Benzonate derivatives of acetophenone as potent α-glucosidase inhibitors: synthesis, structure-activity relationship and mechanism

Ratiometric fluorescence detection of Hg2+ based on gold nanocluster/carbon quantum dots nanohybrids

Ratiometric fluorescence sensing methods are widely used in analysis and detection due to their high sensitivity and stability. In this work, a ratiometric fluorescence method for sensitive detection of Hg2+ was established using a gold nanoclusters/carbon quantum dots (AuNCs/CQDs) nanohybrid probe. The AuNCs/CQDs nanohybrids probe were simply constructed by mixing blue-light-emitting gold nanoclusters (AuNCs) with an orange-emissive carbon quantum dots (CQDs). The probe had two fluorescence emission peaks at 434 nm and 561 nm when the excitation wavelength was 375 nm. With the addition of Hg2+, the fluorescence at 434 nm decreased and the fluorescence at 561 nm remained unchanged; the fluorescence intensity ratio Δ(F434/F561) and Hg2+ concentration have a good linear relationship in the range of 8.32 × 10-7 to 7.69 × 10-5 mol L-1, and the limit of detection (LOD) is 3.58 × 10-7 mol L-1. The method was applied in the detection of Hg2+ in cosmetics and wastewater, and has potential applications for detecting Hg2+ in other samples.

Interactions studies of CYP2D6 with quercetin and hyperoside by spectral analysis and molecular dynamics simulations

Some ingredients from herbal medicine can significantly affect the activity of CYP2D6, thus leading to serious interactions between herbs and drugs. Quercetin and hyperoside are active ingredients widely found in vegetables, fruits, and herbal medicines. Quercetin and hyperoside have many biological activities. In this work, the characteristic bindings of CYP2D6 with quercetin/hyperoside are revealed by multi-spectroscopy analysis, molecular docking, and molecular dynamics simulations. The fluorescence of CYP2D6 is statically quenched by quercetin and hyperoside. The binding constant (Ka ) values of CYP2D6-quercetin/hyperoside range from 104  L mol-1 , which indicates that these two flavonoids bind moderately to CYP2D6. Meanwhile, quercetin has a stronger quenching ability to CYP2D6 than that of hyperoside. The secondary structure of CYP2D6 is obviously changed by binding with quercetin/hyperoside. The docking results reveal that the quercetin/hyperoside enters the active site of CYP2D6 near heme and binds to CYP2D6 by hydrogen bonds and van der Waals forces. The molecular dynamics simulation results indicate that the binding of quercetin/hyperoside can stabilize the two complexes, enhance the flexibility of CYP2D6 backbone atoms, and make a more unfolded and looser structure of CYP2D6.

Anti-diabetic Activity of Brucine in Streptozotocin-Induced Rats: In Silico, In Vitro, and In Vivo Studies

Diabetes mellitus (DM) is a complex and multiple group of disorders, and understanding the molecular mechanisms is a key role in identifying various markers involved in the diagnosis of the disease. Brucine is derived from the seeds of Strychnos nux-vomica L. (Loganiaceae), which has been used in traditional medicine to cure a variety of ailments, such as chronic rheumatism, nervous system diseases, dyspepsia, gonorrhea, anemia, and bronchitis, and has analgesic, anti-inflammatory, anti-oxidant, anti-snake venom, and anti-diabetic properties. The anti-diabetic potential of brucine was studied utilizing in vitro, in silico, in vivo, and molecular methods, including streptozotocin-induced diabetic rat models, α-glucosidase and α-amylase inhibitory assays, and via Auto-DocVina software. Brucine exhibits binding affinities of -5.0 to -10.1 Kcal/mol against chosen protein targets, according to an in silico investigation. In vitro studies revealed that brucine inhibited the enzymes α-amylase and α-glucosidase, and brucine (20 mg/kg) reduced blood glucose levels, oral glucose tolerance overload, body weight, glycosylated hemoglobin levels, total cholesterol, triglycerides, low-density lipoprotein, alanine transaminase, aspartate aminotransferase, total bilirubin, and alkaline phosphatase and elevated high-density lipoprotein levels in in vivo studies. The brucine binding energy against certain protein targets ranges from -5.0 to -10.1 Kcal/mol. It has anti-diabetic, anti-hyperlipidemic, hepatoprotective, anti-oxidant, and anti-inflammatory properties, which are mediated via inhibition of α-glucosidase and α-amylase.

