Enantiomeric separation of flavanone on Chiralpak® IA column and determination of the chiral mechanism.

Thirteen flavanone racemates were successfully separated using a Chiralpak® IA column and isopropanol-hexane (50:50, v/v). The mobile phase flow rate and detection wavelength were 0.5 mL/min and 254 nm. The retention times values ranged from 5.50 and 56.45 min. The values of the retention, separation, and resolution factors ranged from 0.63 to 21.67, 1.12 to 2.45, and 0.13 to 11.94. The docking binding energies ranged from -6.2 to -8.2 kcal/mol, showing enthalpy-determined host-guest complex formation. The molecular docking results and the experimental data were agreed well. The results showed that S-enantiomers had stronger bindings with chiral selectors compared to R-enantiomers. Consequently, the R-enantiomers eluted first followed by S-enantiomers. The reported method is highly useful to determine the enantiomeric composition of the reported flavanone in any sample.

Spectral and HPLC Analyses of Synthesized Butin and Butein.

Butin and butein are significant bioactive flavanones derived from plants, existing as tautomers of each other. However, their physicochemical attributes, such as their spectral profiles under varying experimental conditions in aqueous solutions and established chromatographic methods for distinguishing between them, remain undetermined. In this study, we determined the basic properties of butin and butein using conventional spectroscopic, reversed-phase, and chiral HPLC analyses. The spectra of the synthesized butin and butein were analyzed using a UV-Vis spectrophotometer in several solvents with different polarities as well as in aqueous solutions at various pH values. Furthermore, the behavior of the measured spectra was reproduced by calculations to reveal the effects of the solvent and pH on the spectra of butin and butein in organic and aqueous solutions. Subsequently, we assessed the structural stability of butin and butein using reversed-phase HPLC, which revealed that butein is unstable compared with butin in a general culture medium. The synthesized butin was effectively separated into R- and S-isomers with positive and negative Cotton effects, respectively, via HPLC using a chiral column. These findings will aid in uncovering the individual properties of both butin and butein that may have been concealed by their tautomerism and enable the synthesis of S-butin, which is typically challenging and time-consuming to isolate.

Rapid and comprehensive quality evaluation of Huang-qin from different origins by FT-IR and NIR spectroscopy combined with chemometrics.

INTRODUCTION: Quality evaluation of Huang-qin is significant to ensure its clinical efficacy. OBJECTIVE: This study aims to establish an accurate, rapid and comprehensive Huang-qin quality evaluation method to overcome the time-consuming and laborious shortcomings of traditional herbal medicine quality assessment methods. METHODS: The contents of baicalin, baicalein and scutellarin in Huang-qin from five different origins were analyzed by FT-IR and NIR spectra combined with multivariate data technology. The quality of Huang-qin from different origins was evaluated by TOPSIS and consistency analysis based on the content of three active ingredients. The correlation between ecological factors and the accumulation of active ingredients was explored. RESULTS: Satisfactory prediction results of PLS models were obtained. Relatively, the model based on FT-IR combined with the PLS regression method has higher R2 and smaller RMSE than the NIR combined with the PLS method. TOPSIS and consistency analysis results showed that the quality of Huang-qin from different geographical origins was significantly different. The results showed that the quality of Huang-qin produced in Shanxi Province was the best among the five origins studied. The results also found that the quality of Huang-qin in different growing areas of the same origin was not completely consistent. The correlation study showed that altitude, sunshine duration and rainfall were the main factors that caused the quality difference of medicinal materials in different geographical origins. CONCLUSION: This study provides a reference for the rapid quantitative analysis of the active components of herbal medicine and the quality evaluation of them.

An intelligent process analysis method for rapidly evaluating the quality of Chinese medicine with near-infrared non-contact hyperspectral imaging: A case study of Weifuchun concentrate.

