Kinetics and molecular modeling studies on the inhibition mechanism of GH13 α-glycosidases by small molecule ligands

Alpha-glucosidase inhibitors play an important role in Diabetes Mellitus (DM) treatment since they prevent postprandial hyperglycemia. The Glycoside Hydrolase family 13 (GH13) is the major family of enzymes acting on substrates containing α-glucoside linkages, such as maltose and amylose/amylopectin chains in starch. Previously, our group identified glycoconjugate 1H-1,2,3-triazoles (GCTs) inhibiting two GH13 α-glycosidases: yeast maltase (MAL12) and porcine pancreatic amylase (PPA). Here, we combined kinetic studies and computational methods on nine GCTs to characterize their inhibitory mechanism. They all behaved as reversible inhibitors, and kinetic models encompassed noncompetitive and various mechanisms of mixed-type inhibition for both enzymes. Most potent inhibitors displayed Ki values of 30 μM for MAL12 (GPESB16) and 37 μM for PPA (GPESB15). Molecular dynamics and docking simulations indicated that on MAL12, GPESB15 and GPESB16 bind in a cavity adjacent to the active site, while on the PPA, GPESB15 was predicted to bind at the entrance of the catalytic site. Notably, despite its putative location within the active site, the binding of GPESB15 does not obstruct the substrate's access to the cleavage site. Our study contributes to paving the way for developing novel therapeutic strategies for managing DM-2 through GH13 α-glycosidases inhibition.

Synthesis, anti-diabetic profiling and molecular docking studies of 2-(2-arylidenehydrazinyl)thiazol-4(5H)-ones

Aim: To synthesize novel more potent anti-diabetic agents. Methodology: A simple cost effective Hantzsch's synthetic strategy was used to synthesize 2-(2-arylidenehydrazinyl)thiazol-4(5H)-ones. Results: Fifteen new 2-(2-arylidenehydrazinyl)thiazol-4(5H)-ones were established to check their anti-diabetic potential. From alpha(α)-amylase inhibition, anti-glycation and anti-oxidant activities it is revealed that most of the compounds possess good anti-diabetic potential. All tested compounds were found to be more potent anti-diabetic agents via anti-glycation mode. The results of α-amylase and anti-oxidant inhibition revealed that compounds are less active against α-amylase and anti-oxidant assays. Conclusion: This study concludes that introduction of various electron withdrawing groups at the aryl ring and substitution of different functionalities around thiazolone nucleus could help to find out better anti-diabetic drug.

Development of nano-delivery systems for loaded bioactive compounds: using molecular dynamics simulations

Over the past decade, a remarkable surge in the development of functional nano-delivery systems loaded with bioactive compounds for healthcare has been witnessed. Notably, the demanding requirements of high solubility, prolonged circulation, high tissue penetration capability, and strong targeting ability of nanocarriers have posed interdisciplinary research challenges to the community. While extensive experimental studies have been conducted to understand the construction of nano-delivery systems and their metabolic behavior in vivo, less is known about these molecular mechanisms and kinetic pathways during their metabolic process in vivo, and lacking effective means for high-throughput screening. Molecular dynamics (MD) simulation techniques provide a reliable tool for investigating the design of nano-delivery carriers encapsulating these functional ingredients, elucidating the synthesis, translocation, and delivery of nanocarriers. This review introduces the basic MD principles, discusses how to apply MD simulation to design nanocarriers, evaluates the ability of nanocarriers to adhere to or cross gastrointestinal mucosa, and regulates plasma proteins in vivo. Moreover, we presented the critical role of MD simulation in developing delivery systems for precise nutrition and prospects for the future. This review aims to provide insights into the implications of MD simulation techniques for designing and optimizing nano-delivery systems in the healthcare food industry.

