High-throughput screening and investigation of the inhibitory mechanism of α-glucosidase inhibitors in teas using an affinity selection-mass spectrometry method

Three-dimensional ordered macro-microporous ZIF-8-α-Glu microreactors for α-glucosidase inhibitors screening from green tea

Due to the larger pore structure, the macroporous material can be used as the immobilized carrier to not only increase the enzyme loading capacity, but also facilitate the transfer of reactants and substrates. Based on this, a three-dimensional ordered macro-microporous ZIF-8 (SOM-ZIF-8) was prepared using three-dimensional ordered stacked polystyrene spheres as the hard template. The morphology and structure of SOM-ZIF-8 were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FT-IR) and so on. The macropore size of SOM-ZIF-8 was tested to be about 100 nm by N2 adsorption-desorption isotherms. Then α-glucosidase (α-Glu) was encapsulated into the macropore of SOM-ZIF-8 by physical adsorption method to prepare the immobilized enzyme microreactor. Under the optimal immobilization conditions, the loading capacity of SOM-ZIF-8 to α-Glu reached 113.42 μg/mg. Due to the encapsulation in the three-dimensional macropores, the conformational changes of the enzyme are restricted, endowing the immobilized enzyme with excellent acid and alkali resistance, a long storage time, and almost unchanged relative activity after 7 cycles. Finally, the SOM-ZIF-8-α-Glu microreactors combined with high performance liquid chromatography (HPLC) were applied to offline screen α-Glu inhibitory active components from tea extract. Several components including gallocatechin, catechin and epicatechin gallate were successfully screened out, which verified the application feasibility of the immobilized enzyme microreactor.

A comparative study on the bioactivities and chemical compositions of Dancong summer tea and Anhua dark tea: Excavation of glycolipid-lowering functional factors

Drinking tea is beneficial to reduce the incidence of obesity. Unlike Fuzhuan brick tea (DT, a typical dark tea) widely reported to have good glycolipid-lowering activity (GLA), there is little information on GLA of Dancong summer tea (OT, a typical oolong tea). A comparative study on GLA and chemical compositions of OT and DT was systematically conducted. The results showed that OT had advantages in high content of polyphenols, leading to its better GLA including glycolipid digestion enzyme inhibitory activity and cholesterol micellar solubility inhibition activity than DT's. A total of 21 compounds mainly including catechins, flavonoids, phenolic acids and phenylpropanoids were screened as the key differentially active micromolecules (KDAM) by UPLC-QTOF-MS/MS-based untargeted metabolomic analysis combined with multivariate analysis, which resulted in the difference of GLA between OT and DT. Moreover, the high affinity capacity and interaction mode between KDAM with α-glucosidase/α-amylase/pancreatic lipase/cholesterol esterase were validated by molecular docking. Although the accumulation of polyphenols makes OT has a poor flavor as a beverage, our research demonstrated that OT with high content of polyphenols could be used in functional foods to facilitate the prevention of obesity.

Chemical profile and in-vitro bioactivities of three types of yellow teas processed from different tenderness of young shoots of Huoshanjinjizhong (Camellia sinensis var. sinensis)

In the present study, bud yellow tea (BYT), small-leaf yellow tea (SYT) and large-leaf yellow tea (LYT) were produced from the same local "population" variety Huoshanjinjizhong (Camellia sinensis var. sinensis), and the effects of raw material tenderness on the chemical profile and bioactivities of these teas were investigated. The results showed that 11 crucial compounds were screened by headspace solid-phase microextraction-gas chromatography-mass spectrometry from 64 volatiles in these yellow teas, among which the heterocyclic compounds showed the greatest variations. In addition, 43 key compounds including organic acids, flavan-3-ols, amino acids, saccharides, glycosides and other compounds were screened by liquid chromatography-mass spectrometry from 1781 non-volatile compounds. BYT showed the best α-glucosidase inhibitory activity and antioxidant capacity among the selected yellow teas, which might be contributed by the higher content of galloylated catechins. These findings provided a better understanding of the chemical profile and bioactivities of yellow teas.

Hypoglycaemic activity of the anthocyanin enriched fraction of Lycium ruthenicum Murr. Fruits and its ingredient identification via UPLC-triple-TOF-MS/MS

Lycium ruthenicum Murr. is mainly distributed in the northwest region of China and its berries are rich in anthocyanin. This study evaluated the hypoglycaemic activity of the anthocyanin-enriched fraction (AEF) of L. ruthenicum Murr. on α-glucosidase in vivo and in vitro. Overall, 10 anthocyanins were identified via UPLC-Triple-TOF-MS/MS. The AEF exhibited strong inhibitory activity against α-glucosidase, with an IC50 value of 4.468 mg/mL. It behaved as a reversible, mixed-type inhibitor. Molecular docking and dynamic results indicated that the compounds in AEF interacted with enzymes primarily through van der Waals and hydrogen bond and the complex system was stable. The postprandial blood glucose and area under the curve of diabetic mice was significantly decreased by AEF in the carbohydrate tolerance experiments. The results indicate that the AEF from L. ruthenicum Murr. berries could be as a promising food supplement for managing blood sugar levels in patients with diabetes mellitus.

