Exploring two types of prenylated bitter compounds from hop plant (Humulus lupulus L.) against α-glucosidase in vitro and in silico

Effect of Phenol and Alkylamide Interaction on α-Glucosidase Inhibition and Cellular Antioxidant Activity during In Vitro Digestion: Using Szechuan Pepper (Zanthoxylum genus) as a Model

Although recent evidence indicated significant phenol and alkylamide interaction in aqueous solutions, the gastrointestinal digestion influence of the combination remains unclear. This study aims to investigate phenol and alkylamide interaction during in vitro digestion, focusing on bioaccessibility and bioactivity, including α-glucosidase inhibition and cellular antioxidant activity. Additionally, the structural mechanism of phenol and alkylamide interaction during in vitro digestion was explored. The results indicated that the presence of phenols and alkylamides significantly increased or decreased their respective bioaccessibility, depending on the Zanthoxylum varieties. Furthermore, although antagonistic phenol/alkylamide interaction was evident during α-glucosidase inhibition, cellular oxidative stress alleviation, and antioxidant gene transcription upregulation, this effect weakened gradually as digestion progressed. Glycoside bond cleavage and the methylation of phenols as well as alkylamide isomerization and addition were observed during digestion, modifying the hydrogen bonding sites and interaction behavior. This study provided insights into the phenol/alkylamide interaction in the gastrointestinal tract.

Inhibition of α-glucosidase activity and intestinal glucose transport to assess the in vivo anti-hyperglycemic potential of dodecyl-acylated phlorizin and polydatin derivatives

A diet containing natural active compounds that can inhibit the hydrolytic activity of α-glucosidase on carbohydrates and intestinal glucose absorption is an effective means of controlling postprandial hyperglycemia. Phlorizin and polydatin as phenolic glycosides have a high affinity for the catalytic site of α-glucosidase, but exhibited unsatisfactory competitive inhibitory capacity, with an IC50 of 0.97 and >2 mM, respectively. However, dodecyl-acylated derivatives of phlorizin and polydatin exerted α-glucosidase inhibitory capacity, with an IC50 of 55.10 and 70.95 μM, respectively, which were greatly enhanced and much stronger than that of acarbose with an IC50 of 2.46 mM. The SPR assay suggested the high affinity of dodecyl phlorizin and dodecyl polydatin to α-glucosidase with equilibrium dissociation constant (KD) values of 12.0 and 7.9 μM, respectively. Both dodecyl phlorizin and dodecyl polydatin reduced the catalytic ability of α-glucosidase by reversible noncompetitive and uncompetitive mixed inhibition, which bind noncovalently to the allosteric site 2 through hydrogen bonds and hydrophobic interactions, thereby inducing the secondary structure unfolding and intrinsic fluorescence quenching of α-glucosidase. Confocal microscopy detection visually showed significant inhibitory effects on FITC-labeled glucose uptake in intestinal Caco-2 cells by phlorizin, polydatin, dodecyl phlorizin and dodecyl polydatin. In addition, based on the differentiated Caco-2 cell monolayer model, dodecyl phlorizin and dodecyl polydatin suppressed intestinal glucose transport more effectively than phlorizin and polydatin, suggesting that they were promising in vivo hypoglycemic active compounds.

Deciphering the binding behavior and interaction mechanism of apigenin and α-glucosidase based on multi-spectroscopic and molecular simulation studies

This study investigated the molecular mechanism underlying the binding interaction between apigenin (API) and α-glucosidase (α-glu) by a combination of experimental techniques and computational simulation strategies. The spontaneously formation of stable API-α-glu complex was mainly driven by hydrogen bonds and hydrophobic forces, leading to a static fluorescence quenching of α-glu. The binding of API induced secondary structure and conformation changes of α-glu, decreasing the surface hydrophobicity of protein. Computational simulation results demonstrated that API could bind into the active cavity of α-glu via its interaction with active residues at the binding site. The important roles of key residues responsible for the binding stability and affinity between API and α-glu were further revealed by MM/PBSA results. In addition, it can be found that the entrance of active site tended to close after API binding as a result of its interaction with gate keeping residues. Furthermore, the structural basis for the binding interaction behavior of API was revealed and visualized by weak interaction analysis. The findings of our study revealed atomic-level mechanism of the interaction between API, which might shed light on the development of better inhibitors.

