Recent developments in the design of angiotensin-converting enzyme inhibitors

Elucidation of the relationship between evodiamine-induced liver injury and CYP3A4-mediated metabolic activation by UPLC-MS/MS analysis

Evodiamine (EVD), which has been reported to cause liver damage, is the main constituent of Evodia rutaecarpa (Juss.) Benth and may be bioactivated into reactive metabolites mediated by cytochrome P450. However, the relationships between bioactivation and EVD-induced hepatotoxicity remain unknown. In this study, comprehensive hepatotoxicity evaluation was explored, which demonstrated that EVD caused hepatotoxicity in both time- and dose-dependent manners in mice. By application of UPLC-Q/TOF-MS/MS, two GSH conjugates (GM1 and GM2) derived from reactive metabolites of EVD were identified, in microsomal incubation systems exposed to EVD with glutathione (GSH) as trapping agents. CYP3A4 was proved to be the main metabolic enzyme. Correspondingly, the N-acetyl-L-cysteine conjugate derived from the degradation of GM2 was detected in the urine of mice after exposure to EVD. For the first time, the iminoquinone intermediate was found in EVD-pretreated rat bile by the high-resolution MS platform. Pretreatment with ketoconazole protected the animals from hepatotoxicity, decreased the protein expression of cleaved caspase-1 and -3, but increased the area under the serum-concentration-time curve of EVD in blood determined by UPLC-QQQ-MS/MS. Depletion of GSH by buthionine sulfoximine exacerbated EVD-induced hepatotoxicity. These results implicated that the CYP3A4-mediated metabolic activation was responsible for the observed hepatotoxicity induced by EVD.

Gaussian Accelerated Molecular Dynamics Simulations Investigation on the Mechanism of Angiotensin-Converting Enzyme (ACE) C-Domain Inhibition by Dipeptides

Angiotensin-converting enzyme (ACE)-inhibitory peptides extracted from food proteins can lower blood pressure by inhibiting ACE activity. A recent study showed that the inhibitory activity of IY (Ile-Tyr, a dipeptide derived from soybean protein) against ACE was much higher than that of LL (Leu-Leu), although they had similar hydrophobic and predicted activity values. It was difficult to reveal the deep molecular mechanism underlying this phenomenon by traditional experimental methods. The Apo and two complex systems (i.e., ACE–LL and ACE–IY) were therefore subjected to 1 μs long Gaussian accelerated molecular dynamics (GaMD) simulations. The results showed that the binding of IY can cause obvious contraction of the active site of ACE, mainly manifested by a significant lateral shift of α13, α14, and α15. In addition, hinge 2 and hinge 3 were more stable in the ACE–IY system, while these phenomena were not present in the ACE–LL system. Moreover, the α10 of the IY-bound ACE kept an inward state during the simulation progress, which facilitated the ACE to remain closed. However, for the LL-bound ACE, the α10 switched between two outward states. To sum up, our study provides detailed insights into inhibitor-induced conformational changes in ACE that may help in the design of specific inhibitors targeting ACE for the treatment of hypertension.

The structural reconformation of peptides in enhancing functional and therapeutic properties: Insights into their solid state crystallizations

Therapeutic peptides derived proteins with alpha-reconformation states like antibody shape have shown potential effects in combating terrible diseases linked with earlier signs of angiogensis, mutagenesis and transgenesis. Alpha reconformation in material design refers to the folding of the peptide chains and their transitions under reversible chemical bonds of disulfide chemical bridges and further non-covalence lesions. Thus, the rational design of signal peptides into alpha-helix is intended in increasing the defending effects of peptides into cores like adjuvant antibiotic and/or vaccines. Thereby, the signal peptides are able in displaying multiple eradicating regions by changing crystal-depositions and deviation angles. These types of molecular structures could have multiple advantages in tracing disease syndromes and impurities by increasing the host defense against the fates of pathogens and viruses, eventually leading to the loss in signaling by increasing peptide susceptibility levels to folding and unfolding and therefore, formation of transgenic peptide models. Alpha reconformation peptides is aimed in triggering as well as other regulatory functions such as remodulating metabolic chain disorders of lipolysis and glucolysis by increasing the insulin and leptin resistance for best lipid storages and lipoprotein density distributions.