Probiotic fermentation improves the bioactivities and bioaccessibility of polyphenols in Dendrobium officinale under in vitro simulated gastrointestinal digestion and fecal fermentation

The objective of the research was to investigate and compare the bioactivities and bioaccessibility of the polyphenols (PPs) from Dendrobium officinale (DO) and probiotic fermented Dendrobium officinale (FDO), by using in vitro simulated digestion model under oral, gastric and intestinal phases as well as colonic fermentation. The results indicated that FDO possessed significantly higher total phenolic contents (TPC) and total flavonoid contents (TFC) than DO, and they were released most in the intestinal digestion phase with 6.96 ± 0.99 mg GAE/g DE and 10.70 ± 1.31 mg RE/g DE, respectively. Using high-performance liquid chromatography (HPLC), a total of six phenolic acids and four flavonoids were detected. In the intestinal phase, syringaldehyde and ferulic acid were major released by DO, whereas they were p-hydroxybenzoic acid, vanillic acid, and syringic acid for FDO. However, apigenin and scutellarin were sustained throughout the digestion whether DO or FDO. As the digestive process progressed, their antioxidant ability, α-amylase and α-glucosidase inhibitory activities were increased, and FDO was overall substantially stronger in these activities than that of DO. Both DO and FDO could reduce pH values in the colonic fermentation system, and enhance the contents of short-chain fatty acids, but there were no significantly different between them. The results of the 16S rRNA gene sequence analysis showed that both DO and FDO could alter intestinal microbial diversity during in vitro colonic fermentation. In particular, after colonic fermentation for 24 h, FDO could significantly improve the ratio of Firmicutes to Bacteroidetes, and enrich the abundancy of Enterococcus and Bifidobacterium (p < 0.05), which was most likely through the carbohydrate metabolism signal pathway. Taken together, the PPs from DO and FDO had good potential for antioxidant and modulation of gut bacterial flora during the digestive processes, and FDO had better bioactivities and bioaccessibility. This study could provide scientific data and novel insights for Dendrobium officinale to be developed as functional foods.

Synthesis and Biological Evaluation of 5-Fluoro-2-Oxindole Derivatives as Potential α-Glucosidase Inhibitors

α-Glucosidase inhibitors are known to prevent the digestion of carbohydrates and reduce the impact of carbohydrates on blood glucose. To develop novel α-glucosidase inhibitors, a series of 5-fluoro-2-oxindole derivatives (3a ∼ 3v) were synthesized, and their α-glucosidase inhibitory activities were investigated. Biological assessment results showed that most synthesized compounds presented potential inhibition on α-glucosidase. Among them, compounds 3d, 3f, and 3i exhibited much better inhibitory activity with IC50 values of 49.89 ± 1.16 μM, 35.83 ± 0.98 μM, and 56.87 ± 0.42 μM, respectively, which were about 10 ∼ 15 folds higher than acarbose (IC50 = 569.43 ± 43.72 μM). A kinetic mechanism study revealed that compounds 3d, 3f, and 3i inhibited the α-glucosidase in a reversible and mixed manner. Molecular docking was carried out to simulate the affinity between the compound and α-glucosidase.

Polysaccharides from mulberry (Morus alba L.) leaf prevents obesity by inhibiting pancreatic lipase in high-fat diet induced mice

Pancreatic lipase (PL) is a key enzyme related to the prevention and treatment of obesity. The aim of the study was to evaluate the inhibitory effects of mulberry leaf polysaccharides (MLP) on PL and possible interaction mechanism, inhibition on lipid accumulation in vitro and in vivo. The results revealed that MLP had obvious inhibitory effects on PL (P < 0.05). The interaction of MLP-PL complexes was in a spontaneous way driven by enthalpy, and hydrogen bonds were the main factors in the binding. MLP could significantly inhibit the development of lipid accumulation in HepG2 cells (P < 0.05). Furthermore, consumption of high-fat diet containing MLP showed protective effects on liver and adipose tissue damages in mice, and inhibited the lipid absorption in digestive tract. MLP also significantly reduced the increased expression level of pancreatic digestive enzymes (P < 0.05). The study indicated that the anti-obesity effect of MLP might be caused by inhibition of lipid absorption via reducing PL activity.

