Studies on the inhibition of α-glucosidase by biflavonoids and their interaction mechanisms

Screening, characterization and mechanism of a potential stabiliser for nisin nanoliposomes with high encapsulation efficiency

The encapsulation efficiency (EE%) reflects the amount of bioactive components that can be loaded into nanoliposomes. Obtaining a suitable nanoliposome stabiliser may be the key to improving their EE%. In this study, three polyphenols were screened as stabilisers of nanoliposomes with high nisin EE%, with curcumin nanoliposomes (Cu-NLs) exhibiting the best performance (EE% = 95.94%). Characterizations of particle size, PDI and zeta potential indicate that the Cu-NLs had good uniformity and stability. TEM found that nisin accumulated at the edges of the Cu-NLs' phospholipid layer. DSC and FT-IR revealed that curcumin was involved in the formation of the phospholipid layer and altered its structure. FT-IR and molecular docking simulations indicate that the interactions between curcumin and nisin are mainly hydrogen bonding and hydrophobic. In whole milk, Cu-NLs effectively protected nisin activity. This study provides an effective strategy for improving the EE% of nanoliposomes loaded with nisin and other bacteriocins.

Structural changes of wheat starch and activity inhibition of α-glucosidase by persimmon (Diospyros kaki Thunb.) leaves extract retarding starch digestibility

Elevated blood sugar levels caused by starch digestion was a target for controlling diabetes mellitus. The in vitro and in vivo digestibility of wheat starch was evaluated to find that adding 15 % persimmon leaf extract (PLE) to starch reduced its digestibility by 69.50 % and the peak postprandial blood glucose by 23.63 %. Subsequently, we observed under scanning electron microscopy and atomic force microscopy that the presence of PLE led to the destruction of starch structure and the aggregation of α-glucosidase so as to decrease starch digestion and hinder the binding of starch to α-glucosidase. Through multi-spectral analysis, PLE hindered the clathrate of iodine and starch, and also increased the crystallinity of starch by 48.58 %. For α-glucosidase inhibitory activity (IC50 = 72.49 μg/mL), PLE preferentially occupied the active center of α-glucosidase, changed its fluorescence characteristics and secondary structure through hydrogen bonding and hydrophobic interaction. Moreover, among the 23 potential α-glucosidase inhibitors screened from PLE, combined with molecular simulation, Procyanidin B2 had the strongest inhibitory effect (IC50 = 33.22 μg/mL) and binding energy (-7.09 kcal/mol), which was most effectively inhibitory on digestion. These results indicated the potential of PLE in hypoglycemia targeting both starch and α-glucosidase.

Hinokiflavone resists HFD-induced obesity by promoting apoptosis in an IGF2BP2-mediated Bim m6A modification dependent manner

Obesity has emerged as a major health risk on a global scale. Hinokiflavone (HF), a natural small molecule, extracted from plants like cypress, exhibits diverse chemical structures and low synthesis costs. Using high-fat diet (HFD)-induced obese mice models, we found that HF suppresses obesity by inducing apoptosis in adipose tissue. Adipocyte apoptosis helps maintain tissue health by removing aging, damaged, or excess cells in adipose tissue, which is crucial in preventing obesity and metabolic diseases. We found that HF can specifically bind to insulin-like growth factor 2 mRNA binding protein 2 (IGF2BP2) to promote the stability of N6-methyladenosine (m6A) -modified Bim, inducing mitochondrial outer membrane permeabilization (MOMP). MOMP leads to Caspase9/3-mediated adipocyte mitochondrial apoptosis, alleviating obesity induced by a high-fat diet. The pro-apoptotic effect of HF offers a controlled means for weight loss. This study reveals the potential of small molecule HF in developing new therapeutic approaches in drug development and biomedical research.