Anti-inflammatory potential of some eudesmanolide and guaianolide sesquiterpenes

Ten sesquiterpene lactones isolated from Anvillea garcinii (Burm.f.) DC ethanolic extract were assessed for their anti-inflammatory potential by myeloperoxidase (MPO) activity assignment, and mice paw swelling model. 3α,4α-10β-trihydroxy-8α-acetyloxyguaian-12,6α-olide (1), epi-vulgarin (3), 9a-hydroxyparthenolide (4), garcinamine C (7), garcinamine D (8), garcinamine E (9), and 4, 9-dihydroxyguaian-10(14)-en-12-olide (10) showed explicit anti-inflammatory activity in rodent paw edema and MPO assignment. The findings of this study showed that the α-methylene γ-lactone moiety does not always guarantee an anti-inflammatory effect, but the presence of proline at the C3 of the lactone ring improves the binding of sesquiterpene lactones with MPO isoenzymes, resulting in a more potent inhibition.

Shiitake polysaccharides acted as a non-competitive inhibitor to α-glucosidase and inhibited glucose transport of digested starch from Caco-2 cells monolayer

The inhibition mechanism of shitake mushroom polysaccharides (Lentinula edodes polysaccharides, LEP) against α-glucosidase was studied by enzyme kinetic assay, fluorescence quenching and molecular docking. The effect of LEP on glucose transport of digested starch was investigated via an in vitro digestion/Caco-2 transwell model. LEP exhibited a stronger inhibiting effect (IC50 = 0.66 mg/mL) than acarbose and presented a non-competitive inhibition mechanism. The interaction between LEP and α-glucosidase primarily involved electrostatic interaction and hydrogen bonding. Molecular docking modelling showed that the four structures of LEP were bound to the allosteric tunnel or adjacent pocket of α-glucosidase via electrostatic force and hydrogen bonds. The (1 → 6)-linkages in LEP structures favoured its binding affinity to the α-glucosidase. The α-glucosidase inhibiting activity of LEP was also found to emanate from the reduction in glucose transport of digested starch as deducted from the in vitro digestion/Caco-2 transwell data. The release of glucose from digested starch cooked with LEP was significantly reduced (33.7%) compared to the digested starch without LEP. The findings from the current study suggest that LEP could be a promising ingredient to inhibit α-glucosidase activity as well as control the level of postprandial blood glucose when incorporated into starchy foods.

Scutellarein alleviates chronic obstructive pulmonary disease through inhibition of ferroptosis by chelating iron and interacting with arachidonate 15-lipoxygenase

Ferroptosis, an iron-dependent cell death characterized by lethal lipid peroxidation, is involved in chronic obstructive pulmonary disease (COPD) pathogenesis. Therefore, ferroptosis inhibition represents an attractive strategy for COPD therapy. Herein, we identified natural flavonoid scutellarein as a potent ferroptosis inhibitor for the first time, and characterized its underlying mechanisms for inhibition of ferroptosis and COPD. In vitro, the anti-ferroptotic activity of scutellarein was investigated through CCK8, real-time quantitative polymerase chain reaction (RT-qPCR), Western blotting, flow cytometry, and transmission electron microscope (TEM). In vivo, COPD was induced by lipopolysaccharide (LPS)/cigarette smoke (CS) and assessed by changes in histopathological, inflammatory, and ferroptotic markers. The mechanisms were investigated by RNA-sequencing (RNA-seq), electrospray ionization mass spectra (ESI-MS), local surface plasmon resonance (LSPR), drug affinity responsive target stability (DARTS), cellular thermal shift assay (CETSA), and molecular dynamics. Our results showed that scutellarein significantly inhibited Ras-selective lethal small molecule (RSL)-3-induced ferroptosis and mitochondria injury in BEAS-2B cells, and ameliorated LPS/CS-induced COPD in mice. Furthermore, scutellarein also repressed RSL-3- or LPS/CS-induced lipid peroxidation, GPX4 down-regulation, and overactivation of Nrf2/HO-1 and JNK/p38 pathways. Mechanistically, scutellarein inhibited RSL-3- or LPS/CS-induced Fe2+ elevation through directly chelating Fe2+ . Moreover, scutellarein bound to the lipid peroxidizing enzyme arachidonate 15-lipoxygenase (ALOX15), which resulted in an unstable state of the catalysis-related Fe2+ chelating cluster. Additionally, ALOX15 overexpression partially abolished scutellarein-mediated anti-ferroptotic activity. Our findings revealed that scutellarein alleviated COPD by inhibiting ferroptosis via directly chelating Fe2+ and interacting with ALOX15, and also highlighted scutellarein as a candidate for the treatment of COPD and other ferroptosis-related diseases.

