A new functionality study of vanillin as the inhibitor for α-glucosidase and its inhibition kinetic mechanism

Inhibitory activities and mechanisms of free and bound phenolics on α-glucosidase in fresh fruits of Phyllanthus emblica Linn. using spectroscopy and molecular docking

Phyllanthus emblica Linn. (PE) fresh fruits contain high concentrations of polyphenolics, of which free and bound phenolics are rich in biological activities. In this study, the inhibitory activity and mechanism of PEFP and PEBP on α-glucosidase (α-GLU) were investigated using spectroscopic techniques, kinetic analysis, and molecular docking. The results showed that 13 PEFP and 12 PEBP were identified by UPLC-MS/MS analysis, and Bis-HHDP-hexose and castalagin (vesgalagin) were found for the first time in PE fresh fruits. Kinetic analysis of enzyme inhibition showed that a mixture of free and bound phenolics inhibited α-GLU, and the effect of the conformational relationship of PEFP and PEBP with α-GLU on hypoglycemia was further explored by fluorescence quenching, circular dichroism (CD) spectroscopy, and molecular docking analysis. The findings demonstrated the inhibitory activity and mechanism of free and bound phenolics on α-GLU and provided a theoretical basis for PE polyphenolics as α-GLU inhibitors for hypoglycemia.

Screening of α-Glucosidase Inhibitors in Cichorium glandulosum Boiss. et Huet Extracts and Study of Interaction Mechanisms

Cichorium glandulosum Boiss. et Huet (CGB) extract has an α-glucosidase inhibitory effect (IC50 = 59.34 ± 0.07 μg/mL, positive control drug acarbose IC50 = 126.1 ± 0.02 μg/mL), but the precise enzyme inhibitors implicated in this process are not known. The screening of α-glucosidase inhibitors in CGB extracts was conducted by bioaffinity ultrafiltration, and six potential inhibitors (quercetin, lactucin, 3-O-methylquercetin, hyperoside, lactucopicrin, and isochlorogenic acid B) were screened as the precise inhibitors. The binding rate calculations and evaluation of enzyme inhibitory effects showed that lactucin and lactucopicrin exhibited the greatest inhibitory activities. Next, the inhibiting effects of the active components of CGB, lactucin and lactucopicrin, on α-glucosidase and their mechanisms were investigated through α-glucosidase activity assay, enzyme kinetics, multispectral analysis, and molecular docking simulation. The findings demonstrated that lactucin (IC50 = 52.76 ± 0.21 μM) and lactucopicrin (IC50 = 17.71 ± 0.64 μM) exhibited more inhibitory effects on α-glucosidase in comparison to acarbose (positive drug, IC50 = 195.2 ± 0.30 μM). Enzyme kinetic research revealed that lactucin inhibits α-glucosidase through a noncompetitive inhibition mechanism, while lactucopicrin inhibits it through a competitive inhibition mechanism. The fluorescence results suggested that lactucin and lactucopicrin effectively reduce the fluorescence of α-glucosidase by creating lactucin-α-glucosidase and lactucopicrin-α-glucosidase complexes through static quenching. Furthermore, the circular dichroism (CD) and Fourier transform infrared spectroscopy (FT-IR) analyses revealed that the interaction between lactucin or lactucopicrin and α-glucosidase resulted in a modification of the α-glucosidase's conformation. The findings from molecular docking and molecular dynamics simulations offer further confirmation that lactucopicrin has a robust binding affinity for certain residues located within the active cavity of α-glucosidase. Furthermore, it has a greater affinity for α-glucosidase compared to lactucin. The results validate the suppressive impact of lactucin and lactucopicrin on α-glucosidase and elucidate their underlying processes. Additionally, they serve as a foundation for the structural alteration of sesquiterpene derived from CGB, with the intention of using it for the management of diabetic mellitus.

Impact of the Post-Harvest Period on the Chemical and Sensorial Properties of planifolia and pompona Vanillas

