Inhibition Mechanism of α-Amylase/α-Glucosidase by Silibinin, Its Synergism with Acarbose, and the Effect of Milk Proteins

Potential Antidiabetic Activity of Nordihydroguaiaretic Acid: An Insight into Its Inhibitory Mechanisms on Carbohydrate-Hydrolyzing Enzymes, the Binding Behaviors with Enzymes, and In Vivo Antihyperglycemic Effect

The inhibitory mechanisms and binding behaviors of nordihydroguaiaretic acid (NDGA) to α-glucosidase/α-amylase were investigated by in vitro multispectroscopic methods and in silico modeling technique. The results demonstrated that NDGA reversibly and uncompetitively inhibited α-glucosidase, exhibiting stronger inhibition than acarbose, while it displayed noncompetitive inhibition against α-amylase. Additionally, NDGA could spontaneously bind to α-glucosidase/α-amylase mainly through hydrogen bonds and hydrophobic forces, thus altering the spatial structure of enzymes and reducing their catalytic activity. The presence of crowding reagents/polysaccharides/undigested milk proteins would decrease the inhibitory ability of NDGA, whereas fatty acids exhibited the opposite phenomenon on α-glucosidase. Furthermore, the antidiabetic activity of NDGA in vivo was evaluated using the diabetic Drosophila model induced by a high-sugar diet. It was found that NDGA significantly reduced the glucose levels of diabetic Drosophila. These findings suggested that NDGA was a potential inhibitor of α-glucosidase/α-amylase and could be used as a nutritional adjuvant to prevent diabetes.

A Silibinin-Poly(ε-Caprolactone) Conjugate as an Enhanced Anticancer Agent

Poly(ε-caprolactone) (PCL) is a hydrolytically degradable biopolyester used in drug delivery to enhance drug solubility and bioavailability, where drugs are typically incorporated physically within the biopolymeric matrix rather than covalently bonded, due to the limited availability of functional groups required for covalent attachment. In pursuit of developing a facile method for the production of a biopolyester-drug covalent conjugate with effective drug loading capacity, this study reports the synthesis of a covalent Silibinin-PCL conjugate (Sil-PCLHyd) through a two-step approach. This involves the controlled hydrolysis of a high molecular weight PCL to increase the concentration of carboxylic end groups, which are subsequently used for the catalyzed esterification with Silibinin. The Sil-PCLHyd is characterized with mass spectrometry, gel permeation chromatography, thermogravimetric analysis, differential scanning calorimetry, and NMR and UV-vis spectroscopies. The cytotoxic effects of Sil-PCLHyd against colorectal adenocarcinoma cells (Caco-2) are measured through the MTT assay. The results of the Sil-PCLHyd characterization revealed a Silibinin loading of ≈9.8 wt.%. The MTT assay demonstrated that Sil-PCLHyd induced cytotoxic effects at concentrations a hundred times lower than those required for free Silibinin. The proposed approach might represent a reliable pathway for the development of biopolyester-based covalent conjugates with a high drug loading capacity.

BuZhong YiQi Formula Alleviates Postprandial Hyperglycemia in T2DM Rats by Inhibiting α-Amylase and α-Glucosidase In Vitro and In Vivo

