables affecting the performance of the probe, including the addition sequence of the aluminum nitrate solution, its concentration, that of the Ln-MOF solution, the drying time of the paper probe, the reaction time and the sensitivity parameters of the mobile phone camera (ISO), were optimized. Under optimal conditions, the Al3+/Eu-MOF/paper-based probe has good linear response in the concentration range 7 ~ 80µg mL- 1 and a lower detection limit of 2.07µg mL- 1. The results obtained with the paper-based ratio fluorescence probe and smartphone combination were validated by comparing them with high-performance liquid chromatography (HPLC) measurements. This study provides a potential strategy for fabricating Al3+/Eu-MOF/paper-based probe used for total flavonol glycosides determination.

Determination of Total Flavonol Glycosides in ZhuangGuGuanJieWan Fluidextract Based on Near-Infrared Spectroscopy and Chemometrics

Determination of Total Flavonol Glycosides in ZhuangGuGuanJieWan Fluidextract Based on Near-Infrared Spectroscopy and Chemometrics

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.

Medicinal Values and Potential Risks Evaluation of Ginkgo biloba Leaf Extract (GBE) Drinks Made from the Leaves in Autumn as Dietary Supplements.

Ginkgo tea and ginkgo wine are two familiar Ginkgo biloba leaf extract (GBE) drinks in the form of dietary supplements (DS) used for healthcare in east Asia. Nevertheless, a comprehensive evaluation of their safety and efficacy is still lacking. In this study, GBE drinks were prepared from naturally newly senescent yellow leaves (YL) and green leaves (GL) in autumn. Their total flavonoids, antioxidant capacity and prescribed ingredients were investigated. In brief, the proportions of total flavonoids, total flavonol glycosides (TFs), total terpene trilactones (TTLs) and ginkgolic acids in the GBE drinks all did not meet the standards of worldwide pharmacopoeias. Specifically, the levels of TFs in the ginkgo tea prepared from YL were significantly higher than that prepared from GL. Further analyses revealed a substandard ratio of isorhamnetin/quercetin and an accumulation of leaf-age-related compounds, which were both unqualified. The proportions of specific TTLs varied between the ginkgo tea and ginkgo wine, although no significant differences were detected in terms of the total levels of TTLs. Noticeably, numerous biflavones and thousands of times over the limiting concentration of ginkgolic acids, including newly identified types, were only detected in ginkgo wine. Finally, the use of the GBE drinks as DSs was comprehensively evaluated according to the acceptable daily intake. This study showed the limited healthcare effects of GBE drinks despite their powerful antioxidant capacity.

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.

Screening the Key Region of Sunlight Regulating the Flavonoid Profiles of Young Shoots in Tea Plants (Camellia sinensis L.) Based on a Field Experiment.

Both UV and blue light have been reported to regulate the biosynthesis of flavonoids in tea plants; however, the respective contributions of the corresponding regions of sunlight are unclear. Additionally, different tea cultivars may respond differently to altered light conditions. We investigated the responses of different cultivars (‘Longjing 43’, ‘Zhongming 192’, ‘Wanghai 1’, ‘Jingning 1’ and ‘Zhonghuang 2’) to the shade treatments (black and colored nets) regarding the biosynthesis of flavonoids. For all cultivars, flavonol glycosides showed higher sensitivity to light conditions compared with catechins. The levels of total flavonol glycosides in the young shoots of different tea cultivars decreased with the shade percentages of polyethylene nets increasing from 70% to 95%. Myricetin glycosides and quercetin glycosides were more sensitive to light conditions than kaempferol glycosides. The principal component analysis (PCA) result indicated that shade treatment greatly impacted the profiles of flavonoids in different tea samples based on the cultivar characteristics. UV is the crucial region of sunlight enhancing flavonol glycoside biosynthesis in tea shoots, which is also slight impacted by light quality according to the results of the weighted correlation network analysis (WGCNA). This study clarified the contributions of different wavelength regions of sunlight in a field experiment, providing a potential direction for slightly bitter and astringent tea cultivar breeding and instructive guidance for practical field production of premium teas based on light regimes.

Effects of Light Intensity and Spectral Composition on the Transcriptome Profiles of Leaves in Shade Grown Tea Plants (Camellia sinensis L.) and Regulatory Network of Flavonoid Biosynthesis.

