The Inhibitory Effects of Yixing Black Tea Extracts on A-Glucosidase

Inhibition of α-glucosidase activity by curcumin loaded on ZnO@rGO nanocarrier for potential treatment of diabetes mellitus

Curcumin (Cur) is an acidic polyphenol with some effects on α-glucosidase (α-Glu), but Cur has disadvantages such as being a weak target, lacking passing the blood-brain barrier and having low bioavailability. To enhance the curative effect of Cur, the hybrid composed of ZnO nanoparticles decorated on rGO was used to load Cur (ZnO@rGO-Cur). The use of the multispectral method and enzyme inhibition kinetics analysis certify the inhibitory effect and interaction mechanism of ZnO@rGO-Cur with α-Glu. The static quenching of α-Glu with both Cur and ZnO@rGO-Cur is primarily driven by hydrogen bond and van der Waals interactions. The conformation-changing ability by binding to the neighbouring phenolic hydroxyl group of Cur increased their ability to alter the secondary structure of α-Glu, resulting in the inhibition of enzyme activity. The inhibition constant (Ki, Cur  > Kis,ZnO@rGO-Cur ) showed that the inhibition effect of ZnO@rGO-Cur on α-Glu was larger than that of Cur. The CCK-8 experiments proved that ZnO@rGO nanocomposites have good biocompatibility. These results suggest that the therapeutic potential of ZnO@rGO-Cur composite is an emerging nanocarrier platform for drug delivery systems for the potential treatment of diabetes mellitus.

Antibacterial, antifungal, antidiabetic, and antioxidant activities potential of Coleus aromaticus synthesized titanium dioxide nanoparticles

The nanoparticles based drug delivery and treatment related research has been increased significantly in the recent years. Hence, the antibacterial, antifungal, and antioxidant activity potential of pre synthesized and characterized Titanium dioxide nanoparticles (TiO₂ NPs) were investigated in this study through respective standard protocols. Interestingly, the obtained results revealed that TiO₂ NPs have concentration dependent antibacterial activity against bacterial pathogens such as E. coli, P.mirabilis, V. cholerae, P. aeruginosa, S. typhimurium, and S. aureus at 100 μg mL^-1 concentration. Furthermore, these TiO₂ NPs showed remarkable antifungal activity against aspergillosis causing fungal pathogens such as A. niger, A. fumigatus, A. nidulans, and A. flavus at 100 μg mL^-1 concentration. α-glucosidase. This TiO₂ NPs also effectively inhibit the α-amylase (17%) and α-Glucosidase (37%) enzyme activity at 100 μg mL^-1 dosage. The DPPH assay revealed that TiO₂ NPs effectively scavenge DPPH free radicals by up to 89% at 100 μg mL^-1 concentration, which was comparable to butylated hydroxytoluene (96%). These results suggest that the plant-based TiO₂ NPs have remarkable in-vitro antibacterial, antifungal, and antioxidant activity. These may be considered for additional in-vitro and in-vivo experiments to assess their potential biomedical applications.

The novel homologue of the human α-glucosidase inhibited by the non-germinated and germinated quinoa protein hydrolysates after in vitro gastrointestinal digestion

Quinoa (Chenopodium quinoa Willd) is a potential source of protein with ideal amino acid profiles which its bioactive compounds can be improved during germination and gastrointestinal digestion. The present investigation studies the impact of germination for 24 hr and simulated gastrointestinal digestion on α-glucosidase inhibitory activity of the quinoa protein and bioactive peptides against the novel homologue of human α-glucosidase, PersiAlpha-GL1. The sprouted quinoa after gastroduodenal digestion was the most effective α-glucosidase inhibitor showing 81.10% α-glucosidase inhibition at concentration 4 mg/ml with the half inhibition rate (IC₅₀ ) of 0.07 mg/ml. Based on the kinetic analysis, both the germinated and non-germinated samples before and after digestion were competitive-type inhibitors of α-glucosidase. Results of this study showed the improved α-glucosidase inhibitory activity of the quinoa bioactive peptides after germination and gastrointestinal digestion and highlighted the potential of metagenome-derived PersiAlpha-GL1 as a novel homologue of the human α-glucosidase for developing the future anti-diabetic drugs. PRACTICAL APPLICATIONS: This study aimed to evaluate the effect of germination and gastrointestinal digestion of the quinoa protein and bioactive peptides on α-glucosidase inhibitory activity against the novel PersiAlpha-GL1. Metagenomic data were used to identify the novel α-glucosidase structurally and functionally homologue of human intestinal. The results showed the highest inhibition on PersiAlpha-GL1 by a germinated quinoa after gastroduodenal digestion and confirmed the potential of PersiAlpha-GL1 to enhance the effectiveness of the anti-diabetic drugs for industrial application.