Background/Objectives: BuZhong YiQi Formula (BZYQF) can alleviate type 2 diabetes mellitus (T2DM). However, its efficacy in managing postprandial hyperglycemia in T2DM needs to be further confirmed, and its underlying mechanism and pharmacodynamic material basis have not been sufficiently investigated. Methods: A T2DM rat model was induced to measure postprandial glycemic responses following glucose and starch ingestion. In vitro assays of enzymatic inhibition and the kinetic mode were performed to evaluate the inhibitory effect of BZYQF on α-amylase and α-glucosidase activities. The main constituent contents of BZYQF in a simulated digestion assay were measured to screen the active constituents in BZYQF against α-amylase and α-glucosidase activities via Pearson correlation and multiple linear regression analyses. Finally, the total flavonoids were purified from BZYQF to perform in vitro activity validation, and the flavonoid constituent activity was verified through molecular docking. Results: In vivo assays showed that BZYQF significantly reduced the blood glucose values of CON rats but not T2DM rats after glucose ingestion, while BZYQF significantly reduced the blood glucose levels by 15 min after starch ingestion in CON and T2DM rats, with more significant decreases in blood glucose levels in T2DM rats. In vitro enzymatic assays showed that BZYQF could inhibit the activities of α-amylase and α-glucosidase in competitive and non-competitive modes and in an uncompetitive mode, respectively. Furthermore, BZYQF showed a stronger inhibitory effect on α-glucosidase activity than on α-amylase activity. Simulated digestion showed that simulated gastric fluid and intestinal fluid changed the main constituent contents of BZYQF and their inhibition rates against α-amylase and α-glucosidase activities, and similar results were rarely found in simulated salivary fluid. Pearson correlation and multiple linear regression analyses revealed that the total flavonoids were the active constituents in BZYQF inhibiting α-amylase and α-glycosidase activities. This result was verified by examining the total flavonoids purified from BZYQF. A total of 1909 compounds were identified in BZYQF using UPLC-MS/MS, among which flavones were the most abundant and consisted of 467 flavonoids. Molecular docking showed that flavonoids in BZYQF were bound to the active site of α-amylase, while they were bound to the inactive site of α-glucosidase. This result supported the results of the enzyme kinetic assay. Conclusions: BZYQF significantly alleviated postprandial hyperglycemia in T2DM rats by inhibiting α-amylase and α-glycosidase activities, in which flavonoids in BZYQF were the active constituents.

Quercetin slow-release system delays starch digestion via inhibiting transporters and enzymes

This study investigates the potential of a quercetin-based emulsion system to moderate starch digestion and manage blood glucose levels, addressing the lack of in vivo research. By enhancing quercetin bioaccessibility and targeting release in the small intestine, the emulsion system demonstrates significant inhibition of starch digestion and glucose spikes through both in vitro and in vivo experiments. The system inhibits α-amylase and α-glucosidase via competitive and mixed inhibition mechanisms, primarily involving hydrogen bonds and van der Waals forces, leading to static fluorescence quenching. Additionally, this system downregulates the protein expression and gene transcription of SGLT1 and GLUT2. These findings offer a novel approach to sustaining glucose equilibrium, providing a valuable foundation for further application of quercetin emulsion in food science.

Inhibition of Human Salivary and Pancreatic α-Amylase by Resveratrol Oligomers

A key strategy to mitigate postprandial hyperglycemia involves inhibiting α-amylases, which commence the starch digestion process in the gut. This study examined the inhibitory effects of resveratrol and stilbenoid tetramers, vaticanol B, (-)-hopeaphenol, and vatalbinoside A on human salivary and pancreatic α-amylases experimentally and through molecular docking studies. Vaticanol B demonstrated the most potent inhibition with IC50 values of 5.3 ± 0.3 μM for salivary and 6.1 ± 0.5 μM for pancreatic α-amylase (compared to acarbose with IC50 values of 1.2 ± 0.1 μM and 0.5 ± 0.0 μM, respectively). Kinetic analysis suggested a competitive inhibition mode for vaticanol B. Resveratrol and vatalbinoside A were poor inhibitors of human α-amylases, while (-)-hopeaphenol exhibited moderate inhibition. Molecular docking supported the inhibition data, and several aspects of the structural configurations explained the stronger inhibition exerted by vaticanol B. Overall, vaticanol B shows promise as a natural alternative to acarbose for inhibiting α-amylase.