Prescribed drugs containing nitrogen heterocycles: an overview

Heteroatoms as well as heterocyclic scaffolds are frequently present as the common cores in a plethora of active pharmaceuticals natural products. Statistically, more than 85% of all biologically active compounds are heterocycles or comprise a heterocycle and most frequently, nitrogen heterocycles as a backbone in their complex structures. These facts disclose and emphasize the vital role of heterocycles in modern drug design and drug discovery. In this review, we try to present a comprehensive overview of top prescribed drugs containing nitrogen heterocycles, describing their pharmacological properties, medical applications and their selected synthetic pathways. It is worth mentioning that the reported examples are actually limited to current top selling drugs, being or containing N-heterocycles and their synthetic information has been extracted from both scientific journals and the wider patent literature.

Evaluating the benefits of renin-angiotensin system inhibitors as cancer treatments

G-protein-coupled receptors (GPCRs) are the largest and most diverse group of cellular membrane receptors identified and characterized. It is estimated that 30 to 50% of marketed drugs target these receptors. The angiotensin II receptor type 1 (AT1R) is a GPCR which signals in response to systemic alterations of the peptide hormone angiotensin II (AngII) in circulation. The enzyme responsible for converting AngI to AngII is the angiotensin-converting enzyme (ACE). Specific inhibitors for the AT1R (more commonly known as AT1R blockers or antagonists) and ACE are well characterized for their effects on the cardiovascular system. Combined with the extensive clinical data available on patient tolerance of AT1R blockers (ARBs) and ACE inhibitors (ACEIs), as well as their non-classical roles in cancer, the notion of repurposing this class of medications as cancer treatment(s) is explored in the current review. Given that AngII-dependent AT1R activity directly regulates angiogenesis, remodeling of vasculature, pro-inflammatory responses, stem cell programming and hematopoiesis, and electrolyte balance; the modulation of these processes with pharmacologically well characterized medications could present a valuable complementary treatment option for cancer patients.

Built to bind: biosynthetic strategies for the formation of small-molecule protease inhibitors

The discovery and characterization of natural product protease inhibitors has inspired the development of numerous pharmaceutical agents.

Studies on the Interaction between Angiotensin-Converting Enzyme (ACE) and ACE Inhibitory Peptide from Saurida elongata

Angiotensin-converting enzyme (ACE) inhibitory peptides derived from food protein exhibited antihypertensive effects by inhibiting ACE activity. In this work, the interaction between ACE inhibitory peptide GMKCAF (GF-6) and ACE was studied by isothermal titration calorimetry (ITC), molecular docking, ultraviolet absorption spectroscopy, fluorescence spectroscopy, and circular dichroism spectroscopy. Experimental results revealed that the binding of GF-6 to ACE was a spontaneous exothermic process driven by both enthalpy and entropy. The interaction occurred via a static quenching mechanism and involved the alteration of the conformation of ACE. In addition, ITC and molecular docking results indicated binding of GF-6 to ACE via multiple binding sites on the protein surface. This study could be deemed helpful for the better understanding of the inhibitory mechanism of ACE inhibitory peptides.

Cyanobacteria Nostoc Punctiforme from Abyssal Benthos of Lake Baikal: Unique Ecology and Metabolic Potential

A strain of Nostoc punctiforme was isolated from the bottom sediments of the oil seep at Gorevoy Utes (Central Baikal) at a depth of 890 m. The Baikal strain is highly similar (98-99%) to the N. punctiforme CCAP 1453/9 strain and the typical N. punctiforme PCC 73103 strain isolated from soil ecotopes. Based on the analysis of functional genes and mass spectrometry data, we determined that the strain can produce bioactive peptides and polyketides, but does not produce known cyanobacterial toxins, saxitoxin or its analogs, or microcystins. The peptides aeruginosinamide, aeruginosin 606, aeruginosin 98-A, kasumigamide C, and microginin 91-D were recorded in the metabolic profile of the strain. The major ion found in the MALDI mass spectrum is most likely to be an ion of a polyketide substance with unknown function.

