Synthesis of oleanolic acid derivatives: In vitro, in vivo and in silico studies for PTP-1B inhibition

Recent advances in the chemistry and biology of oleanolic acid and its derivatives

The pentacyclic triterpenes represent a significant class of plant bioactives with a variety of structures and a wide array of biological activities. These are biosynthetically produced via the mevalonate pathway although occasionally mixed pathways may also occur to introduce structural divergence. Oleanolic acid is one of the most explored bioactive from this class of compounds and possesses a broad spectrum of pharmacological and biological activities including liver protection, anti-cancer, atherosclerosis, anti-inflammation, antibacterial, anti-HIV, anti-oxidative, anti-diabetic etc. This review provides an overview of the latest research findings, highlighting the versatile medicinal and biological potential of oleanolic and its future prospects.

Green synthesized extracts/Au complex of Phyllospongia lamellosa: Unrevealing the anti-cancer and anti-bacterial potentialities, supported by metabolomics and molecular modeling

The anti-cancer and anti-bacterial potential of the Red Sea sponge Phyllospongia lamellosa in its bulk (crude extracts) and gold nanostructure (loaded on gold nanaoparticles) were investigated. Metabolomics analysis was conducted, and subsequently, molecular modeling studies were conducted to explore and anticipate the P. lamellosa secondary metabolites and their potential target for their various bioactivities. The chloroformic extract (CE) and ethyl acetate extract (EE) of the P. lamellosa predicted to include bioactive lipophilic and moderately polar metabolites, respectively, were used to synthesize gold nanoparticles (AuNPs). The prepared AuNPs were characterized through transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), and UV-vis spectrophotometric analyses. The cytotoxic activities were tested against MCF-7, MDB-231, and MCF-10A. Moreover, the anti-bacterial, antifungal, and anti-biofilm activity were assessed. Definite classes of metabolites were identified in CE (terpenoids) and EE (brominated phenyl ethers and sulfated fatty amides). Molecular modeling involving docking and molecular dynamics identified Protein-tyrosine phosphatase 1B (PTP1B) as a potential target for the anti-cancer activities of terpenoids. Moreover, CE exhibited the most powerful activity against breast cancer cell lines, matching our molecular modeling study. On the other hand, only EE was demonstrated to possess powerful anti-bacterial and anti-biofilm activity against Escherichia coli. In conclusion, depending on their bioactive metabolites, P. lamellosa-derived extracts, after being loaded on AuNPs, could be considered anti-cancer, anti-bacterial, and anti-biofilm bioactive products. Future work should be completed to produce drug leads.

A review of structural modification and biological activities of oleanolic acid

Oleanolic acid (OA), a pentacyclic triterpenoid, exhibits a broad spectrum of biological activities, including antitumor, antiviral, antibacterial, anti-inflammatory, hepatoprotective, hypoglycemic, and hypolipidemic effects. Since its initial isolation and identification, numerous studies have reported on the structural modifications and pharmacological activities of OA and its derivatives. Despite this, there has been a dearth of comprehensive reviews in the past two decades, leading to challenges in subsequent research on OA. Based on the main biological activities of OA, this paper comprehensively summarized the modification strategies and structure-activity relationships (SARs) of OA and its derivatives to provide valuable reference for future investigations into OA.

Isosteviol derivatives as protein tyrosine Phosphatase-1B inhibitors: Synthesis, biological evaluation and molecular docking

Protein tyrosine phosphatase (PTP1B) antagonizes insulin signaling and acts as a potential therapeutic target for insulin resistance associated with obesity and type II diabetes. In this work, a series of isosteviol derivatives 1-28 was synthesized and the inhibitory activity on PTP1B was evaluated by double antibody sandwich ELISA (DAS-ELISA) in vitro. Most isosteviol derivatives showed moderate PTP1B inhibitory activities. Among them, derivatives 10, 13, 24, 27 showed remarkable bioactivities with IC₅₀ values ranging from 0.24 to 0.40 µM. Particularly, derivative 24 exhibited the best inhibitory activity against PTP1B (IC₅₀ = 0.24 µM) in vitro; moreover, it showed 7-fold selectivity to PTP1B over T-cell protein tyrosine phosphatase (TCPTP) and 14-fold selectivity to PTP1B over cell division cycle 25 homolog B (CDC25B). Molecular docking studies demonstrated the hydrogen bond interaction between 24 and LYS-116 residue in PTP1B might be essential for the inhibitory activity. The results suggested that derivative 24 has great potential to be employed as drug candidate for the treatment of obesity and type II diabetes.