The screening of α-glucosidase inhibitory peptides from β-conglycinin and hypoglycemic mechanism in HepG2 cells and zebrafish larvae

Inhibition of carbohydrate digestive enzymes is a key focus across diverse fields, given the prominence of α-glucosidase inhibitors as preferred oral hypoglycaemic drugs for diabetes treatment. β-conglycinin is the most abundant functional protein in soy; however, it is unclear whether the peptides produced after its gastrointestinal digestion exhibit α-glucosidase inhibitory properties. Therefore, we examined the α-glucosidase inhibitory potential of soy peptides. Specifically, β-conglycinin was subjected to simulated gastrointestinal digestion by enzymatically cleaving it into 95 peptides with gastric, pancreatic and chymotrypsin enzymes. Eight soybean peptides were selected based on their predicted activity; absorption, distribution, metabolism, excretion and toxicity score; and molecular docking analysis. The results indicated that hydrogen bonding and electrostatic interactions play important roles in inhibiting α-glucosidase, with the tripeptide SGR exhibiting the greatest inhibitory effect (IC50 = 10.57 μg/mL). In vitro studies revealed that SGR markedly improved glucose metabolism disorders in insulin-resistant HepG2 cells without affecting cell viability. Animal experiments revealed that SGR significantly improved blood glucose and decreased maltase activity in type 2 diabetic zebrafish larvae, but it did not result in the death of zebrafish larvae. Transcriptomic analysis revealed that SGR exerts its anti-diabetic and hypoglycaemic effects by attenuating the expression of several genes, including Slc2a1, Hsp70, Cpt2, Serpinf1, Sfrp2 and Ggt1a. These results suggest that SGR is a potential food-borne bioactive peptide for managing diabetes.

Revealing the interaction between alpha-chymotrypsin and eugenol: An integrated multi-spectral and dynamic simulation approach

The study aims to explore the effects of Eugenol (EUG) as an antioxidant on α-Chymotrypsin (α-Chy) and its interaction mechanism, with potential implications for new therapy development. The interaction between EUG and α-Chy was demonstrated through ultraviolet (UV) spectroscopy, which resulted in a shift in absorption with docking energies of -22.76 kJ/mol. An increase in fluorescence intensity indicated that the Trp residues moved to a less polar environment, which is consistent with the changes in accessible surface area (ASA) values. The presence of EUG led to a decrease in α-helix, β-turn, and random coil structures as shown by circular dichroism (CD) and Fourier-transform infrared (FTIR) analysis. Additionally, there was a slight increase in β-sheet structures, indicating a decrease in enzyme stability. However, tests for thermal stability showed a decrease in folding upon the introduction of EUG, which contradicted the results obtained from molecular dynamics (MD) simulations. The docking studies revealed that EUG forms hydrogen bonds and van der Waals forces with the enzyme, indicating the interaction mechanism. Kinetic studies confirmed that EUG acts as a mixed inhibitor. However, further research involving live organisms is necessary to fully understand its potential.

Deciphering the inhibitory mechanisms of betanin and phyllocactin from Hylocereus polyrhizus peel on protein glycation, with insights into their application in bread

Protein glycation closely intertwines with the pathogenesis of various diseases, sparking a growing interest in exploring natural antiglycation agents. Herein, high-purity betacyanins (betanin and phyllocactin) derived from Hylocereus polyrhizus peel were studied for their antiglycation potential using an in vitro bovine serum albumin (BSA)-glucose model. Notably, betacyanins outperformed aminoguanidine, a recognized antiglycation agent, in inhibiting glycation product formation across different stages, especially advanced glycation end-products (AGEs). Interestingly, phyllocactin displayed stronger antiglycation activity than betanin. Subsequent mechanistic studies employing molecular docking analysis and fluorescence quenching assay unveiled that betacyanins interact with BSA endothermically and spontaneously, with hydrophobic forces playing a dominant role. Remarkably, phyllocactin demonstrated higher binding affinity and stability to BSA than betanin. Furthermore, the incorporation of betacyanins into bread dose-dependently suppressed AGEs formation during baking and shows promise for inhibiting in vivo glycation process post-consumption. Overall, this study highlights the substantial potential of betacyanins as natural antiglycation agents.