Black net shade treatment attenuates flavonoid biosynthesis in tea plants, while the effect of light quality is still unclear. We investigated the flavonoid and transcriptome profiles of tea leaves under different light conditions, using black nets with different shade percentages, blue, yellow and red nets to alter the light intensity and light spectral composition in the fields. Flavonol glycosides are more sensitive to light intensity than catechins, with a reduction percentage of total flavonol glycosides up to 79.6% compared with 38.7% of total catechins under shade treatment. A total of 29,292 unigenes were identified, and the KEGG result indicated that flavonoid biosynthesis was regulated by both light intensity and light spectral composition while phytohormone signal transduction was modulated under blue net shade treatment. PAL, CHS, and F3H were transcriptionally downregulated with light intensity. Co-expression analysis showed the expressions of key transcription factors MYB12, MYB86, C1, MYB4, KTN80.4, and light signal perception and signaling genes (UVR8, HY5) had correlations with the contents of certain flavonoids (p < 0.05). The level of abscisic acid in tea leaves was elevated under shade treatment, with a negative correlation with TFG content (p < 0.05). This work provides a potential route of changing light intensity and spectral composition in the field to alter the compositions of flavor substances in tea leaves and regulate plant growth, which is instructive to the production of summer/autumn tea and matcha.

Simultaneous Preparation of Abundant Flavonol Triglycosides from Tea Leaves.

Flavonol glycosides are important components of tea leaves, contributing to the bioactivities as well as bitterness and astringency of tea. However, the standards of many flavonol triglycosides are still not available, which restricts both sensory and bioactivity studies on flavonol glycosides. In the present study, we established a simultaneous preparation method of seven flavonol triglycoside individuals from tea leaves, which consisted of two steps: polyamide column enrichment and preparative HPLC isolation. The structures of seven flavonol triglycoside isolates were identified by mass and UV absorption spectra, four of which were further characterized by nuclear magnetic resonance spectra, namely, quercetin-3-O-glucosyl-rhamnosyl-glucoside, quercetin-3-O-rhamnosyl-rhamnosyl-glucoside, kaempferol-3-O-glucosyl-rhamnosyl-glucoside and kaempferol-O-rhamnosyl-rhamnosyl-glucoside. The purities of all isolated flavonol triglycosides were above 95% based on HPLC, and the production yield of total flavonol glycosides from dry tea was 0.487%. Our study provides a preparation method of flavonol triglycosides from tea leaves, with relatively low cost of time and solvent but high production yield.

Polyphenol oxidase dominates the conversions of flavonol glycosides in tea leaves

Flavonol glycosides are associated with astringency and bitterness of teas. To clarify the dominant enzymatic reaction of flavonol glycosides in tea leaves, the catalytic effects of polyphenol oxidase (PPO), peroxidase (POD) and β-glucosidase were studied, with the maintaining rates of total flavonol glycosides (TFG) being 73.0%, 99.8% and 94.3%. PPO was selected for further investigations, including the effects of pH value (3.5 ~ 6.5), temperature (25 °C ~ 55 °C) and dosage (39 ~ 72 U/mL PPO and 36 U/mL PPO, 3 ~ 36 U/mL POD). The oxidation of flavonol glycosides were intensified at pH 6.5, with 51.8% and 15.4% of TFG maintained after PPO and PPO + POD treatments, suggesting an enhancement from POD. The sensitivity ranking to PPO was: myricetin glycosides > quercetin glycosides > kaempferol glycosides. The inhibitor treatment testified the leading role of PPO in catalyzing flavonol glycosides in tea leaves. Sugar moiety enhanced the docking affinity of flavonol glycosides for PPO. PPO shows the potential of modifying flavonol glycoside composition.

Quality control analyses for Ginkgo extracts require analysis of intact flavonol glycosides

Ten commercial standardized Ginkgo biloba extracts were examined for flavonol glycoside and terpene lactone content. All samples arrived with certificates of analysis stating that the extracts were standardized Ginkgo biloba leaf extract and that they contained a minimum of 24% total flavonol glycosides and 6% terpene lactones. Samples were analyzed for total flavonol glycosides using a method involving acid hydrolysis and subsequent quantification of the flavonol aglycones by HPLC coupled with UV diode array absorbance detection. Analysis of intact flavonol glycosides and terpene lactones was accomplished using HPLC coupled with UV diode array detection and electrospray mass spectrometric detection. Of the ten standardized extracts eight samples provided chromatograms and chemical values characteristic of previously published analyses of ginkgo leaf extracts. One sample provided analyses that suggested that the extract had been adulterated with rutin in order to elevate total flavonol glycoside levels. Another sample indicated that it was not an extract of Ginkgo biloba leaf at all. Adulteration with rutin was not strongly evident when the acid hydrolysis method was used to analyze the sample for total flavonol glycosides. However, this particular adulteration was easily evident when analyzing the samples for characteristic intact flavonol glycosides. This work demonstrates the need for extensive quality control analyses for herbal products and that the analysis of intact characteristic compounds provides a reliable method for detecting adulteration.