Protein and Peptide-Based Nanotechnology for Enhancing Stability, Bioactivity, and Delivery of Anthocyanins

Anthocyanin, a unique natural polyphenol, is abundant in plants and widely utilized in biomedicine, cosmetics, and the food industry due to its excellent antioxidant, anticancer, antiaging, antimicrobial, and anti-inflammatory properties. However, the degradation of anthocyanin in an extreme environment, such as alkali pH, high temperatures, and metal ions, limits its physiochemical stabilities and bioavailabilities. Encapsulation and combining anthocyanin with biomaterials could efficiently stabilize anthocyanin for protection. Promisingly, natural or artificially designed proteins and peptides with favorable stabilities, excellent biocapacity, and wide sources are potential candidates to stabilize anthocyanin. This review focuses on recent progress, strategies, and perspectives on protein and peptide for anthocyanin functionalization and delivery, i.e., formulation technologies, physicochemical stability enhancement, cellular uptake, bioavailabilities, and biological activities development. Interestingly, due to the simplicity and diversity of peptide structure, the interaction mechanisms between peptide and anthocyanin could be illustrated. This work sheds light on the mechanism of protein/peptide-anthocyanin nanoparticle construction and expands on potential applications of anthocyanin in nutrition and biomedicine.

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.

Chromogenic Assay Is More Efficient in Identifying α-Amylase Inhibitory Properties of Anthocyanin-Rich Samples When Compared to the 3,5-Dinitrosalicylic Acid (DNS) Assay

The inhibition of carbohydrate digestion by plant bioactive compounds is a potential dietary strategy to counteract type 2 diabetes. Indeed, inhibition of α-amylase, a key enzyme that carries out the bulk of starch digestion, has been demonstrated for a range of bioactive compounds including anthocyanins; however, sample pigmentation often interferes with measurements, affecting colorimetric assay outcomes. Therefore, the present study compared the performance of a direct chromogenic assay, using 2-chloro-4 nitrophenyl α-D-maltotrioside (CNPG3) as a substrate, with the commonly used 3,5-dinitrosalicylic acid (DNS) assay. The direct chromogenic assay demonstrated a 5-10-fold higher sensitivity to determine α-amylase inhibition in various samples, including acarbose as a reference, pure anthocyanins, and anthocyanin-rich samples. The IC50 values of acarbose presented as 37.6 μg/mL and 3.72 μg/mL for the DNS assay and the direct chromogenic assay, respectively, whereas purified anthocyanins from blackcurrant showed IC50 values of 227.4 µg/mL and 35.0 µg/mL. The direct chromogenic assay is easy to perform, fast, reproducible, and suitable for high-throughput screening of pigmented α-amylase inhibitors.

Green synthesis of nanolipo-fibersomes using Nutriose® FB 06 for delphinidin-3-O-sambubioside delivery: Characterization, physicochemical properties, and application

Anthocyanins are potential bioactive compounds with less bioavailability due to instability in physicochemical and physiological harsh environments. This study synthesized a "nanolipo-fibersomes (NLFS)" using Lipoid® S75 and Nutriose® FB 06 (dextrinization of wheat starch) through a self-assembly technique with probe sonication. We aimed to encapsulate delphinidin-3-O-sambubioside (D3S) successfully and evaluate physicochemical and controlled release properties with improved antioxidant activity on palmitic acid (PA)-induced colonic cells (Caco-2 cells). D3S-loaded nanolipo-fibersomes (D3S-NLFS) were nanosized (<150 nm), spherical shaped, and homogenously dispersed in solution with promising encapsulation efficiency (~ 89.31 to 97.31 %). Particles formation was further verified by FTIR. NLFS were well-stable in thermal, storage, and gastrointestinal mimic environments. NLFS exhibited better-controlled release and mucoadhesive properties compared to nanoliposomes (NL). The NLFS showed better cellular uptake than NL, which was correlated to higher mucoadhesive properties. Furthermore, D3S-NLFS exhibited promising protective effects against PA-induced cytotoxicity, O2•- radicals generation, mitochondrial dysfunctions, and GSH depletion, while the free D3S was ineffective. Among D3S-loaded nanoparticles, D3S-NLFS 3 was the most efficient nanocarrier followed by D3S-NLFS 2, D3S-NLFS 1, and D3S-NL, respectively. The above data suggest that nanolipo-fibersomes can be considered as promising nanovesicles for improving colonic delivery of hydrophilic compounds with controlled release properties and greater antioxidant activity.