Purification and characterization of betacyanin monomers from Hylocereus polyrhizus peel: A comparative study of their antioxidant and antidiabetic activities with mechanistic insights

Betacyanins have garnered escalating research interest for their promising bioactivities. However, substantial challenges in purification and separation have impeded a holistic comprehension of the distinct bioactivities of individual betacyanins and their underlying mechanisms. Herein, betanin and phyllocactin monomers with purity exceeding 95% were successfully obtained from Hylocereus polyrhizus peel using a feasible protocol. These monomers were subsequently employed for comparative bioactivity assessments to uncover underlying mechanisms and illuminate structure-activity relationships. Interestingly, phyllocactin exhibited superior antioxidant activities and 36.1% stronger inhibitory activity on α-glucosidase compared to betanin. Mechanistic studies have revealed that they function as mixed-type inhibitors of α-amylase and competitive inhibitors of α-glucosidase, with interactions predominantly driven by hydrogen bonding. Notably, phyllocactin demonstrated a greater binding affinity with enzymes than betanin, thereby substantiating its heightened inhibitory activity. Overall, our results highlight novel bioactivities of betacyanin monomers and provide profound insights into the intricate interplay between structures and properties.

Antioxidant, In Vitro Cytotoxicity, and Anti-diabetic Attributes of a Drug-Free Guar Gum Nanoformulation as a Novel Candidate for Diabetic Wound Healing

The escalating intersection of diabetes and impaired wound healing poses a substantial societal burden, marked by an increasing prevalence of chronic wounds. Diabetic individuals struggle with hindered recovery, attributed to compromised blood circulation and diminished immune function, resulting in prolonged healing periods and elevated healthcare expenditures. To address this challenge, we report here a drug-free novel guar gum (GG)-based nano-formulation which is effective against diabetic wound healing. Nanoparticles with an average particle size of 32.4 nm display stability with negative zeta potential. Differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR) analysis reveal alterations in thermal properties and molecular structures induced by the nano-particulation process. In vitro studies highlight the antioxidant potential of GGNP through concentration-dependent free radical scavenging activity in DPPH and ABTS assays. The nanoformulation also exhibits inhibitory effects on α-glucosidase and α-amylase enzymes. Cell viability studies have indicated moderate cytotoxicity in L929 cells and significant proliferation and migration in HaCaT cells, suggesting a positive impact on skin cells. In vitro enzymatic activity assessments under hyperglycaemic conditions reveal the potential of GGNP to modulate glutathione-S-transferase (GST), superoxide dismutase (SOD), and catalase activities as well as decreasing lipid peroxidation (LPO) levels, showcasing an antioxidant response. These results suggest GGNP as a promising candidate in diabetic wound healing.

Exploring the binding behavior mechanism of vitamin B12 to α-Casein and β-Casein: multi-spectroscopy and molecular dynamic approaches

The aim of this study was to investigate the behavior interaction of α-Casein-B12 and β-Casein-B12 complexes as binary systems through the methods of multiple spectroscopic, zeta potential, calorimetric, and molecular dynamics (MD) simulation. Fluorescence spectroscopy denoted the role ofB12as a quencher in both cases of α-Casein and β-Casein fluorescence intensities, which also verifies the existence of interactions. The quenching constants of α-Casein-B12 and β-Casein-B12 complexes at 298 K in the first set of binding sites were 2.89 × 104 and 4.41 × 104 M-1, while the constants of second set of binding sites were 8.56 × 104 and 1.58 × 105 M-1, respectively. The data of synchronized fluorescence spectroscopy at Δλ = 60 nm were indicative of the closer location of β-Casein-B12 complex to the Tyr residues. Additionally, the binding distance between B12 and the Trp residues of α-Casein and β-Casein were obtained in accordance to the Förster's theory of nonradioactive energy transfer to be 1.95 nm and 1.85 nm, respectively. Relatively, the RLS results demonstrated the production of larger particles in both systems, while the outcomes of zeta potential confirmed the formation of α-Casein-B12 and β-Casein-B12 complexes and approved the existence of electrostatic interactions. We also evaluated the thermodynamic parameters by considering the fluorescence data at three varying temperatures. According to the nonlinear Stern-Volmer plots of α-Casein and β-Casein in the presence of B12 in binary systems, the two sets of binding sites indicated the detection of two types of interaction behaviors. Time-resolved fluorescence results revealed that the fluorescence quenching of complexes are static mechanism. Furthermore, the outcomes of circular dichroism (CD) represented the occurrence of conformational changes in α-Casein and β-Casein upon their binding to B12 as the binary system. The experimental results that were obtained throughout the binding of α-Casein-B12 and β-Casein-B12 complexes were confirmed by molecular modeling.Communicated by Ramaswamy H. Sarma.