Study on assay strategy of total tritepenoid saponins in traditional Chinese medicines using total saponins from Akebiae Caulis as an example

Due to lack of reference substances,the content of triterpenoid saponins in traditional Chinese medicines is usually characterized by colorimetric determination of total saponins. However,the specificity of colorimetric method is poor,and the determination result is not accurate enough. So,in this paper,the content determination method of total triterpenoid saponins was studied by taking Akebiae Caulis saponins as an example. The contents of three main saponin aglycones,including arjunolic acid,hederagenin and oleanolic acid,were determined by HPLC method. Referring to the content determination method of total flavonol glycosides in Ginkgo biloba leaves in the 2015 edition of Chinese Pharmacopoeia,the content of Akebiae Caulis saponins was obtained by multiplying the total content of the three above-mentioned aglycones with conversion coefficient. LC-MS/MS analysis results showed that mutongsaponin C and aponin PJIwere the two main triterpene saponins in Akebiae Caulis,and they shared the same molecular formula. So,the average value of the ratios of the molecular weight between mutongsaponin C and the three aglycones was defined as the conversion coefficient.The three aglycones were separated on an ACE Excel 3 C18-AR column( 4. 6 mm×150 mm,3 μm),and methanol-water( containing0. 04% glacial acetic acid and 0. 02% triethylamine) was used as mobile phase with gradient elution. The detection wavelength was set at 210 nm,and the flow rate was 0. 5 m L·min-1. The results showed that there was a good linearity among the ranges of 1. 053-16. 84,0. 200-3. 200 and 1. 515-24. 24 μg for arjunolic acid,hederagenin and oleanolic acid,respectively. Their average recoveries were97. 90%,97. 50% and 100. 5%,with RSD of 2. 0%,2. 9% and 2. 9%,respectively. The results of methodological investigation met the requirements of content determination. The conversion coefficient was 2. 31. This method is simple and reliable,and can be used for the determination of total triterpenoid saponins in Akebiae Caulis. The assay strategy can be used for the determination of total triterpenoid saponins in other traditional Chinese medicines.

Influence of Mineral Supplementation on the Results from Analysis of Flavonol Glycoside Content in Ginkgo biloba Dietary Supplements.

Flavonoids are a major component of Ginkgo biloba extract (GBE). Several studies have investigated chelate formation and the redox reaction between flavonoids and metal ions; however, the effect of mineral supplements on the results from the analysis of the flavonol glycoside content in products containing GBE dietary supplement remains unknown. In this study, the effects of commonly used mineral supplements on the recovery of quercetin from GBE-containing dietary supplements were investigated using conventional methods of flavonol glycoside determination. Mineral supplements containing Zn (II), Mn (II), and Fe (II) did not affect quercetin recovery, whereas Cu (II) and Fe (III) significantly reduced recovery (P<0.05). Quercetin oxidation was prevented by adding an antioxidant to the diluent (extraction solvent). Among the tested synthetic antioxidants, tert-butyl hydroquinone (TBHQ) promoted the greatest increase in quercetin recovery. The flavonol glycoside content of commercially available GBE-containing dietary supplements was analyzed using a conventional diluent or a diluent containing 20 mg/mL TBHQ. The amount of quercetin recovered from products containing Cu (II) was found to decrease with increasing hydrolysis duration and the duration in the final test solution state using the conventional diluent, while the TBHQ-containing diluent yielded consistent quercetin contents (P<0.05). These findings suggest that quercetin, a major aglycone of GBE flavonol glycosides, can be oxidized by Cu (II) and Fe (III) during the analytical process and, therefore, the total flavonol glycoside content may be underestimated. The addition of TBHQ to the diluent can improve the accuracy and reproducibility of flavonol glycoside content analysis in GBE-containing dietary products supplemented with minerals.

Dynamic changes in flavonol glycosides during production of green, yellow, white, oolong and black teas from Camellia sinensis L. (cv. Fudingdabaicha)

SummaryFlavonol glycosides with low thresholds are important flavour substances in tea leaves. This study monitored the dynamic changes in flavonol glycosides during the production of different teas. The fresh leaves of cv. Fudingdabaicha with 15.77 mg g−1 of total flavonol glycosides (TFG) were respectively processed into green, yellow, white, oolong and black teas. A reduction of TFG was observed for different teas, amongst which black tea contained the lowest level of TFG (9.83 mg g−1), followed by oolong tea (11.96 mg g−1), while green, yellow and white teas contained similar levels of TFG (~13.70 mg g−1). Fixation was crucial to maintain the stability of flavonol glycosides due to its inactivation effect on enzymes at high temperature. Principal component analysis results indicated that flavonol glycosides were vulnerable to fermentation, and the stabilities of flavonol glycosides were related with aglycone and glycoside moiety.

