Hydrolysis of flavonoid glycosides by propolis β-glycosidase

Dynamic Metabolomics and Transcriptomics Analyses for Characterization of Phenolic Compounds and Their Biosynthetic Characteristics in Wheat Grain

Phenolic compounds are important bioactive phytochemicals with potential health benefits. In this study, integrated metabolomics and transcriptomics analysis was used to analyze the metabolites and differentially expressed genes in grains of two wheat cultivars (HPm512 with high antioxidant activity, and ZM22 with low antioxidant activity) during grain development. A total of 188 differentially expressed phenolic components, including 82 phenolic acids, 81 flavonoids, 10 lignans, and 15 other phenolics, were identified in the developing wheat grains, of which apigenin glycosides were identified as the primary flavonoid component. The relative abundance of identified phenolics showed a decreasing trend with grain development. Additionally, 51 differentially expressed phenolic components were identified between HPm512 and ZM22, of which 41 components, including 23 flavonoids, were up-regulated in HPm512. In developing grain, most of the identified differentially expressed genes involved in phenolic accumulation followed a similar trend. Integrated metabolomics and transcriptomics analysis revealed that certain genes encoding structural proteins, glycosyltransferase, and transcription factors were closely related to metabolite accumulation. The relatively higher accumulation of phenolics in HPm512 could be due to up-regulated structural and regulatory genes. A sketch map was drawn to depict the synthetic pathway of identified phenolics and their corresponding genes. This study enhanced the current understanding of the accumulation of phenolics in wheat grains. Besides, active components and their related genes were also identified, providing crucial information for the improvement of wheat's nutritional quality.

Red Propolis as a Source of Antimicrobial Phytochemicals: Extraction Using High-Performance Alternative Solvents

Propolis is a resinous material rich in flavonoids and involved in several biological activities such as antimicrobial, fungicide, and antiparasitic functions. Conventionally, ethanolic solutions are used to obtain propolis phytochemicals, which restrict their use in some cultures. Given this, we developed an alcohol-free high-performance extractive approach to recover antibacterial and antioxidants phytochemicals from red propolis. Thus, aqueous-solutions of ionic liquids (IL) and eutectic solvents were used and then tested for their total flavonoids, antioxidant, and antimicrobial activities. The surface-responsive technique was applied regarding some variables, namely, the time of extraction, the number of extractions, and cavitation power (W), to optimize the process (in terms of higher yields of flavonoids and better antioxidant activity). After that, four extractions with the same biomass (repetitions) using 1-hexyl-3-methylimidazolium chloride [C6mim]Cl, under the operational conditions fixed at 3.3 min and 300 W, were able to recover 394.39 ± 36.30 mg RuE. g-1 of total flavonoids, with total antioxidant capacity evaluated up to 7595.77 ± 5.48 μmol TE. g-1 dried biomass, besides inhibiting the growth of Staphylococcus aureus and Salmonella enteritidis bacteria (inhibition halo of 23.0 ± 1.0 and 15.7 ± 2.1, respectively). Aiming at the development of new technologies, the antimicrobial effect also presented by [C6mim]Cl may be appealing, and future studies are required to understand possible synergistic actions with propolis phytochemicals. Thereby, we successfully applied a completely alcohol-free method to obtain antimicrobials phytochemicals and highly antioxidants from red propolis, representing an optimized process to replace the conventional extracts produced until now.

Molecular mechanism and pharmacokinetics of flavonoids in the treatment of resistant EGF receptor-mutated non-small-cell lung cancer: A narrative review

Here, we review the molecular mechanism and pharmacokinetics of flavonoids in the treatment of resistant EGF receptor (EGFR)-mutated non-small-cell lung cancer (NSCLC) and particularly the possible mechanism(s) of delicaflavone, a biflavonoid extracted from Selaginella doederleinii Hieron. EGFR TK inhibitors (EGFR-TKI) are ubiquitously used in the treatment of NSCLC bearing EGFR mutations. However, patients treated with EGFR-TKI inevitably and continuously develop resistance. In laboratory studies, flavonoids, as potential adjuvants for cancer chemotherapy, exhibited anti-cancer properties such as inhibition of chemoresistance by interference with ABC transporters-induced drug efflux, curbing of c-MET amplification, or reversal of T790M mutation-mediated resistance. The current review aims at summarizing the association between the anti-cancer potentials of flavonoids and their possible regulatory roles in certain types of mutation that could trigger EGFR-TKI resistance in NSCLC. Potential practical applications of these phytochemicals, as well as the relevant pharmacokinetics, are also discussed.

