l-Pyroglutamic Acid-Modified CdSe/ZnS Quantum Dots: A New Fluorescence-Responsive Chiral Sensing Platform for Stereospecific Molecular Recognition.

Stereoselective recognition of amino acids is extremely important due to its high chirality-dependent interactions and physiological activities in life activities. We herein report a novel functionalized chiral fluorescent nanosensor prepared from surface modification of CdSe/ZnS quantum dots (QDs) with pyroglutamic acid derivatives, which could serve as a chiral recognition module for fluorescence detection of chiral molecules. The sensor exhibited a unique stereoselective fluorescence response to histidine (His), glutamate (Glu), and dihydroxyphenylalanine (Dopa) and had preferable response performance to l-enantiomers. The enantiomeric fluorescence difference ratios of His, Glu, and Dopa enantiomers were 3.90, 3.40, and 2.49, respectively. The mechanism for the enantiomeric fluorescence recognition was systematically studied through a fluorescence spectrum, fluorescence life, and density functional theory (DFT) calculation. Presumably, the different hydrogen bonding capacity of the chiral recognition module with two enantiomers mainly contributed to the difference in fluorescence signals. As a result, a broader application of the pyroglutamic acid derivative-coated QDs as a fluorescence-responsive chiral sensing platform for enantiomeric detection would be expected.

Flavonoid aglycone-oriented data-mining in high-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry: efficient and targeted profiling of flavonoids in Scutellaria barbata.

The high-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (HPLC-QTOF-MS/MS) technique is a powerful tool for compound identification in complex natural products. However, untargeted MS/MS data analysis needs skillful experience and sometimes neglects minor compounds, which are co-eluted with major ones or overshadowed by the matrix. Flavonoids are the main bioactive components in Scutellaria barbata, and the total flavonoid content is 47.02 ± 3.23 mg QE/g DW. Although some flavonoid aglycones and their O-glycosides have been found in S. barbata, comprehensive profiling of flavonoids is unknown. Therefore, we report a flavonoid aglycone-oriented data-mining strategy for efficient and targeted profiling of flavonoids in S. barbata. The strategy includes four steps: (1) HPLC-QTOF-MS analysis of S. barbata; (2) construction of a flavonoid aglycone-based database according to biosynthetic pathway analysis and reported data; (3) extraction of through flavonoid aglycone-based ion chromatography; (4) identification of targeted flavonoids by MS/MS analysis. As a result, 45 flavonoids, including 24 flavones, 1 flavonol, 13 flavanones, and 7 flavanonols, were unambiguously or tentatively identified, while 20 of them were reported in S. barbata for the first time. Moreover, 14 available flavonoids were sensitively, precisely, and accurately determined by standard calibration curves, with limit of detection at 0.06 to 1.55 µg/g, limit of quantification at 0.16 to 3.70 µg/g, relative standard deviation (RSD) less than 9.0% for intra- and inter-day variations, and recovery at 92.6-108.1%. The matrix did not obviously suppress or enhance the ionization of 14 flavonoids, and finally their contents ranging from 0.04 to 4.49 mg/g in S. barbata were successfully achieved. Collectively, our results demonstrate that an efficient, reliable, and valuable strategy has been provided to rapidly and sensitively screen, profile, and quantify chemical components of complex natural products. Graphical abstract.

Homoisoflavonoids profiling of Ophiopogon japonicus by off-line coupling high-speed countercurrent chromatography with high-performance liquid chromatography-diode array detector-quadrupole time-of-flight tandem mass spectrometry.

Roots of Ophiopogon japonicus have been used as a functional food ingredient and traditional Chinese medicine for a long time in China. Homoisoflavonoids are one of the major kinds of bioactive compounds in O. japonicus; however, literature data about its homoisoflavonoids profile are scarce because of the complex ingredients with low abundance. Here, homoisoflavonoid fraction was prepared by petroleum ether extraction. Then, a high-speed countercurrent chromatography off-line coupling with high-performance liquid chromatography-diode array detector-quadrupole time-of-flight tandem mass spectrometry was developed for systematic identification of homoisoflavonoids. After that, 39 homoisoflavonoids, including 29 homoisoflavanone and 10 homoisoflavone, were unambiguously or tentatively identified, while 12 of them were reported in O. japonicus for the first time. Finally, eight available homoisoflavonoids were sensitively, precisely, and accurately determined by standard calibration curves, with limit of detection and limit of quantification in the range of 0.05-0.30 µg/mL and 0.12-0.66 µg/mL, relative standard deviation less than 7.3% for intra- and interday variations, and recovery at 94.5-105.2%. Collectively, our developed method is efficient, reliable, and valuable to profile chemical components of complex natural products.

Online extraction and cleanup-quadrupole time-of-flight tandem mass spectrometry for rapid analysis of bioactive components in natural products.