Special issue: molecular nutrition and chronic diseases

"Let food be thy medicine and medicine be thy food"-the ancient adage proposed by Greek philosopher Hippocrates of Kos thousands of years ago already acknowledged the importance of the beneficial and health-promoting effects of food nutrients on the body (Mafra et al., 2021). Recent epidemiological and large-scale community studies have also reported that unhealthy diets or eating habits may contribute heavily to the burden of chronic, non-communicable diseases, such as obesity, type 2 diabetes mellitus (T2DM), hypertension, cardiovascular disease (CVD), cancer, neurodegenerative diseases, arthritis, chronic kidney disease (CKD), and chronic obstructive pulmonary disease (COPD) (Jayedi et al., 2020; Gao et al., 2022). Emerging evidence highlights that a diet rich in fruits and vegetables can prevent various chronic diseases (Chen et al., 2022). Food bioactive compounds including vitamins, phytochemicals, and dietary fibers are responsible for these nutraceutical benefits (Boeing et al., 2012). Recently, phytochemicals such as polyphenols, phytosterols, and carotenoids have gained increasing attention due to their potential health benefits to alleviate chronic diseases (van Breda and de Kok, 2018). Understanding the role of phytochemicals in health promotion and preventing chronic diseases can inform dietary recommendations and the development of functional foods. Therefore, it is crucial to investigate the health benefits of phytochemicals derived from commonly consumed foods for the prevention and management of chronic diseases.

Anthocyanins as Promising Molecules Affecting Energy Homeostasis, Inflammation, and Gut Microbiota in Type 2 Diabetes with Special Reference to Impact of Acylation

Anthocyanins, the red-orange to blue-violet colorants present in fruits, vegetables, and tubers, have antidiabetic properties expressed via modulating energy metabolism, inflammation, and gut microbiota. Acylation of the glycosyl moieties of anthocyanins alters the physicochemical properties of anthocyanins and improves their stability. Thus, acylated anthocyanins with probiotic-like property and lower bioavailability are likely to have different biological effects from nonacylated anthocyanins on diabetes. This work highlights recent findings on the antidiabetic effects of acylated anthocyanins from the perspectives of energy metabolism, inflammation, and gut microbiota compared to the nonacylated anthocyanins and particularly emphasizes the cellular and molecular mechanisms associated with the beneficial effects of these bioactive molecules, providing a new perspective to explore the different biological effects induced by structurally different anthocyanins. Acylated anthocyanins may have greater modulating effects on energy metabolism, inflammation, and gut microbiota in type 2 diabetes compared to nonacylated anthocyanins.

Structure-activity relationships and the underlying mechanism of α-amylase inhibition by hyperoside and quercetin: Multi-spectroscopy and molecular docking analyses

Inhibiting the activity of α-amylase has been considered an effective strategy to manage hyperglycemia. Hyperoside and quercetin are the main natural flavonoids in various plants, and the inhibition mechanism on α-amylase remains unclear. In this study, the structure-activity relationships between hyperoside/quercetin and α-amylase were evaluated by enzyme kinetic analysis, multi-spectroscopic techniques, and molecular docking analysis. Results showed that hyperoside and quercetin exhibited significant α-amylase inhibitory activities with IC₅₀ values of 0.491 and 0.325 mg/mL, respectively. The α-amylase activity decreased in the presence of hyperoside and quercetin in a competitive and noncompetitive manner, respectively. UV-vis spectra suggested that the aromatic amino acid residues (Trp and Tyr) microenvironment of α-amylase changed in the presence of these two flavonoids. FTIR and CD spectra showed the vibrations of the amide bands and the secondary structure content changes. The fluorescence quenching mechanism of α-amylase by hyperoside and quercetin belonged to the static quenching type. Finally, molecular docking intuitively showed that hyperoside/quercetin formed hydrogen bonds with the key active site residues (Asp197, Glu233, and Asp300) in α-amylase. MD simulation indicated hyperoside/quercetin-α-amylase docked complexes had good stability. Taken together, this research provides new sights to developing potent drugs or functional foods with hyperoside and quercetin, offering new avenues for hyperglycemia treatment.

