•Improved stability of gliadin nanoparticles by OVA-Gemini-C12 complex.•Cooperative nature of OVA and Gemini-C12 interaction with gliadin.•Critical modulating effect of Gemini-C12 for stabilization of gliadin.In this work, gliadin nanoparticles were fabricated by liquid antisolvent precipitation (LAS) method using a synergistic combination of thermally denatured ovalbumin (OVA) with cosurfactant gemini dodecyl O-glucoside (Gemini-C12) as stabilizers. The interaction between OVA and Gemini-C12 was characterized by surface tension, fluorescence spectroscopy, isothermal titration calorimetry, and circular dichroism analysis, respectively. The relationship between the properties of gliadin nanoparticles and Gemini-C12 concentration was interpreted on the basis of OVA-Gemini-C12 interaction. When the concentration below critical micelle concentration (CMC), Gemini-C12 could decrease the interfacial tension and enhance the adsorption strength of OVA on particle surface, thereby increasing the nucleation rate and giving gliadin nanoparticles with smaller size. Besides, the monomeric cosurfactant could plug the vacancies left by OVA at solid-liquid interface and therefore prohibit the aggregation and agglomeration of gliadin nanoparticles during storage and freeze-drying. Above CMC, free micelles were formed in the bulk and the surfactant molecules tended to reside in micelles rather than be adsorbed at the solid-liquid interface, which compromised the protective effect of cosurfactant and resulted in gliadin nanoparticles with larger size and lower storage stability and redispersibility.Download high-res image (160KB)Download full-size image

•Extraction kinetics of typical ingredients in feature white tea.•Structure transformation between epicatechins and trans-catechins.•Peleg's modeling of extraction kinetics and condition optimization.In this work extraction kinetics of typical ingredients in representative white teas was investigated. Aqueous extraction of 4 epicatechins (EGC, EC, EGCG, ECG), 4 trans-catechins (GC, C, GCG, CG), gallic acid (GA) and caffeine at 65 °C, 75 °C, 85 °C, 95 °C respectively from Fuding Silver Needle (FSN), Fuding White Peony (FWP), Zhenghe Silver Needle (ZSN) and Zhenghe White Peony (ZWP) was examined. The total catechins, gallic acid, caffeine, EGCG, epicatechins, trans-catechins were compared in terms of rate, peak value, peak time and the extraction kinetics at different temperatures. It is exhibited that the contents of 8 catechins in ZWP, ZSN and FSN follow the order of EGCG > ECG > GC > EGC > GCG > CG > EC > C, and that in FWP is EGCG > ECG > EGC > GC > EC > GCG > CG > C. Structural transformation from epicatechins to trans-catechins and dissociation of gallic acid were observed during extraction by data analysis. Extraction kinetics over 240 min period were successfully modeled using Peleg's model with low MSR (0–2.232) and high R2 adj (0.903–0.999). Optimal extraction conditions (FSN(43.3 min, 95 °C); FWP(43.3 min, 95 °C); ZSN(53.8 min, 95 °C); ZWP(41.5 min, 95 °C)) were suggested by Peleg's model. As a result, this study will facilitate quality control of white tea during processing.

•Integrated use of spectroscopic and computational methods for investigation.•Established reliability of chemical shift of phenolic hydroxyl hydrogen.•Structure profiling with hydroxyl hydrogen chemical shift fingerprint.Proton NMR signals of the phenolic hydroxyl groups of the substituted catechins were successfully collected. The identities of these signals were elucidated and confirmed by a combination of computational and experimental investigations including GIAO-B3LYP NMR chemical shift calculation, kinetic analysis of acylation, and NOESY correlation. Furthermore, the reliability of chemical shifts of hydrogens of phenolic hydroxyl groups was confirmed by evaluation of the influence of acidic, basic and water residues. Finally, the chemical shift profiles of phenolic hydroxyl groups were developed for instant structural recognition. This study demonstrated the feasibility of application of chemical shifts of hydrogens of phenolic hydroxyl groups as fingerprint for structural determination and the concept could be extended to other polyphenols.

•Superb stability and redispersibility of the nanogel by Maillard modification.•Notable improvement of bioavailability of curcumin by the nanogel carrier.•Detailed mechanistic speculation by comparison with the nanoparticle.In this work, ovalbumin-dextran nanogels were fabricated via the Maillard reaction followed by a heat-gelation process and their potential to improve curcumin bioavailability was investigated using an in vitro gastrointestinal tract. The result of electrophoresis, conjugation efficiency and yield, and far-UV circular dichroism verified the covalent attachment of dextran to ovalbumin by the Maillard reaction. The conjugates were then heated at the isoelectric point of ovalbumin to give stable nanogels. The transmission electron microscopy observation suggested that nanogels displayed a spherical structure. Curcumin was loaded into nanogels by a pH-driven method and the incorporation of curcumin affected the morphology of nanogels marginally. The transformation of curcumin in nanogels was significantly higher than that in ovalbumin nanoparticle. On the other hand, the bioaccessibility was similar for curcumin in nanogels and nanoparticle. The ovalbumin-dextran nanogels hold the potential as delivery systems for curcumin to fortify functional foods and beverages.