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.

Phenolic composition and biological activities of geographically different type of propolis and black cottonwood resins against oral streptococci, vaginal microbiota and phytopathogenic Fusarium species

AIMS

A multidisciplinary approach was used to compare phenolic composition, radical scavenging and antimicrobial activity of propolis samples from different geographical localities, and plant resin against various microorganisms.

METHODS AND RESULTS

Using UHPLC-qqqMS quantitative analysis, 28 phenolic compounds were determined. Caffeic and p-coumaric acids were identified as main phenolic acids in poplar propolis samples, except samples from Russia (P6) and China (P7). Radical scavenging activity (applying DPPH spectrophotometric assay) showed the highest activity of Serbian (40·51%) and Chinese (53·21%) propolis samples. Broth microdilution method was used for the oral cavity, fungal phytopathogenic and human vaginal isolates which have been identified at a molecular level. The most sensitive bacterial isolates were Lactobacillus acidophilus (MIC of 0·03-0·13 mg ml^-1 ) and the oral streptococci isolates (MIC values of 0·19-0·13 mg ml^-1 ). The most sensitive fungal phytopathogenic isolate was Fusarium oxysporum (MIC 0·003 mg ml^-1 ). All samples, except propolis from Serbia (P4) and Turkey (P5), showed a strong antifungal activity against Fusarium sporotrichioides, Fusarium subglutinans and Fusarium proliferatum.

CONCLUSION

The results of various tests indicate good radical scavenging and antimicrobial activity against important human and plant pathogens.

SIGNIFICANCE AND IMPACT OF THE STUDY

A detailed propolis analysis is important when proposing a preparation of new biological antimicrobial products which have a positive impact on human health and reduce antibacterial resistance.

Differences in flavonoid pathway metabolites and transcripts affect yellow petal colouration in the aquatic plant Nelumbo nucifera

BACKGROUND

The Asia lotus (Nelumbo nucifera Gaertn.) is an ornamental aquatic plant with high economic value. Flower colour is an important ornamental trait, with much of N. nucifera breeding focusing on its yellow flowers. To explore the yellow flower colouration mechanism in N. nucifera, we analysed its pigment constituents and content, as well as gene expression in the flavonoid pathway, in two N. nucifera cultivars.

RESULTS

We performed metabolomic and gene expression analyses in two N. nucifera cultivars with yellow and white flowers, Molinqiuse (MLQS) and Yeguangbei (YGB), respectively, at five stages of flower colouration. Based on phenotypic observation and metabolite analyses, the later stages of flower colouration (S3-S5) were determined to be key periods for differences between MLQS and YGB, with dihydroflavonols and flavonols differing significantly between cultivars. Dihydroquercetin, dihydrokaempferol, and isorhamnetin were significantly higher in MLQS than in YGB, whereas kaempferol was significantly higher in YGB. Most of the key homologous structural genes in the flavonoid pathway were significantly more active in MLQS than in YGB at stages S1-S4.

CONCLUSION

In this study, we performed the first analyses of primary and secondary N. nucifera metabolites during flower colouration, and found that isorhamnetin and kaempferol shunting resulted in petal colour differences between MLQS and YGB. Based on our data integration analyses of key enzyme expression in the putative flavonoid pathways of the two N. nucifera cultivars, NnFLS gene substrate specificity and differential expression of NnOMTs may be related to petal colour differences between MLQS and YGB. These results will contribute to determining the mechanism of yellow flower colouration in N. nucifera, and will improve yellow petal colour breeding in lotus species.

Targeted and untargeted LC-MS polyphenolic profiling and chemometric analysis of propolis from different regions of Croatia

Propolis is a complex biological matrix consisting mostly of plant resins and waxes, and in a small proportion of the herbal secondary metabolites, phenols. Phenols are components that are responsible for biological activities of propolis, however, their qualitative and quantitative composition is strongly influenced by climate and vegetation. Although studies on profiling of propolis samples from different countries have been carried out for some time propolis from Croatia is still not characterized till now. Targeted liquid chromatography coupled to triple quadrupole (LC-QQQ), untargeted liquid chromatography coupled to quadrupole time-of-flight (LC-QTOF) and direct injection QTOF methods were developed and 56 propolis samples from different geographical regions of Croatia were analyzed. Results revealed that there is not only one expected type of propolis in the territory of Croatia; i.e. beside expected European "poplar" propolis another type can be distinguished. Principal component analysis (PCA) and Partial least squares Discriminant Analysis (PLS-DA) indicated that the phenolic content of propolis samples significantly changes under the influence of the Mediterranean, so the "European" propolis type mixes with the Mediterranean type on the Croatian coast, especially on the islands. For fast screening of propolis type, direct injection QTOF analysis demonstrated to be fast and reliable method, but for unambiguous identification of phenolic compounds, chromatographic separation is indispensable. This paper presents the findings from the first research on phenolic profiling of propolis from Croatia.