Vanilla production in Guadeloupe is expanding. The main species grown is Vanilla planifolia, but other species such as Vanilla pompona are also present and required by industries. To upgrade the value of vanilla production on this Caribbean Island, this study was performed to evaluate the aromatic specifies of these vanilla species according to the length of the post-harvest period (2 months and 9 months). For this purpose, Vanilla planifolia and Vanilla pompona were compared through scald and scarification transformation processes, as well as two different refining times (T1 and T2). For chemical characterization, 0.1 g of vanilla bean seeds was used for SMPE/GC-MS measurements, while 0.05 g of vanilla samples was subjected to infusion in milk (0.15%) for sensory evaluation. The latter involved generation of terms of aroma through olfaction and gustation sessions. The chemical results showed a significant difference between the two species, where vanillin was mostly present in Vanilla planifolia, unlike Vanilla pompona, where it was mainly rich in 4-methoxybenzyl alcohol. Interestingly, the second refining time was characterized by the appearance of two major components, 1,3-octadien and acetic acid. For sensory analysis, all the vanillas exhibited a high diversity of aromas including "sweet", "gourmand", "spicy" flavors and so on. The application of factorial correspondence analysis (FAC) as well as the agglomerative hierarchical clustering (AHC) showed differences between the vanilla samples according to both the species and refining time. The combination of these analyses makes it possible to establish a chemical and organoleptic profile of vanillas. Varietal and processing factors both have a major impact on the aroma profile of vanillas.

Inhibitory mechanism of chrysin and diosmetin to α-glucosidase: insights from kinetics, multispectroscopy and molecular docking investigations

Inhibition of α-glucosidase activity is a promising method to prevent postprandial hyperglycemia. The inhibitory effect and interaction of chrysin and diosmetin on α-glucosidase were studied in this study. The results of inhibition kinetics showed that chrysin and diosmetin reversibly inhibited α-glucosidase activity with IC50 value of 26.445 ± 1.406 μmol L-1 and 18.380 ± 1.264 μmol L-1, respectively. Further research revealed that chrysin exhibited a mixed-type inhibitory pattern against α-glucosidase, while diosmetin was noncompetitive inhibitory with Ki value of (2.6 ± 0.04) ×10-4 mol L-1. Fluorescence spectroscopy showed that both chrysin and diosmetin could quench the intrinsic fluorescence of α-glucosidase, the maximum emission wavelength of tyrosine (Tyr) and tryptophan (Trp) were not moved by chrysin, but red shifted by diosmetin. UV-Vis, fourier transform infrared spectroscopy (FT-IR) and circular dichroism (CD) measurements showed that the secondary structure and microenvironment of α-glucosidase were changed by chrysin and diosmetin. Further analysis of molecular docking showed that chrysin and diosmetin could bind with α-glucosidase and might cause the decrease of α-glucosidase activity. The results of molecular dynamics (MD) simulation showed that the stability of chrysin (or diosmetin)-α-glucosidase complex system was changed during binding process. In conclusion, chrysin and diosmetin are good α-glucosidase inhibitors.Communicated by Ramaswamy H. Sarma.

Inhibitory Mechanism of Quercimeritrin as a Novel α-Glucosidase Selective Inhibitor

In this study, 12 flavonoid glycosides were selected based on virtual screening and the literature, and Quercimeritrin was selected as the best selective inhibitor of α-glucosidase through in vitro enzyme activity inhibition experiments. Its IC50 value for α-glucosidase was 79.88 µM, and its IC50 value for α-amylase >250 µM. As such, it could be used as a new selective inhibitor of α-glucosidase. The selective inhibition mechanism of Quercimeritrin on the two starch-digesting enzymes was further explored, and it was confirmed that Quercimeritrin had a strong binding affinity for α-glucosidase and occupied the binding pocket of α-glucosidase through non-covalent binding. Subsequently, animal experiments demonstrated that Quercimeritrin can effectively control postprandial blood glucose in vivo, with the same inhibitory effect as acarbose but without side effects. Our results, therefore, provide insights into how flavone aglycones can be used to effectively control the rate of digestion to improve postprandial blood glucose levels.

Effective Therapeutic Verification of Crocin I, Geniposide, and Gardenia (Gardenia jasminoides Ellis) on Type 2 Diabetes Mellitus In Vivo and In Vitro

For many centuries, Gardenia (Gardenia jasminoides Ellis) was highly valued as a food homologous Chinese herbal medicine with various bioactive compounds, including crocin I and geniposide. However, the functional mechanism underlying the hypoglycemic effect of gardenia is absent in the literature. To evaluate the effect of gardenia and its different extracts on type 2 diabetes mellitus (T2DM) in in vivo and in vitro experiments, the dried gardenia powder was extracted using 60% ethanol and eluted at different ethanol concentrations to obtain the corresponding purified fragments. After that, the active chemical compositions of the different purified gardenia fragments were analyzed using HPLC. Then, the hypoglycemic effects of the different purified gardenia fragments were compared using in vitro and in vivo experiments. Finally, the different extracts were characterized using UPLC-ESI-QTOF-MS/MS and the mass spectrometric fragmentation pathway of the two main compounds, geniposide and crocin I, were identified. The experimental results indicated that the inhibitory effect of the 40% EGJ (crocin I) on the α-glucosidase was better than the 20% EGJ (geniposide) in vitro. However, the inhibitory effect of geniposide on T2DM was better than crocin I in the animal experiments. The different results in vivo and in vitro presumed potentially different mechanisms between crocin I and geniposide on T2DM. This research demonstrated that the mechanism of hypoglycemia in vivo from geniposide is not only one target of the α-glucosidase but provides the experimental background for crocin I and the geniposide deep processing and utilization.