LC-MS guided isolation of phenolic glycosides from Viburnum luzonicum Rolfe leaves and their α‑amylase and α-glucosidase inhibitory activities

Viburnum luzonicum Rolfe is widely used in China as folk medicine. The bioactivity evaluation indicated that the n-BuOH fraction of V. luzonicum leaves (VLLB) could significantly inhibit α‑amylase and α-glucosidase. In order to clarify its active constituents, the phytochemical analysis on VLLB was first performed using HPLC-QTOF-MS/MS, and three new phenolic compounds, viburosides A-C (1-3), along with seven known analogues (4-10) were isolated through preparative HPLC. The undescribed compounds were determined by extensive spectroscopic analyses (1H and 13C NMR, HSQC, HMBC, HRESIMS, and ORD) and enzymatic hydrolysis. In the in vitro enzyme assays, compounds 1-8 showed potent α‑amylase and α-glucosidase inhibitory activities. The enzymatic kinetics and molecular docking of the strongest inhibitors 2 and 3 against the corresponding target enzyme were also performed.

A narrative review on the mechanism of natural flavonoids in improving glucolipid metabolism disorders

Glucolipid metabolism disorder (GLMD) is a complex chronic disease characterized by glucose and lipid metabolism disorders with a complex and diverse etiology and rapidly increasing incidence. Many studies have identified the role of flavonoids in ameliorating GLMD, with mechanisms related to peroxisome proliferator-activated receptors, nuclear factor kappa-B, AMP-activated protein kinase, nuclear factor (erythroid-derived 2)-like 2, glucose transporter type 4, and phosphatidylinositol-3-kinase/protein kinase B pathway. However, a comprehensive summary of the flavonoid effects on GLMD is lacking. This study reviewed the roles and mechanisms of natural flavonoids with different structures in the treatment of GLMD reported globally in the past 5 years and provides a reference for developing flavonoids as drugs for treating GLMD.

Computational investigation of 2, 4-Di Tert Butyl Phenol as alpha amylase inhibitor isolated from Coccinia grandis (L.) Voigt using molecular docking, and ADMET parameters

INTRODUCTION

Diabetes Mellitus is the metabolic disorder most prevalent globally, accounting for a substantial morbidity rate. The conventional drugs available for the management of diabetes are either expensive or lack the required efficacy. The purpose of this research is to isolate and characterize an active phytoconstituent from Coccinia grandis and assess its anti-diabetic properties.

METHODS AND MATERIALS

Stems of Coccinia grandis are subjected to successive extraction and isolation. The isolated compound by column chromatography was characterized by FTIR (fourier-transform infrared), 1 H NMR (proton nuclear magnetic resonance), and Mass spectroscopy. The antidiabetic potential of the isolated compound was evaluated by in-vitro alpha-amylase inhibitory activity. Further, the compound was subjected to molecular docking studies to study its interaction with the human pancreatic alpha-amylase (Molegro Virtual Docker) as well to determine the pharmacokinetic and toxicity profile using computational techniques (OSIRIS property explorer, Swiss ADME, pkCSM, and PreADMET).

RESULTS

The characterization of the compound suggests the structure to be 2,4-ditertiary butyl phenol. The in-vitro alpha-amylase inhibitory study indicated a concentration-dependent inhibition and the IC50 (median lethal dose) value of the isolated compound was found to be 64.36 μg/ml. The docking study with the A chain of receptor 5EMY yielded a favorable docking score of -81.48 Kcal mol-1, suggesting that the compound binds to the receptor with high affinity through electrostatic, hydrophobic, and hydrogen bonds. Furthermore, the silico ADME analysis of the compound revealed improved metabolism, a skin permeability of -3.87 cm/s, gastrointestinal absorption of 95.48 %, and a total clearance of 0.984 log ml min-1 kg-1. In silico toxicity analysis also predicted cutaneous irritations but no carcinogenicity, mutagenicity, or hepatotoxicity.