Side Chain Cyclized Aromatic Amino Acids: Great Tools as Local Constraints in Peptide and Peptidomimetic Design

Constraining the conformation of flexible peptides is a proven strategy to increase potency, selectivity, and metabolic stability. The focus has mostly been on constraining the backbone dihedral angles; however, the correct orientation of the amino acid side chains (χ-space) that constitute the peptide pharmacophore is equally important. Control of χ-space utilizes conformationally constrained amino acids that favor, disfavor, or exclude the gauche (-), the gauche (+), or the trans conformation. In this review we focus on cyclic aromatic amino acids in which the side chain is connected to the peptide backbone to provide control of χ¹- and χ²-space. The manifold applications for cyclized analogues of the aromatic amino acids Phe, Tyr, Trp, and His within peptide medicinal chemistry are showcased herein with examples of enzyme inhibitors and ligands for G protein-coupled receptors.

Spermidine Derivatives in Lulo (Solanum quitoense Lam.) Fruit: Sensory (Taste) versus Biofunctional (ACE-Inhibition) Properties

The bitterness in lulo (Solanum quitoense Lam.) fruit is increased during processing (juicing or drying). To identify the bitter-active compounds, the ethanolic fruit pulp extract was subjected to RP-18 solid-phase extraction, and then sensory-guided fractionated by HPLC. Two spermidine derivatives, N(1),N(4),N(8)-tris(dihydrocaffeoyl)spermidine and N(1),N(8)-bis(dihydrocaffeoyl)spermidine, were isolated and their structures confirmed by analysis of their HPLC-ESI/MS and (1)H and (13)C NMR data. The N(1),N(4),N(8)-tris(dihydrocaffeoyl)spermidine was synthesized and used as an authentic sample to unequivocally confirm the structure of this compound and to quantitate it in both fresh and dried fruit. In silico analyses demonstrated that spermidine derivatives identified in lulo pulp exhibited a strong ACE-I (angiotensin I-converting enzyme) inhibitory activity. Subsequently, these results were confirmed by in vitro analyses and showed the potential use of lulo fruit pulp as an ingredient of functional foods related to the prevention of blood hypertension.

Green chemistry approaches as sustainable alternatives to conventional strategies in the pharmaceutical industry

Green chemistry is a rapidly developing field for the sustainable development of future science and technology. Incorporating green chemistry into the synthesis of active pharmaceutical ingredients and intermediates is of ongoing importance to the pharmaceutical industry.

Study of the chelating properties of Ge(OH)2 functionality as metal binding group for Zn2+ cation in simplified protease-like environments: a DFT analysis

The development of protease's inhibitors is an active field of research in the pharmaceutical industry. As concerns the design of new inhibitors, the theoretical study of the binding patterns and energies of known metal binding groups (MBGs) toward Zn(2+) using quantum-chemical calculations may offer a better understanding of their interaction models and may be useful for the improvement and design of novel ZBGs. Here the properties of gem-Ge(OH)(2)-based compounds as ZBG were assessed theoretically using DFT calculations. [Zn(Imdz)(2) R - OH(2)](2+) complexes (Imdz =imidazole rings; R = imidazole ring, acetic acid molecule or acetate anion) were used to partially reproduce the coordination sphere in metalloproteases (ACE, amgiotensin converting enzyme, and TLN, thermolysine) being inhibited by related compounds (i.e., silanediols). The MBG- Zn(2+) interaction was analyzed through the energy of the reaction: [Zn(Imdz)(2) R - OH(2)](2+) + L → [Zn(Imdz)(2) R - L](2+) + H(2)O using DFT (M06L/cc-pVDZ) in gas-phase and in solution (IEF-PCM). Although the functional used (M06L) has proven its efficiency to study systems containing transition metal governed by non-covalent interactions, dispersion effects were implemented by the correction of the computed energies using the DFT-D3 program. Accounting for dispersion effects produced a systematic increase of c.a. 13 kJ mol(-1) on the energies, whereas the effect of solvent goes in the opposite direction (i.e., BE under the IEF-PCM model are on average 125 kJ mol(-1) lower). The Ge(OH)(2) - Zn(2+) interaction seems to be similar (or even stronger) than the Si(OH)(2) -Zn(2+). Their better performance as ZBG is explained by the combined NBO-AIM analysis. The results of this work may encourage the preparation, isolation, and experimental assay of the chelating properties of these compounds, which may propose a new family of protease's inhibitors.