INTRODUCTION: The quality of Chinese medicine preparations can be greatly influenced by the quality of the intermediates such as extracts or concentrates. However, it is highly challenging to evaluate the quality in a rapid and non-contact manner during manufacturing. Here, we introduce an intelligent hyperspectral analysis method integrating a self-built abnormal region removal algorithm with machine learning and demonstrate its utility using the concentrate of Weifuchun (WFC), a traditional Chinese medicine preparation made from Ginseng Radix et Rhizoma Rubra, Rabdosia Amethystoides, and Aurantii Fructus. OBJECTIVE: To rapidly and non-destructively detect quality attributes of the intermediates in the manufacturing processes of Chinese medicine, an intelligent hyperspectral analysis method was developed for simultaneously quantifying the contents of naringin, neohesperidin, rosmarinic acid, and relative density of WFC concentrates. METHODOLOGY: Samples were evenly spread on solid white flat bottom containers, which were batch placed on a horizontal sample stage. Subsequent to the acquisition of near-infrared (NIR) hyperspectral images, abnormal pixels such as large/small bubbles and fine solids were first removed according to the differential pixel values in the binary grayscale map and the Mahalanobis distance metric. Then, partial least squares (PLS) and support vector machine (SVM) algorithms were used to construct hyperspectral quantitative calibration models for quality attributes. The hyperspectral images were reconstructed based on these models to visually evaluate the quality of the concentrates during manufacturing. RESULTS: As a case study, quality attributes of the WFC concentrates including contents of naringin, neohesperidin, rosmarinic acid, and relative density were determined simultaneously, and coefficients of determination of these quantitative correction models were 0.900, 0.891, 0.851, and 0.920, respectively. CONCLUSION: The method proposed in this study favors real-time determination of multiple attributes in viscous samples with industrial application prospects.

Comparison of vitamin C and flavanones between freshly squeezed orange juices and commercial 100% orange juices from four European countries.

Knowing the true levels of nutrients and dietary bioactives in fruit juices at the point of consumption is key to properly understand their potential health benefits. The objective was to characterise the vitamin C and flavanone content in commercial orange juices consumed in Europe, compared with fresh-squeezed juices. Commercial juices were a rich source of vitamin C (>30% of the Nutrient Reference Value). Vitamin C in fresh-squeezed juices, at the end of their shelf-life, remained 33% higher than the levels found in the commercial juices. Flavanones had similar values from both commercial and fresh juices, except for fresh samples stored for 48 h, where fresh juices had higher values (22.36 mg/100 mL). Thus, orange juices preserve their bioactive compounds during storage, with very little influence of the brand, country, industrial process or storage conditions. Main bioactive compounds in commercial juices are present at nutritionally significant levels to the freshly-squeezed ones.

The Effect of the Extraction Conditions on the Antioxidant Activity and Bioactive Compounds Content in Ethanolic Extracts of Scutellaria baicalensis Root.

Ethanolic extracts of Baikal skullcap (Scutellaria baicalensis) root were obtained using various techniques, such as maceration, maceration with shaking, ultrasound-assisted extraction, reflux extraction, and Soxhlet extraction. The influence of the type and time of isolation technique on the extraction process was studied, and the quality of the obtained extracts was determined by spectrophotometric and chromatographic methods to find the optimal extraction conditions. Radical scavenging activity of the extracts was analyzed using DPPH assay, while total phenolic content (TPC) was analyzed by the method with the Folin-Ciocalteu reagent. Application of gas chromatography with mass selective detector (GC-MS) enabled the identification of some bioactive substances and a comparison of the composition of the particular extracts. The Baikal skullcap root extracts characterized by both the highest antioxidant activity and content of phenolic compounds were obtained in 2 h of reflux and Soxhlet extraction. The main biologically active compounds identified in extracts by the GC-MS method were wogonin and oroxylin A, known for their broad spectrum of biological effects, including antioxidant, anti-inflammatory, antiviral, anticancer, and others.

[Comparison on tissue distribution of five components in Shuganning Injection and Scutellariae Radix extract by UPLC-MS/MS].