Triterpene Derivatives as Potential Inhibitors of the RBD Spike Protein from SARS-CoV-2: An In Silico Approach

The appearance of a new coronavirus, SARS-CoV-2, in 2019 kicked off an international public health emergency. Although rapid progress in vaccination has reduced the number of deaths, the development of alternative treatments to overcome the disease is still necessary. It is known that the infection begins with the interaction of the spike glycoprotein (at the virus surface) and the angiotensin-converting enzyme 2 cell receptor (ACE2). Therefore, a straightforward solution for promoting virus inhibition seems to be the search for molecules capable of abolishing such attachment. In this work, we tested 18 triterpene derivatives as potential inhibitors of SARS-CoV-2 against the receptor-binding domain (RBD) of the spike protein by means of molecular docking and molecular dynamics simulations, modeling the RBD S1 subunit from the X-ray structure of the RBD-ACE2 complex (PDB ID: 6M0J). Molecular docking revealed that at least three triterpene derivatives of each type (i.e., oleanolic, moronic and ursolic) present similar interaction energies as the reference molecule, i.e., glycyrrhizic acid. Molecular dynamics suggest that two compounds from oleanolic and ursolic acid, OA5 and UA2, can induce conformational changes capable of disrupting the RBD-ACE2 interaction. Finally, physicochemical and pharmacokinetic properties simulations revealed favorable biological activity as antivirals.

Recent advances in medicinal chemistry of oleanolic acid derivatives

Oleanolic acid (OA), a ubiquitous pentacyclic oleanane-type triterpene isolated from edible and medicinal plants, exhibits a wide spectrum of pharmacological activities and tremendous therapeutic potential. However, the undesirable pharmacokinetic properties limit its application and development. Numerous researches on structural modifications of OA have been carried out to overcome this limitation and improve its pharmacokinetic and therapeutic properties. This review aims to compile and summarize the recent progresses in the medicinal chemistry of OA derivatives, especially on structure-activity relationship in the last few years (2010-2021). It gives insights into the rational design of bioactive derivatives from OA scaffold as promising therapeutic agents.

Recent advances in PTP1B signaling in metabolism and cancer

Protein tyrosine phosphorylation is one of the major post-translational modifications in eukaryotic cells and represents a critical regulatory mechanism of a wide variety of signaling pathways. Aberrant protein tyrosine phosphorylation has been linked to various diseases, including metabolic disorders and cancer. Few years ago, protein tyrosine phosphatases (PTPs) were considered as tumor suppressors, able to block the signals emanating from receptor tyrosine kinases. However, recent evidence demonstrates that misregulation of PTPs activity plays a critical role in cancer development and progression. Here, we will focus on PTP1B, an enzyme that has been linked to the development of type 2 diabetes and obesity through the regulation of insulin and leptin signaling, and with a promoting role in the development of different types of cancer through the activation of several pro-survival signaling pathways. In this review, we discuss the molecular aspects that support the crucial role of PTP1B in different cellular processes underlying diabetes, obesity and cancer progression, and its visualization as a promising therapeutic target.

PPARα/γ, adiponectin and GLUT4 overexpression induced by moronic acid methyl ester influenced on glucose and triglycerides levels of experimental diabetic mice