CONCLUSION

The data suggested that the isolated compound (2, 4-tertiary butyl phenol) has the potential to inhibit the alpha-amylase activity and possess optimal ADME properties as well as tolerable side effects.

Revealing the Hypoglycemic Effect of Red Yeast Rice: Perspectives from the Inhibition of α-Glucosidase and the Anti-Glycation Capability by Ankaflavin and Monascin

Red yeast rice dietary supplements have been proven to ameliorate hyperglycemia, but the mechanism was unclear. In this work, ankaflavin (AK) and monascin (MS), as typical pigments derived from red yeast rice, were found to exert noteworthy inhibitory ability against α-glucosidase, with an IC50 of 126.5 ± 2.5 and 302.6 ± 2.5 μM, respectively, compared with acarbose (IC50 = 341.3 ± 13.6 μM). They also exhibited mixed-type inhibition of α-glucosidase in vitro and caused fluorescence quenching through the static-quenching process. Molecular-docking studies indicated that AK and MS bind to amino acid residues outside the catalytic center, which induces structural changes in the enzyme, thus influencing its catalytic activity. The anti-glycation ability of Monascus-fermented products was evaluated, and they exhibited a high inhibition rate of 87.1% in fluorescent advanced glycation end-product formation at a concentration of 0.2 mg mL-1, while aminoguanidine showed a rate of 75.7% at the same concentration. These results will be significant in broadening the application scope of Monascus pigments, especially AK and MS, in treating type 2 diabetes.

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.

Anti-diabetic and anti-inflammatory indole diterpenes from the marine-derived fungus Penicillium sp. ZYX-Z-143

Seven new indole-diterpenoids, penpaxilloids A-E (1-5), 7-methoxypaxilline-13-ene (6), and 10-hydroxy-paspaline (7), along with 20 known ones (8-27), were isolated from the marine-derived fungus Penicillium sp. ZYX-Z-143. Among them, compound 1 was a spiro indole-diterpenoid bearing a 2,3,3a,5-tetrahydro-1H-benzo[d]pyrrolo[2,1-b][1,3]oxazin-1-one motif. Compound 2 was characterized by a unique heptacyclic system featuring a rare 3,6,8-trioxabicyclo[3.2.1]octane unit. The structures of the new compounds were established by extensive spectroscopic analyses, NMR calculations coupled with the DP4 + analysis, and ECD calculations. The plausible biogenetic pathway of two unprecedented indole diterpenoids, penpaxilloids A and B (1 and 2), was postulated. Compound 1 acted as a noncompetitive inhibitor against protein tyrosine phosphatase 1B (PTP1B) with IC50 value of 8.60 ± 0.53 μM. Compound 17 showed significant α-glucosidase inhibitory activity with IC50 value of 19.96 ± 0.32 μM. Moreover, compounds 4, 8, and 22 potently suppressed nitric oxide production on lipopolysaccharide-stimulated RAW264.7 macrophages.

Antidiabetic Property Optimization from Green Leafy Vegetables Using Ultrasound-Assisted Extraction to Improve Cracker Production

Here we test a method of incorporating of plant extracts into popular snack foods to help control diabetes. Since some fresh vegetables contain antidiabetic compounds, ultrasound-assisted extraction was used to optimize their extraction of from spring onions, bunching onions, and celery for later incorporation into crackers. We compared various concentrations of ethanol used during extraction, after which they were exposed to an ultrasound processor whose amplitude and sonication time were also varied. The optimal extraction conditions were found to be an ethanol concentration of 44.08%, an amplitude of 80%, and a sonication time of 30 min. This resulted in the highest level of α-glucosidase inhibitory activity (i.e., 1,449.73 mmol ACE/g) and the highest extraction yield (i.e., 24.16%). The extract produced from these optimum conditions was then used as a constituent component of crackers at 0.625%, 1.25%, or 2.5% w/w. These biscuits were then produced at baking temperatures of 140°C, 150°C, or 160°C. We then measured the physical characteristics and bioactivities of sample biscuits from each treatment. We found that biscuits containing 2.5% vegetable combination extract and baked at 140°C had the highest total phenolic content, the strongest antioxidant performance, and showed the most substantial antidiabetic and antiobesity effects. Here we establish conditions for the effective extraction of antidiabetic functional ingredients via ultrasound from green leafy vegetables. We also provide a method of using these ingredients to prepare crackers with the aim of developing a functional antidiabetic snack food.