This study established an ultra-high performance liquid chromatography-tandem mass spectrometry(UPLC-MS/MS) method to determine the content of five index components in rat tissues and organs after administration of Shuganning Injection or Scutellariae Radix extract. The dynamic changes and differences of the distribution of the five index components over time between the two groups were studied, and the effects of Scutellariae Radix alone or in combination with other medicines on the tissue distribution of the five components were explored. After Shuganning Injection or Scutellariae Radix extract was injected into the tail vein of rats, the heart, liver, spleen, lung, kidney, stomach, intestine, and brain tissue samples were collected at four time points of 0.17, 0.5, 1, and 2 h, respectively. UPLC-MS/MS was employed to measure the concentrations of the five index components(baicalin, baicalein, oroxylin A, oroxylin A-7-O-ß-D-glucuronide, and scutellarin) in the samples of the two groups. The results showed that the established method was simple, fast, and exclusively stable. After the administration of Shuganning Injection and Scutellariae Radix extract, the five index components presented wide distribution and had differences in vivo. The two groups showcased abundant distribution of baicalin, baicalein, and oroxylin A in the kidney and liver, oroxylin A-7-O-ß-D-glucuronide in the kidney and brain, and scutellarin in the kidney and heart. The content of baicalin in the heart, liver, kidney, and intestine, baicalein in the liver and kidney, and oroxylin A in the lung after administration of Shuganning Injection(Scutellariae Radix in combination with other medicines) was significantly higher than that after administration of Scutellariae Radix extract. The results of this study suggested that the five components of Shuganning Injection and Scutellariae Radix extract demonstrated wide distribution without accumulation in rats. The combination of Scutellariae Radix with other medicines can increase the distribution of active components in rats, which provided a basis for explaining the rationality of the compatibility of Shuganning Injection from in vivo processes.

Dracocephalum jacutense Peschkova from Yakutia: Extraction and Mass Spectrometric Characterization of 128 Chemical Compounds.

Dracocephalum jacutense Peschkova is a rare and endangered species of the genus Dracocephalum of the Lamiaceae family. The species was first described in 1997 and listed in the Red Data Book of Yakutia. Significant differences in the multicomponent composition of extracts from D. jacutense collected in the natural environment and successfully introduced in the Botanical Garden of Yakutsk were identified by a team of authors earlier in a large study. In this work, we studied the chemical composition of the leaves, stem, and inflorescences of D. jacutense using the tandem mass spectrometry method. Only three cenopopulations of D. jacutense were found by us in the territory of the early habitat-in the vicinity of the village of Sangar, Kobyaysky district of Yakutia. The aboveground phytomass of the plant was collected, processed and dried as separate parts of the plant: inflorescences, stem and leaves. Firstly, a total of 128 compounds, 70% of which are polyphenols, were tentatively identified in extracts of D. jacutense. These polyphenol compounds were classified as 32 flavones, 12 flavonols, 6 flavan-3-ols, 7 flavanones, 17 phenolic acids, 2 lignans, 1 dihydrochalcone, 4 coumarins, and 8 anthocyanidins. Other chemical groups were presented as carotenoids, omega-3-fatty acids, omega-5-fatty acids, amino acids, purines, alkaloids, and sterols. The inflorescences are the richest in polyphenols (73 polyphenolic compounds were identified), while 33 and 22 polyphenols were found in the leaves and stems, respectively. A high level of identity for polyphenolic compounds in different parts of the plant is noted for flavanones (80%), followed by flavonols (25%), phenolic acids (15%), and flavones (13%). Furthermore, 78 compounds were identified for the first time in representatives of the genus Dracocephalum, including 50 polyphenolic compounds and 28 compounds of other chemical groups. The obtained results testify to the unique composition of polyphenolic compounds in different parts of D. jacutense.

Acute effect of oat ß-glucan on the bioavailability of orange juice flavanones.