Preparation of Dendrobium officinale Flower Anthocyanin and Extended Lifespan in Caenorhabditis elegans

The Dendrobium officinale flower is a non-medicinal part of the plant, rich in a variety of nutrients and bioactive ingredients. The purpose of this article was to explore the preparation conditions of anthocyanins (ACNs) from the D. officinale flower. Subsequently, its anti-aging effects were evaluated with Caenorhabditis elegans. Results showed that the ACNs had antioxidant activities on scavenging free radicals (DPPH· and ABTS⁺·), and the clearance rate was positively correlated with the dose. Additionally, ACNs significantly increased the activity of superoxide dismutase (SOD) in C. elegans, which was 2.068-fold higher than that of the control. Treatment with ACNs at 150 μL extended the lifespan of C. elegans by 56.25%, and treatment with ACNs at 50 μL promoted fecundity in C. elegans. Finally, the protective effect of ACNs enhanced stress resistance, thereby increasing the survival numbers of C. elegans, which provided insights for the development and practical application of functional products.

Preparation, characterization and antioxidant activity of sinapic acid grafted chitosan and its application with casein as a nanoscale delivery system for black rice anthocyanins

Anthocyanins (ACNs) have attracted considerable research attention because of their excellent health benefits, but their low stability and bioavailability limit their applications. In this study, sinapic acid-grafted-chitosan (SA-g-CS) conjugate was synthesized by grafting SA onto CS via a free radical mediated method. Nanoparticles were prepared using casein (CA) together with SA-g-CS to improve the performance and sustained release of black rice anthocyanins (BRA). The results of UV-Vis, FTIR and ¹H NMR spectra for SA-g-CS conjugates demonstrated the successful grafting of SA onto CS. The results of DPPH, ABTS and ferric ion reducing antioxidant power assays showed that the SA-g-CS conjugates had strong antioxidant capacities, and the higher the pH of the grafting reaction system, the stronger the antioxidant capacity of the conjugates. X-ray diffraction and scanning electron microscopy analyses showed that the crystallographic property and microstructure of CS were improved by the grafting of SA. Compared with BRA loaded nanoparticles prepared with CA alone or the combination of CS and CA, the BRA loaded nanoparticles constructed by SA-g-CS and CA have smaller particle size, better dispersion, encapsulation efficiency and sustained-release property. These results provided great potential for the application of phenolic acid grafted CS in stabilizing ACNs.

Hypoglycemic bioactivity of anthocyanins: A review on proposed targets and potential signaling pathways

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disease with complicated interrelationships responsible for initiating its pathogenesis. Novel strategies for the treatment of this devastating disease have attracted increasing attention worldwide. Anthocyanins are bioactive compounds that are widely distributed in the plant kingdom, and multiple studies have elucidated their beneficial role in preventing and managing T2DM. This review summarizes and comments on the hypoglycemic actions of anthocyanins from the perspective of molecular mechanisms and different target-related signaling pathways in vitro, in vivo, and clinical trials. Anthocyanins can ameliorate T2DM by functioning as carbohydrate digestive enzyme inhibitors, facilitating glucose transporter 4 (GLUT4) translocation, suppressing the effectiveness of dipeptidyl peptidase IV (DPP-IV), promoting glucagon-like peptide-1 (GLP-1) secretion, inhibiting protein tyrosine phosphatase 1B (PTP1B) overexpression, and interacting with sodium-glucose co-transporter (SGLT) to delay glucose absorption in various organs and tissues. In summary, anthocyanin is a promising and practical small molecule that can hyperglycemic symptoms and accompanying complications suffered by patients with diabetes. However, rational and potent doses for daily intake and clinical studies are required in the future.