Synthesis of (2S,3R)-3-amino-2-hydroxydecanoic acid and its enantiomer: a non-proteinogenic amino acid segment of the linear pentapeptide microginin

A directed manipulation of the functional groups at C3 and C4 of D-glucose was demonstrated to synthesize naturally occurring (2S,3R)-α-hydroxy-β-aminodecanoic acid (AHDA, 2a) and its enantiomer 2b. The enantiomer of 2a is the N-terminal part of the natural linear pentapeptide microginin, which is used as an antihypertensive agent.

Chemical informatics uncovers a new role for moexipril as a novel inhibitor of cAMP phosphodiesterase-4 (PDE4)

PDE4 is one of eleven known cyclic nucleotide phosphodiesterase families and plays a pivotal role in mediating hydrolytic degradation of the important cyclic nucleotide second messenger, cyclic 3′5′ adenosine monophosphate (cAMP). PDE4 inhibitors are known to have anti-inflammatory properties, but their use in the clinic has been hampered by mechanism-associated side effects that limit maximally tolerated doses. In an attempt to initiate the development of better-tolerated PDE4 inhibitors we have surveyed existing approved drugs for PDE4-inhibitory activity. With this objective, we utilised a high-throughput computational approach that identified moexipril, a well tolerated and safe angiotensin-converting enzyme (ACE) inhibitor, as a PDE4 inhibitor. Experimentally we showed that moexipril and two structurally related analogues acted in the micro molar range to inhibit PDE4 activity. Employing a FRET-based biosensor constructed from the nucleotide binding domain of the type 1 exchange protein activated by cAMP, EPAC1, we demonstrated that moexipril markedly potentiated the ability of forskolin to increase intracellular cAMP levels. Finally, we demonstrated that the PDE4 inhibitory effect of moexipril is functionally able to induce phosphorylation of the small heat shock protein, Hsp20, by cAMP dependent protein kinase A. Our data suggest that moexipril is a bona fide PDE4 inhibitor that may provide the starting point for development of novel PDE4 inhibitors with an improved therapeutic window.

Specificity of binding with matrix metalloproteinases

Matrix metalloproteinases (MMPs) regulate a wide range of biological functions; hence, they have invited great attention for the studies on their structures and functions, and since their overactivation leads to several diseases, the design and discovery of their potent inhibitors have become the need of the day. Since there have been so far discovered 28 different types of human MMPs, the specificity of binding of inhibitors with each different MMP needs special attention. The chapter presents the X-ray crystallographic and NMR studies on three-dimensional structures of a number of MMPs to reveal their catalytic site, subsites, specificity of binding with substrate and inhibitors, and catalytic mechanism. In addition to catalytic site, MMPs possess some subsites designated by unprimed and primed S, e.g., S1, S2, S3 and S1', S2', S3'. Among these, the S1' pocket varies the most among the different MMPs varying in both the amino acid makeup and depth of the pocket (shallow, intermediate, and deep pocket MMPs). This, along with the flexibility in the structures of MMPs, could be of great help in the design and the development of selective MMP inhibitors (MMPIs). The determination of affinity of inhibitors and the cleavage position of peptide substrates is mainly based on P1'-S1' interaction (P1', the group in inhibitor or substrate binding to S1' pocket of the enzyme), and it is the main determinant for the affinity of inhibitors and the cleavage position of peptide substrates.

Towards non-peptide ANG II AT1 receptor antagonists based on urocanic acid: rational design, synthesis and biological evaluation

A series of o-, m- and p-benzyl tetrazole derivatives 11a-c has been designed, synthesized and evaluated as potential Angiotensin II AT1 receptor antagonists, based on urocanic acid. Compound 11b with tetrazole moiety at the m-position showed moderate, however, higher activity compared to the o- and p-counterpart analogues. Molecular modelling techniques were performed in order to extract their putative bioactive conformations and explore their binding modes.