Inhibition of starch digestion by phenolic acids with a cinnamic acid backbone: Structural requirements for the inhibition of α-amylase and α-glucosidase

This study investigated the inhibition mechanism of cinnamic acid-based phenolic acids (cinnamic acid: CIA, 3,4-dimethoxy cinnamic acid: 3,4-mCIA, caffeic acid: CA, ferulic acid: FA) on starch digestion. CA, FA, and 3,4-mCIA contributed to reducing the rapidly digested starch content and increasing the resistant starch content. The enzyme activity inhibition results responded that the four phenolic acids inhibited α-amylase activity better than α-glucosidase. The order of IC50 against α-amylase and α-glucosidase was CA > FA > 3,4-mCIA > CIA. Phenolic acid's benzene ring formed conjugated Pi-systems with the amino acid residues of α-amylase. Salt-bridge interactions were the main driving forces for the binding of phenolic acids to α-glucosidase. The binding was stabilized by the hydroxyl (OH) group and the methoxy on the benzene ring, where the OH exerted a better effect. These results illuminate the inhibition mechanism of starch digestion with cinnamic acid-based phenolic acids from an interaction perspective.

Flavonoids as dual-target inhibitors against α-glucosidase and α-amylase: a systematic review of in vitro studies

Diabetes mellitus remains a major global health issue, and great attention is directed at natural therapeutics. This systematic review aimed to assess the potential of flavonoids as antidiabetic agents by investigating their inhibitory effects on α-glucosidase and α-amylase, two key enzymes involved in starch digestion. Six scientific databases (PubMed, Virtual Health Library, EMBASE, SCOPUS, Web of Science, and WHO Global Index Medicus) were searched until August 21, 2022, for in vitro studies reporting IC50 values of purified flavonoids on α-amylase and α-glucosidase, along with corresponding data for acarbose as a positive control. A total of 339 eligible articles were analyzed, resulting in the retrieval of 1643 flavonoid structures. These structures were rigorously standardized and curated, yielding 974 unique compounds, among which 177 flavonoids exhibited inhibition of both α-glucosidase and α-amylase are presented. Quality assessment utilizing a modified CONSORT checklist and structure-activity relationship (SAR) analysis were performed, revealing crucial features for the simultaneous inhibition of flavonoids against both enzymes. Moreover, the review also addressed several limitations in the current research landscape and proposed potential solutions. The curated datasets are available online at https://github.com/MedChemUMP/FDIGA .

Screening and Characterization of an α-Amylase Inhibitor from Carya cathayensis Sarg. Peel

Inhibiting α-amylase can lower postprandial blood glucose levels and delay glucose absorption, offering an effective approach for the development of antidiabetic diets. In this study, an active constituent with inhibitory activity against α-amylase was isolated and purified by bioassay-guided fractionation from Carya cathayensis Sarg. peel (CCSP). The active constituent was identified by NMR and Q-Exactive Orbitrap Mass Spectrometry as 5-O-p-coumaroylquinic acid (5-CQA). 5-CQA possessed strong inhibitory activity against α-amylase, with an IC50 value of 69.39 µM. In addition, the results of the kinetic study indicated that 5-CQA was a potent, reversible, noncompetitive inhibitor against α-amylase. The findings indicate that 5-CQA derived from CCSP has potential as a novel inhibitor against α-amylase, which can help mitigate postprandial blood sugar spikes, making it suitable for inclusion in antidiabetic diets.

