Camellia nitidissima Chi flower extracts inhibit α-amylase and α-glucosidase: In vitro by analysis of optimization of addition methods, inhibitory kinetics and mechanisms

α-Glucosidase inhibitory flavonol glycosides from Cyclocarya paliurus (Batalin) Iljinskaja and their kinetics characteristics

Seven previously undescribed flavonol glycosides including four rare flavonol glycoside cyclodimers, dicyclopaliosides A-C (1-3) with truxinate type and dicyclopalioside D (4) with truxillate type, as well as three kaempferol glycoside derivatives cyclopaliosides A-C (5-7), were obtained from the leaves of Cyclocarya paliurus. Their structures were elucidated by extensive spectroscopic methods and chemical analyses. All compounds were evaluated for their inhibitory α-glucosidase activities. Among them, compounds 1-4 display strong inhibitory activities with IC50 values of 82.76 ± 1.41, 62.70 ± 4.00, 443.35 ± 16.48, and 6.31 ± 0.88 nM, respectively, while compounds 5-7 showed moderate activities with IC50 values of 4.91 ± 0.75, 3.64 ± 0.68, and 5.32 ± 0.53 μΜ, respectively. The structure-activity relationship analysis assumed that the cyclobutane cores likely contribute to the enhancement of α-glucosidase inhibitory activities of dimers. Also, the interaction mechanism between flavonol glycoside dimers and α-glucosidase were explored by the enzyme kinetic assay, indicating that compounds 1-3 exhibited mixed-type inhibition, while 4 showed uncompetitive inhibition. Additionally, the active compounds have also undergone molecular docking evaluation.

Novel litchi-like Au-Ag nanospheres driven dual-readout lateral flow immunoassay for sensitive detection of pyrimethanil

Pyrimethanil (PYR) is a fungicide that is harmful to consumers when present in foods at concentrations greater than maximum permitted residue levels. High-performance immunoprobes and dual-readout strategy may be useful for constructing sensitive lateral flow immunoassay (LFIA). Herein, the prepared litchi-like Au-Ag bimetallic nanospheres (LBNPs) exhibited high mass extinction coefficients and fluorescence quenching constants. Benefiting from LBNPs and dual-readout mode, the limits of detection of LBNPs-CM-LFIA and LBNPs-FQ-LFIA for PYR were 0.957 and 0.713 ng mL-1, which were 2.54- and 3.41-fold lower than that of gold nanoparticles-based LFIA, respectively. The limits of quantitation of LBNPs-CM-LFIA and LBNPs-FQ-LFIA were 3.740 and 1.672 ng mL-1, respectively. LBNPs-LFIA was applied to detect PYR in cucumber and grape samples with satisfactory recovery (90%-111%). LBNPs-LFIA showed good agreement with LC-MS/MS for the detection of PYR in the samples. Accordingly, this sensitive and accurate dual-readout LFIA based on LBNPs can be effectively applied for food safety.

Preparation of Ribes nigrum L. polysaccharides-stabilized selenium nanoparticles for enhancement of the anti-glycation and α-glucosidase inhibitory activities

Seven kinds of selenium nanoparticles (RP-SeNPs) were prepared by using the polysaccharides extracted from Ribes nigrum L. (RP) as the stabilizer and dispersant. Among them, RP-SeNPs-1 (94.2 nm), RP-SeNPs-2 (101.2 nm) and RP-SeNPs-3 (107.6 nm) with relatively smaller mean particle size exhibited stronger α-glucosidase inhibitory activity than other RP-SeNPs (115.3-164.2 nm) and SeNPs (288.9 nm). Ultraviolet-visible spectrophotometry, Fourier transform-infrared, X-ray diffraction, energy dispersive X-ray and X-ray photoelectron spectroscopy analyses confirmed that SeNPs were ligated with RP to form nanocomposites and displayed amorphous form. Electron microscopy images revealed that RP-SeNPs-1 - RP-SeNPs-3 were regular shape spherical nanocomposites with much better dispersion than SeNPs. Compared with SeNPs, RP-SeNPs displayed relatively high thermal, storage, pH and salt ion stability. Moreover, RP-SeNPs-1-RP-SeNPs-3 showed significantly better anti-glycation and α-glucosidase inhibitory activity than SeNPs, especially RP-SeNPs-1 with the smallest particle size. Inhibitory kinetics analysis indicated that SeNPs and RP-SeNPs inhibited α-glucosidase with competitive type and reversible mechanism. In addition, the conformation of the α-glucosidase was changed after binding with the SeNPs and RP-SeNPs-1. Fluorescence quenching and isothermal titration calorimetry assays revealed that these two nanoparticles could interact with α-glucosidase to form non-fluorescent complexes through hydrogen bonding, and the formation was spontaneously driven by enthalpy.