Convenient Synthesis of Valsartan via a Suzuki Reaction

An efficient synthesis of the angiotensin II inhibitor Valsartan (Diovan) is presented. The formation of the aryl–aryl bond represents the key step of its synthesis, which has been done by a Suzuki coupling of aryl boronate with 2-bromophenyl oxazoline with good yield and purity. This method overcomes many of the drawbacks associated with the previously reported syntheses.

A short and efficient synthesis of valsartan via a Negishi reaction

An efficient synthesis of the angiotensin-II inhibitor valsartan (Diovan®) is presented. Directed ortho-metalation of 5-phenyl-1-trityl-1H-tetrazole (6) and its Negishi coupling with aryl bromide 5 are the key steps of the synthesis. This method overcomes many of the drawbacks associated with previously reported syntheses.

Identification of Bacillus cereus in a chungkukjang that showed high anticancer effects against AGS human gastric adenocarcinoma cells

Anticancer effects of chungkukjang (a Korean short-term fermented soy paste) were studied in human gastric adenocarcinoma cells, and Bacillus strains from chungkukjang were isolated and identified. Before the experiments, six different chungkukjang products (K-, M-, Mn-, O-, Os-, and H-chungkukjangs) were purchased from a folk village in the Sunchang region, Jeonbuk, Republic of Korea. Based on sensory evaluation tests and general chemical and quality studies, K-, H-, and M-chungkukjangs were selected for the experiments. All chungkukjang samples exhibited in vitro anticancer activities; however, K-chungkukjang revealed the highest anticancer activity in the previous studies. In this experiment, K-chungkukjang again showed the highest anticancer effect in the AGS cells. At the concentration of 1 mg/mL, K-chungkukjang (87%) showed the highest growth inhibitory effect, followed by H-chungkukjang (85%) and MC-chungkukjang (69%) (P < .05). K-chungkukjang induced apoptosis as determined by 4,6-diamidino-2-phenylindole staining and exhibited increased bax and decreased bcl-2 mRNA expression. Three representative Bacillus strains from K-chungkukjang were isolated and identified by recA gene sequencing as Bacillus cereus, Bacillus amyloliquefaciens, and Bacillus subtilis. Identifying B. cereus in the chungkukjang means that when chungkukjang is prepared by the traditional method, B. cereus, which is a common cause of foodborne disease, can grow during the natural fermentation process. All B. cereus strains, of course, are not pathogens, but its presence causes food safety concerns. Therefore, using a starter culture is safer than the traditional natural fermentation for the industrialization of chungkukjang in Korea.

Metallotherapeutics: novel strategies in drug design

A new paradigm for drug activity is presented, which includes both recognition and subsequent irreversible inactivation of therapeutic targets. Application to both RNA and protein biomolecules has been demonstrated. In contrast to RNA targets that are subject to strand scission chemistry mediated by ribose H-atom abstraction, proteins appear to be inactivated either through oxidative damage to amino acid side chains around the enzyme active site, or by backbone hydrolysis.

Therapeutic application of peptides and proteins: parenteral forever?

Varied therapeutic peptides and proteins represent a rapidly growing part of marketed drugs and have an undisputed place alongside other established therapies. Nevertheless, such biodrugs have several drawbacks that hinder their therapeutic application. These are undesirable physicochemical properties, such as variable solubility, low bioavailability and limited stability. These issues can be overcome by addition of stabilizing agents and directed injectable administration, which can however result in low patient compliance. Hence, there is a drive in the biotechnology industry to produce needle-free and more user-friendly drugs, and this has led to the growth of nano-enabled drug delivery systems in the last decade. As discussed here, nanobiotechnology is becoming a commercially feasible and promising opportunity for oral, pulmonary and transdermal administration routes.

Discovery of potent thermolysin inhibitors using structure based virtual screening and binding assays

In the present work, 22 compounds of the U.S. NCI compound library (size 273K) were identified as putative thermolysin binders by structure based virtual screening with the ICM software (ICM-VLS). In vitro competitive binding assays confirmed that 12 were thermolysin binders. Thermolysin binding modes of the 12 compounds were studied by docking using ICM and Molegro Virtual Docker (MVD). The most potent inhibitor had an IC(50) value of 6.4 x 10(-8) mM (NSC250686, 1 beta-D-arabinofuranosyl-N(4)-lauroylcytosine). The structure of this compound is quite different from the other 11 compounds. Nine out of the 12 compounds contained a similar chemical skeleton (3-nitrobenzamide derivatives) and have IC(50) values ranging from 697.48 to 0.047 mM. The ICM-VLS score and the activity profiles (pIC(50) values) were compared and found to be somewhat linearly correlated (R(2) = 0.78). Kinetic studies showed that, except for NSC285166 (oxyquinoline), the compounds are competitive thermolysin inhibitors.