The impact of ß-glucan on the bioavailability of orange juice (OJ) flavanones was investigated in a randomised controlled trial. Volunteers consumed 500 mL of OJ without or with either 3 g (OB-3) or 6 g (OB-6) of ß-glucan. Urine samples, collected 12 h before and over a 0-24 h period post-supplementation, were analysed by high-performance liquid chromatography-high resolution mass spectrometry. The overall 0-24 h urinary excretion of the 17 flavanone metabolites identified and quantified in urine after OJ ingestion corresponded to 29.7 µmol, and 25.0 and 9.3 µmol, respectively, after OB-3 and OB-6 intake. This corresponds to 9.3, 7.9, and 2.9% recoveries of the 318 µmol of the ingested flavanones. The acute ingestion of OJ with 6 g, but not 3 g of ß-glucan led to a significant reduction (p < 0.05) in the excretion of flavanone metabolites compared with consumption of OJ alone.

Systematic characterization of chemical constituents in Mahuang decoction by UHPLC tandem linear ion trap-Orbitrap mass spectrometry coupled with feature-based molecular networking.

Comprehensive characterization of traditional Chinese medicine prescriptions has long been a hurdle due to the chemical complexity and the lack of analytical tools. Mahuang decoction is a well-known traditional Chinese medicine prescription widely used for sweating and relieving the exterior, relieving cough and asthma, but it was insufficiently chemically scrutinized. In this study, the chemical component information of Mahuang decoction was investigated by ultrahigh-performance liquid chromatography tandem linear ion trap-Orbitrap mass spectrometry. A new data processing tool, feature-based molecular networking, was introduced for grouping and elucidating the compounds. In this way, 156 chemical components were identified or tentatively characterized, including alkaloids, triterpenoid saponins, flavanone-O-glycosides, flavone-C-glycosides, and procyanidins. Thus, this research provides a solid foundation for further development of Mahuang decoction, and the adopted method is expected to be applied to other traditional Chinese medicine prescriptions.

Development and evaluation of poly adenosine 5'-diphosphate-ribose polymerase 1 immobilization-based receptor chromatography.

Yanghe decoction is a traditional Chinese medicine prescription and has been used for breast cancer treatment for many years. However, the effective ingredients in the decoction have not been identified. The expression of poly(ADP-ribose) polymerase-1 is highly related to breast cancer. Using poly(ADP-ribose) polymerase-1 as a probe, we expressed the haloalkane dehalogenase-tagged protein in BL21(DE3) E. coli, immobilized it on hexachlorocaproic acid-modified macroporous silica gel, and established a poly(ADP-ribose) polymerase-1 chromatographic model. The feasibility of the model was verified by testing the retention behaviors of five drugs on the protein column. We applied the model in screening the bioactive components in yanghe decoction. Rutin, liquiritin, and a compound ([M-H]- 681.7) were identified to be the potential bioactive ingredients. We studied the binding property between rutin and poly(ADP-ribose) polymerase-1 by injection amount dependent method, competitive studies, and molecular docking. We found that rutin can bind to the protein through the typical inhibitor binding site of the protein. Therefore, the chromatographic model is a useful tool to screen bioactive compounds from traditional Chinese medicine. The method is fast, reliable, and applicable to other functional proteins that can screen the potential lead compounds for the treatment of the related diseases.

Simultaneous determination of asarinin, ß-eudesmol, and wogonin in rats using ultraperformance liquid chromatography-tandem mass spectrometry and its application to pharmacokinetic studies following administration of standards and Gumiganghwal-tang.