Influence of storage conditions in the evolution of phytochemicals in nutraceutical products applying high resolution mass spectrometry

An adequate knowledge about possible transformation of bioactive compounds in nutraceutical products during long storage is important in order to know potential modifications of this type of compounds. In this study, one year monitoring was performed in different types of nutraceutical products based on natural extracts (green tea, soy, royal jelly and grapes) observing the appearance of new bioactive compounds, which were not detected at the initial conditions, as well as the decrease of some of the detected compounds. To determine these transformation products, an analytical procedure based on high resolution mass spectrometry (Exactive-Orbitrap analyzer) was applied. It was noted that transformation products were detected after 3 months of storage in green tea and soy products, while 6 months were necessary to observe transformation products in royal jelly.

Identification of Multiple Loci Associated with Social Parasitism in Honeybees

In colonies of the honeybee Apis mellifera, the queen is usually the only reproductive female, which produces new females (queens and workers) by laying fertilized eggs. However, in one subspecies of A. mellifera, known as the Cape bee (A. m. capensis), worker bees reproduce asexually by thelytoky, an abnormal form of meiosis where two daughter nucleii fuse to form single diploid eggs, which develop into females without being fertilized. The Cape bee also exhibits a suite of phenotypes that facilitate social parasitism whereby workers lay such eggs in foreign colonies so their offspring can exploit their resources. The genetic basis of this switch to social parasitism in the Cape bee is unknown. To address this, we compared genome variation in a sample of Cape bees with other African populations. We find genetic divergence between these populations to be very low on average but identify several regions of the genome with extreme differentiation. The regions are strongly enriched for signals of selection in Cape bees, indicating that increased levels of positive selection have produced the unique set of derived phenotypic traits in this subspecies. Genetic variation within these regions allows unambiguous genetic identification of Cape bees and likely underlies the genetic basis of social parasitism. The candidate loci include genes involved in ecdysteroid signaling and juvenile hormone and dopamine biosynthesis, which may regulate worker ovary activation and others whose products localize at the centrosome and are implicated in chromosomal segregation during meiosis. Functional analysis of these loci will yield insights into the processes of reproduction and chemical signaling in both parasitic and non-parasitic populations and advance understanding of the process of normal and atypical meiosis.

Poplar-type Propolis: Chemical Composition, Botanical Origin and Biological Activity

Propolis is one of the most used natural products known for centuries for its beneficial effects. Due to significant differences in chemical composition of samples originating from different geographic and climatic zones it is crucial to characterize reliably each type of propolis. This article comprises the latest findings concerning the poplar type propolis, i.e. it gives a cross section of chemical composition, botanical origin and biological activity of poplar type propolis in order to encourage further investigations that would indicate its beneficial effects.

Isolation of Luteolin and Luteolin-7-O-glucoside from Dendranthema morifolium Ramat Tzvel and Their Pharmacokinetics in Rats