Application of molecular dynamics simulation for exploring the roles of plant biomolecules in promoting environmental health

Understanding the dynamic changes of plant biomolecules is vital for exploring their mechanisms in the environment. Molecular dynamics (MD) simulation has been widely used to study structural evolution and corresponding properties of plant biomolecules at the microscopic scale. Here, this review (i) outlines structural properties of plant biomolecules, and the crucial role of MD simulation in advancing studies of the biomolecules; (ii) describes the development of MD simulation in plant biomolecules, determinants of simulation, and analysis parameters; (iii) introduces the applications of MD simulation in plant biomolecules, including the response of the biomolecules to multiple stresses, their roles in corrosive environments, and their contributions in improving environmental health; (iv) reviews techniques integrated with MD simulation, such as molecular biology, quantum mechanics, molecular docking, and machine learning modeling, which bridge gaps in MD simulation. Finally, we make suggestions on determination of force field types, investigation of plant biomolecule mechanisms, and use of MD simulation in combination with other techniques. This review provides comprehensive summaries of the mechanisms of plant biomolecules in the environment revealed by MD simulation and validates it as an applicable tool for bridging gaps between macroscopic and microscopic behavior, providing insights into the wide application of MD simulation in plant biomolecules.

Phytochemistry and pharmacology of natural prenylated flavonoids

Prenylated flavonoids are a special kind of flavonoid derivative possessing one or more prenyl groups in the parent nucleus of the flavonoid. The presence of the prenyl side chain enriched the structural diversity of flavonoids and increased their bioactivity and bioavailability. Prenylated flavonoids show a wide range of biological activities, such as anti-cancer, anti-inflammatory, neuroprotective, anti-diabetic, anti-obesity, cardioprotective effects, and anti-osteoclastogenic activities. In recent years, many compounds with significant activity have been discovered with the continuous excavation of the medicinal value of prenylated flavonoids, and have attracted the extensive attention of pharmacologists. This review summarizes recent progress on research into natural active prenylated flavonoids to promote new discoveries of their medicinal value.

Adding functional properties to beer with jasmine tea extract

Hops provide the characteristic bitter taste and attractive aroma to beer; in this study, hops were replaced by jasmine tea extract (JTE) during late-hopping. The addition of JTE improved the beer foam stability 1.52-fold, and increased the polyphenol and organic acid contents. Linalool was the most important aroma compound in hopped (HOPB) and jasmine tea beer (JTB), but other flavor components were markedly different, including dimeric catechins, flavone/flavonol glycosides, and bitter acids and derivatives. Sensory evaluation indicated that addition of JTE increased the floral and fresh-scent aromas, reduced bitterness and improved the organoleptic quality of the beer. The antioxidant capacity of JTB was much higher than that of HOPB. The inhibition of amylase activity by JTB was 30.5% higher than that of HOPB. Functional properties to beer were added by substituting jasmine tea extract for hops during late hopping.

Improving Regulation of Polymeric Proanthocyanidins and Tea Polyphenols against Postprandial Hyperglycemia via Acid-Catalyzed Transformation

A novel protocol was established to synthesize novel α-glucosidase inhibitors (prodelphinidin B gallates) from proanthocyanidins from Chinese bayberry leaves (BLPs) and epigallocatechin gallate (EGCG) via acid-catalyzed transformation, which had improved regulation against postprandial hyperglycemia. Their structural-activity relationship was clarified by enzymatic kinetics, multispectroscopic method, molecular docking analysis, and sucrose loading test. ProDB MG and DG were noncompetitive inhibitors of α-glucosidase with IC₅₀ values of 7.82 and 7.52 μg/mL, respectively. They bound with α-glucosidase spontaneously through van der Waals force and hydrogen bonding interaction, inducing the change of spatial conformation and secondary structure of α-glucosidase. Molecular docking studies suggested that proDB MG and DG attached to another one nonactive pocket with strong affinity. ProDB DG exerted significant improvement of postprandial hyperglycemia in a dose-dependent manner. Hence, proDB MG and DG, potential antidiabetic compounds, alleviate postprandial hyperglycemia by inhibiting α-glucosidase.