The challenges in direct analysis of a complex system (e.g., natural product, food, biological samples) by mass spectrometry (MS) are the sophisticated sample preparation methods and ionization suppression by matrix interferences. Consequently, a novel online extraction and cleanup-quadrupole time-of-flight tandem mass spectrometry (OLEC-QTOF-MS/MS) system was developed for rapid, efficient, and sensitive analysis of flavonoids in Citri Reticulatae Pericarpium (CRP). For the OLEC strategy, a guard column packed with solid CRP (0.5 mg) and C18 gel was positioned on a manual injection valve, in which interferences with large polarities were online removed by methanol-0.1% formic acid (25:75, v/v) for 3 min, while target flavonoids were online extracted by methanol-0.1% formic acid (70:30, v/v) for 10 min for the subsequent QTOF-MS/MS analysis. The method was validated using official marker, hesperidin, by external standard method. Excellent linear ranges from 0.02 to 52.0 µg L-1 (R2, 0.9935) with a limit of detection (LOD) of 0.006 µg were obtained. Acceptable reproducibility (RSD 8.1 and 9.6% for intra- and inter-day variations) and recoveries (from 99.5 to 112.0%) were also attained. In addition, 20 flavonoids in CRP were identified according to their exact mass and fragmentation ions in MS/MS spectra, and five of them were reported for the first time. Obviously, OLEC-QTOF-MS/MS presented several advantages, such as simple operation and high sensitivity, which provided new perspectives for rapid analysis of bioactive components in complex natural products. Graphical Abstract ᅟ.

Hinge-like paper-based dual-channel enzyme-free ratiometric fluorescent microfluidic platform for simultaneous visual detection of carbaryl and glyphosate.

On-site multi-pesticide residues detection is particularly urgent and challenging. Here, we fabricated an enzyme-free ratiometric fluorescent detection system in combination with a hinge-like dual-channel 3D microfluidic paper analytical device (3D µPAD) for simultaneous visual detection of carbaryl and glyphosate. Blue-emission 1-naphthol (Em. 470 nm) was hydrolyzed from carbaryl, while yellow-emission 2,3-diaminophenazine (Em. 570 nm) was produced with the aid of Cu2+ for glyphosate sensing. Inner-filter effect between 1-naphthol or 2,3-diaminophenazine and green-emission carbon dots (Em. 510 nm) realized two ratiometric fluorescent detection systems. Remarkable color variation of green-blue for carbaryl (50.00-1100 µΜ) and yellow-green for glyphosate (5.00-600 µΜ) were observed on a dual-channel 3D µPAD without crosstalk. Their detection limits were 1.11 and 0.63 µΜ, respectively. The strategy realized simultaneous visual detection of carbaryl and glyphosate in food/herbal with excellent accuracy (spiked recoveries, 91.00-107.2%), high precision (RSD ≤ 8.43%), and superior selectivity.

White pepper-derived ratiometric carbon dots for highly selective detection and imaging of coenzyme A.

A new-style white pepper derived dual-emission carbon dots (CDs) with a quantum yield of 10.4% was designed and facile constructed with one-pot solvothermal method. The green emission (520 nm) had an efficient and special "turn-on" fluorescence sensing of coenzyme A (CoA) with the aid of Cu2+, while red emission (668 nm) barely changed and worked as reference. In the concentration range (0-150 µM), relative fluorescence intensity ratios (F520/F668) showed excellent linear correlation with concentrations of CoA, and detection limit was as low as 8.75 nm. Moreover, the strategy has been successfully applied for label-free detection of CoA in real pig liver samples with good recoveries (93.3-108.0%). Notably, the synthesized CDs had durable fluorescence, low cytotoxicity, and good biocompatibility for cellular imaging, which demonstrated wide and promising applicability for biosensing and bioimaging in the future.

Profiling of tyrosinase inhibitors in mango leaves for a sustainable agro-industry.

Although mango leaves are the main ingredients in some traditional Chinese medicine preparations and folk tea, they with considerable quantities are usually discarded as agricultural waste. Thus, to extend their potential, reverse ultrafiltration-HPLC-DAD-QTOF-MS/MS combining with key ion filtering strategy was proposed to efficiently fish and systematically identify tyrosinase inhibitors in ethyl acetate fraction of mango leaves, which has the highest total phenolic content (40.00 ± 0.84 mg GAE/g DW) and tyrosinase inhibition activity (IC50, 17.62 ± 1.26 µg/mL). Finally, 36 polyphenolic tyrosinase inhibitors were unambiguously characterized or tentatively identified, and three of them were found in mango leaves for the first time. Results suggested that the proposed strategy was powerful for effective identification of bioactive compounds in complex mixtures (e.g. food, agricultural and sideline products), and the findings would lay a foundation for potential applications of mango leaves in pharmaceutical, cosmetic, and food industrial fields.

