Synthesis, Molecular Docking and β-Glucuronidase Inhibitory Potential of Indole Base Oxadiazole Derivatives

β-Glucuronidase-triggered reaction for fluorometric and colorimetric dual-mode assay based on the in situ formation of silicon nanoparticles

BACKGROUND

β-Glucuronidase (GUS) is considered as a promising biomarker for primary cancer. Thus, the reliable detection of GUS has great practical significance in the discovery and diagnosis of cancer. Compared with traditional organic probes, silicon nanoparticles (Si NPs) have emerged as robust optical nanomaterials due to their facile preparation, superior photobleaching resistance and excellent biocompatibility. However, most nanomaterials-based methods only output a single signal which is easily influenced by external factors in complex systems. Hence, developing nanomaterial-based multi-signal optical assays for highly sensitive GUS determination is still urgently desired.

RESULTS

In this study, we developed a simple and efficient one-step method for the in situ preparation of yellow color and yellow-green fluorescent Si NPs. This was achieved by combining 3-[2-(2-aminoethylamino) ethylamino] propyl-trimethoxysilane with p-aminophenol (AP) in an aqueous solution. The obtained Si NPs showed yellow-green fluorescence at 535 nm when excited at 380 nm, while also exhibiting an absorption peak at a wavelength of 490 nm. Taking inspiration from the easy synthesis step regulated by AP, which is generated through the hydrolysis of 4-aminophenyl β-D-glucuronide catalyzed by GUS, we constructed a direct fluorometric and colorimetric dual-mode method to measure GUS activity. The developed fluorometric and colorimetric sensing platform showed high sensitivity and accuracy with detection limits for GUS determination as low as 0.0093 and 0.081 U/L, respectively.

SIGNIFICANCE

This study provides a facile dual-mode fluorometric and colorimetric approach for determination of GUS activity based on novel Si NPs for the first time. This designed sensing approach was successfully employed for the quantification of GUS in human serum samples and screening of GUS inhibitors, indicating the feasibility and potential applications in clinical cancer diagnosis and anti-cancer drug discovery.

Lactoferrin: A Nutraceutical with Activity against Colorectal Cancer

Homeostasis in the human body results from the tight regulation of several events, since too little inflammation disrupts the process of tissue repair and remodeling, whereas too much exerts a collateral effect by causing tissue damage with life-threatening consequences. In some clinical conditions, such as inflammatory bowel disease (IBD), inflammation functions as a double-edged sword by either enabling or inhibiting cancer development and progression. Generally, cancer develops through evasion mechanisms that regulate cell growth, causing a high rate of uncontrolled proliferation, and mechanisms for evading cell death, such as apoptosis. Moreover, chronic inflammation is a factor that contributes to colorectal cancer (CRC), as observed in individuals with IBD; all these conditions favor an increased rate of angiogenesis and eventual metastasis. Lactoferrin (Lf) is a mammalian iron-binding multifunctional glycoprotein regarded as a natural compound that up- and downregulates both humoral and cellular components of immunity involved in regulating the inflammatory response and maintaining gut homeostasis. Human and bovine Lf share high sequence homology and have very similar antimicrobial, anti-inflammatory, and immunomodulatory activities. Bovine Lf from milk is considered a safe molecule and is commercially available in large quantities. This review mainly focuses on the regulatory effects of orally administered bovine Lf on the inflammatory response associated with CRC; this approach indicates that CRC is one of the most frequently diagnosed cancers and affects the intestinal tract with high clinical and epidemiologic relevance. Thus, this review may provide foundations for the potential use of bovine Lf alone or as a natural adjunct agent to increase the effectiveness and reduce the side effects of anticancer chemotherapy.

Discovery of a naturally occurring broad-spectrum inhibitor against gut bacterial β-glucuronidases from Ginkgo biloba

