Pyrrole-2,5-dione analogs as a promising antioxidant agents: microwave-assisted synthesis, bio-evaluation, SAR analysis and DFT studies/interpretation

Novel Pyrrole Derivatives as Multi-Target Agents for the Treatment of Alzheimer's Disease: Microwave-Assisted Synthesis, In Silico Studies and Biological Evaluation

Considering the complex pathogenesis of Alzheimer's disease (AD), the multi-target ligand strategy is expected to provide superior effects for the treatment of the neurological disease compared to the classic single target strategy. Thus, one novel pyrrole-based hydrazide (vh0) and four corresponding hydrazide-hydrazones (vh1-4) were synthesized by applying highly efficient MW-assisted synthetic protocols. The synthetic pathway provided excellent yields and reduced reaction times under microwave conditions compared to conventional heating. The biological assays indicated that most of the novel pyrroles are selective MAO-B inhibitors with IC50 in the nanomolar range (665 nM) and moderate AChE inhibitors. The best dual-acting MAO-B/AChE inhibitor (IC50hMAOB-0.665 μM; IC50eeAChE-4.145 μM) was the unsubstituted pyrrole-based hydrazide (vh0). Importantly, none of the novel molecules displayed hMAOA-blocking capacities. The radical-scavenging properties of the compounds were examined using DPPH and ABTS in vitro tests. Notably, the hydrazide vh0 demonstrated the best antioxidant activities. In addition, in silico simulations using molecular docking and MM/GBSA, targeting the AChE (PDB ID: 4EY6) and MAO-B (PDB: 2V5Z), were utilized to obtain active conformations and to optimize the most prominent dual inhibitor (vh0). The ADME and in vitro PAMPA studies demonstrated that vh0 could cross the blood-brain barrier, and it poses good lead-like properties. Moreover, the optimized molecular structures and the frontier molecular orbitals were examined via DFT studies at 6-311G basis set in the ground state.

Silver Complexes of Miconazole and Metronidazole: Potential Candidates for Melanoma Treatment

Melanoma, arguably the deadliest form of skin cancer, is responsible for the majority of skin-cancer-related fatalities. Innovative strategies concentrate on new therapies that avoid the undesirable effects of pharmacological or medical treatment. This article discusses the chemical structures of [(MTZ)2AgNO3], [(MTZ)2Ag]2SO4, [Ag(MCZ)2NO3], [Ag(MCZ)2BF4], [Ag(MCZ)2SbF6] and [Ag(MCZ)2ClO4] (MTZ-metronidazole; MCZ-miconazole) silver(I) compounds and the possible relationship between the molecules and their cytostatic activity against melanoma cells. Molecular Hirshfeld surface analysis and computational methods were used to examine the possible association between the structure and anticancer activity of the silver(I) complexes and compare the cytotoxicity of the silver(I) complexes of metronidazole and miconazole with that of silver(I) nitrate, cisplatin, metronidazole and miconazole complexes against A375 and BJ cells. Additionally, these preliminary biological studies found the greatest IC50 values against the A375 line were demonstrated by [Ag(MCZ)2NO3] and [(MTZ)2AgNO3]. The compound [(MTZ)2AgNO3] was three-fold more toxic to the A375 cells than the reference (cisplatin) and 15 times more cytotoxic against the A375 cells than the normal BJ cells. Complexes of metronidazole with Ag(I) are considered biocompatible at a concentration below 50 µmol/L.

Phytochemistry, pharmacology, and medical uses of Oldenlandia (family Rubaceae): a review