Rapid and non-destructive discrimination of special-grade flat green tea using Near-infrared spectroscopy

Special-grade green tea is a premium tea product with the best rank and high value. Special-grade green tea is normally classified by panel sensory evaluation which is time and sample costly. Near-infrared spectroscopy is considered as a promising rapid and non-destructive analytical technique for food quality evaluation and grading. This study established a discrimination method of special-grade flat green tea using Near-infrared spectroscopy. Full spectrum was used for partial least squares (PLS) modelling to predict the sensory scores of green tea, while specific spectral regions were used for synergy interval-partial least squares (siPLS) modelling. The best performance was achieved by the siPLS model of MSC + Mean Centering pretreatments and subintervals from 15 intervals. The optimal model was used to discriminate special-grade flat green tea with the prediction accuracy of 97% and 93% in the cross-validation and external validation respectively. The chemical compositions of green tea samples were also analyzed, including polyphenols (total polyphenols, catechins and flavonol glycosides), alkaloids and amino acids. Principal components analysis result showed that there is potential correlation between specific spectral regions and the presence of polyphenols and alkaloids. Thus, NIR technique is a practical method for rapid and non-destructive discrimination of special-grade flat green tea with chemical support.

Antioxidative and antibacterial activities of aqueous ethanol extracts of berries, leaves, and branches of berry plants

Phenolic compounds were extracted with food grade solvent of acidified aqueous ethanol from leaves, berries, berry press cakes, and branches of Finnish berry plants and analyzed with HPLC-DAD, UPLC-DAD-ESI-MS and NMR. In addition, press cakes from two berry species and branches from one species were also extracted and analyzed with the same methods. The antioxidant activities of the extracts were evaluated using Folin-Ciocalteau, oxygen radical absorbance capacity (ORAC), DPPH free radical scavenging, and total radical trapping antioxidant parameter (TRAP) assays. The antibacterial activities were investigated against various Gram-negative and Gram-positive foodborne pathogens. The leaf extracts showed higher antioxidative activities (3–20 fold in ORAC assay, 10–20 fold in TRAP) than the berry extracts, in association with the higher contents of phenolic compounds in the leaf extracts; Strongest anti-bacterial effects was observed in the leaf extracts of lingonberry (Vaccinium vitis-idaea), sea buckthorn (Hippophaë rhamnoides ssp. rhamnoides) and saskatoon (Amelanchier alnifolia) on Staphylococcus aureus, Listeria monocytogenes, and Bacillus cereus. However, the antibacterial efficacy varied with bacterial species and strains. The Folin-Ciocalteu, ORAC, and TRAP values was strongly correlated with the total content of flavonoids with less association shown with the content of total phenolics and flavonol glycosides. The results suggest a major contribution of pranthocyanidins and flavan‐3-ols to the antioxidative activities of the extracts. The growth inhibition on Staphylococcus aureus and Bacillus cereus was clearly associated with the content of total phenolics and ellagitannins.

Screening the cultivar and processing factors based on the flavonoid profiles of dry teas using principal component analysis

This study screened the effects of cultivar and processing method on the flavonoid profiles of different teas. Four tea cultivars ‘Jiulongpao’, ‘Zhenong 902’, ‘Jinxuan’ and ‘Huangjingui’ were respectively processed into green tea, oolong tea and black tea. The concentrations of 13 flavonol glycosides and 8 catechins in teas were simultaneously determined by UHPLC-DAD-MS/MS in combination with SRM mode. The intercultivar difference of flavonol glycosides in the same type of teas was greater than that of catechins. The contents of total flavonol glycosides and total catechins in black teas were respectively 14.2% ∼ 28.8% and 82.9% ∼ 84.6% lower than those of green teas made from the same cultivar. Myricetin glycosides, mono-glycosides, tri-glycosides and catechins are vulnerable to fermentation. Principal component analysis results indicated that the flavonol glycoside profiles of dry teas were well discriminated by tea plant cultivar rather than manufacturing procedure, whereas the catechin profiles of black teas were distinguished by fermentation process. Thus, tea plant cultivar is an important factor to be considered for consumption decision on dry teas, especially non-fermented and semi-fermented teas, due to remarkable intercultivar difference in flavonol glycosides.