The current study aimed to determine the antidiabetic and antidyslipidemic activities of moronic acid methyl ester (1) by in vivo, in vitro, in silico and molecular biology studies. Compound 1 was evaluated to establish its dose-dependent antidiabetic and antihyperglycemic (50 mg/kg) activities, in diabetic and normoglycemic male CD1 mice, respectively. Also, compound 1 was subjected to a sub-acute study (50 mg/kg/day for eight days) to determine blood biochemical profiles and the expression of PTP-1B, GLUT4, PPAR-α, PPAR-γ, adiponectin, IL-1β, and MCP1 in adipose tissue of animals after treatment. Different doses in acute administration of 1 decreased glycemia (p < 0.05), compared with vehicle, showing greater effectiveness in the range 50-160 mg/kg. Also, the oral glucose tolerance test (OGTT) showed that 1 induced a significant antihyperglycemic action by opposing the hyperglycemic peak (p < 0.05). Moreover, 1 subacute administration decrease glucose and triglycerides levels after treatment (p < 0.05); while the expression of PPAR-α and γ, adiponectin and GLUT4 displayed an increase (p< 0.05) compared with the diabetic control group. In conclusion, compound 1 showed antihyperglycemic, antidiabetic and antidyslipidemic effects in normal and diabetic mice, probably due to insulin sensitization through increase mRNA expression of GLUT4, PPAR-α, PPAR-γ and adiponectin genes.

Chemistry, Biological Activities and In Silico Bioprospection of Sterols and Triterpenes from Mexican Columnar Cactaceae

The Cactaceae family is an important source of triterpenes and sterols. The wide uses of those plants include food, gathering, medicinal, and live fences. Several studies have led to the isolation and characterization of many bioactive compounds. This review is focused on the chemistry and biological properties of sterols and triterpenes isolated mainly from some species with columnar and arborescent growth forms of Mexican Cactaceae. Regarding the biological properties of those compounds, apart from a few cases, their molecular mechanisms displayed are not still fully understand. To contribute to the above, computational chemistry tools have given a boost to traditional methods used in natural products research, allowing a more comprehensive exploration of chemistry and biological activities of isolated compounds and extracts. From this information an in silico bioprospection was carried out. The results suggest that sterols and triterpenoids present in Cactaceae have interesting substitution patterns that allow them to interact with some bio targets related to inflammation, metabolic diseases, and neurodegenerative processes. Thus, they should be considered as attractive leads for the development of drugs for the management of chronic degenerative diseases.

Protein Tyrosine Phosphatase (PTP1B): A promising Drug Target Against Life-threatening Ailments

Background:

Protein tyrosine phosphatases are enzymes which help in the signal transduction in diabetes, obesity, cancer, liver diseases and neurodegenerative diseases. PTP1B is the main member of this enzyme from the protein extract of human placenta. In phosphate inhibitors development, significant progress has been made over the last 10 years. In early-stage clinical trials, few compounds have reached whereas in the later stage trials or registration, yet none have progressed. Many researchers investigate different ways to improve the pharmacological properties of PTP1B inhibitors.

Objective:

In the present review, authors have summarized various aspects related to the involvement of PTP1B in various types of signal transduction mechanisms and its prominent role in various diseases like cancer, liver diseases and diabetes mellitus.

Conclusion:

There are still certain challenges for the selection of PTP1B as a drug target. Therefore, continuous future efforts are required to explore this target for the development of PTP inhibitors to treat the prevailing diseases associated with it.

Design and synthesis of tricyclic terpenoid derivatives as novel PTP1B inhibitors with improved pharmacological property and in vivo antihyperglycaemic efficacy

Overexpression of protein tyrosine phosphatase 1B (PTP1B) induces insulin resistance in various basic and clinical research. In our previous work, a synthetic oleanolic acid (OA) derivative C10a with PTP1B inhibitory activity has been reported. However, C10a has some pharmacological defects and cytotoxicity. Herein, a structure-based drug design approach was used based on the structure of C10a to elaborate the smaller tricyclic core. A series of tricyclic derivatives were synthesised and the compounds 15, 28 and 34 exhibited the most PTP1B enzymatic inhibitory potency. In the insulin-resistant human hepatoma HepG2 cells, compound 25 with the moderate PTP1B inhibition and preferable pharmaceutical properties can significantly increase insulin-stimulated glucose uptake and showed the insulin resistance ameliorating effect. Moreover, 25 showed the improved in vivo antihyperglycaemic potential in the nicotinamide–streptozotocin-induced T2D. Our study demonstrated that these tricyclic derivatives with improved molecular architectures and antihyperglycaemic activity could be developed in the treatment of T2D.

Modified diterpenoids from the tuber of Icacina oliviformis as protein tyrosine phosphatase 1B inhibitors

Two modified diterpenoids featuring a novel 4,12-dioxatetracyclo[8.6.0.0^2,7.0^10,14]hexadecane core, together with a 3,4-seco-pimarane, a 3,4-seco-cleistanthane, and eight pimarane derivatives were isolated from the tuber of Icacina oliviformis.