Asarinin, ß-eudesmol, and wogonin have common antiangiogenic activities and have the potential for use in chemotherapy. Besides, they are multivalent substances that are combined in various herbal medicines. The purpose of this study was to develop a method for simultaneous analysis of asarinin, ß-eudesmol, and wogonin, which are representative pharmacological components of Asarum heterotropoides, Atractylodes lancea, and Scutellaria baicalensis, respectively, in rat biosamples using ultraperformance liquid chromatography-tandem mass spectrometry. The three components were separated using 5 mm aqueous ammonium acetate containing 0.1% formic acid and acetonitrile as a mobile phase, equipped with a KINETEX core-shell C18 column. The analysis was quantitated on a triple-quadrupole mass-spectrometer employing electrospray ionization, and operated in the multiple reaction monitoring mode. The chromatograms showed high resolution, sensitivity, and selectivity with no interference with plasma, urine, and feces constituents. The developed analytical method satisfied international guidance criteria and could be successfully applied to the pharmacokinetic (PK) studies evaluating oral bioavailability of asarinin, ß-eudesmol, and wogonin after oral and intravenous administration and their urinary and fecal excretion ratios after oral administration to rats. Furthermore, the analysis was extended to PK studies following oral administration of Gumiganghwal-tang. This study was the first simultaneous analysis of the aforesaid three constituents in rat plasma, urine, and feces that also determined their PK parameters.

Development of a LC-HRMS based approach to boost structural annotation of isomeric citrus flavanones.

INTRODUCTION: The structural annotation of target relies on high-resolution mass spectrometry (HRMS) information resulting in dubious identities in most cases. The accurate annotation of isomeric structures is still challenging to be confirmed with significant bottleneck. OBJECTIVE: This study focused on the improvement of structural annotation of candidate structures via four pairs of isomeric flavanone-7-O-diglucosides and their basic flavanone aglycones commonly detected in citrus products. METHOD: An integrated liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS) approach merging retention time, accurate mass, tandem mass spectrometry (MS/MS) information (diagnostic ions), ion ratio at selected collision energy was established successfully. RESULTS: Feasibility of this approach was validated confidently in biological samples with relative standard deviation (RSD) of ion ratio range from 3.91 to 12.28%. Differences of fragmentation patterns of citrus flavanones were illustrated reasonably. MS/MS fragments of (S)-hesperetin and (S)-isosakuranetin were complicated and showed typical radical ion [1,2 A - H]•- (m/z 164) in negative ESI mode due to the methoxyl group on B-ring, which showed huge difference with (R)-hesperetin and (R)-isosakuranetin. CONCLUSION: This study integrated multiple levels to boost the confidence of structural annotation relied on LC-HRMS, and provided important values in practice for precise identification of citrus flavanones in biological matrices.

Colorectal Adenocarcinoma Cell Culture in a Microfluidically Controlled Environment with a Static Molecular Gradient of Polyphenol.

To study the simultaneous effect of the molecular gradient of polyphenols (curcumin, trans-resveratrol, and wogonin) and biological factors released from tumor cells on apoptosis of adjacent cells, a novel microfluidic system was designed and manufactured. The small height/volume of microfluidic culture chambers and static conditions allowed for establishing the local microenvironment and maintaining undisturbed concentration profiles of naturally secreted from cells biochemical factors. In all trials, we observe that these conditions significantly affect cell viability by stimulating cell apoptosis at lower concentrations of polyphenols than in traditional multiwell cultures. The observed difference varied between 20.4-87.8% for curcumin, 11.0-37.5% for resveratrol, and 21.7-62.2% for wogonin. At low concentrations of polyphenols, the proapoptotic substances released from adjacent cells, like protein degradation products, significantly influence cell viability. The mean increase in cell mortality was 38.3% for microfluidic cultures. Our research has also confirmed that the gradient microsystem is useful in routine laboratory tests in the same way as a multiwell plate and may be treated as its replacement in the future. We elaborated the new repetitive procedures for cell culture and tests in static gradient conditions, which may become a gold standard of new drug investigations in the future.

Development and validation of an LC-MS/MS method for the quantification of flavonoid glucuronides (wogonoside, baicalin, and apigenin-glucuronide) in the bile and blood samples: Application to a portal vein infusion study.