Aspulvinones Suppress Postprandial Hyperglycemia as Potent α-Glucosidase Inhibitors From Aspergillus terreus ASM-1

Chemical investigation of Aspergillus terreus ASM-1 fermentation resulted in the isolation of three new prenylated aspulvinones V–X (1–3), together with the previously reported analogs, aspulvinone H (4), J-CR (5), and R (6). Their structures were elucidated by various spectroscopic methods including HRESIMS and NMR, and the absolute configurations of 2 and 3 were determined by ECD comparison. Compounds 1–6 were evaluated for α-glucosidase inhibitory effects with acarbose as positive control. As a result, compounds 1 and 4 exhibited potent α-glucosidase inhibitory activities with IC₅₀ values of 2.2 and 4.6 µM in mixed-type manners. The thermodynamic constants recognized the interaction between inhibitors and α-glucosidase was hydrophobic force-driven spontaneous exothermic reaction. The CD spectra also indicate that the compounds 1 and 4 changed the enzyme conformation. Furthermore, compound 4 significantly suppressed the increases in postprandial blood glucose levels in the C57BL/6J mice.

Phytochemical Composition, Antioxidant Activity, and Enzyme Inhibitory Activities (α-Glucosidase, Xanthine Oxidase, and Acetylcholinesterase) of Musella lasiocarpa

In this study, we aimed to investigate the chemical components and biological activities of Musella lasiocarpa, a special flower that is edible and has functional properties. The crude methanol extract and its four fractions (petroleum ether, ethyl acetate, n-butanol, and aqueous fractions) were tested for their total antioxidant capacity, followed by their α-glucosidase, acetylcholinesterase, and xanthine oxidase inhibitory activities. Among the samples, the highest total phenolic and total flavonoid contents were found in the ethyl acetate (EtOAc) fraction (224.99 mg GAE/g DE) and crude methanol extract (187.81 mg QE/g DE), respectively. The EtOAc fraction of Musella lasiocarpa exhibited the strongest DPPH· scavenging ability, ABTS·⁺ scavenging ability, and α-glucosidase inhibitory activity with the IC₅₀ values of 22.17, 12.10, and 125.66 μg/mL, respectively. The EtOAc fraction also showed the strongest ferric reducing antioxidant power (1513.89 mg FeSO₄/g DE) and oxygen radical absorbance capacity ability (524.11 mg Trolox/g DE), which were higher than those of the control BHT. In contrast, the aqueous fraction demonstrated the highest acetylcholinesterase inhibitory activity (IC₅₀ = 10.11 μg/mL), and the best xanthine oxidase inhibitory ability (IC₅₀ = 5.23 μg/mL) was observed from the crude methanol extract as compared with allopurinol (24.85 μg/mL). The HPLC-MS/MS and GC-MS analyses further revealed an impressive arsenal of compounds, including phenolic acids, fatty acids, esters, terpenoids, and flavonoids, in the most biologically active EtOAc fraction. Taken together, this is the first report indicating the potential of Musella lasiocarpa as an excellent natural source of antioxidants with possible therapeutic, nutraceutical, and functional food applications.

Design, synthesis, molecular docking, and in vitro α-glucosidase inhibitory activities of novel 3-amino-2,4-diarylbenzo[4,5]imidazo[1,2-a]pyrimidines against yeast and rat α-glucosidase

In an attempt to find novel, potent α-glucosidase inhibitors, a library of poly-substituted 3-amino-2,4-diarylbenzo[4,5]imidazo[1,2-a]pyrimidines 3a-ag have been synthesized through heating a mixture of 2-aminobenzimidazoles 1 and α-azidochalcone 2 under the mild conditions. This efficient, facile protocol has been resulted into the desirable compounds with a wide substrate scope in good to excellent yields. Afterwards, their inhibitory activities against yeast α-glucosidase enzyme were investigated. Showing IC50 values ranging from 16.4 ± 0.36 µM to 297.0 ± 1.2 µM confirmed their excellent potency to inhibit α-glucosidase which encouraged us to perform further studies on α-glucosidase enzymes obtained from rat as a mammal source. Among various synthesized 3-amino-2,4-diarylbenzo[4,5]imidazo[1,2-a]pyrimidines, compound 3k exhibited the highest potency against both Saccharomyces cerevisiae α-glucosidase (IC50 = 16.4 ± 0.36 μM) and rat small intestine α-glucosidase (IC50 = 45.0 ± 8.2 μM). Moreover, the role of amine moiety on the observed activity was studied through substituting with chlorine and hydrogen resulted into a considerable deterioration on the inhibitory activity. Kinetic study and molecular docking study have confirmed the in-vitro results.

Biological evaluation the 2-aryl-2,3-dihydrobenzodiazaborinin-4(1H)-ones as potential dual α-glucosidase and α-amylase inhibitors with antioxidant properties

The 2-aryl-2,3-dihydrobenzodiazaborinin-4(1H)-ones (azaborininone) were synthesized as analogues of the 2-arylquinazoline-4-ones and screened through enzymatic assay in vitro for inhibitory effect against α-glucosidase and α-amylase activities. These azaborininones exhibited moderate to good inhibitory effect against these enzymes compared to acarbose used as a reference standard. The results are supported by the enzyme-ligand interactions through kinetics (in vitro) and molecular docking (in silico) studies. The test compounds also exhibited significant antioxidant activity through the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and nitric oxide (NO) free radical scavenging assays. These azaborininone derivatives exhibited no effect on the viability of the human lung cancer (A549) cell line after 24 hr and were also not toxic towards the Vero cells.