Lactic acid bacteria as a tool for biovanillin production: A review

Vanilla is the most commonly used natural flavoring agent in industries like food, flavoring, medicine, and fragrance. Vanillin can be obtained naturally, chemically, or through a biotechnological process. However, the yield from vanilla pods is low and does not meet market demand, and the use of vanillin produced by chemical synthesis is restricted in the food and pharmaceutical industries. As a result, the biotechnological process is the most efficient and cost-effective method for producing vanillin with consumer-demanding properties while also supporting industrial applications. Toxin-free biovanillin production, based on renewable sources such as industrial wastes or by-products, is a promising approach. In addition, only natural-labeled vanillin is approved for use in the food industry. Accordingly, this review focuses on biovanillin production from lactic acid bacteria (LAB), which is generally recognized as safe (GRAS), and the cost-cutting efforts that are utilized to improve the efficiency of biotransformation of inexpensive and readily available sources. LABs can utilize agro-wastes rich in ferulic acid to produce ferulic acid, which is then employed in vanillin production via fermentation, and various efforts have been applied to enhance the vanillin titer. However, different designs, such as response surface methods, using immobilized cells or pure enzymes for the spontaneous release of vanillin, are strongly advised.

Chalcone-1-Deoxynojirimycin Heterozygote Reduced the Blood Glucose Concentration and Alleviated the Adverse Symptoms and Intestinal Flora Disorder of Diabetes Mellitus Rats

Chalcone-1-deoxynojirimycin heterozygote (DC-5), a novel compound which was designed and synthesized in our laboratory for diabetes treatment, showed an extremely strong in vitro inhibitory activity on α-glucosidase in our previous studies. In the current research, its potential in vivo anti-diabetic effects were further investigated by integration detection and the analysis of blood glucose concentration, blood biochemical parameters, tissue section and gut microbiota of the diabetic rats. The results indicated that oral administration of DC-5 significantly reduced the fasting blood glucose and postprandial blood glucose, both in diabetic and normal rats; meanwhile, it alleviated the adverse symptoms of elevated blood lipid level and lipid metabolism disorder in diabetic rats. Furthermore, DC-5 effectively decreased the organ coefficient and alleviated the pathological changes of the liver, kidney and small intestine of the diabetic rats at the same time. Moreover, the results of 16S rDNA gene sequencing analysis suggested that DC-5 significantly increased the ratio of Firmicutes to Bacteroidetes and improved the disorder of gut microbiota in diabetic rats. In conclusion, DC-5 displayed a good therapeutic effect on the diabetic rats, and therefore had a good application prospect in hypoglycemic drugs and foods.

Recent Updates on Phytoconstituent Alpha-Glucosidase Inhibitors: An Approach towards the Treatment of Type Two Diabetes

Diabetes is a common metabolic disorder marked by unusually high plasma glucose levels, which can lead to serious consequences such as retinopathy, diabetic neuropathy and cardiovascular disease. One of the most efficient ways to reduce postprandial hyperglycemia (PPHG) in diabetes mellitus, especially insulin-independent diabetes mellitus, is to lower the amount of glucose that is absorbed by inhibiting carbohydrate hydrolyzing enzymes in the digestive system, such as α-glucosidase and α-amylase. α-Glucosidase is a crucial enzyme that catalyzes the final stage of carbohydrate digestion. As a result, α-glucosidase inhibitors can slow D-glucose release from complex carbohydrates and delay glucose absorption, resulting in lower postprandial plasma glucose levels and control of PPHG. Many attempts have been made in recent years to uncover efficient α-glucosidase inhibitors from natural sources to build a physiologic functional diet or lead compound for diabetes treatment. Many phytoconstituent α-glucosidase inhibitors have been identified from plants, including alkaloids, flavonoids, anthocyanins, terpenoids, phenolic compounds, glycosides and others. The current review focuses on the most recent updates on different traditional/medicinal plant extracts and isolated compounds' biological activity that can help in the development of potent therapeutic medications with greater efficacy and safety for the treatment of type 2 diabetes or to avoid PPHG. For this purpose, we provide a summary of the latest scientific literature findings on plant extracts as well as plant-derived bioactive compounds as potential α-glucosidase inhibitors with hypoglycemic effects. Moreover, the review elucidates structural insights of the key drug target, α-glucosidase enzymes, and its interaction with different inhibitors.