Bioavailability, Absorption, and Metabolism of Pelargonidin-Based Anthocyanins Using Sprague-Dawley Rats and Caco-2 Cell Monolayers

The present study is aimed to clarify the absorption and metabolism properties of pelargonidin-based anthocyanins. Results showed that pelargonidin-3-O-rutinoside (Pg3R) was absorbed in its intact form after oral administration and reached a maximum plasma concentration of 175.38 ± 55.95 nM at 60 min. Three main metabolites were identified in plasma, including Pg3R-monoglucuronide (m/z 755.2046), Pg3R-hydroxylated (m/z 595.1644), and Pg3R-demethylated (m/z 565.1569) metabolites. The plasma concentration of the Pg3R-demethylated metabolite (57.04 ± 23.15 nM) was much higher than that of other two metabolites, indicating that demethylation was the main metabolic pathway for Pg3R, while the glucuronide conjugate was detected as the dominant metabolic form of pelargonidin-3-O-glucoside (Pg3G). The bioavailability of Pg3R (1.13%) was fourfold higher than that of Pg3G (0.28%), demonstrating that anthocyanins linked to the rutinoside may exhibit higher bioavailability than that of glucoside. In vitro transport study unveiled that passive diffusion and active efflux were involved in the absorption of Pg3R and Pg3G.

Inhibition mechanism of diacylated anthocyanins from purple sweet potato (Ipomoea batatas L.) against α-amylase and α-glucosidase

This study aimed to evaluate inhibitory activity of anthocyanins from purple sweet potato and blueberries against α-amylase and α-glucosidase, as well as investigate the inhibition mechanism of diacylated anthocyanins (Diacylated AF-PSP). Diacylated AF-PSP better inhibited α-amylase (IC₅₀ = 0.078 mg mL^-1) and α-glucosidase (IC₅₀ = 1.56 mg mL^-1) than other anthocyanin fractions, which was a mixed-type inhibitor. Fluorescence analysis indicated that Diacylated AF-PSP bound to the enzymes mainly through hydrogen bonds and influenced the microenvironments of proteins. Additionally, surface hydrophobicity and circular dichroism spectra results confirmed conformational changes in the enzymes induced by Diacylated AF-PSP. Molecular docking further demonstrated the interaction of Diacylated AF-PSP with enzyme active site, which might be stabilized by its acyl groups. Finally, 160 mg kg^-1 Diacylated AF-PSP significantly decreased (p < 0.01) blood glucose level peak by 20.52% after starch administration in SD rats. This study provided theoretical evidences for utilization of diacylated anthocyanins in hyperglycemia-management functional foods.

Nutritional Properties and In Vitro Antidiabetic Activities of Blue and Yellow Corn Extracts: A Comparative Study

The objective of this research was to designate and identify the profile of fatty acids, sterols, and polyphenol compounds and to demonstrate the antidiabetic activity, in blue corn extracts (BCE) in comparison with the yellow variant of this raw material. All of the maize lines, including the blue corn, were grown in Europe (southwestern part of Poland) and not in the place of origin (South America). In the extracts of the blue corn variety, eight anthocyanin compounds were isolated. The compound found in the largest amount was pelargonidin, followed by cyanidin-3-glucoside and other glycoside derivatives. Unsaturated fatty acids were the main ones found in the lipid fraction of blue and yellow corn, including linoleic acid and oleic acid. Saturated fatty acids, such as stearic and palmitic acid, were present in smaller amounts. The blue corn’s sterol profile was similar to other varieties of this corn, with β-sitosterol and campesterol occurring in the largest amount, alongside smaller amounts of stigmastanol and stigmasterol. The blue corn variety was characterized by a high content of polyphenolic compounds, which show several biological activities, including antidiabetic activity. The strongest in vitro antidiabetic effect was found in the blue corn lines. Among the polyphenolic compounds in both the blue and yellow corn varieties, in the largest amounts, were caffeic acid, procyanidin B2, and gallic acid. Despite the known and proven biological activity of polyphenolic compounds, the fat fraction showed the highest in vitro antidiabetic activity in the BCE studied.

