Natural urease inhibitors from Aloe vera resin and Lycium shawii and their structural-activity relationship and molecular docking study

Chlorogenic acid, caffeic acid and luteolin from dandelion as urease inhibitors: insights into the molecular interactions and inhibition mechanism

BACKGROUND

Dandelion contains hundreds of active compounds capable of inhibiting urease activity, but the individual compounds have not yet been fully identified, and their effects and underlying mechanisms are not clear. The present study aimed to screen the urease inhibition active compounds of dandelion by urease inhibitory activity evaluation HPLC-tandem mass spectrometry analysis, their mechanism of urease inhibition by polyphenols was explored using enzyme kinetic studies via Lineweaver-Burk plots. Other investigations included isothermal titration calorimetry and surface plasmon resonance sensing, fluorescence quenching experiments, and single ligand molecular docking and two-ligand simultaneous docking techniques.

RESULTS

The results indicated that the ethyl acetate fraction of dandelion flower exhibited the greatest inhibition (lowest IC50 0.184 ± 0.007 mg mL-1). Chlorogenic acid, caffeic acid and luteolin could be effective urease inhibitors that acted in a non-competitive inhibition manner. Individually, chlorogenic acid could not only fast bind to urease, but also dissociate rapidly, whereas luteolin might interact with urease with the weakest affinity. The chlorogenic acid-caffeic acid combination exhibited an additive effect in urease inhibition. However, the chlorogenic acid-luteolin and caffeic acid-luteolin combinations exhibited antagonistic effects, with the caffeic acid-luteolin combination showing greater antagonism.

CONCLUSION

The present study reveals that chlorogenic acid, caffeic acid and luteolin are major bioactive compounds for urease inhibition, indicating the molecular mechanisms. The antagonistic effects were observed between luteolin and chlorogenic acid/caffeic acid, and the interactions of the catalytic site and flap may account for the antagonistic effects. © 2024 Society of Chemical Industry.

Stimulatory effects of Lycium shawii on human melanocyte proliferation, migration, and melanogenesis: In vitro and in silico studies

There is no first-line treatment for vitiligo, a skin disease characterized by a lack of melanin produced by the melanocytes, resulting in an urgent demand for new therapeutic drugs capable of stimulating melanocyte functions, including melanogenesis. In this study, traditional medicinal plant extracts were tested for cultured human melanocyte proliferation, migration, and melanogenesis using MTT, scratch wound-healing assays, transmission electron microscopy, immunofluorescence staining, and Western blot technology. Of the methanolic extracts, Lycium shawii L. (L. shawii) extract increased melanocyte proliferation at low concentrations and modulated melanocyte migration. At the lowest tested concentration (i.e., 7.8 μg/mL), the L. shawii methanolic extract promoted melanosome formation, maturation, and enhanced melanin production, which was associated with the upregulation of microphthalmia-associated transcription factor (MITF), tyrosinase, tyrosinase-related protein (TRP)-1 and TRP-2 melanogenesis-related proteins, and melanogenesis-related proteins. After the chemical analysis and L. shawii extract-derived metabolite identification, the in silico studies revealed the molecular interactions between Metabolite 5, identified as apigenin (4,5,6-trihydroxyflavone), and the copper active site of tyrosinase, predicting enhanced tyrosinase activity and subsequent melanin formation. In conclusion, L. shawii methanolic extract stimulates melanocyte functions, including melanin production, and its derivative Metabolite 5 enhances tyrosinase activity, suggesting further investigation of the L. shawii extract-derived Metabolite 5 as a potential natural drug for vitiligo treatment.