Molecular docking studies, DFT, and ADMET calculations of some flavonoids and their characteristic structural features involved in inhibition of pro-inflammatory enzymes

Inflammation is an immune system response triggered by pathogens, damaged cells, or stimuli. Some regulatory enzymes, such as phosphodiesterase, hyaluronidase, collagenase, and lipoxygenase, play an essential role in the inflammatory process. Polyphenolic compounds, such as flavonoids, are active suppressors of inflammatory cytokines, modulators of transcription factors, and inflammation-related pathways. A set of flavonoid structures was screened and docked against inflammation pathway enzymes. Amentoflavone has been shown to cause interactions with phosphodiesterase enzymes, while Bilobetin and Silibinin demonstrated an increase in binding energy with collagenase enzymes. The retrieved compounds from the docking study were subjected to DFT theory. The results showed that the LUMO orbital is located on the flavonoid part. The thermochemical parameters indicated that Silibinin is more stable than other compounds. The ADMET profile predicted that Silibinin can be used orally among the compounds. Silibinin can be introduced as a promising anti-inflammatory agent demonstrating phosphodiesterase and collagenase inhibitory properties.

Characterization of microencapsulated powders rich in saponins from cocoa pod husk (Theobroma cacao L.) and medicinal plant an xoa (Helicteres hirsuta Lour.)

Cocoa pod husk (CPH) is a major residue of cocoa processing industry, while medicinal plant H. hirsuta is used for treatment of malaria and diabetes mellitus in folk medicine. This study aimed to produce microencapsulated powders from saponin-enriched CPH and H. hirsuta extracts and assess their physicochemical, phytochemical, antioxidant, and α-glucosidase inhibition properties. The findings show that the microencapsulated powders were achieved diserable physicochemical properties (moisture of 3.22-4.76 %, water activity of 0.43-0.46, water solubility index of 74.18-88.77 %, particle size of 254.2-719.7 nm, and zeta potential from -6.97 to -15.1 mV). The phytochemical content of microencapsulated CPH powders gained at high levels (total saponin content of 151.87-193.46 mg EE/g DS, total flavonoid content of 33.80-46.05 mg CE/g DS), total alkaloid content of 15.20-24.23 mg AA/g DS, and total phenolic content of 5.41-6.49 mg GAE/g DS). The antioxidant potential of microencapsulated CPH powders using ARSC and FRAP assays was 15.51-18.20 and 9.61-11.89 mg TE/g DS, respectively, while their α-glucosidase inhibition capacity at 100 μg/mL was found at 51.74-52.16 %. The phytochemical content (except total alkaloid content), antioxidant, and α-glucosidase inhibitory potential of microencapsulated CPH powders were smaller than those of microencapsulated H. hirsuta and combined powders. This study reveals that the microencapsulated CPH and H. hirsuta powders were prospective in reducing hyperglycemia activity. Therefore, this study provided an evidence for further application of CPH and H. hirsuta plant for functional food development.

Polyketides with α-glucosidase inhibitory and neuroprotective activities from Aspergillus versicolor associated with Pedicularis sylvatica

Aspergillus versicolor, an endophytic fungus associated with the herbal medicine Pedicularis sylvatica, produced four new polyketides, aspeversins A-D (1-2 and 5-6) and four known compounds, O-methylaverufin (2), aversin (3), varilactone A (7) and spirosorbicillinol A (8). Their structures were elucidated by extensive spectroscopic data analysis, and their absolute configurations were determined by calculated electronic circular dichroism (ECD) and Mo2(AcO)4-induced CD data. Compound 5 was found to exhibit α-glucosidase inhibitory activity with an IC50 value of 25.57 μM. An enzyme kinetic study indicated that 5 was a typical uncompetitive inhibitor toward α-glucosidase, which was supported by a molecular docking study. Moreover, compounds 1-3 and 5 also improved the cell viability of PC12 cells on a 1-methyl-4-phenylpyridinium (MPP+)-induced Parkinson's disease model, indicating their neuroprotective potential as antiparkinsonian agents.

Dietary phenolic compounds as promising therapeutic agents for diabetes and its complications: A comprehensive review

