Ligand-targeted fishing of α-glucosidase inhibitors from Tribulus terrestris L. based on chitosan-functionalized multi-walled carbon nanotubes with immobilized α-glucosidase

In-depth investigation of the therapeutic effect of Tribulus terrestris L. on type 2 diabetes based on intestinal microbiota and feces metabolomics

ETHNOPHARMACOLOGICAL RELEVANCE

The fruit of Tribulus terrestris L. (TT) is extensively documented in the Tibetan medical literature 'Si Bu Yi Dian', has been used to treat diabetes mellitus for more than a thousand years. However, the underlying mechanisms and comprehensive effects of TT on diabetes have yet to be investigated.

AIM OF THE STUDY

The aim of the study was to systemically elucidate the potential mechanisms of TT in treating diabetes mellitus, and further investigate the therapeutic effects of the water extract, small molecular components and saccharides from TT.

MATERIALS AND METHODS

Fecal metabolomics was employed to draw the metabolic profile based on UHPLC-Q-TOF-MS/MS. The V3-V4 hypervariable regions of the bacteria 16S rRNA gene were amplified to explore the structural changes of the intestinal microbiome after TT intervention and to analyze the differential microbiota. The microbial metabolites SCFAs were determined by GC-MS, and the BAs and tryptophan metabolites were quantified by UPLC-TQ-MS. Spearman correlation analysis was carried out to comprehensively investigate the relationship among the endogenous metabolites profile, intestinal microbiota and their metabolites.

RESULTS

TT exhibited remarkably therapeutic effect on T2DM rats, as evidenced by improved glucolipid metabolism and intestinal barrier integrity, ameliorated inflammation and remission in insulin resistance. A total of 24 endogenous biomarkers were screened through fecal metabolomics studies, which were mainly related to tryptophan metabolism, fatty acid metabolism, bile acid metabolism, steroid hormone biosynthesis and arachidonic acid metabolism. Investigations on microbiomics revealed that TT significantly modulated 18 differential bacterial genera and reversed the disordered gut microbial in diabetes rats. Moreover, TT notably altered the content of gut microbiota metabolites, both in serum and fecal samples. Significant correlation among microbial community, metabolites and T2DM-related indicators was revealed.

CONCLUSIONS

The multiple components of TT regulate the metabolic homeostasis of the organism and the balance of intestinal microbiota and its metabolites, which might mediate the anti-diabetic capacity of TT.

Catechol-tetraethylenepentamine co-deposition modified cellulose filter paper for α-glucosidase immobilization and inhibitor screening from traditional Chinese medicine

Cellulose filter paper (CFP) is expected to be an ideal carrier for enzyme immobilization due to its sustainability and biocompatibility. However, the interaction between the carrier and enzyme might change the spatial conformation of the enzyme and its microenvironment, and thus the flexibility of the enzyme molecule or the transport of the substrate to the active site would be hampered. In this work, a two-component system of catechol and tetraethylene pentamine was used to replace dopamine, and a polydopamine-like composite layer was deposited on the surface of CFP to introduce amino groups, which was similar to the self-polymerization-adhesion behavior of dopamine. Using polyethylene glycol diglycidyl ether with flexible spacer arms as the cross-linking agent, α-glucosidase was covalently bonded to amino-modified CFP through an epoxy ring-opening reaction. The immobilized α-glucosidase exhibited greater tolerance to pH and high temperature. After 10 repeated uses, the immobilized α-glucosidase maintained relatively high enzyme activity. Its kinetic behavior was investigated to illustrate the reliability for enzyme inhibitor screening. Finally, a screening method combining an immobilized enzyme and capillary electrophoresis analysis was proposed and applied to screening inhibitors from 11 kinds of traditional Chinese medicines, among which Chebulae Fructus, Phyllanthi Fructus and Terminaliae Relliricae Fructus exhibited strong enzyme inhibitory activities.

Enzyme immobilized on magnetic fluorescent bifunctional nanoparticles for α-glucosidase inhibitors virtual screening from Agrimonia pilosa Ledeb extracts accompanied with molecular modeling

Agrimonia pilosa Ledeb (APL) is a significant source of inhibitors for α-glucosidase, which is an essential target enzyme for the treatment of type 2 diabetes, cancer and acquired immune deficiency syndrome. Ligand fishing is a suitable approach for the highly selective screening of bioactive substances in complex mixtures. Yet it is unable to conduct biomedical imaging screening, which is crucial for real-time identification. In this case, a bioanalytical platform combining magnetic fluorescent ligand fishing and in-situ imaging technique was established for the screening and identification of α-glucosidase inhibitors (AGIs) from APL crude extract, utilizing α-glucosidase coated CuInS2/ZnS-Fe3O4@SiO2 (AG-CIZSFS) nanocomposites as extracting material and fluorescent tracer. The AG-CIZSFS nanocomposites prepared through solvothermal and crosslinking methods displayed fast magnetic separation, excellent fluorescence performance and high enzyme activity. The tolerance of immobilized enzyme to temperature and pH was stronger than that of free enzyme. Prior to proof-of-concept with APL crude extract, a number essential parameters (glutaraldehyde concentration, immobilized time, enzyme amount, reaction solution pH, incubation temperature, incubation time, percentage of methanol in eluen, elution times and eluent volume) were optimized using an artificial test mixture. The fished ligands were identified by UPLC-MS/MS and their biological activities were preliminarily evaluated by real-time cellular morphological imaging of human colon carcinoma (HCT-116) cells based on confocal laser scanning microscope (CLSM). Their α-glucosidase inhibitory activities were further verified and studied by classical pNPG method and molecular docking. The isolated compounds exhibited significant α-glucosidase inhibitory activities with a IC50 value of 11.57 µg·mL-1. Six potential AGIs including tribuloside, ivorengenin A, tormentic acid, 1β, 2β, 3β, 19α-Tetra hydroxyurs-12-en-28-oic acid, corosolic acid and pomolic acid were ultimately screened out and identified from APL crude extracts. The proposed approach, which combined highly specific screening with in-situ visual imaging, provided a powerful platform for discovering bioactive components from multi-component and multi-target traditional Chinese medicine (TCM).