Process optimization of vanillin production by conversion of ferulic acid by Bacillus megaterium

BACKGROUND

Vanillin is an important flavoring and aromatic ingredient found mainly in the pods of the tropical plant vanilla and is widely used in the food industry. Attempts have been made to produce vanillin from ferulic acid esters in agricultural residues of wheat bran.

RESULTS

The results showed that a strain with high tolerance to the substrate ferulic acid was isolated and screened from soil and identified as belonging to the genus Bacillus (Bacillus megaterium). The concentration of vanillin produced by this strain was 0.048 g L^-1 , and the molar conversion of vanillin was 12.25%. The production of vanillin was optimized by orthogonal experiments. Beef pastes 6.0 g L^-1 , soybean meal 5.0 g L^-1 , magnesium sulfate heptahydrate 1.0 g L^-1 , iron(II) sulfate heptahydrate 1.0 g L^-1 , calcium chloride 1.0 g L^-1 , dipotassium hydrogen phosphate trihydrate 1.0 g L^-1 ; fermentation culture conditions were pH 7.0, inoculum level 5%, loading volume 20%, ferulic acid 1.0 g L^-1 , fermentation culture temperature 35 °C. The concentration of vanillin obtained was 0.218 g L^-1 . Finally, transcriptomic analysis of the strain samples before and after the optimization of the fermentation conditions was carried out to study the effect of the optimization of the fermentation conditions on the concentration of vanillin produced by the strain.

CONCLUSION

This study provides a theoretical basis for further improving the yield of vanillin and gradually realizing efficient industrial production. © 2022 Society of Chemical Industry.

Identification, potency evaluation, and mechanism clarification of α-glucosidase inhibitors from tender leaves of Lithocarpus polystachyus Rehd

Lithocarpus polystachyus Rehd. known as Sweet Tea in China has attracted lots of interest for its good hypoglycemic effect and the potential as a hypoglycemic agent. Based on affinity separation-UPLC-Q-TOF-MS/MS, 54 potential α-glucosidase inhibitiors were identified and 44 were structurally determined. Out of them, 41 were identified for the first time from this plant including flavonoids, fatty acids, triterpenes, alkaloids, and coumarins. Enzyme assays revealed that flavonoids exhibited higher inhibitory activity against α-glucosidase than others with astilbin (IC₅₀ = 6.14 μg·mL^-1), morin (IC₅₀ = 8.46 μg·mL^-1), and naringenin (IC₅₀ = 10.03 μg·mL^-1) showing 2- to 4-fold higher potency than the positive control acarbose. They were proved as reversible inhibitors with mixed inhibition mechanism. K_i (K_i^') values and molecular dockings strongly supported the potency order of astilbin, morin and naringenin that showed in the enzyme assays.

Quality assessment of Succus Bambusae oral liquids based on gas chromatography/mass spectrometry fingerprints and chemometrics

RATIONALE

Succus Bambusae is consumed as a kind of herbal medicine and natural beverage in China. However, the current quality standards for Succus Bambusae are low and lack safety indicators, which makes it difficult to effectively guarantee its quality. Therefore, it is of great significance to study the identification and quality control technology for the product.

METHODS

We have developed a set of qualitative and quantitative methods based on gas chromatography/mass spectrometry (GC/MS) for the analysis of volatile components in Succus Bambusae oral liquid (SBOL). Combining GC/MS fingerprint analysis and related chemometrics algorithms, with similarity evaluation, Hotelling T² and distance to Model X (DModX) as criteria, the quality consistency of different batches was evaluated, and SBOL samples from different manufacturers were differentiated.

RESULTS

Twenty-nine volatile components were preliminarily identified from 40 batches of SBOL samples from six manufacturers, and six Q-markers (Quality Markers) for the SBOLs were discussed and determined using GC/MS. The products from different manufacturers were distinguished using chemometrics.

CONCLUSIONS

The results showed that the quality of the SBOL samples from different batches and different manufacturers fluctuated greatly, which suggested that research into the raw materials and manufacturing techniques should be strengthened to improve the quality of SBOL and ensure its quality consistency.