In the middle of an ever-changing landscape of diabetes care, precision medicine, and lifestyle therapies are becoming increasingly important. Dietary polyphenols are like hidden allies found in our everyday meals. These biomolecules, found commonly in fruits, vegetables, and various plant-based sources, hold revolutionary potential within their molecular structure in the way we approach diabetes and its intimidating consequences. There are currently numerous types of diabetes medications, but they are not appropriate for all patients due to limitations in dosages, side effects, drug resistance, a lack of efficacy, and ethnicity. Currently, there has been increased interest in practicing herbal remedies to manage diabetes and its related complications. This article aims to summarize the potential of dietary polyphenols as a foundation in the treatment of diabetes and its associated consequences. We found that most polyphenols inhibit enzymes linked to diabetes. This review outlines the potential benefits of selected molecules, including kaempferol, catechins, rosmarinic acid, apigenin, chlorogenic acid, and caffeic acid, in managing diabetes mellitus as these compounds have exhibited promising results in in vitro, in vivo, in silico, and some preclinical trials study. This encompassing exploration reveals the multifaceted impact of polyphenols not only in mitigating diabetes but also in addressing associated conditions like inflammation, obesity, and even cancer. Their mechanisms involve antioxidant functions, immune modulation, and proinflammatory enzyme regulation. Furthermore, these molecules exhibit anti-tumor activities, influence cellular pathways, and activate AMPK pathways, offering a less toxic, cost-effective, and sustainable approach to addressing diabetes and its complications.

Globunoids A-D, undescribed bichalconoid and biflavanoids with α-glucosidase and α-amylase inhibitory activities from Knema globularia stems

A bichalconoid, globunoid A (1) and three biflavanones, globunoids B-D (2-4), previously undescribed, were isolated from the stems of Knema globularia, along with fourteen known analogues 5-18. The chemical structures of 1-4 were elucidated by the comprehensive spectroscopic analysis including UV, IR, HRESIMS, and NMR; the absolute configurations were determined based on their NOESY data, DP4+ statistical analysis, and ECD calculation. Up to now, compounds 2 and 3 represent the first 3,3″-linked biflavanone structures. Among the isolated compounds, 2, 3, and 2,3-dihydrocalodenin B (6) potently inhibited α-glucosidase and α-amylase activities, with IC50 values in the range 1.1-7.5 μM. Furthermore, the most active compound 6 was found to be a non-competitive inhibitor against these two enzymes.

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

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

Acetylation of the polysaccharide from Houttuynia cordata rhizome and their α-glucosidase inhibition mechanism

In this study, the polysaccharide (RHCP) extracted from Houttuynia cordata rhizome was acetylated through the acetic anhydride method. The physicochemical properties of RHCP and its acetylated derivatives (Ac-RHCP) were determined by infrared spectra, scanning electron microscopy, and Congo red test. Meanwhile, the α-glucosidase inhibition mechanism of RHCP and Ac-RHCP was analyzed by inhibition kinetics, and circular dichroism and fluorescence spectroscopy. Ac-RHCP resulted in a more porous surface structure and 1.83-fold higher solubility compared with RHCP. At a concentration of 6 mg/mL, the α-glucosidase inhibition rate of Ac-RHCP was 75.40%, while that of RHCP was 44.68%. RHCP and Ac-RHCP inhibited α-glucosidase in a mixed-type manner, reduced the endogenous fluorescence of α-glucosidase, affected the microenvironment of amino acid residues, and changed the conformation of α-glucosidase. The study indicates that Ac-RHCP exhibits a certain level of α-glucosidase inhibition, demonstrating its potential as a functional food for glycemic control.

Characterization, multivariate analysis and bioactivity evaluation of coumarins in the bark of Fraxinus mandshurica