Glucuronidation is one of the major metabolic pathways for flavonoids. However, quantification of flavonoid glucuronides in biological samples, especially in the bile, is sometimes challenging due to signal suppression by bile acids. The purpose of this study is to establish a robust LC-MS/MS method for directly measuring flavonoid glucuronides in bile and blood. Wogonoside (wogonin-7-O-glucuronide), baicalin (baicalein-7-O-glucuronide) and apigenin-7-O-glucuronide were used as the model compounds and taurocholic acid (T-CA) were used as the model bile acid to establish the method. Bile samples were processed using solid phase extraction (SPE) and blood samples were prepared using protein precipitation method. The analytes were separated on a Resteck HPLC (50 mm × 2.1 mm ID, 1.7 µm) column using acetonitrile and 0.1% formic acid in water as the mobile phases. The mass analysis was performed in an AB Sciex 5500 Qtrap mass spectrometer via multiple reaction monitoring (MRM) in the positive mode. The results showed that the linear range of the above three analytes were 10 nM-5000 nM in the bile and 1.56 nM-4000 nM in the blood, respectively. The recoveries of three glucuronides were >85% and the matrix effects were <20% at low, medium and high concentrations in the bile and the blood. The results also showed that >90% of these bile acids were removed by the selected SPE procedure to facilitate glucuronide analysis. The validated method was successfully applied to a portal vein infusion study using rats to quantify baicalin, wogonoside, and apigenin-glucuronide in bile and blood samples.

Quantitative analysis of multicomponents by single marker combined with HPLC fingerprint qualitative analyses for comprehensive evaluation of Aurantii Fructus.

The present study aimed to develop a strategy involving quantitative analysis of multicomponents by single marker in combination with high-performance liquid chromatography fingerprint qualitative analysis for performing the quality control of Aurantii Fructus. The content of 12 components (eriocitrin, neoeriocitrin, narirutin, naringin, hesperidin, neohesperidin, meranzin, poncirin, naringenin, nobiletin, tangeretin, and auraptene) in samples was determined using reliable relative correction factors that were obtained using naringin as an internal reference standard. The new method demonstrated good applicability, and no significant differences were observed between the external standard method and the new method as determined by calculating standard method difference. Qualitative evaluation of samples was conducted using similarity analysis, hierarchical cluster analysis, and quality fluctuation analysis. Chromatographic fingerprint data were divided into three groups by similarity and hierarchical cluster analyses, and seven components may have a more significant impact on the quality of Aurantii Fructus in quality fluctuation analysis. Overall, the study suggests that the qualitative and quantitative analyses of multicomponents using quantitative analysis of multicomponents by single marker combined with chromatographic fingerprinting can be considered good quality criteria for performing quality control and providing technical support for the further pharmacological and pharmaceutical research of Aurantii Fructus.

Dalbergia ecastaphyllum (L.) Taub. and Symphonia globulifera L.f.: The Botanical Sources of Isoflavonoids and Benzophenones in Brazilian Red Propolis.

The Brazilian red propolis (BRP) constitutes an important commercial asset for northeast Brazilian beekeepers. The role of Dalbergia ecastaphyllum (L.) Taub. (Fabaceae) as the main botanical source of this propolis has been previously confirmed. However, in addition to isoflavonoids and other phenolics, which are present in the resin of D. ecastaphyllum, samples of BRP are reported to contain substantial amounts of polyprenylated benzophenones, whose botanical source was unknown. Therefore, field surveys, phytochemical and chromatographic analyses were undertaken to confirm the botanical sources of the red propolis produced in apiaries located in Canavieiras, Bahia, Brazil. The results confirmed D. ecastaphyllum as the botanical source of liquiritigenin (1), isoliquiritigenin (2), formononetin (3), vestitol (4), neovestitol (5), medicarpin (6), and 7-O-neovestitol (7), while Symphonia globulifera L.f. (Clusiaceae) is herein reported for the first time as the botanical source of polyprenylated benzophenones, mainly guttiferone E (8) and oblongifolin B (9), as well as the triterpenoids ß-amyrin (10) and glutinol (11). The chemotaxonomic and economic significance of the occurrence of polyprenylated benzophenones in red propolis is discussed.

[An analysis of the ingredients in decoctions and extracts of Kampo medicines: Amounts of baicalin and baicalein in Kampo medicines containing Scutellariae Radix].