Three New Quinazoline-Containing Indole Alkaloids From the Marine-Derived Fungus Aspergillus sp. HNMF114

By feeding tryptophan to the marine-derived fungus Aspergillus sp. HNMF114 from the bivalve mollusk Sanguinolaria chinensis, 3 new quinazoline-containing indole alkaloids, named aspertoryadins H–J (1–3), along with 16 known ones (4–19), were obtained. The structures of the new compounds were elucidated by the analysis of spectroscopic data combined with quantum chemical calculations of nuclear magnetic resonance (NMR) chemical shifts and electron capture detector (ECD) spectra. Structurally, compound 3 represents the first example of this type of compound, bearing an amide group at C-3. Compounds 10 and 16 showed potent α-glucosidase inhibitory activity with IC₅₀ values of 7.18 and 5.29 μM, and compounds 13 and 14 showed a clear activation effect on the ryanodine receptor from Spodoptera frugiperda (sfRyR), which reduced the [Ca²⁺]_ER by 37.1 and 36.2%, respectively.

Structurally Diverse Sesquiterpenoids with Anti-neuroinflammatory Activity from the Endolichenic Fungus Cryptomarasmius aucubae

Two new sterpurane sesquiterpenoids named sterpurol D (1) and sterpurol E (2), and one skeletally new sesquiterpene, cryptomaraone (3), bearing a 5,6-fused bicyclic ring system, along with five known ones, sterpurol A (4), sterpurol B (5), paneolilludinic Acid (6), murolane-2α, 9β-diol-3-ene (7) and (-)-10,11-dihydroxyfarnesol (8) were isolated from an endolichenic fungus Cryptomarasmius aucubae. The structures of the new compounds were elucidated by analysis of NMR spectroscopic spectra and HRESIMS data. The absolute configurations of 1 and 2 were established by spectroscopic data analysis and comparison of specific optical rotation, as well as the biosynthetic consideration. Additionally, compounds 1, 2, 4-6, and 8 showed significant nitric oxide (NO) production inhibition in Lipopolysaccharide (LPS)-induced BV-2 microglial cells with the IC50 values ranging from 9.06 to 14.81 μM.

Identification of polyphenols from Broussonetia papyrifera as SARS CoV-2 main protease inhibitors using in silico docking and molecular dynamics simulation approaches

The current COVID-19 pandemic is caused by SARS CoV-2. To date, ∼463,000 people died worldwide due to this disease. Several attempts have been taken in search of effective drugs to control the spread of SARS CoV-2 infection. The main protease (Mpro) from SARS CoV-2 plays a vital role in viral replication and thus serves as an important drug target. This Mpro shares a high degree of sequence similarity (>96%) with the same protease from SARS CoV-1 and MERS. It was already reported that Broussonetia papyrifera polyphenols efficiently inhibit the catalytic activity of SARS CoV-1 and MERS Mpro. But whether these polyphenols exhibit any inhibitory effect on SARS CoV-2 Mpro is far from clear. To understand this fact, here we have adopted computational approaches. Polyphenols having proper drug-likeness properties and two repurposed drugs (lopinavir and darunavir; having binding affinity −7.3 to −7.4 kcal/mol) were docked against SARS CoV-2 Mpro to study their binding properties. Only six polyphenols (broussochalcone A, papyriflavonol A, 3'-(3-methylbut-2-enyl)-3',4',7-trihydroxyflavane, broussoflavan A, kazinol F and kazinol J) had interaction with both the catalytic residues (His41 and Cys145) of Mpro and exhibited good binding affinity (−7.6 to −8.2 kcal/mol). Molecular dynamic simulations (100 ns) revealed that all Mpro-polyphenol complexes are more stable, conformationally less fluctuated; slightly less compact and marginally expanded than Mpro-darunavir/lopinavir complex. Even the number of intermolecular H-bond and MM-GBSA analysis suggested that these six polyphenols are more potent Mpro inhibitors than the two repurposed drugs (lopinavir and darunavir) and may serve as promising anti-COVID-19 drugs.