Insights into an α-Glucosidase Inhibitory Profile of 4,4-Dimethylsterols by Multispectral Techniques and Molecular Docking

Inhibition of α-glucosidase activity is closely related to the treatment of type 2 diabetes. However, the potential mechanism by which 4,4-dimethylsterols inhibit α-glucosidase has not been elucidated. In this work, the inhibitory activity and mechanism of 4,4-dimethylsterols against α-glucosidase were studied through kinetic analysis, fluorescence spectroscopy, ultraviolet spectroscopy, circular dichroism, and molecular docking. 4,4-Dimethylsterols showed higher inhibition activity against α-glucosidase than acarbose with an IC₅₀ value of 0.71 mg/mL and a noncompetitive inhibition type. They could bind to α-glucosidase through van der Waals forces and hydrogen bonds and quench its endofluorescence with a static quenching mechanism. Changes in the secondary structure of α-glucosidase were induced by its binding interaction with 4,4-dimethylsterols. Molecular docking further indicated that a hydrogen bond was generated between OH at the C-3 position of 4,4-dimethylsterols and the α-glucosidase residue Arg-442. This study provides new insights into the potential utilization of 4,4-dimethylsterols as antidiabetic phytochemicals in dietary supplements.

Omeprazole inhibits α-glucosidase activity and the formation of nonenzymatic glycation products: Activity and mechanism

In this study, the inhibitory effect and mechanism of omeprazole on α-glucosidase and nonenzymatic glycation were investigated in vitro by using multi-spectroscopic methods and molecular docking. Enzyme kinetic results showed that omeprazole inhibited α-glucosidase in a reversible and noncompetitive manner (IC₅₀= 0.595 ± 0.003 mM). The results from fluorescence quenching and thermomechanical analyses signified that omeprazole reduced the fluorescence intensity of α-glucosidase by forming an omeprazole-α-glucosidase complex primarily driven by hydrogen bonds. Molecular docking further confirmed that hydrogen bonds and hydrophobic forces were the major driving forces for omeprazole binding to α-glucosidase. The nonenzymatic glycation assays revealed that omeprazole had a moderate inhibition against the formation of fructosamine, dicarbonyl compounds, and advanced glycation end products (AGEs). This study provides a new inhibitor of both α-glucosidase and nonenzymatic glycation and provides a practicable candidate for treating diabetes and its complications.

Chondroitin Sulfate-Based Cryogels for Biomedical Applications

Cryogels attained from natural materials offer exceptional properties in applications such as tissue engineering. Moreover, Halloysite Nanotubes (HNT) at 1:0.5 weight ratio were embedded into CS cryogels to render additional biomedical properties. The hemolysis index of CS cryogel and CS:HNT cryogels was calculated as 0.77 ± 0.41 and 0.81 ± 0.24 and defined as non-hemolytic materials. However, the blood coagulation indices of CS cryogel and CS:HNT cryogels were determined as 76 ± 2% and 68 ± 3%, suggesting a mild blood clotting capability. The maximum% swelling capacity of CS cryogel was measured as 3587 ± 186%, 4014 ± 184%, and 3984 ± 113%, at pH 1.0, pH 7.4 and pH 9.0, respectively, which were reduced to 1961 ± 288%, 2816 ± 192, 2405 ± 73%, respectively, for CS:HNT cryogel. It was found that CS cryogels can hydrolytically be degraded 41 ± 1% (by wt) in 16-day incubation, whereas the CS:HNT cryogels degraded by 30 ± 1 wt %. There is no chelation for HNT and 67.5 ± 1% Cu(II) chelation for linear CS was measured. On the other hand, the CS cryogel and CS:HNT cryogel revealed Cu(II) chelating capabilities of 60.1 ± 12.5%, and 43.2 ± 17.5%, respectively, from 0.1 mg/mL Cu(II) ion stock solution. Additionally, at 0.5 mg/mL CS, CS:HNT, and HNT, the Fe(II) chelation capacity of 99.7 ± 0.6, 86.2 ± 4.7% and only 11.9 ± 4.5% were measured, respectively, while no Fe(II) was chelated by linear CS chelated Fe(II). As the adjustable and controllable swelling properties of cryogels are important parameters in biomedical applications, the swelling properties of CS cryogels, at different solution pHs, e.g., at the solution pHs of 1.0, 7.4 and 9.0, were measured as 3587 ± 186%, 4014 ± 184%, and 3984 ± 113%, respectively, and the maximum selling% values of CS:HNT cryogels were determined as 1961 ± 288%, 2816 ± 192, 2405 ± 73%, respectively, at the same conditions. Alpha glucosidase enzyme interactions were investigated and found that CS-based cryogels can stimulate this enzyme at any CS formulation.