Discovery of highly functionalized 5,6-seco-grayanane diterpenoids as potent competitive PTP1B inhibitors

Three competitive PTP1B inhibitory diterpenoids with a 5,6-seco-grayanane carbon skeleton (1–3) were isolated and identified fromRhododendron molle. A more potent competitive PTP1B inhibitor (9) was designed and prepared based on a docking study.

Protein Tyrosine Phosphatase 1B Inhibitory Iridoids from Psydrax subcordata

Phytochemical investigation of the leaves and bark of Psydrax subcordata has led to the isolation of six new iridoids, subcordatanols I-V (1-4 and 6) and 1-O-methylcrescentin I (5), along with two known analogues (7 and 8). Among them, subcordatanol I (1) is the first example of a 3,8-monoepoxy-iridoid featuring a caged 2-oxa-bicyclo[3.2.1]octane core. The absolute stereochemistry at C-4 of 3, 4, and 6 was established through their acid-catalyzed reaction products subcordatalactones A (3a), B (4a), and C (6a), respectively. Subcordatanols I (1) and II (2), as well as subcordatalactones A (3a) and B (4a), displayed inhibitory activity against protein tyrosine phosphatase 1B (PTP1B). Enzyme kinetic studies indicated that 3a and 4a are competitive inhibitors. A molecular docking study is also reported.

Identification and characterization of potent and selective inhibitors targeting protein tyrosine phosphatase 1B (PTP1B)

Protein tyrosine phosphatase 1B (PTP1B) plays an important role in the negative regulation of insulin and leptin signaling. The development of small molecular inhibitors targeting PTP1B has been validated as a potential therapeutic strategy for Type 2 diabetes (T2D). In this work, we have identified a series of compounds containing dihydropyridine thione and particular chiral structure as novel PTP1B inhibitors. Among those, compound 4b showed moderate activity with IC₅₀ value of 3.33 μM and meanwhile with good selectivity (>30-fold) against TCPTP. The further MOA study of PTP1B demonstrated that compounds 4b is a substrate-competitive inhibitor. The binding mode analysis suggested that compound 4b simultaneously occupies the active site and the second phosphotyrosine (pTyr) binding site of PTP1B. Furthermore, the cell viability assay of compound 4b showed tolerable cytotoxicity in L02 cells, thus 4b may be prospectively used to further in vivo study.

Pentacyclic triterpenes: New tools to fight metabolic syndrome

BACKGROUND

Metabolic syndrome is a combination of dysregulated cardiometabolic risk factors characterized by dyslipidemia, impaired glucose tolerance, insulin resistance, inflammation, obesity as well as hypertension. These factors are tied to the increased risk for type-II diabetes and cardiovascular diseases including myocardial infarction in patients with metabolic syndrome.

PURPOSE

To review the proposed molecular mechanisms of pentacyclic triterpenes for their potential use in the metabolic syndrome.

METHODS

PubMed, Science Direct, and Google Scholar database were searched from commencement to April 2018. Following keywords were searched in the databases with varying combinations: "metabolic syndrome", "pentacyclic triterpenes", "transcription factors", "protein kinase", "lipogenesis", "adipogenesis", "lipolysis", "fatty acids", "gluconeogenesis", "cardiovascular", "mitochondria", "oxidative stress", "pancreas", "hepatic cells", "skeletal muscle", "3T3-L1", "C2C12", "obesity", "inflammation", "insulin resistance", "glucose uptake", "clinical studies" and "bioavailability".

RESULTS

Pentacyclic triterpenes, such as asiatic acid, ursolic acid, oleanolic acid, 18β-glycyrrhetinic acid, α,β-amyrin, celastrol, carbenoxolone, corosolic acid, maslinic acid, bardoxolone methyl and lupeol downregulate several metabolic syndrome components by regulating transcription factors, protein kinases and enzyme involved in the adipogenesis, lipolysis, fatty acid oxidation, insulin resistance, mitochondria biogenesis, gluconeogenesis, oxidative stress and inflammation.

