Effect of whey protein isolate on the stability and antioxidant capacity of blueberry anthocyanins: A mechanistic and in vitro simulation study.

The processing stability and antioxidant capacity of blueberry anthocyanins (ANs) in the presence of whey protein isolate (WPI) were examined. WPI was found to enhance both the stability and antioxidant activity of ANs during processing and simulated in vitro digestion, especially at a concentration of 0.15 mg·mL-1. Fluorescence and ultraviolet-visible absorption spectroscopy showed that ANs were primarily stabilized by hydrophobic forces between WPI and malvidin-3-O-galactoside (M3G), the major anthocyanin monomer. Circular dichroism and Fourier-transform infrared spectroscopy confirmed that the structure of WPI changed and the microenvironments of certain amino acid residues were modulated by non-covalent binding to M3G; furthermore, fewer α-helices and more ß-sheets were formed. Molecular docking studies revealed that WPI, especially immunoglobulin (IgG), contributed the most to ANs stability via hydrogen bonds and hydrophobic forces according to molecular docking scores (-141.30 kcal/mol). These results provided an important fundamental basis for improving the stabilities of ANs in milk systems.

Identification of Cyanidin-3-arabinoside Extracted from Blueberry as a Selective Protein Tyrosine Phosphatase 1B Inhibitor.

Protein tyrosine phosphatase 1B (PTP1B) is an important target for type 2 diabetes. PTP1B inhibitors can reduce blood glucose levels by increasing insulin sensitivity. Anthocyanins often play a hypoglycemic effect, but the research about them have mainly focused on glucosidase. At present, the research about protein tyrosine phosphatase 1B (PTP1B) target is less, and the corresponding molecular mechanism is still unclear. Therefore, in this present study, anthocyanins isolated from blueberry were used to study the inhibitory activity on PTP1B. The isolated cyanidin-3-arabinoside (Cya-3-Ara) exhibited a better inhibitory activity with IC50 = 8.91 ± 0.63 µM, which was higher than the positive control (oleanolic acid, IC50 = 13.9 ± 1.01 µM), and the mechanism of PTP1B inhibition was reversible mixed pattern. The structure-activity relationship (SAR) between anthocyanins and PTP1B inhibition was investigated. The enzyme activity inhibition and molecular docking showed that anthocyanins had high selectivity for PTP1B inhibition. Further study showed that Cya-3-Ara could promote glycogen synthesis through ameliorating PTP1B-involved IRS-1/PI3K/Akt/GSK3ß pathways. Cya-3-Ara could also be regarded as a synergistic inhibitor (CI ≤ 0.54) of oleanolic acid to obtain a better inhibitory effect on PTP1B. Taken together, our study clearly illustrates the SAR between anthocyanins and PTP1B inhibition and the mechanism of Cya-3-Ara in the insulin signaling pathway.

Protective effects of bovine serum albumin on blueberry anthocyanins under illumination conditions and their mechanism analysis.

This study investigates the effects of bovine serum albumin (BSA) on blueberry anthocyanins and their interaction. Findings showed that BSA could protect blueberry anthocyanins against degradation and retain their antioxidant activity at an ideal concentration of 0.15 mg/mL under three deteriorating treatments: illumination, vitamin C + illumination, and sucrose + illumination. The fluorescence and UV absorption spectra showed that malvidin-3-o-galactoside (M3G), the major monomer in blueberry anthocyanins, led to a static quenching of BSA and the binding site of M3G to BSA was approximately one. Further, the interaction was a spontaneous process with electrostatic interactions being the main force. CD spectra and synchronous fluorescence spectra presented alterations in the secondary structure and microenvironment of Trp and Tyr residues of BSA, respectively, upon interaction with M3G. Finally, molecular docking analysis showed that M3G mainly bound the II and III domains of BSA by hydrogen bonds and electrostatic interaction. In conclusion, our study highlights the protective effects of BSA on the stability and anti-oxidant activity of blueberry anthocyanins and their interaction analysis.

A "Green" Homogenate Extraction Coupled with UHPLC-MS for the Rapid Determination of Diterpenoids in Croton Crassifolius.

Clerodane diterpenoids are the main bioactive constituents of Croton crassifolius and are proved to have multiple biological activities. However, quality control (QC) research on the constituents are rare. Thus, the major research purpose of the current study was to establish an efficient homogenate extraction (HGE) process combined with a sensitive and specific ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC⁻MS) technique together for the rapid extraction and determination of clerodane diterpenoids in C. crassifolius. All calibration curves showed good linearity (r > 0.9943) within the test ranges and the intra- and inter-day precisions and repeatability were all within required limits. This modified HGE⁻UHPLC⁻MS method only took 5 min to extract nine clerodane diterpenoids in C. crassifolius and another 12 min to quantify these components. The results indicated that the quantitative analysis based on UHPLC⁻MS was a feasible method for QC of clerodane diterpenoids in C. crassifolius, and the findings outlined in the current study also inferred the potential of the method in the QC of clerodane diterpenoids in other complex species of plants.