The bark of Fraxinus mandshurica is a traditional folk herb used to clear heat and dry dampness. To investigate the differences in coumarins content in the bark of F. mandshurica, 24 batches of samples from four origins were collected and analyzed. Eight coumarins were obtained by traditional natural product extraction, isolation and identification techniques and quantified by high performance liquid chromatography-photodiode array (HPLC-DAD). The quantitative results showed that the overall content of compound 30 (Fraxinol) was higher at 100.23 mg/g, while the overall content of compound 23 (Cichoriin) was lower, which may be related to environmental factors in different regions. The method validation showed that the linear range of the eight standards was between 10 and 2500 μg/mL with correlation coefficient (R2) values >0.9991; the relative standard deviation (RSD, %) values of intra-day precision were between 0.35 and 1.38, while the RSD values of inter-day precision were between 0. 29-1.78; the RSD (%) values for the reproducibility experiments ranged from 0.29 to 1.87, while the RSD (%) values for the stability experiments ranged from 0.22 to 2.33; the spiked recovery of the samples ranged from 98.65 to 101.34%, and the RSD (%) values ranged from 0.22 to 1.96. The method validation results showed that the instrument used for the analysis had good precision, the reproducibility and stability of the samples were good, and the accuracy of the experimental method was high. In addition, a total of 54 chemical components were identified from F. mandshurica bark by ultra performance liquid chromatography-electrospray quadrupole time-of-flight mass spectrometry (UPLC-ESI-Q-TOF-MS). Based on this, fingerprinting, heatmap and multivariate analysis, including principal component analysis (PCA) and partial least squares discriminant analysis (PLS-DA), were established for 24 batches of samples, and four marker compounds that could be used to distinguish different origins of F. mandshurica were screened. To further investigate the bioactivities of the eight coumarins, in vitro enzyme activity inhibition studies were performed, and the results showed that they all exhibited different degrees of inhibition of acetylcholinesterase, tyrosinase and α-glucosidase, thus having potential applications in the treatment of Alzheimer's disease, blemish whitening and anti-diabetes, and becoming a new source of natural enzyme activity inhibitors. This study established an identification and evaluation method applicable to plants of different origins, which provides a strong reference for quality control, origin evaluation and clinical application of traditional medicinal plants.

Natural Sweetener, Glycyrrhetinic Acid 3-O-Mono-beta-d-glucuronide, for Postprandial Hyperglycemia Management

This study examines the inhibitory effects of a range of sweeteners on α-glucosidase. Our findings revealed that only one natural sweetener, namely, glycyrrhetinic acid 3-O-mono-beta-d-glucuronide (GAMG), derived from licorice, exhibited a mixed-type inhibition against α-glucosidase with a IC50 value of 0.73 ± 0.05 mg/mL. The fluorescence intensity of α-glucosidase was quenched by GAMG in the formation of an α-glucosidase-GAMG complex. GAMG has been shown to induce conformational changes in α-glucosidase, likely through hydrogen bonding, van der Waals force, and alkyl-alkyl interactions with amino acid residues, including Arg 281, Leu 283, Trp 376, Asp 404, Asp 443, Trp 481, Asp 518, Phe 525, Ala 555, and Asp 616. Additional animal validation experiments demonstrated that GAMG slowed starch digestion, thereby attenuating the postprandial glycemic response. Taken together, these findings provide evidence that GAMG is a natural sweetener with potent inhibitory activity that selectively targets α-glucosidase. This study supports the use of GAMG as a natural sweetener, which holds a high biological value and may be beneficial for managing postprandial hyperglycemia.

Chemical profile of phenolic extracts from rapeseed meal and inhibitory effects on α-glucosidase: UPLC-MS/MS analysis, multispectral approaches, molecular simulation and ADMET analysis

Rapeseed meal (RSM) is the by-product of rapeseed processing that enriches phenolic compounds. However, the comprehensive characterization of its phenolic substances in terms of composition and potential activities remains incomplete, leading to limited utilization in the food industry. In this study, the phenolic profile from RSM (referred to as RMP) was identified, and their inhibitory effects on α-glucosidase were investigated. UPLC-MS/MS analysis showed that a total of 466 phenolic compounds were detected in RMP. The primary components were sinapic acid (SA), caffeic acid (CA), salicylic acid (SAA), and astragalin (AS). Multispectral approaches demonstrated significant inhibitory capacity of RMP against α-glucosidase with a half inhibition value (IC50) of 0.32 mg/mL, with a stronger inhibition compared to CA/SAA/AS (IC50: 4.0, 5.9, and 0.9 mg/mL) in addition to the previously reported SA, suggesting a synergistic effect. Both RMP and CA/SAA/AS altered the secondary structure of α-glucosidase to quench its intrinsic fluorescence. Molecular simulation results revealed that hydrogen bonds and van der Waals forces primarily contributed to the interaction between CA/SAA/AS and α-glucosidase, as well as verified the stability of the binding process over the entire simulation duration. The ADMET analysis showed that CYP2D6 was not inhibited by CA/SAA/AS, which had no AMES toxicity, hepatotoxicity, and skin sensitization. This finding suggests the potential of RMP against α-glucosidase for the treatment of diabetes.