CONCLUSION

In vitro and in vivo studies suggests that pentacyclic triterpenes effectively downregulate various factors related to metabolic syndrome. These phytochemicals may serve as promising candidates for clinical trials for the management of metabolic syndrome.

Ursolic acid derivatives as potential antidiabetic agents: In vitro, in vivo, and in silico studies

Hit, Lead & Candidate Discovery Protein tyrosine phosphatase 1B (PTP-1B) has attracted interest as a novel target for the treatment of type 2 diabetes, this because its role in the insulin-signaling pathway as a negative regulator. Thus, the aim of current work was to obtain seven ursolic acid derivatives as potential antidiabetic agents with PTP-1B inhibition as main mechanism of action. Furthermore, derivatives 1-7 were submitted in vitro to enzymatic PTP-1B inhibition being 3, 5, and 7 the most active compounds (IC50  = 5.6, 4.7, and 4.6 μM, respectively). In addition, results were corroborated with in silico docking studies with PTP-1B orthosteric site A and extended binding site B, showed that 3 had polar and Van der Waals interactions in both sites with Lys120, Tyr46, Ser216, Ala217, Ile219, Asp181, Phe182, Gln262, Val49, Met258, and Gly259, showing a docking score value of -7.48 Kcal/mol, being more specific for site A. Moreover, compound 7 showed polar interaction with Gln262 and Van der Waals interactions with Ala217, Phe182, Ile219, Arg45, Tyr46, Arg47, Asp48, and Val49 with a predictive docking score of -6.43 kcal/mol, suggesting that the potential binding site could be localized in the site B adjacent to the catalytic site A. Finally, derivatives 2 and 7 (50 mg/kg) were selected to establish their in vivo antidiabetic effect using a noninsulin-dependent diabetes mice model, showing significant blood glucose lowering compared with control group (p < .05).

Novel Mixed-Type Inhibitors of Protein Tyrosine Phosphatase 1B. Kinetic and Computational Studies

The Atlas of Diabetes reports 415 million diabetics in the world, a number that has surpassed in half the expected time the twenty year projection. Type 2 diabetes is the most frequent form of the disease; it is characterized by a defect in the secretion of insulin and a resistance in its target organs. In the search for new antidiabetic drugs, one of the principal strategies consists in promoting the action of insulin. In this sense, attention has been centered in the protein tyrosine phosphatase 1B (PTP1B), a protein whose overexpression or increase of its activity has been related in many studies with insulin resistance. In the present work, a chemical library of 250 compounds was evaluated to determine their inhibition capability on the protein PTP1B. Ten molecules inhibited over the 50% of the activity of the PTP1B, the three most potent molecules were selected for its characterization, reporting Ki values of 5.2, 4.2 and 41.3 µM, for compounds 1, 2, and 3, respectively. Docking and molecular dynamics studies revealed that the three inhibitors made interactions with residues at the secondary binding site to phosphate, exclusive for PTP1B. The data reported here support these compounds as hits for the design more potent and selective inhibitors against PTP1B in the search of new antidiabetic treatment.

Oleanolic acid derivative DKS26 exerts antidiabetic and hepatoprotective effects in diabetic mice and promotes glucagon-like peptide-1 secretion and expression in intestinal cells

BACKGROUND AND PURPOSE

Glucagon-like peptide-1 (GLP-1) is an important target for diabetes therapy based on its key role in maintaining glucose and lipid homeostasis. This study was designed to investigate antidiabetic and hepatoprotective effects of a novel oleanolic acid derivative DKS26 in diabetic mice and elucidate its underlying GLP-1 related antidiabetic mechanisms in vitro and in vivo.

EXPERIMENTAL APPROACH

The therapeutic effects of DKS26 were investigated in streptozotocin (STZ)-induced and db/db diabetic mouse models. Levels of plasma glucose, glycosylated serum protein (GSP), lipid profiles, insulin, alanine aminotransferase (ALT) and aspartate aminotransferase (AST), oral glucose tolerance (OGT), pancreatic islets and hepatic histopathological morphology, liver lipid levels and expression of pro-inflammatory cytokines were assessed. Intestinal NCI-H716 cells and diabetic models were used to further validate its potential GLP-1-related antidiabetic mechanisms.