Natural edible materials made of protein-functionalized aerogel particles for postprandial hyperglycemia management

α-Amylase inhibitors (α-AIs) delay digestion of dietary starch by inhibiting α-amylase in the gut, thereby reducing the postprandial glycemia, which is beneficial to the patients with obesity and diabetes. The proteinaceous α-AIs from wheat can effectively control starch digestion and regulate postprandial hyperglycemia. However, their gastric intolerance remains a challenge, which limits its commercial production and industrial application. In this study, sodium alginate/chitosan aerogels loaded with wheat protein α-AIs were prepared and evaluated as potential transportation and protection matrices for important components in food or pharmaceutical applications. Specifically, the biodegradable aerogel cross-linked with sodium alginate-chitosan-calcium chloride, has a large surface area and open porous structure, which can adsorb staple wheat proteins as an integrated edible material to block around 88,660 U/g of α-amylase activity. The aerogel particles were able to protect the activity of wheat α-AIs in the stomach, leading to the slow passage of the wheat α-AIs through the small intestine to inhibit starch digestion more effectively. Animal experiments further showed that the postprandial blood glucose levels in rats were effectively controlled through delayed increase, after administration of wheat protein-functionalized aerogel particles loaded with wheat α-AIs, which are natural biological macromolecules. This is a novel, safe, and economical method for the prevention and pretreatment of diabetes.

Discovery of anthocyanins from cranberry extract as pancreatic lipase inhibitors using a combined approach of ultrafiltration, molecular simulation and spectroscopy

Obesity is a chronic disease that has been causing serious problems all over the world. However, there is a lack of available therapeutic approaches to treat obesity. The FDA-approved drug orlistat has severe side effects, such as abdominal pain, flatulence and oily stool. As the therapeutic target of orlistat is pancreatic lipase, there is an urgent need for discovery of new pancreatic lipase inhibitors from natural sources that have reduced side effects compared with orlistat. In this study, ultrafiltration in combination with molecular simulation and spectroscopy was reported as an effective approach for identifying new pancreatic lipase inhibitors from anthocyanin-rich berry sources. Using this approach, four monomeric anthocyanins cyanidin-3-O-arabinoside (C3A), cyanidin-3-O-galactoside (C3Ga), peonidin-3-O-arabinoside (Pn3A) and peonidin-3-O-galactoside (Pn3Ga) from cranberries were discovered as potent pancreatic lipase inhibitors. These four cranberry anthocyanins were shown to form hydrophobic interactions and hydrogen bonds with pocket amino acid residues in molecular docking and molecular dynamics simulations. C3A showed greater impact on secondary structures of the enzyme and showed higher binding capacity with the enzyme compared with C3Ga, Pn3A and Pn3Ga as observed by CD and fluorescence spectroscopy. The structure-activity relationships were then investigated and summarized as both the structures of the B ring and glycosyl group were related to the inhibitory activities of anthocyanins. In short, our results suggested that cranberry anthocyanins could be developed as food supplements to facilitate the prevention and treatment of obesity.

Targets and mechanisms of dietary anthocyanins to combat hyperglycemia and hyperuricemia: a comprehensive review

Hyperglycemia and hyperuricemia are both metabolic disorders related to excessive amount of metabolites in blood, which are considered as high risk factors for the development of many chronic diseases. Enzymes, cells, tissues and organs, which are relevant to metabolism and excretion of glucose and UA, are usually regarded to be the targets in treatment of hyperglycemia and hyperuricemia. Several drugs have been commonly applied to combat hyperglycemia and hyperuricemia through various targets but with unignorable side effects. Anthocyanins have become promising alternatives against hyperglycemia and hyperuricemia because of their bio-activities with little side effects. Structurally different anthocyanins from berry fruits, cherries and purple sweet potato lead to the diverse functional activity and property. This review is aimed to illustrate the specific targets that are available for anthocyanins from berry fruits, cherries and purple sweet potato in hyperglycemia and hyperuricemia management, as well as discuss the structure-activity relationship, and the underlying mechanisms associated with intracellular signaling pathway, anti-oxidative stress and anti-inflammation. In addition, the relationship of hyperglycemia and hyperuricemia, and the possibly regulative role of anthocyanins against them, along with the effects of anthocyanins in clinical trial are mentioned.