Effect of fermentation temperature on the non-volatile components and in vitro hypoglycemic activity of Jinxuan black tea

Fermentation significantly influences the chemical composition of black tea, yet the effects of different fermentation temperatures on non-volatile components and their in vitro hypoglycemic activity are insufficiently studied. This research investigates how varying temperatures (20, 25, and 30°C) affect the bioactive profile and the inhibitory activity of Jinxuan black tea against α-glucosidase and α-amylase. Our results show that lower fermentation temperatures (20°C) lead to elevated levels of key bioactive compounds, including tea polyphenols (9.24%), soluble sugars (8.24%), thearubigins (7.17%), and theasinesin A (0.15%). These compounds correlate strongly with enhanced α-glucosidase inhibition (R = 0.76-0.97). Non-targeted metabolomic analysis revealed that 36 differential metabolites, including catechins, exhibited altered levels with increasing fermentation temperature. Notably, tea fermented at 20°C exhibited superior hypoglycemic activity, with α-glucosidase inhibition (IC50 = 14.00 ± 1.00 μg/ml) significantly outperforming α-amylase inhibition (IC50 = 2.48 ± 0.28 mg/ml). The findings of this research underscore the importance of fermentation temperature in optimizing the bioactive profile of black tea. It is proposed that recommendations for future processing or formulation should emphasize the use of lower fermentation temperatures, aimed at augmenting the health benefits linked to higher polyphenol content and stronger hypoglycemic activity.

Screening and identification of peptidyl arginine deiminase 4 inhibitors from herbal plants extracts and purified natural products by a trypsin assisted sensitive immunoassay based on streptavidin magnetic beads

Peptidyl arginine deiminase 4 (PAD4) plays a critical role in many autoimmune diseases including rheumatoid arthritis. Herein, a trypsin assisted highly immunoassay method was established to determine PAD4 activity and screen potent inhibitors from herbal plants extracts and purified natural products. The method was applied to determine endogenous PAD4 activity in both cell and tissue lysates, as well as the inhibitory effects of 20 herbal plants and 50 purified natural products. The Cinnamomi ramulus extract showed strongest inhibitory potency with IC50 value lower than 5 μg/mL. Meanwhile, pyrroloquinoline quinone (PQQ), widely used as a dietary supplement, was discovered as a promising PAD4 inhibitor with an IC50 value lower than 4 μM. The inhibition kinetic analysis, drug affinity response target stability (DARTS) and molecular docking were performed to confirm the interaction between PQQ and PAD4. This method has great potential for researchers to monitor activities and discover potential inhibitors of PAD4.

Investigations of the highly efficient processing technique, chemical constituents, and anti-inflammatory effect of N-ethyl-2-pyrrolidinone-substituted flavan-3-ol (EPSF)-enriched white tea

N-Ethyl-2-pyrrolidinone-substituted flavan-3-ols (EPSFs) are a newly discovered compound class in tea with various bioactivities. This study aimed to develop a novel processing technique to enhance EPSF contents in white tea efficiently. Using optimal processing parameters of 125 °C and 30 min in a high-temperature sterilizing oven, total EPSF content significantly increased by 1.42-18.80-fold to 1.57-6.22 mg/g without impacting sensory characteristics. Metabolomics analysis revealed elevated levels of nucleosides, nucleotides, bases, theaflavins, flavonol aglycones, EPSFs, and most flavone-C-glycosides, as well as decreased levels of amino acids, procyanidins, theasinensins, several flavanols, and flavonol-O-glycosides after EPSF-enrichment treatment. Furthermore, the EPSF-enriched white tea exhibited notable anti-inflammatory effects, mitigating xylene-induced ear edema in mice and carrageenan-induced paw edema and cotton ball-induced granulomas in rats. This study developed a new processing technique for highly efficient enhancement of EPSFs in white tea and demonstrated that EPSF-enriched white tea has a potential to serve as effective anti-inflammatory dietary supplement.

Rapid screening of the novel bioactive peptides with notable α-glucosidase inhibitory activity by UF-LC-MS/MS combined with three-AI-tool from black beans

This work aimed to propose a rapid method to screen the bioactive peptides with anti-α-glucosidase activity instead of traditional multiple laborious purification and identification procedures. 242 peptides binding to α-glycosidase were quickly screened and identified by bio-affinity ultrafiltration combined with LC-MS/MS from the double enzymatic hydrolysate of black beans. Top three peptides with notable anti-α-glucosidase activity, NNNPFKF, RADLPGVK and FLKEAFGV were further rapidly screened and ranked by the three artificial intelligence tools (three-AI-tool) BIOPEP database, PeptideRanker and molecular docking from the 242 peptides. Their IC50 values were in order as 4.20 ± 0.11 mg/mL, 2.83 ± 0.03 mg/mL, 1.32 ± 0.09 mg/mL, which was opposite to AI ranking, for the hydrophobicity index of the peptides was not included in the screening criteria. According to the kinetics, FT-IR, CD and ITC analyses, the binding of the three peptides to α-glucosidase is a spontaneous and irreversible endothermic reaction that results from hydrogen bonds and hydrophobic interactions, which mainly changes the α-helix structure of α-glucosidase. The peptide-activity can be evaluated vividly by AFM in vitro. In vivo, the screened FLKEAFGV and RADLPGVK can lower blood sugar levels as effectively as acarbose, they are expected to be an alternative to synthetic drugs for the treatment of Type 2 diabetes.