The Oldenlandia genus comprises approximately 240 species of plants, yet only a limited number of these have been investigated for their chemical composition and medicinal properties. These species contain a wide range of compounds such as iridoids, anthraquinones, triterpenes, phytosterols, flavonoids, anthocyanidins, vitamins, essential oils, phenolic acids, and coumarins. These diverse phytochemical profiles underscore the pharmacological potential of Oldenlandia plants for various medical purposes. Among other chemical constituents, ursolic acid stands out as the most important active compound in Oldenlandia, owing to its proven anticancer, anti-inflammatory, antimicrobial, and hepatoprotective properties. The evaluation of Oldenlandia's pharmacological prospects indicates that the holistic utilization of the entire plant yields the most significant effects. Oldenlandia diffusa showcases anticancer and anti-inflammatory capabilities attributed to its varying constituents. Across a broad spectrum of pharmacological capacities, anticancer research predominates, constituting the majority of medical uses. Oldenlandia diffusa emerges as a standout for its remarkable anticancer effects against diverse malignancies. Antioxidant applications follow, with O. corymbosa demonstrating potent antioxidant properties alongside O. umbellata and O. diffusa. Subsequent priority lies in anti-inflammatory studies, wherein O. diffusa exhibits noteworthy efficacy, trailed by O. corymbosa also takes the lead in antimicrobial activity, with O. umbellata as a strong contender. Additional investigation is essential to ascertain the relative significance of these species in various pharmacological applications. This comprehensive assessment underscores the multifaceted potential of Oldenlandia as a versatile herbal resource, offering diverse pharmacological capacities. The call for sustained exploration and research remains essential to unlock the full extent of Oldenlandia's medicinal benefits.

Clauson-Kaas pyrrole synthesis using diverse catalysts: a transition from conventional to greener approach

Pyrrole is an important aromatic heterocyclic scaffold found in many natural products and predominantly used in pharmaceuticals. Continuous efforts are being made to design and synthesize various pyrrole derivatives using different synthetic procedures. Among them, the Clauson-Kaas reaction is a very old and well-known method for synthesizing a large number of N-substituted pyrroles. In recent years, due to global warming and environmental concern, research laboratories and pharmaceutical industries around the world are searching for more environmentally friendly reaction conditions for synthesizing compounds. As a result, this review describes the use of various eco-friendly greener protocols to synthesize N-substituted pyrroles. This synthesis involves the reaction of various aliphatic/aromatic primary amines, and sulfonyl primary amines with 2,5-dimethoxytetrahydrofuran in the presence of numerous acid catalysts and transition metal catalysts. The goal of this review is to summarize the synthesis of various N-substituted pyrrole derivatives using a modified Clauson-Kaas reaction under diverse conventional and greener reaction conditions.

Activation of xanthine oxidase by 1,4-naphthoquinones: A novel potential research topic for diet management and risk assessment

Oral intake of 1,4-naphthoquinones could be a potential risk factor for hyperuricemia and gout via activation of xanthine oxidase (XO). Herein, 1,4-naphthoquinones derived from food and food-borne pollutants were selected to investigate the structure and activity relationship (SAR) and the relative mechanism for activating XO in liver S9 fractions from humans (HLS9) and rats (RLS9). The SAR analysis showed that introduction of electron-donating substituents on the benzene ring or electron-withdrawing substituents on the quinone ring improved the XO-activating effect of 1,4-naphthoquinones. Different activation potential and kinetics behaviors were observed for activating XO by 1,4-naphthoquinones in HLS9/RLS9. Molecular docking simulation and density functional theory calculations showed a good correlation between -LogEC₅₀ and docking free energy or HOMO-LUMO energy gap. The risk of exposure to the 1,4-naphthoquinones was evaluated and discussed. Our findings are helpful to guide diet management in clinic and avoid adverse events attributable to exposure to food-derived 1,4-naphthoquinones.

Screening of potent α-glucosidase inhibitory and antioxidant polyphenols in Prunella vulgaris L. by bioreaction-HPLC-quadrupole-time-of-flight-MS/MS and in silico analysis

Prunella vulgaris L. is a well-known traditional Chinese medicine for blood glucose homeostasis and antioxidant potential. Ethyl acetate fraction of P. vulgaris L. demonstrated higher phenolic content (85.53 ± 6.74 mg gallic acid equivalents per gram dry weight), α-glucosidase inhibitory (IC₅₀ , 69.13 ± 2.86 μg/mL), and antioxidant (IC₅₀ , 8.68 ± 1.01 μg/mL) activities. However, the bioactive polyphenols responsible for the beneficial properties remain unclear. Here, bioreaction-HPLC-quadrupole-time-of-flight-MS/MS method was developed for rapid, accurate, and efficient screening and identification of polyphenols with α-glucosidase inhibitory and antioxidant activities from P. vulgaris L. Bioactive polyphenols can specifically bind with α-glucosidase or react with 1,1-diphenyl-2-picryl-hydrazyl radical, which was easily discriminated from nonactive compounds. Subsequently, twenty bioactive polyphenols (sixteen phenyl propionic acid derivatives and four flavonoids) were screened and identified. Furthermore, molecular docking analysis revealed that screened twenty polyphenols bind with the active sites of α-glucosidase through hydrogen bonding and π-π stacking. Density functional theory calculations demonstrated their electron transport ability and chemical reactivity. The in silico analysis confirmed the screened results. In summary, this study provided a valuable strategy for rapid discovering bioactive compounds from complex natural products, and offered scientific evidence for further development and application of P. vulgaris L. This article is protected by copyright. All rights reserved.