AIM: Kampo medicines containing Scutellariae Radix (the root of Scutellaria baicalensis Georgi; SR) sometimes cause serious adverse effects, including interstitial pneumonia and liver dysfunction. Baicalin (BL) is the major active component of SR and is presumed to be responsible for the adverse effects. We analyzed the amounts of BL in Kampo medicines to better understand how they can be used safely. METHODS: We determined the amounts of BL in 28 Kampo decoctions containing SR (recommended daily dose: 1.5-4 g/day) and corresponding Kampo extract products by high-performance liquid chromatography. RESULTS: The amounts of BL in the Kampo decoctions were 1.7-4.0-fold higher than those of the corresponding Kampo extract products. Inter-product variations in the amounts of BL in Shosaikoto, Otsujito, Daisaikoto, Saibokuto, Orengedokuto, and Saireito Kampo extracts from various companies were also examined. Significant differences in the amounts of BL were observed for Shosaikoto, Otsujito, Daisaikoto, and Saibokuto extract products (up to 2.6, 1.6, 1.5, and 1.3-fold differences, respectively), whereas no significant differences were observed for Orengedokuto and Saireito extract products. CONCLUSIONS: Because the Kampo decoctions containing SR that we examined contained 1.7-4.0 times as much BL as the corresponding Kampo extract products, medical doctors and pharmacists should be aware that Kampo decoctions containing SR might cause more severe side effects than corresponding Kampo extract products. Furthermore, we recommend that the amounts of BL and its aglycone, baicalein (BA), in Kampo extract products be made known to practitioners and patients.

Fine-tuning the (2S)-naringenin synthetic pathway using an iterative high-throughput balancing strategy.

Metabolic engineering consistently demands to produce the maximum carbon and energy flux to target chemicals. To balance metabolic flux, gene expression levels of artificially synthesized pathways usually fine-tuned using multimodular optimization strategy. However, forward construction is an engineering conundrum because a vast number of possible pathway combinations need to be constructed and analyzed. Here, an iterative high-throughput balancing (IHTB) strategy was established to thoroughly fine-tune the (2S)-naringenin biosynthetic pathway. A series of gradient constitutive promoters from Escherichia coli were randomly cloned upstream of pathway genes, and the resulting library was screened using an ultraviolet spectrophotometry-fluorescence spectrophotometry high-throughput method, which was established based on the interactions between AlCl3 and (2S)-naringenin. The metabolic flux of the screened high-titer strains was analyzed and iterative rounds of screening were performed based on the analysis results. After several rounds, the metabolic flux of the (2S)-naringenin synthetic pathway was balanced, reaching a final titer of 191.9 mg/L with 29.2 mg/L p-coumaric acid accumulation. Chalcone synthase was speculated to be the rate-limiting enzyme because its expression level was closely related to the production of both (2S)-naringenin and p-coumaric acid. The established IHTB strategy can be used to efficiently balance multigene pathways, which will accelerate the development of efficient recombinant strains.

Polyphenols and bioavailability: an update.

Based on many cell culture, animal and human studies, it is well known that the most challenge issue for developing polyphenolics as chemoprevention or anti-diabtetic agents is the low oral bioavailability, which may be the major reason relating to its ambiguous therapeutic effects and large inter-individual variations in clinical trials. This review intends to highlight the unscientific evaluation on the basis of the published data regarding in vitro bioactivity of polyphenols, which may sometimes mislead the researchers and to conclude that: first, bio-accessibilities values obtained in the studies for polyphenols should be highly reconsidered in accordance with the abundant newly identified circulating and excreted metabolites, with a particular attention to colonic metabolic products which are obviously contributing much more than expected to their absorptions; second, it is phenolic metabolites, which are formed in the small intestine and hepatic cells,low molecular weight catabolic products of the colonic microflora to travel around the human body in the circulatory system or reach body tissues to elicit bioactive effects. It is concluded that better performed in vivo intervention and in vitro mechanistic studies are needed to fully understand how these molecules interact with human physiological and pathological processes.