Gut bacterial β-glucuronidases (GUS) play an important role in deconjugation of various O-glucuronides, which are tightly linked with the drug-induced intestinal toxicity. Increasing evidence has indicated that inhibition of bacterial GUS could alleviate GUS-associated intestinal toxicity, but the potent and broad-spectrum inhibitors against multiple bacterial GUS have been rarely reported. This study aimed to find potent and broad-spectrum GUS inhibitors from Ginkgo biloba. It was found that amentoflavone displayed relatively strong inhibition on three GUS including CpGUS, SpasGUS and EcGUS. Further investigations demonstrated that amentoflavone could inhibit GUS-mediated PNPG hydrolysis in a dose-dependent manner with IC₅₀ values of 2.36 μM, 2.88 μM and 3.43 μM for CpGUS, SpasGUS and EcGUS, respectively. Inhibition kinetic studies showed that amentoflavone functioned as a non-competitive inhibitor against all tested GUS with K_i values of less than 2 μM. Docking simulations indicated that amentoflavone could tightly bind on allosteric sites of three GUS mainly via hydrogen bonding interactions, and the number of hydroxyl groups of amentoflavone played crucial roles in these interactions. Collectively, our findings suggested that amentoflavone was a potent broad-spectrum inhibitor against bacterial GUS, which can be used as a promising lead compound for developing novel agents to alleviate GUS-associated intestinal toxicity.

Synthesis of indole derivatives as diabetics II inhibitors and enzymatic kinetics study of α-glucosidase and α-amylase along with their in-silico study

In this study, we have investigated a series of indole-based compounds for their inhibitory study against pancreatic α-amylase and intestinal α-glucosidase activity. Inhibitors of carbohydrate degrading enzymes appear to have an essential role as antidiabetic drugs. All analogous exhibited good to moderate α-amylase (IC₅₀ = 3.80 to 47.50 μM), and α-glucosidase inhibitory interactions (IC₅₀ = 3.10-52.20 μM) in comparison with standard acarbose (IC₅₀ = 12.28 μM and 11.29 μM). The analogues 4, 11, 12, 15, 14 and 17 had good activity potential both for enzymes inhibitory interactions. Structure activity relationships were deliberated to propose the influence of substituents on the inhibitory potential of analogues. Docking studies revealed the interaction of more potential analogues and enzyme active site. Further, we studied their kinetic study of most active compounds showed that compounds 15, 14, 12, 17 and 11 are competitive for α-amylase and non- competitive for α-glucosidase.

Beta-Glucuronidase Inhibition by Constituents of Mulberry Bark

Intestinal bacterial β-glucuronidases, the key enzymes responsible for the hydrolysis of various glucuronides into free aglycone, have been recognized as key targets for treating various intestinal diseases. This study aimed to investigate the inhibitory effects and mechanisms of the Mulberry bark constituents on E. coli β-glucuronidase (EcGUS), the most abundant β-glucuronidases produced by intestinal bacteria. The results showed that the flavonoids isolated from Mulberry bark could strongly inhibit E. coli β-glucuronidase, with IC₅₀ values ranging from 1.12 µM to 10.63 µM, which were more potent than D-glucaric acid-1,4-lactone. Furthermore, the mode of inhibition of 5 flavonoids with strong E. coli β-glucuronidase inhibitory activity (IC₅₀ ≤ 5 µM) was carefully investigated by a set of kinetic assays and in silico analyses. The results demonstrated that these flavonoids were noncompetitive inhibitors against E. coli β-glucuronidase-catalyzed 4-nitrophenyl β-D-glucuronide hydrolysis, with Ki values of 0.97 µM, 2.71 µM, 3.74 µM, 3.35 µM, and 4.03 µM for morin (1: ), sanggenon C (2: ), kuwanon G (3: ), sanggenol A (4: ), and kuwanon C (5: ), respectively. Additionally, molecular docking simulations showed that all identified flavonoid-type E. coli β-glucuronidase inhibitors could be well-docked into E. coli β-glucuronidase at nonsubstrate binding sites, which were highly consistent with these agents' noncompetitive inhibition mode. Collectively, our findings demonstrated that the flavonoids in Mulberry bark displayed strong E. coli β-glucuronidase inhibition activity, suggesting that Mulberry bark might be a promising dietary supplement for ameliorating β-glucuronidase-mediated intestinal toxicity.

Synthetic approaches to unsymmetrical 2,5-disubstituted 1,3,4-oxadiazoles and their MAO-B inhibitory activity. A review

Selective monoamine oxidase type B (MAO-B) inhibitors are currently used as coadjuvants for treating early motor symptoms of Parkinson's disease. Aiming at the elucidation of MAO-B inhibitors with 1,3,4-oxadiazole scaffolds, we make a comprehensive update on the new and old chemical methods employed for the synthesis of the unsymmetrical oxadiazole derivatives that lead to high yield compounds. We summarize a state of the selective MAO-B inhibitors with oxadiazole scaffold, describing the results, structures, structure-activity relationships (SARs) and medicinal chemistry strategies over the years. The analysis of the recent papers would facilitate tracking the increasing number of oxadiazole derivatives as new chemical spaces with MAO-B inhibitory potential designed to ensure the safe use of the compounds and elimination of the unwanted drug-drug interactions.