•Integrated use of biochemical and visual methods for investigation.•Morphology of erythrocytes unveiled a sensitive indicator for oxidative stress.•Excellent protective effects of the novel antioxidant on human erythrocytes.Notable protective effect of the novel galloyl phytosterol antioxidant on human erythrocytes was disclosed in this study. 2,2′-Azo-bis (2-amidinopropane) hydrochloride (AAPH) induced haemolysis of erythrocytes, and depletion of cellular glutathione were effectively inhibited by the galloyl phytosterol antioxidant. It was revealed that the level of glutathione was a more sensitive indicator than haemolysis for cellular oxidative stress. The morphology of erythrocytes obtained through laser scanning confocal microscopy (LSCM) imaging provided structural details for haemolysis and glutathione investigation and was more sensitive than the level of glutathione. The liposome model exhibited that the novel antioxidant preferred to anchor in the membrane and had better performance for membrane protection than gallic acid. The strategy of integrated use of biochemical and visual methods developed in this study is valuable for investigation on mechanistic behaviours of antioxidants.

•Targeted acylation of individual hydroxyl of (+)-catechin.•Establishment of reactivity profile of all the hydroxyl groups in (+)-catechin.•Establishment of profile of radical scavenging activity of all the hydroxyls.•Detailed mechanistic rationalization of origin of radical scavenging activity.The reactivity profile of all the hydroxyl groups in (+)-catechin towards acylation and their respective contribution to radical scavenging activity were systematically explored in this work. Selective acylation of the hydroxyls on different rings was carried out employing either a basic or acidic activation strategy. Monoacylation of B ring was achieved effectively with the aid of dimethyltin dichloride. Monoacylation of A ring was accomplished by sequential protection and deprotection of B and C rings. Based on specific acylation of all the individual hydroxyls of (+)-catechins, the structure radical scavenging activity relationship of each hydroxyl of (+)-catechin was established. It was demonstrated that the vicinal phenolic hydroxyls on B ring played the most important role in the ABTS radical scavenging activity and those on A and C rings made a much smaller contribution. This study has laid solid groundwork for further modification of the catechins and improvement of their properties.

•Anionic absorption by electrostatic decoration of Gemini surfactant micelles.•Improved capability to inhibit degradation of trianionic curcumin.•Detailed mechanism speculation by multiple approaches.Improved capability to inhibit degradation of trianionic curcumin has been realized in this study. The interaction between trianionic curcumin (Cur3−) and gemini dodecyl or tetradecyl O-glucoside micelles, tetradecyltrimethylammonium chloride (TTAC) or hexadecyltrimethylammonium bromide (CTAB) micelles as well as gemini alkyl O-glucosides (AGs)/alkyl trimethyl ammonium halides mixed micelles have been characterized. It is demonstrated that Cur3− cannot be incorporated into gemini AGs micelles since the lack of electrostatic attraction and degraded as rapidly as in aqueous phase. Cur3− tend to reside at palisade layer − water interface of TTAC or CTAB micelles due to the strong electrostatic interaction while moderate electrostatic interaction allows Cur3− to locate more deeply in the palisade layer of mixed micelles. Additionally, mixed micelles tend to form a more compact and hydrophobic palisade layer than pure TTAC and CTAB ones. These factors bring about enhanced fluorescence intensity and blue − shift of emission maxima, improved fluorescence anisotropy and quantum yield, as well as reduced decay rate of Cur3− in mixed micelles than in pure TTAC and CTAB ones.

•Simultaneous preparation of naturally rare EGC and EC.•Separation of the four catechins by HSCCC under normal and reversed phase modes.•Cooperative employment of tannase biotransformation and HSCCC separation.Simultaneous preparation of naturally rare catechins, EGC and EC, has been realized by tannase-mediated biotransformation combining high speed counter current chromatography. In addition, simultaneous preparation of the four catechins, EGCG, ECG, EGC, and EC in green tea extract has also been achieved by HSCCC under the normal phase and the reversed phase modes. The identity of the catechins was determined by HPLC-DAD-ESI-MS and quantification of the catechins was performed by HPLC-DAD. In a typical HSCCC separation, 27.2 mg 98.8% EGCG, 14.1 mg 94.7% EGC, and 9.3 mg 97.5% EC were obtained. This new method is efficient, time-saving and valuable for biological studies.

•Addressing the issue of colour fluctuation of anthocyanins.•Novel strategy employing surfactant micellation for buffering colour fluctuation.•Unveiling excellent colour buffering activity of SDS for anthocyanins.•Colorimetric and spectroscopic analysis of excellent colour buffering activity of SDS.Anthocyanins are intriguing natural pigments with beneficial bioactivities and their colour is extremely susceptible to acidity variation. Minimisation of colour fluctuation is essential to maintain quality consistency in food industry. A new strategy employing surfactants to mimic encapsulation was attempted with typical anionic, cationic and nonionic surfactants and proved effective although the traditional copigmentation method was inactive. The exceptional colour fluctuation buffering effect of anionic surfactants especially sodium dodecyl sulphate (SDS) was revealed and then carefully analysed by colorimetric and spectroscopic methods. The outstanding activity of SDS presumably resulted from effective shielding of anthocyanins from external acidity through strong interaction with the positively charged flavylium cations owing to its anionic nature. These results suggest SDS is a valuable additive for buffering colour fluctuation of anthocyanins. The strategy of surfactant will be useful for buffering colour fluctuation of natural colourants.