Mechanochemical-Assisted Extraction and Biological Activity Research of Phenolic Compounds from Lotus Seedpod (Receptaculum Nelumbinis)

To explore the feasibility of the mechanochemical-assisted extraction (MCAE) of phenolic compounds from lotus seedpod (Receptaculum Nelumbinis), a single-factor experiment combined with response-surface methodology (RSM) was used to optimize the extraction process. The results showed the optimal extraction conditions as follows: Li2CO3 as a solid reagent (25%), an extraction time of 80 min, liquid/solid ratio of 42.8 mL/g, and extraction temperature of 80.7 °C; and the maximum value of total phenolic content (TPC) was 106.15 ± 1.44 gallic acid equivalents (GAE)/g dry weight (DW). Additionally, the 2,2-Diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and ferric reducing antioxidant power (FRAP) were 279.75 ± 18.71, 618.60 ± 2.70, and 634.14 ± 7.17 µmol TE/g, respectively. Ultra-high pressure liquid chromatography combined with triple-time-of-flight mass spectrophotometry (UPLC-Triple-TOF/MS) analysis identified eight phenolic compounds mainly consisting of polyphenols and flavonoids. Moreover, the phenolic compounds showed potent inhibitory effects on both α-amylase and α-glucosidase, with inhibition rates of over 80%. Furthermore, the results showed different degrees of inhibition activity against Bacillus subtilis, Staphylococcus aureus, and Escherichia coli, among which the inhibitory effect on the growth of B. subtilis was the best. This paper shows that the phenolic compounds have good biological activities, which provides a reference for the further exploitation of LSP.

Triterpenes and Pheophorbides from Camellia ptilosperma and Their Cytotoxicity, Photocytotoxicity, and Photodynamic Antibacterial Activity

Phytochemical investigation of the leaves of Camellia ptilosperma S. Y. Liang et Q. D. Chen led to the isolation of ten undescribed compounds, including six new triterpenes (1-6) and four new pheophorbide-related compounds (7-10). Meanwhile, the cytotoxic activity of the six triterpenes against six cancer cell lines was evaluated by MTT assay. Compound 2 showed potent cytotoxicity toward HepG2 cells with an IC50 value of 2.57 μM. Compounds 4 and 5 exhibited cytotoxicity against MDA-MB231 cells, with IC50 values of 11.31 and 5.52 μM, respectively. Additionally, the cytotoxicity of four new pheophorbides against these cancer cells was evaluated both in the presence and absence of light treatment. Compound 7 exhibited exceptional photocytotoxicity against Hela, MCF-7, and A549 cells, with IC50 values of 0.43 μM, 0.28 μM, and 0.92 μM, respectively. Compound 10 demonstrated significant photodynamic cytotoxic activity against BEL-7402 and HepG2 cells with IC50 values of 0.77 μM and 0.33 μM, respectively. The photodynamic antibacterial activity of 7-10 was also tested for S. aureus, E. coli, K. pneumoniae, and P. aeruginosa under direct illumination. Compounds 8 and 10 exhibited sensitivity to E. coli and demonstrated a photodynamic antibacterial effect, with a MIC value of 0.625 μM.

Research progress of gut microbiota and obesity caused by high-fat diet

Obesity, a chronic metabolic disorder caused by an energy imbalance, has been increasingly prevalent and poses a global health concern. The multifactorial etiology of obesity includes genetics factors, high-fat diet, gut microbiota, and other factors. Among these factors, the implication of gut microbiota in the pathogenesis of obesity has been prominently acknowledged. This study endeavors to investigate the potential contribution of gut microbiota to the development of high-fat diet induced obesity, as well as the current state of probiotic intervention therapy research, in order to provide novel insights for the prevention and management of obesity.

Optimization of Extraction Process of Polysaccharides MAP-2 from Opuntia Milpa Alta by Response Surface Methodology and Evaluation of Its Potential as α-Glucosidase Inhibitor

The α-glucosidase inhibitors play an important role in blood glucose control in patients with type 2 diabetes. At present, the development of new α-glucosidase inhibitors is an urgent clinical need. Our previous studies have found that the polysaccharide MAP-2 in the cactus Opuntia Milpa Alta has significantly better activity than acarbose (one of the most widely used first-line α-glucosidase inhibitors in clinical practice), but its optimal extraction process parameters and inhibition kinetic characteristics are not clear, and whether it has the potential to become a new α-glucosidase inhibitors is also unclear. In this study, based on previous research, we used the combination of single factor experiments and the response surface method (RSM) to identify the optimal extraction conditions for MAP-2 as follows: solid-liquid ratio 1:4, extraction temperature 90 °C, extraction time 1 h. Under these conditions, the extraction yield of MAP-2 was 3.47 ± 0.062%. When the concentration of MAP-2 was 16 mg/mL, the inhibition rate of α-glucosidase was 91.13 ± 0.62%. In addition, the results of inhibition kinetics showed that the inhibition rate of MAP-2 on α-glucosidase was the highest at pH 7.4 for 30 min, and showed a good dose-effect relationship, which was a reversible competitive inhibition. Meanwhile, we also compared the activities of MAP-2 and acarbose on the side effects of acarbose related enzymes. Compared with acarbose, MAP-2 not only had a better activation effect on lactase, but also inhibited the activity of hyaluronidase, and the activation and inhibition rate were positively correlated with the concentration. However, under the same conditions, the effect of acarbose on hyaluronidase was opposite to that of MAP-2. At low concentration, acarbose had a certain activation effect on lactase, but gradually attained an inhibitory effect with the increase in concentration. In contrast, MAP-2 not only activates lactase activity, improves diarrhea, abdominal distension, and abdominal pain, but also inhibits hyaluronidase activity, to solve the side effects of allergic reactions, suggesting that MAP-2 has the potential to become a novel and effective inhibitor of α-glucosidase with fewer side effects.