Luteolin and luteolin-7-O-glucoside were isolated from the ethanolic extract of Dendranthema morifolium Ramat Tzvel. The structures of these analytes were identified by nuclear magnetic resonance ((1)H and (13)C NMR) and mass spectrometry. Ethanolic and water extracts contained luteolin-7-O-glucoside at 4.19 and 6.56%, respectively. However, the level of luteolin was only 0.19% in the ethanolic extract, and luteolin was not detected in the water extract. To examine the pharmacokinetics and bioavailability of luteolin and luteolin-7-O-glucoside in rats, parallel studies of luteolin (10 mg/kg, iv; and 100 mg/kg, po) and luteolin-7-O-glucoside (10 mg/kg, iv; and 1 g/kg, po) were conducted. The analytes were detected by high-performance liquid chromatography coupled with a photodiode array detector. A phenyl-hexyl (150 × 4.6 mm iv; 5.0 μm) column was used to separate the analytes from the biological samples. The pharmacokinetic data demonstrate that the areas under the concentration curves (AUCs) of luteolin were 261 ± 33 and 611 ± 89 (min μg/mL) after luteolin administration (10 mg/kg, iv; and 100 mg/kg, po, respectively). The oral bioavailability of luteolin was 26 ± 6%. The AUCs of luteolin-7-O-glucoside were 229 ± 15 and 2109 ± 350 (min μg/mL) after administration of luteolin-7-O-glucoside (10 mg/kg, iv; and 1 g/kg, po, respectively). The oral bioavailability of luteolin-7-O-glucoside was approximately 10 ± 2%. In the group that received luteolin-7-O-glucoside orally, a biotransformed luteolin product was detected, but this product was not detected in the group that received luteolin-7-O-glucoside intravenously. The biotransformation ratio of luteolin to luteolin-7-O-glucoside (the AUC ratio of metabolite/parent compound) was approximately 48.78 ± 0.12%. These results demonstrate that luteolin-7-O-glucoside is primarily hydrolyzed to luteolin in the gastrointestinal tract and then absorbed into the systemic circulation.

Ultrahigh-performance liquid chromatography and mass spectrometry (UHPLC-LTQ/Orbitrap/MS/MS) study of phenolic profile of Serbian poplar type propolis

INTRODUCTION

Propolis is a resinous natural substance collected by honeybees from different plant sources. Due to the presence of various phytochemicals, this bee-product exhibits numerous biological activities, including anti-bacterial, anti-viral, anti-inflammatory, anti-oxidant, immunostimulating and anti-tumour effects. As the chemical composition and biological activity of propolis depend on its botanical and geographical origin, searching for new bioactive substances in various types of propolis from unexplored regions is of great importance.

OBJECTIVE

The aim of this study is the evaluation of the phenolic profile of poplar propolis samples in order to characterise Serbian propolis, to identify possible new constituents and to specify the phenolic components relevant for differentiation of poplar propolis samples into two subgroups through simultaneous analysis of poplar bud extracts.

METHODS

Ethanolic extracts of propolis and poplar buds were comprehensively analysed using ultrahigh-performance liquid chromatography coupled with hybrid mass spectrometry, which combines the linear trap quadrupole and Orbitrap MS/MS mass analyser together with chemometric methods.

RESULTS

Extensive fingerprint analysis of Serbian propolis was achieved for the first time. Seventy-five phenolic compounds were detected. Eight of them were identified in propolis for the first time. Pattern-recognition methods applied to the content of ten quantified phenolics verified the existence of two subgroups of propolis, with galangin, chrysin and pinocembrin as the most influential distinguishing factors.

CONCLUSION

The phenolic composition of the analysed propolis samples confirm their affiliation to the European poplar type propolis and the existence of two subgroups according to botanical origin.

Identification of catechol as a new marker for detecting propolis adulteration

Adulteration of propolis with poplar extract is a serious issue in the bee products market. The aim of this study was to identify marker compounds in adulterated propolis, and examine the transformation of chemical components from poplar buds to propolis. The chemical profiles of poplar extracts and propolis were compared, and a new marker compound, catechol, was isolated and identified from the extracts of poplar buds. The polyphenol oxidase, catechol oxidase, responsible for catalyzing oxidation of catechol was detected in poplar buds and propolis. The results indicate catechol can be used as a marker to detect propolis adulterated with poplar extract.

Development of high-performance liquid chromatographic for quality and authenticity control of Chinese propolis

A RP-high-performance liquid chromatography (HPLC) method was developed for quality control of Chinese propolis by simultaneous analysis of 12 flavonoids and 8 phenolic acids. The results showed that vanillic acid, rutin, myricetin, and luteolin were not detected in all of the analyzed propolis and poplar tree gum samples. The caffeic acid, ferulic acid and p-coumaric acid were not detected in poplar tree gum but were detected in propolis, which suggest that they are practical indexes of distinguishing propolis from poplar tree gum. The flavonoid profiles of poplar tree gum were found to be similar to those of propolis, which are dominated by pinobanksin, pinocembrin, 3-O-acetylpinobanksin, chrysin, and galangin. Therefore, the proposed method could be applied to exclude poplar tree gum from propolis with cafferic acid, ferulic acid, and p-coumaric acid as qualitative markers, and distinguish poplar source resin from other illegal substances, and evaluate the quality grading of poplar-type propolis with pinobanksin, pinocembrin, 3-O-acetylpinobanksin, chrysin, and galangin as qualitative and quantitative markers.