Surfactants have long been underestimated in synthetic organic chemistry despite their great potential in promoting solubility, reactivity and selectivity in metal-mediated cross-couplings. In this study the strategy of surfactant promotion was exemplified in copper-catalyzed N-arylation of indoles in water. The different effects of surfactants during the coupling reaction were first explored. The superior promoting effect of the natural zwitterionic surfactant, betaine, was found and attributed to the capability of the formed complex to stabilize the copper intermediate in the catalytic transformation and facilitate transportation of the reactants. The concept of surfactant promotion through complexation is valuable in metal-mediated cross-couplings. This method also exhibited good recycling ability. This study will greatly facilitate exploration of surfactant promotion in metal-mediated cross-couplings.

A novel efficient synthesis of ginkgolic acid (13:0) from abundant 2,6-dihydroxybenzoic acid was successfully developed through a state-of-the-art palladium-catalyzed cross-coupling reaction and catalytic hydrogenation with an overall yield of 34% in five steps. The identity of the synthesized ginkgolic acid (13:0) was confirmed by nuclear magnetic resonance, mass spectrometry, infrared, and high-performance liquid chromatography. The reaction sequence of this method can be readily extended to the synthesis of other ginkgolic acids. The synthesized ginkgolic acid (13:0) exhibited promising anti-tyrosinase activity (IC50 = 2.8 mg/mL) that was not correlated to antioxidant activity as probed by 1,1-diphenyl-2-picrylhydrazyl, 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), ferric reducing ability of plasma, and oxygen radical absorbance capacity assays. The synthetic strategy developed in this work will significantly facilitate biological studies of ginkgolic acids that have great potential applications in food and pharmaceuticals.

A highly sensitive method for quantification of phytosterols based on HPLC has been developed by derivatization with the benzoyl chromophore. Introduction of the chromophore, benzoyl group, to phytosterols via simple and inexpensive derivatization greatly improved the UV response at 254 nm. Quantification of phytosterols was effectively performed by HPLC analysis with methyl benzoate as the internal standard after derivatization. This new method demonstrated outstanding yield of recovery (>95%) and excellent sensitivity (ng level) and was applicable for sterols from either plant or animal sources. This method is generally useful in phytosterol studies.Highlights► Highly sensitive quantification of phytosterols with routine UV detector has been achieved. ► Derivatization was performed by inexpensive reagents and simple operation. ► Inexpensive internal standard method makes this method robust and practical.

A novel type of highly effective gemini alkyl glucosides has been rationally designed and synthesized. The gemini surfactants have been readily prepared by glycosylation of the gemini alkyl chains that are synthesized with regioselective ring-opening of ethylene glycol epoxides by the alkyl alcohols. The new gemini alkyl glucosides exhibit significantly better surface activity than the known results. Then rheological, DLS, and TEM studies have revealed the intriguing self-assembly behavior of the novel gemini surfactants. This study has proved the effectiveness of the design of gemini alkyl glucosides which is modular, extendable, and synthetically simple. The new gemini surfactants have great potential as nano carriers in drug and gene delivery.

A fluorescent-labeled jasmonate was rationally designed based on examination of the model of interaction between the jasmonate and its receptor. An efficient synthetic route has been developed for this molecule. The biological activity of this fluorescent probe was retained which was similar to that of the methyl jasmonate as examined by root growth inhibition bioassay. This fluorescent probe will greatly facilitate biological studies of jasmonates through fluorescent imaging.

•Gemini surfactant-based vesicles with high loading capacity for catechin laurate.•Regulation effects of catechin laurate on vesicle bilayer fluidity.•Notable inhibitory effect of vesicle-loaded catechin laurate on liposome oxidation.In this work, gemini dodecyl O-glucoside-based vesicles were successfully developed employing (+)-catechin (C) and (−)-epigallocatechin (EGC) laurate as model compounds. Results revealed that vesicles displayed high loading capacity for both C and EGC laurate and the incorporation of C or EGC laurate were confirmed by dynamic light scattering, transmission electron microscope, Fourier-transform infrared spectra, and differential scanning calorimetry analyses. C and EGC laurate stiffened the vesicle bilayer at low concentrations but created a remarkable increase in the membrane fluidity afterward. Vesicles readily underwent aggregation under thermal treatment and osmotic stress. The thermal stability of C and EGC laurate were significantly improved by vesicle encapsulation. Compared with C and EGC, encapsulated C and EGC laurate exhibited lower 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radical-scavenging activity due to the shielding effect of vesicles but higher lipid-oxidation inhibitory ability because they preferentially concentrated in the liposome membrane.