KEY RESULTS

DKS26 treatment (100 mg·kg^-1 ·day^-1 ) decreased plasma levels of glucose, GSP, ALT and AST; ameliorated OGT and plasma lipid profiles; augmented plasma insulin levels; alleviated islets and hepatic pathological morphology; and reduced liver lipid accumulation, inflammation and necrosis in vivo. Furthermore, DKS26 enhanced GLP-1 release and expression, accompanied by elevated levels of cAMP and phosphorylated PKA in vitro and in vivo.

CONCLUSION AND IMPLICATIONS

DKS26 exerted hypoglycaemic, hypolipidaemic and islets protective effects, which were associated with an enhanced release and expression of GLP-1 mediated by the activation of the cAMP/PKA signalling pathway, and alleviated hepatic damage by reducing liver lipid levels and inflammation. These findings firmly identified DKS26 as a new viable therapeutic option for diabetes control.

Synthesis and Cytotoxic Activity of Triterpenoid Thiazoles Derived from Allobetulin, Methyl Betulonate, Methyl Oleanonate, and Oleanonic Acid

A total of 41 new triterpenoids were prepared from allobetulone, methyl betulonate, methyl oleanonate, and oleanonic acid to study their influence on cancer cells. Each 3-oxotriterpene was brominated at C2 and substituted with thiocyanate; subsequent cyclization with the appropriate ammonium salts gave N-substituted thiazoles. All compounds were tested for their in vitro cytotoxic activity on eight cancer cell lines and two non-cancer fibroblasts. 2-Bromoallobetulone (2 b) methyl 2-bromobetulonate (3 b), 2-bromooleanonic acid (5 b), and 2-thiocyanooleanonic acid (5 c) were best, with IC₅₀ values less than 10 μm against CCRF-CEM cells (e.g., 3 b: IC₅₀ =2.9 μm) as well as 2'-(diethylamino)olean-12(13)-eno[2,3-d]thiazole-28-oic acid (5 f, IC₅₀ =9.7 μm) and 2'-(N-methylpiperazino)olean-12(13)-eno[2,3-d]thiazole-28-oic acid (5 k, IC₅₀ =11.4 μm). Compound 5 c leads to the accumulation of cells in the G₂ phase of the cell cycle and inhibits RNA and DNA synthesis significantly at 1×IC₅₀ . The G₂ /M cell-cycle arrest probably corresponds to the inhibition of DNA/RNA synthesis, similar to the mechanism of action of actinomycin D. Compound 5 c is new, active, and nontoxic; it is therefore the most promising compound in this series for future drug development. Methyl 2-bromobetulonate (3 b) and methyl 2-thiocyanometulonate (3 c) were found to inhibit nucleic acid synthesis only at 5×IC₅₀ . We assume that in 3 b and 3 c (unlike in 5 c), DNA/RNA inhibition is a nonspecific event, and an unknown primary cytotoxic target is activated at 1×IC₅₀ or lower concentration.

Recent advances in the development of protein tyrosine phosphatase 1B inhibitors for Type 2 diabetes

Diabetes mellitus is the most serious and prevalent metabolic disorders worldwide, complications of which can decrease significantly the quality of life and contribute to premature death. Resistance to insulin is a predominant pathophysiological factor of Type 2 diabetes (T2D). Protein tyrosine phosphatase 1B (PTP1B) is an important negative factor of insulin signal and a potent therapeutic target in T2D patients. This review highlights recent advances (2012-2015) in research related to the role of PTP1B in signal transduction processes implicated in pathophysiology of T2D, and novel PTP1B inhibitors with an emphasis on their chemical structures and modes of action.

Why Antidiabetic Vanadium Complexes are Not in the Pipeline of "Big Pharma" Drug Research? A Critical Review

Public academic research sites, private institutions as well as small companies have made substantial contributions to the ongoing development of antidiabetic vanadium compounds. But why is this endeavor not echoed by the globally operating pharmaceutical companies, also known as "Big Pharma"? Intriguingly, today's clinical practice is in great need to improve or replace insulin treatment against Diabetes Mellitus (DM). Insulin is the mainstay therapeutically and economically. So, why do those companies develop potential antidiabetic drug candidates without vanadium (vanadium- free)? We gathered information about physicochemical and pharmacological properties of known vanadium-containing antidiabetic compounds from the specialized literature, and converted the data into explanations (arguments, the "pros and cons") about the underpinnings of antidiabetic vanadium. Some discoveries were embedded in chronological order while seminal reviews of the last decade about the Medicinal chemistry of vanadium and its history were also listed for further understanding. In particular, the concepts of so-called "noncomplexed or free" vanadium species (i.e. inorganic oxido-coordinated species) and "biogenic speciation" of antidiabetic vanadium complexes were found critical and subsequently documented in more details to answer the question.