Pharmacokinetic study of a new angiotensin-AT1 antagonist by HPLC

Recently an innovative novel class angiotensin-AT1 antagonist has been developed by Rottapharm. In this study, we present a validated method for detecting CR 3834 in biological matrices using high-performance liquid chromatography (HPLC) with diode array detection. After oral administration (30mg/kg) to Wistar rats, the plasma and urine concentrations of CR 3834 and its potential metabolic products were determined. Moreover, the plasmatic time course in rats has been determined after intravenous (IV) administration of CR 3834 (5mg/kg). Biological samples (0.5ml of plasma and 1ml of urine) were purified using solid-phase extraction (SPE) of analytes and the internal standard Idebenone, 2,3-dimethoxy-5-methyl-6-(10-hydroxydecyl)-1-4-benzoquinone. A chromatographic separation was performed on an Adsorboshere C18 at 25 degrees C, with a pre-column of the same matrix; the eluent was made up of acetonitrile/acidified water with CF3COOH (pH 2.01) in ratio of 75:25 (v/v); the flow rate was 1.0ml/min and a 100microl loop. The lower limit of detection (LOD) was taken as 25ng/ml in plasma and 50ng/ml in urine samples. The lower limit of quantification (LOQ) was taken as 0.1 and 0.2microg/ml in plasma and urine samples, respectively. The procedures were validated according to international standards with a good reproducibility and linear response (r=0.9916 in plasma; r=0.9997 in urine). The coefficients of variation inter assay ranged between 2.579 and 4.951% in plasma, and between 0.813 and 2.460% in urine. Mean recovery for CR 3834 was 79% in plasma and 97% in urine samples. The experiments performed demonstrated that the method presented was suitable for determining this new angiotensin-AT1 antagonist in rat plasma and urine.

The antihypertensive effect of peptides: a novel alternative to drugs?

Many types of bioactive peptides that inhibit angiotensin I, angiotensin I converting enzyme (ACE) and Ang II type 1 receptor (AT1) in the cardiovascular system contribute to the prevention and treatment of hypertension. These inhibitory peptides are derived from many food proteins or artificial synthetic products. Further research examining the bioavailability of ACE inhibitory peptides will lead to the development of more effective ACE inhibitory peptides and foods. Our research also demonstrates that ACE inhibitory peptide LAP may lower blood pressure with no adverse effects.

Production of active angiotensin-I converting enzyme inhibitory peptides derived from bovine β-casein by recombinant DNA technologies

A wide range of anti-hypertensive peptides potentially able to lower blood pressure through the inhibition of vasoactive enzymes such as angiotensin-I converting enzyme (ACE) are known. Currently, ACE-inhibitory peptides can be produced from precursor proteins via enzymatic hydrolysis by proteolytic enzymes, or food fermentation with proteolytic starter cultures. These approaches are neither selective nor easy. In this study a novel procedure has been developed, based on recombinant DNA technologies, for the production of highly purified fractions of three polypeptides derived from bovine beta-casein active as ACE inhibitors in vitro. The procedure includes peptide expression in Escherichia coli cells as recombinant fusion proteins, purification by affinity chromatography, cleavage by proteinase from a selected strain of Lactobacillus helveticus and isolation of bioactive peptides (BPs). The reported concentration of inhibitor needed to reduce at 50% ACE activity (IC(50)) values for single BP calculated in inhibiting the ACE enzyme gave results in agreement with the same parameters available in literature for other milk-derived BPs. This procedure could be used to obtain quantities of pure peptides to determine their interactions with ACE, with the aim of designing peptides that have stronger inhibitory properties and exhibit new pharmacological profiles. Moreover, its scale up would be of commercial interest for the production of functional foods, e.g., milk beverages with blood pressure-lowering effects.