Structure and Functional Properties of Antioxidant Nanoemulsions Prepared with Tea Polyphenols and Soybean Protein Isolate.

In this study, tea polyphenols (TP) was added to a soy protein isolate (SPI) to prepare nanoemulsions by ultra-high pressure homogenization (UHPH). The nanoemulsions were characterized by a confocal laser scanning electron microscopy, infrared spectroscopy, dynamic rheometer and size-potential analyzer. The effects of TP on the hydrophobicity, emulsifiability, particle size, potential and antioxidant capacity of the prepared nanoemulsions were investigated. The properties of the nanoemulsions with different concentrations of TP were analyzed. The results indicated that ultra-high pressure homogenization treatment contributed to the formation of the SPI-TP complex that showed higher antioxidant activity. The nanoemulsions with good emulsifying properties and high DPPH scavenging ability at the concentration of TP ranged from 0.15-0.20g / mL. Furthermore, nanoemulsions prepared in this way also had a uniform particle size. Therefore, this nanoemulsions exhibited a good potential to act as an efficient emulsifier.

Determination of endogenous brassinosteroids using sequential magnetic solid phase extraction followed by in situ derivatization/desorption method coupled with liquid chromatography-tandem mass spectrometry.

In this study, a sequential magnetic solid phase extraction followed by in situ derivatization/desorption method was proposed for the fast, selective and sensitive determination of brassinosteroids (BRs) in plant tissues. Magnetic sorbent for quick, easy, cheap, effective, rugged and safe method (mQuEChERS) and polymer(4-vinylphenylboronic acid-co-ethylene glycol dimethacrylate) coated Fe3O4@SiO2 (p(4-VPBA-co-EGDMA) coated Fe3O4@SiO2) were prepared and characterized. Using them as sorbents, pigments and hydrophilic interferents were firstly removed from plant extract by mQuEChERS, and then endogenous BRs were selectively enriched by p(4-VPBA-co-EGDMA) coated Fe3O4@SiO2 through boronate affinity interaction. After loading BRs on p(4-VPBA-co-EGDMA) coated Fe3O4@SiO2, instead of directly eluting free BRs, the adsorbed BRs were released by adding 4-(N,N-dimethyamino)phenylboronic acid (4-DMAPBA) solution for in situ derivatizaiton/desorption of BRs based on a transesterification reaction between the boronate moieties of p(4-VPBA-co-EGDMA) coated Fe3O4@SiO2 and 4-DMAPBA, finally the resultant solution was submitted to LC-MS/MS for quantification. The whole procedure of the sequential MSPE could be accomplished within 1h, and the matrix effect to MS signal after the sample pretreatment was estimated to be in the range of 93.0-97.4%. The established method provided broad linear dynamics ranges (1.0-100.0pg/mL) with correlation coefficients (R) >0.9978, substantial sensitivity (limits of detection ranged from 0.27 to 1.29pg/mL), high reproducibility (intra-day and inter-day relative standard deviations (RSDs) less than 14.8%) and satisfactory accuracy (recoveries ranged from 74.0%-116.6%). Furthermore, endogenous BRs were successfully detected in one flower of Brassica napus L. (22.5-542.7pg/g fresh weight) and other plant tissues (13.7-289.8pg/g fresh weight).