Protonated montmorillonite-mediated highly specific isomerization of oleanolic acid esters: application to the synthesis of Δ13(18)-CDDO-Me

A one-pot highly specific isomerization of oleanolic acid esters (5a–g) to δ-oleanolic acid esters (6a–g) was achieved in the presence of proton-exchanged montmorillonite (H-mont) under mild reaction conditions.

Oleanolic acid acrylate elicits antidepressant-like effect mediated by 5-HT1A receptor

The development of new drugs for the treatment of depression is strategic to achieving clinical needs of patients. This study evaluates antidepressant-like effect and neural mechanisms of four oleanolic acid derivatives i.e. acrylate (D1), methacrylate (D2), methyl fumarate (D3) and ethyl fumarate (D4). All derivatives were obtained by simple one-step esterification of oleanolic acid prior to pharmacological screening in the forced swimming (FS) and open field (OF) tests. Pharmacological tools like α-methyl-p-tyrosine (AMPT, catecholamine depletor), p-chlorophenylalanine (serotonin depletor), prazosin (PRAZ, selective α1-receptor antagonist), WAY-100635 (selective serotonin 5-HT_1A receptor antagonist) as well as monoamine oxidase (MAO) and functional binding assays were conducted to investigate possible neural mechanisms. In the FS test, D1 showed the most promising antidepressant-like effect without eliciting locomotor incoordination. Unlike group of mice pretreated with AMPT 100 mg/kg, PCPA 100 mg/kg or PRAZ 1 mg/kg, the effect of D1 was attenuated by WAY-100635 0.3 mg/kg pretreatment. D1 demonstrated moderate inhibition of MAO-A (IC₅₀ = 48.848 ± 1.935 μM), potency (pEC₅₀ = 6.1 ± 0.1) and intrinsic activity (E_max = 26 ± 2.0%) on 5-HT_1A receptor. In conclusion, our findings showed antidepressant-like effect of D1 and possible involvement of 5-HT_1A receptor.

Synthesis of novel 3-aryl-1-oxa-2,8-diazaspiro[4.5]dec-2-ene derivatives and their biological evaluation against protein tyrosine phosphatase 1B

A series of novel 3-aryl-1-oxa-2,8-diazaspiro[4.5]dec-2-ene derivatives were designed, synthesized, and evaluated as a new class of inhibitors against protein tyrosine phosphatase 1B. Among them, compound 6f displayed moderate inhibitory activity with IC50 of 2.87 ± 0.24 μm and can be used as a novel lead compound for the design of inhibitors of protein tyrosine phosphatase 1B.

Design, synthesis and structural exploration of novel fluorinated dabigatran derivatives as direct thrombin inhibitors

Twenty-one fluorinated dabigatran derivatives were designed based on the bioisosteric principle. All derivatives were synthesised and evaluated for their thrombin inhibitory activity in vitro. Among these compounds, 14h, 14m, 14s and 14t were potent and the activity was in the range of reference drug, dabigatran. Three structural changes were introduced in these 21 compounds to elucidate the structure-activity relationship of the drugs. In addition, prodrugs of compounds 14h and 14s were developed to investigate their anticoagulant activities in vivo. In these experiments, compound 16 showed a fairly strong inhibitory effect on thrombin-induced platelet aggregation, and demonstrated potent activity for inhibiting arteriovenous thrombosis with an inhibition rate of (73 ± 6) %, which was comparable to that of dabigatran etexilate (76 ± 2) %. Moreover, molecular docking studies were performed to understand the binding interactions of active compounds 14h, 14s and 14t with thrombin protein (PDB ID:1KTS). Contour maps obtained from the 3D-QSAR model are meaningful in designing more active molecules to act as direct inhibitors of thrombin.