Screening natural product extracts for potential enzyme inhibitors: protocols, and the standardisation of the usage of blanks in α-amylase, α-glucosidase and lipase assays

BACKGROUND

Enzyme assays have widespread applications in drug discovery from plants to natural products. The appropriate use of blanks in enzyme assays is important for assay baseline-correction, and the correction of false signals associated with background matrix interferences. However, the blank-correction procedures reported in published literature are highly inconsistent. We investigated the influence of using different types of blanks on the final calculated activity/inhibition results for three enzymes of significance in diabetes and obesity; α-glucosidase, α-amylase, and lipase. This is the first study to examine how different blank-correcting methods affect enzyme assay results. Although assays targeting the above enzymes are common in the literature, there is a scarcity of detailed published protocols. Therefore, we have provided comprehensive, step-by-step protocols for α-glucosidase-, α-amylase- and lipase-inhibition assays that can be performed in 96-well format in a simple, fast, and resource-efficient manner with clear instructions for blank-correction and calculation of results.

RESULTS

In the three assays analysed here, using only a buffer blank underestimated the enzyme inhibitory potential of the test sample. In the absorbance-based α-glucosidase assay, enzyme inhibition was underestimated when a sample blank was omitted for the coloured plant extracts. Similarly, in the fluorescence-based α-amylase and lipase assays, enzyme inhibition was underestimated when a substrate blank was omitted. For all three assays, method six [Raw Data - (Substrate + Sample Blank)] enabled the correction of interferences due to the buffer, sample, and substrate without double-blanking, and eliminated the need to add substrate to each sample blank.

CONCLUSION

The choice of blanks and blank-correction methods contribute to the variability of assay results and the likelihood of underestimating the enzyme inhibitory potential of a test sample. This highlights the importance of standardising the use of blanks and the reporting of blank-correction procedures in published studies in order to ensure the accuracy and reproducibility of results, and avoid overlooked opportunities in drug discovery research due to inadvertent underestimation of enzyme inhibitory potential of test samples resulting from unsuitable blank-correction. Based on our assessments, we recommend method six [RD - (Su + SaB)] as a suitable method for blank-correction of raw data in enzyme assays.

Proanthocyanidin B2 attenuates postprandial blood glucose and its inhibitory effect on alpha-glucosidase: analysis by kinetics, fluorescence spectroscopy, atomic force microscopy and molecular docking

As a dimer of proanthocyanidin, proanthocyanidin B₂ (PB₂) was found to effectively attenuate postprandial blood glucose in mice after sucrose loading.

Analysis of Chemical Constituents Changing in Physical Process and Nutritional Components of Malus halliana Koehne Tea

This study aimed to establish a HPLC method for simultaneous determination of the changing of quercitrin, 3-hydroxyphloridzin, and phloridzin in physical process of M. halliana tea. Meanwhile, the nutritional compositions were determined, using anthrone-sulfuric acid colorimetry and direct titration determination of total sugar and reducing sugar, respectively, in order to provide theoretical basis for quality control and tea production. The results showed that the regression equations for quercitrin, 3-hydroxyphloridzin, and phloridzin were linear in the range of 0.0972–12.15 μg (r=0.999 8), 0.0932~11.65 μg (r=0.999 1), and 0.9~112.5 μg (r=0.999 6), respectively. The average recoveries ranged from 98.19% to 99.35%. The contents of crude protein and the crude fat were measured by spectrophotometric detection and soxhlet extraction detection, respectively. The contents of total sugar, reducing sugar, the fat, and protein were 6.8 g/100 g, 8.5 mg/100 g, 2.399 g/100 g, and 4.362 g/100 g, respectively, in M. halliana tea.