Identification of minor lignans, alkaloids, and phenylpropanoid glycosides in Magnolia officinalis by HPLC‒DAD‒QTOF-MS/MS.

An effective strategy based on high-speed counter-current chromatography (HSCCC) knockout combination with HPLC-DAD-QTOF-MS/MS analysis were developed to identify minor lignans, alkaloids, and phenylpropanoid glycosides in M. officinalis. Petroleum ether/ethyl acetate/methanol/water (8:4:7:5, v/v/v/v) as solvent system was firstly selected to separate the crude extract of M. officinalis. Two major lignans, honokiol and magnolol were knocked out, and minor components were enriched. Then, five standards (honokiol, magnolol, magnocurarine, magnoflorine and acteoside) were used as examples to discuss their fragmentation patterns for structural identification. By comprehensive screening, sixteen lignans, nine alkaloids, six phenylpropanoid glycosides were unambiguously or tentatively identified by comparing their retention time, UV spectra, accurate mass and fragmentation patterns with standards or reported components. Eight of them, as far as was known, were discovered from M. officinalis for the first time. The proposed method might provide a model for the effective identification of minor components from complex herbs. Additionally, this study laid a foundation for the study of quality control, and clinical applications of M. officinalis.

Novel natural myricetin with AIE and ESIPT characteristics for selective detection and imaging of superoxide anions in vitro and in vivo.

A novel AIE probe with ESIPT characteristics, myricetin, has been easily purified from vine tea for reversible, selective and sensitive targeting of O2˙- in turn-on mode. Its AIE nanocrystals exhibit large Stokes shift, high photostability, excellent biocompatibility, and low cytotoxicity for endogenous O2˙- detection and imaging in vitro and in vivo.

Migration of mouse antibody-secreting hybridoma cells from blood to genital tract and its regulation by sex hormones are associated with the differential expression patterns of adhesion molecules and chemokines in the tract rather than in the antibody-secreting cells.

To understand better the molecular mechanisms of differential migration of antibody-secreting cells (ASCs) into mouse genital tracts, and regulation by sex hormones, surface markers, hormone receptors and adhesion molecules in mouse SG2 and PA4 hybridoma cells, respectively, secreting IgG2b and polymeric IgA antibody were detected by flow cytometry or RT-PCR. Semi-quantitative RT-PCR was also used for measuring mRNA expression of adhesion molecules and chemokines (VCAM-1, ICAM-1, P-selectin, JAM-1 and CXCL12) in genital tracts of various adult mouse groups. The mRNAs of androgen receptor, estrogen receptor beta and CXCR4 were expressed in the ASCs. Sex hormones had no effect on expression of these molecules in ASCs. Except for VCAM-1, mRNA of all examined genes was expressed in normal mouse genital tracts. The mean of relative amounts of ICAM-1 and CXCL12 mRNA in all examined organs of females were higher (2.1- and 1.9-fold) than those in males. After orchiectomy or ovariectomy, the expression of ICAM-1, CXCL12 and P-selectin mRNA in the examined organs increased, except JAM-1 in male and CXCL12 in female. Sex hormone treatment recovered the changes to normal levels of mRNA expression in many examined genital tissues. In combination with our previous work, preferential migration of ASCs into female genital tract and regulation of migration by sex hormones are associated with expression patterns of adhesion molecules and chemokines in genital tract rather than in ASCs.

Effects of testosterone undecanoate as a male contraceptive candidate on rat immunological features.

Testosterone undecanoate (TU) is under phase III clinical trial as a hormonal male contraceptive in China. Sex hormones can modulate the immune system. Female hormonal contraceptives may affect SIV/HIV-1 transmission. To evaluate the safety of TU and to understand whether long-term use of TU for a male contraceptive affects users' immunological features, adult male rats were treated for a 32-week TU-treated phase at the dose of 20 mg TU/kg body weight and a 24-week recovery phase. The reproductive and immunological parameters of 4-6 rats in each subgroup were examined at the stated time point. The mean sperm count and viability in the treated rats were significantly suppressed (p < 0.01). In the TU-treated group: the mean blood leukocyte and lymphocyte counts; the proliferation indexes of T cells from peripheral blood mononuclear cells (PBMC) and spleen; and, of B cells from spleen, as well as the mean counts of blood T, NK, and B cells decreased in comparison with those of control group. These decreases were not significant (p > 0.01). Similarly, the mean serum IgM, IgG, and IgA levels and complement activity in TU-treated rats were lower than those in control group (p > 0.01), and the changes in the antibody levels of the examined genital secretions were not significant (p > 0.01). The changes in the thickness of urethra epithelium, and in secretory component (SC) expression in genitals were not observed in the treated group. These results demonstrated that long-term supraphysiological TU injection did not obviously affect the examined rat immunological parameters.