Inhibition of α-glucosidase by trilobatin and its mechanism: kinetics, interaction mechanism and molecular docking

α-Glucosidase is related to the increase in postprandial blood glucose in vivo. Inhibition of α-glucosidase is supposed to be an effective approach to treat type 2 diabetes mellitus (T2DM). Trilobatin, a member of the dihydrochalcone family, shows anti-oxidant, anti-inflammatory and anti-diabetic activities. In this study, the inhibitory activity and mechanism of trilobatin on α-glucosidase were investigated using multispectroscopic and molecular docking techniques. The kinetic analysis showed that trilobatin reversibly inhibited α-glucosidase in a noncompetitive-type manner and the value of IC₅₀ was 0.24 ± 0.02 mM. The analysis of fluorescence spectra demonstrated that the formation of the trilobatin-α-glucosidase complex was driven mainly by hydrogen bonding and van der Waals forces, resulting in the conformational changes of α-glucosidase. Fourier transform infrared spectroscopy (FT-IR) and circular dichroism (CD) measurements suggested that the interaction could change the micro-environment and conformation of α-glucosidase affected by trilobatin. Molecular docking analysis determined the exact binding sites of trilobatin on α-glucosidase. These results indicated that trilobatin is a strong α-glucosidase inhibitor, thus it could be conducive to ameliorate T2DM.

Characterization of selenized polysaccharides from Ribes nigrum L. and its inhibitory effects on α-amylase and α-glucosidase

The polysaccharide from Ribes nigrum L. (RCP) was modified by nitric acid-sodium selenite method. After purification by Sepharose-6B, high purity native (PRCP) and three selenized polysaccharides (PRSPs) with different selenium contents were obtained. Compared with PRCP, PRSPs possessed the lower molecular weight, better water-solubility, physical stability and rheological properties. FT-IR and NMR spectra confirmed PRSPs had the characteristic absorption peaks of polysaccharides and the glycosidic bond types were not changed after selenylation modification, whereas the selenyl groups existing in PRSPs were mainly introduced at the C-6 position of sugar residue →4)-β-d-Manp-(1→. Moreover, PRSPs displayed obviously smoother and smaller flaky structure than PRCP, and their inhibitory effects on α-amylase and α-glucosidase also were greater than PRCP. PRSPs exhibited a reversible inhibition on two enzymes in competitive manner and quenched their fluorescence through the static quenching mechanism. The polysaccharide-enzyme complex was spontaneously formed mainly driven by the hydrophobic interaction and hydrogen bonding.

Camellia nitidissima Chi flower extract alleviates obesity and related complications and modulates gut microbiota composition in rats with high-fat-diet-induced obesity

BACKGROUND

The aim of this study was to investigate the potential anti-obesity effects of Camellia nitidissima Chi flower extract (Cnfe) by examining its effects in terms of the regulation of lipid levels and modulation of gut microbiota in rats with high-fat-diet-induced obesity.

RESULTS

Our results demonstrated that Cnfe significantly decreased weight gain by reducing appetite and decreasing high-fat food intake. Further, Cnfe restored normal lipid metabolism and improved insulin sensitivity and glucose tolerance in rats fed a high-fat diet. Real-time reverse transcription polymerase chain reaction and western blot results showed that Cnfe significantly decreased the expression of genes and proteins involved in adipogenesis and lipogenesis, and upregulated the expression of lipolysis genes. 16S ribosomal RNA sequencing of feces showed that Cnfe dramatically reversed dysbacteriosis in rats with high-fat-diet-induced obesity by decreasing the abundance of Firmicutes and increasing that of Bacteroidetes and Verrucomicrobia at the phylum level.

CONCLUSION

The results demonstrate that Cnfe is a potential anti-obesity prebiotic nutrient that can prevent weight gain, ameliorate obesity-related dyslipidemia and hyperglycemia, inhibit liver fat accumulation, and modulate gut microbiota. © 2020 Society of Chemical Industry.