Synthesis Strategies and Medicinal Value of Pyrrole and its Fused Heterocyclic Compounds

For several decades, interest in pyrrole and pyrrolopyrimidine derivatives increases owing to their biological importance, such as anti-tumor, anti-microbial, anti-inflammatory, anti-diabetic, anti-histaminic, anti-malarial, anti-Parkinson, antioxidant and anti-viral, specially recently against COVID-19. These tremendous biological features motivated scientists to discover more pyrrole and fused pyrrole derivatives, owing to the great importance of the pyrrole nucleus as a pharmacophore in many drugs, and motivated us to present this article, highlighting on the different synthetic pathways of pyrrole and its fused compounds specially pyrrolopyrimidine, as well as their medicinal value from 2017 till 2021.

Structure-antioxidant activity relationships of dendrocandin analogues determined using density functional theory

Quantum-chemical calculations based on the density functional theory (DFT) at the B3LYP/6-311 + + G(2d,2p)//B3LYP/6-31G(d,p) level were employed to study the relationship between the antioxidant properties and chemical structures of six dendrocandin (DDCD) analogues in the gas phase and two solvents (methanol and water). The hydrogen atom transfer (HAT), electron-transfer-proton-transfer (ET-PT), and sequential proton-loss-electron-transfer (SPLET) mechanisms are explored. The highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), reactivity indices (η, μ, ω, ω +, and ω - ), and molecular electrostatic potentials (MEPs) were also evaluated. The results suggest that the D ring plays an important role in mediating the antioxidant activity of DDCDs. For all the studied compounds, indicating that HAT was identified as the most favorable mechanism, whereas the SPLET mechanism was the most thermodynamically favorable pathway in polar solvents. The results of our study should aid in the development of new or modified antioxidant compounds.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11224-022-01895-2.

(E)-1-(3-Benzoyl-4-phenyl-1H-pyrrol-1-yl)-3-phenylprop-2-en-1-one

Over the last decade, there has been an increasing effort to fight inflammatory conditions establishing new multitarget approaches. Chronic inflammation is implicated in many multifactorial diseases, constituting a great economic burden and a chronic health problem. In an attempt to develop new potent multifunctional anti-inflammatory agents, a cinnamic-pyrrole hybrid (6) was synthesized and screened for its antioxidant and anti-Lipoxygenase potential. The new compound, in comparison with its pyrrole precursor (4), showed improved biological activities. In silico calculations were performed to predict its drug-likeness. The examined derivative is considered orally bioavailable according to Lipinski’s rule of five. Compound 6 could be used as a lead for the synthesis of more effective hybrids.

Improving the antioxidant activity of natural antioxidant honokiol by introducing the amino group

Exploring and synthesizing the compounds with stronger antioxidant activity have always been the goal of researchers. Herein, the substitution effects of the amino (NH₂-) group with the excellent electron-donating ability in different positions on the antioxidant activity of Honokiol (Hon) were systematically explored by using the quantum chemistry calculation based on the density functional theory method. The three possible antioxidant mechanisms of Hon and its four NH₂-substituted derivatives (Hon1-Hon4), containing the hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET), were explored in depth considering the gas and solvent phases. In addition, the frontier molecular orbital energies, natural bond orbital (NBO) charge population, and global descriptive parameters were used to study their antioxidant activity. The results indicate that compared with the original molecule Hon, the NH₂ substituents would have the stronger antioxidant activity. Moreover, the radical scavenging process of Hon and its derivatives has a disposition to the HAT and SPLET mechanisms in the gas and solvent phases, respectively. Meaningfully, owing to the lowest bond dissociation enthalpy and proton affinity values, Hon4 would show the most prominent antioxidant activity by comparison with the other compounds. In conclusion, this work will provide the purposeful reference for designing and synthesizing the antioxidants with more outstanding performance.