Therapeutic significance of β-glucuronidase activity and its inhibitors: A review

The emergence of disease and dearth of effective pharmacological agents on most therapeutic fronts, constitutes a major threat to global public health and man's existence. Consequently, this has created an exigency in the search for new drugs with improved clinical utility or means of potentiating available ones. To this end, accumulating empirical evidence supports molecular target therapy as a plausible egress and, β-glucuronidase (βGLU) - a lysosomal acid hydrolase responsible for the catalytic deconjugation of β-d-glucuronides has emerged as a viable molecular target for several therapeutic applications. The enzyme's activity level in body fluids is also deemed a potential biomarker for the diagnosis of some pathological conditions. Moreover, due to its role in colon carcinogenesis and certain drug-induced dose-limiting toxicities, the development of potent inhibitors of βGLU in human intestinal microbiota has aroused increased attention over the years. Nevertheless, although our literature survey revealed both natural products and synthetic scaffolds as potential inhibitors of the enzyme, only few of these have found clinical utility, albeit with moderate to poor pharmacokinetic profile. Hence, in this review we present a compendium of exploits in the present millennium directed towards the inhibition of βGLU. The aim is to proffer a platform on which new scaffolds can be modelled for improved βGLU inhibitory potency and the development of new therapeutic agents in consequential.

Antiproliferative activity and possible mechanism of action of certain 5-methoxyindole tethered C-5 functionalized isatins

Background

Cancer is one of the most dreaded human diseases, that has become an ever-increasing health problem and is a prime cause of death globally. The potential antiproliferative activity of certain indole-isatin molecular hybrids 5a-w was evaluated in vitro against three human cancer cell lines.

Methods

Standard protocols were adopted to examine the antiproliferative potential and mechanisms of compounds 5a-w. Western blot analysis was carried out on compound 5o.

Results

Compounds 5a-w demonstrated in vitro antiproliferative activity in the range of 22.6-97.8%, with compounds 5o and 5w being the most active antiproliferative compounds   with IC₅₀ values of 1.69 and 1.91 µM, which is fivefold and fourfold more potent than sunitinib (IC₅₀=8.11 µM), respectively. Compound 5o was selected for in-depth pharmacological testing to understand its possible mechanism of antiproliferative activity. It caused a lengthening of the G1 phase and a reduction in the S and G2/M phases of the cell cycle and had an IC₅₀ value of 10.4 μM with the resistant NCI-H69AR cancer cell line. Moreover, compound 5o significantly decreased the amount of phosphorylated Rb protein in a dose-dependent fashion, which was confirmed via Western blot analysis.

Conclusion

The current investigation highlighted the potential antiproliferative activity of compounds 5a-w as well as the antiproliferative profile of compound 5o. These compounds can be harnessed as new lead antiproliferatives in the preclinical studies of cancer chemotherapy.

The green synthesis and molecular docking of novel N-substituted rhodanines as effective inhibitors for carbonic anhydrase and acetylcholinesterase enzymes

Recently, inhibition effects of enzymes such as acetylcholinesterase (AChE) and carbonic anhydrase (CA) has appeared as a promising approach for pharmacological intervention in a variety of disorders such as epilepsy, Alzheimer's disease and obesity. For this purpose, novel N-substituted rhodanine derivatives (RhAs) were synthesized by a green synthetic approach over one-pot reaction. Following synthesis the novel compounds, RhAs derivatives were tested against AChE and cytosolic carbonic anhydrase I, and II (hCAs I, and II) isoforms. As a result of this study, inhibition constant (Ki) were found in the range of 66.35 ± 8.35 to 141.92 ± 12.63 nM for AChE, 43.55 ± 14.20 to 89.44 ± 24.77 nM for hCA I, and 16.97 ± 1.42 to 64.57 ± 13.27 nM for hCA II, respectively. Binding energies were calculated with docking studies as -5.969, -5.981, and -9.121 kcal/mol for hCA I, hCA II, and AChE, respectively.