Communicated by Ramaswamy H. Sarma

New Metabolite With Inhibitory Activity Against α-Glucosidase and α-Amylase From Endophytic Chaetomium globosum

An efficient bioactive tracking separation strategy based on liquid-liquid extraction and high-speed counter-current chromatography (HSCCC) was developed and used to isolate bioactive natural products from the endophytic fungus Chaetomium globosum residing in Ginkgo biloba. Using HSCCC, the novel metabolite chaetoglobol acid (1) as well as 11 known compounds (2-12), including 6 chlorinated azaphilones and 3 cytochalasans, were successfully isolated. The structure of compound 1 was elucidated through spectroscopic analyses and HRESIMS data. Compound 1 possesses a rare C11-polyketide skeleton. All isolates were evaluated for their α-glucosidase and α-amylase inhibitory activities in vitro. Compound 1 showed high inhibition against α-glucosidase (IC50 = 3.04 μM), 18-fold higher than that of acarbose (IC50 = 54.74 μM), and also displayed moderate inhibitory activity against α-amylase (IC50 = 22.18 μM). As the results indicated that 1 has inhibitory effects against both α-glucosidase and α-amylase, 1 may be a promising candidate for mediating type 2 diabetes.

Synthesis, In Vitro Evaluation and Molecular Docking of the 5-Acetyl-2-aryl-6-hydroxybenzo[b]furans against Multiple Targets Linked to Type 2 Diabetes

The 5-acetyl-2-aryl-6-hydroxybenzo[b]furans 2a-h have been evaluated through in vitro enzymatic assay against targets which are linked to type 2 diabetes (T2D), namely, α-glucosidase, protein tyrosine phosphatase 1B (PTP1B) and β-secretase. These compounds have also been evaluated for antioxidant activity using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free-radical scavenging method. The most active compounds against α-glucosidase and/or PTP1B, namely, 4-fluorophenyl 2c, 4-methoxyphenyl 2g and 3,5-dimethoxyphenyl substituted 2h derivatives were also evaluated for potential anti-inflammatory properties against cyclooxygenase-2 activity. The Lineweaver-Burk and Dixon plots were used to determine the type of inhibition on compounds 2c and 2h against α-glucosidase and PTP1B receptors. The interactions were investigated in modelled complexes against α-glucosidase and PTP1B via molecular docking.

Meroterpene-Like α-Glucosidase Inhibitors Based on Biomimetic Reactions Starting from β-Caryophyllene

BACKGROUND

Natural meroterpenes derived from phloroglucinols and β-caryophyllene have shown high inhibitory activity against α-glucosidase or cancer cells, however, the chemical diversity of this type of skeletons in Nature is limited.

METHODS

To expand the chemical space and explore their inhibitory activities against α-glucosidase (EC 3.2.1.20), we employed β-caryophyllene and some natural moieties (4-hydroxycoumarins, lawsone or syncarpic acid) to synthesize new types of meroterpene-like skeletons. All the products (including side products) were isolated and characterized by NMR, HR-MS, and ECD.

RESULTS

In total, 17 products (representing seven scaffolds) were generated through a one-pot procedure. Most products (12 compounds) showed more potential activity (IC₅₀ < 25 μM) than the positive controls (acarbose and genistein, IC₅₀ 58.19, and 54.74 μM, respectively). Compound 7 exhibited the most potent inhibition of α-glucosidase (IC₅₀ 3.56 μM) in a mixed-type manner. The CD analysis indicated that compound 7 could bind to α-glucosidase and influence the enzyme's secondary structure.

CONCLUSIONS

Compound 7 could serve as a new type of template compound to develop α-glucosidase inhibitors. Full investigation of a biomimic reaction can be used as a concise strategy to explore diverse natural-like skeletons and search for novel lead compounds.

Anti-inflammatory and α-Glucosidase Inhibitory Activities of Labdane and Norlabdane Diterpenoids from the Rhizomes of Amomum villosum

A new tetranorditerpenoid (1), two new labdane diterpenoids (2, 3), and nine known analogues (4-12) were isolated from the rhizomes of Amomum villosum var. xanthioides. Compound 1 is an unprecedented rearranged tetranorlabdane diterpenoid, featuring a 6/6/5 fused tricarbocyclic skeleton with an α,β-unsaturated cyclopentenone unit, while 2 is a structurally rare labdane diterpenoid carrying a five-membered cyclic anhydride moiety. Their structures and absolute configurations were established on the basis of spectroscopic data and the experimental and calculated ECD data. Compound 4 showed inhibitory activity against nitric oxide production, with an IC₅₀ value of 2.4 μM, and also inhibited α-glucosidase activity (IC₅₀ = 10.0 μM).