Increased therapeutic effect of nanotized silibinin against glycation and diabetes: An in vitro and in silico-based approach

BACKGROUND

The global prevalence of diabetes has increased sharply, with the number of cases expected to rise from 424.9 million in 2017 to 628.6 million by 2045. Flavonoids are plant derived molecules with well-established antioxidant potential in addition to other therapeutic properties. Silibinin is a naturally occurring flavonoid with antioxidant and antidiabetic properties. However, its rapid metabolism and low bioavailability limit its therapeutic effects.

AIMS & OBJECTIVES

In this study, we have synthesized the nanoformulation of silibinin and compared its antiglycating and antidiabetic potential with the soluble form.

METHODOLOGY

The inhibitory effect was tested on carbohydrate-hydrolyzing enzymes as well as glycation of human serum albumin (HSA). The structural and biochemical changes in HSA were assessed by spectroscopic analyses and different assays.

KEY FINDINGS

The nanoforms were found to be better inhibitors of α-amylase and α-glucosidase compared to the bulk forms. Glycation of HSA in the presence of nano-silibinin resulted in the formation of lower level of early and advanced glycation products. This was also confirmed by spectroscopic studies and by estimating protein oxidation and free lysine residues. Molecular docking studies further supported the experimental outcomes. These results indicate that the nano form has significantly stronger antidiabetic and antiglycating effects than the bulk form. Nano-silibinin could therefore be recommended as a dietary supplement for diabetics to help control glycation and other associated complications.

A comprehensive insight into the effects of caffeic acid (CA) on pepsin: Multi-spectroscopy and MD simulations methods

The interaction between caffeic acid (CA) and pepsin was investigated using multi-spectroscopy approaches and molecular dynamic simulations (MDS). The effects of CA on the structure, stability, and activity of pepsin were studied. Fluorescence emission spectra and UV-vis absorption peaks all represented the static quenching mechanism of pepsin by CA. Moreover, the fluorescence spectra displayed that the interaction of CA exposed the tryptophan chromophores of pepsin to a more hydrophilic micro-environment. Consistent with the simulation results, thermodynamic parameters revealed that CA was bound to pepsin with a high binding affinity. The Van der Waals force and Hydrogen bond interaction were the dominant driving forces during the binding process. The circular dichroism (CD) spectroscopy analysis showed that the CA binding to pepsin decreased the contents of α-Helix and Random Coil but increased the content of β-sheet in the pepsin structure. Accordingly, MD simulations confirmed all the experimental results. As a result, CA is considered an inhibitor with adverse effects on pepsin activity.

α-Glucosidase Inhibitory Activities and the Interaction Mechanism of Novel Spiro-Flavoalkaloids from YingDe Green Tea

Flavoalkaloids are a unique class of compounds in tea, most of which have an N-ethyl-2-pyrrolidinone moiety substituted at the A ring of a catechin skeleton. 1-Ethyl-5-hydroxy-pyrrolidone, a decomposed product of theanine, was supposed to be the key intermediate to form tea flavoalkaloids. However, we have also detected another possible theanine intermediate, 1-ethyl-5-oxopyrrolidine-2-carboxylic acid, and speculated if there are related conjugated catechins. Herein, four novel spiro-flavoalkaloids with a spiro-γ-lactone structural moiety were isolated from Yingde green tea (Camellia sinensis var. assamica) in our continuing exploration of new chemical constituents from tea. The structures of the new compounds, spiro-flavoalkaloids A-D (1-4), were further elucidated by extensive nuclear magnetic resonance (NMR) spectroscopy together with the calculated ¹³C NMR, IR, UV-vis, high-resolution mass, optical rotation, experimental, and calculated circular dichroism spectra. We also provided an alternative pathway to produce these novel spiro-flavoalkaloids. Additionally, their α-glucosidase inhibitory activities were determined with IC₅₀ values of 3.34 (1), 5.47 (2), 22.50 (3), and 15.38 (4) μM. Docking results revealed that compounds 1 and 2 mainly interacted with residues ASP-215, ARG-442, ASP-352, GLU-411, HIS-280, ARG-315, and ASN-415 of α-glucosidase through hydrogen bonds. The fluorescence intensity of α-glucosidase could be quenched by compounds 1 and 2 in a static style.