Utilizing bio-affinity ultrafiltration combined with UHPLC Q-Exactive Plus Orbitrap HRMS to detect potential α-glucosidase inhibitors in Oxalis corniculate L

Oxalis corniculate L. (O. corniculate) was used to treat diabetes in Chinese folk as a popular tea drink. In this work, 31 compounds from O. corniculate were screened and identified as potential α-Glucosidase inhibitors (α-GIs). Among them, 6 compounds displayed stronger inhibitory activity than acarbose (IC50 = 212.9 ± 5.98 μg/mL). Especially, the most effective compounds quercetin (Qu, IC50 = 4.70 ± 0.40 μg/mL) and luteolin (Lu, IC50 = 15.72 ± 0.75 μg/mL) inhibited α-Glu in competitive and mixed manners, respectively. Moreover, fluorescence quenching, circular dichroism (CD), and molecular docking study revealed that they can arouse the changes in the secondary structure and hydrophobic micro-environment of the enzyme mainly through a hydrophobic binding. Furthermore, it was observed that oral administration of Qu (20 mg/kg) can significantly reduce postprandial blood glucose (PBG) levels in mice vs. the control group. To sum up, the above research confirmed that O. corniculate could prevent and treat postprandial hyperglycemia as a good tea drink, and the plant was an excellent source to obtain natural α-GIs.

A Comparative Analysis of Radical Scavenging, Antifungal and Enzyme Inhibition Activity of 3'-8″-Biflavones and Their Monomeric Subunits

Biflavonoids are dimeric forms of flavonoids that have recently gained importance as an effective new scaffold for drug discovery. In particular, 3'-8″-biflavones exhibit antiviral and antimicrobial activity and are promising molecules for the treatment of neurodegenerative and metabolic diseases as well as cancer therapies. In the present study, we directly compared 3'-8″-biflavones (amentoflavone, bilobetin, ginkgetin, isoginkgetin, and sciadopitysin) and their monomeric subunits (apigenin, genkwanin, and acacetin) and evaluated their radical scavenging activity (with DPPH), antifungal activity against mycotoxigenic fungi (Alternaria alternata, Aspergillus flavus, Aspergillus ochraceus, Fusarium graminearum, and Fusarium verticillioides), and inhibitory activity on enzymes (acetylcholinesterase, tyrosinase, α-amylase, and α-glucosidase). All the tested compounds showed weak radical scavenging activity, while antifungal activity strongly depended on the tested concentration and fungal species. Biflavonoids, especially ginkgetin and isoginkgetin, proved to be potent acetylcholinesterase inhibitors, whereas monomeric flavonoids showed higher tyrosinase inhibitory activity than the tested 3'-8″-biflavones. Amentoflavone proved to be a potent α-amylase and α-glucosidase inhibitor, and in general, 3'-8″-biflavones showed a stronger inhibitory potential on these enzymes than their monomeric subunits. Thus, we can conclude that 3'-8″-dimerization enhanced acetylcholinesterase, α-amylase, and α-glucosidase activities, but the activity also depends on the number of hydroxyl and methoxy groups in the structure of the compound.

Multi-target action of Garcinia livingstonei extract and secondary metabolites against fatty acid synthase, α-glucosidase, and xanthine oxidase

Garcinia livingstonei is a traditional herbal medicine that showed beneficial health effects and bioactivities. Four compounds have been isolated from the plant leaves and were elucidated as lupeol, betulin, podocarpusflavone A, and amentoflavone. The inhibitory activities of G. livingstonei extract and isolated metabolites against fatty acid synthase (FAS), α-glucosidase, and xanthine oxidase (XO) were investigated in vitro. The affinity of the compounds toward the studied enzymes was investigated in silico. The plant extract inhibited FAS, α-glucosidase, and XO with IC50 values of 26.34, 67.88, and 33.05 µg/mL, respectively. Among the isolated metabolites, betulin exhibited the most inhibitory activity against α-glucosidase and XO with IC50 values of 38.96 and 30.94 µg/mL, respectively. Podocarpusflavone A and betulin were the most potent inhibitors of FAS with IC50 values of 24.08 and 27.96 µg/mL, respectively. Computational studies corroborated these results highlighting the interactions between metabolites and the enzymes. In conclusion, G. livingstonei and its constituents possess the potential to modulate enzymes involved in metabolism and oxidative stress.