Enzymes Inhibition and Antioxidant Potential of Medicinal Plants Growing in Oman

The recent study was designed to explore Dodonaea viscosa, Juniperus excelsa, Helianthemum lippii, and Euryops pinifolius using methanolic (MeOH) extract. Their subfractions were examined against urease, carbonic anhydrase II (CA-II), α-glucosidase enzymes, and free radicals scavenging significance based on local practices via standard methods. Significance potential against the urease enzyme was presented by ethyl acetate fraction (EtOAc) of D. viscosa with (IC₅₀ = 125 ± 1.75 μg/mL), whereas the H. lippii (IC₅₀ = 146 ± 1.39 μg/mL) in the EtOAc was found efficient to scavenge the free radicals. Besides, that appreciable capacity was observed by the J. excelsa, D. viscosa, J. excelsa, and E. pinifolius as compared to the standard acarbose (IC₅₀ = 377.24 ± 1.14 μg/mL). Maximum significance was noticed in methanolic (MeOH) extract of J. excelsa and presented carbonic anhydrase CA-II (IC₅₀ = 5.1 ± 0.20 μg/mL) inhibition as compared to the standard (acetazolamide). We are reporting, for the first time, the CA-II inhibition of all the selected medicinal plants and α-glucosidase, urease, and antioxidant activities of the E. pinifolius. Thus, further screening is needed to isolate the promising bioactive ingredients which act as an alternative remedy to scavenge the free radicals, antiulcer, and act as a potential source to develop new antidiabetic drugs for controlling postprandial blood sugar as well as carbonic anhydrase inhibitors.

In-silico predicting as a tool to develop plant-based biomedicines and nanoparticles: Lycium shawii metabolites

INTRODUCTION AND PURPOSE

In silico approach helps develop biomedicines and is useful for exploring the pharmacology of potential therapeutics using computer-simulated models. In vitro assays were used to determine the anti-microbial and cytotoxic efficacies of silver nanoparticles (AgNPs) synthesized with the shrub Lycium shawii.

METHODS

In silico predicting was performed to assess the L. shawii metabolites identified using QTOF-LCMS for their pharmacological properties. L. shawii mediated AgNPs were synthesized and characterized (FTIR, TEM, SEM, DLS and EDX). The anti-bacterial efficacies of L. shawii extract, AgNPs, and penicillin-conjugated AgNPs (pen-AgNPs) were determined. The cytotoxicity of the AgNPs was measured against colorectal cancer cell line (HCT116), normal breast epithelium (MCF 10 A), and breast cancer cell line (MDA MB 231).

RESULTS AND DISCUSSION

Five molecules (costunolide, catechin, emodin, lyciumaside, and aloe emodin 11-O-rhamnoside) were detected in the L. shawii extract. AgNPs (69 nm) were spherical with crystallographic structure. All three agents prepared showed inhibitory activity against the tested bacteria, the most efficacious being pen-AgNPs. High cytotoxicity of AgNPs (IC₅₀ 62 μg/ml) was observed against HCT116, IC₅₀ was 78 μg/ml for MCF 10 A, and 250 μg/ml for MDA MB 231, of which cells showed apoptotic features under TEM examination. The in silico approach indicated that the carbonic anhydrase IX enzyme was the target molecule mediating anti-cancer and anti-bacterial activities and that emodin was the metabolite in action.

CONCLUSIONS

Combining in vitro studies and in silico molecular target prediction helps find novel therapeutic agents. Among L. shawii metabolites, emodin is suggested for further studies as an agent for drug development against pathogenic bacteria and cancer.

Recent Efforts in the Discovery of Urease Inhibitor Identifications

Urease is an attractive drug target for designing anti-infective agents against pathogens such as Helicobacter pylori, Proteus mirabilis, and Ureaplasma urealyticum. In the past century, hundreds of medicinal chemists focused their efforts on explorations of urease inhibitors. Despite the FDA's approval of acetohydroxamic acid as a urease inhibitor for the treatment of struvite nephrolithiasis and the widespread use of N-(n-butyl)thiophosphoric triamide as a soil urease inhibitor as nitrogen fertilizer synergists in agriculture, urease inhibitors with high potency and safety are urgently needed. Exploration of novel urease inhibitors has therefore become a hot research topic recently. Herein, inhibitors identified worldwide from 2016 to 2021 have been reviewed. They structurally belong to more than 20 classes of compounds such as urea/thioure analogues, hydroxamic acids, sulfonamides, metal complexes, and triazoles. Some inhibitors showed excellent potency with IC50 values lower than 10 nM, having 10000-fold higher potency than the positive control thiourea.

Rotenoids and Other Specialized Metabolites from the Roots of Mirabilis multiflora: Opioid and Cannabinoid Receptor Radioligand Binding Affinities

Mirabilis multiflora is an acclaimed hallucinogen consumed traditionally by the Hopi Indians to induce diagnostic visions. Its root extract afforded a new (3) and four known (2, 5, 6, and 7) 12a-hydroxyrotenoids, a known rotenoid (4), and two known secondary metabolites (1 and 8). The structures of the compounds were elucidated based on spectroscopic and spectrometric data analysis. Electronic circular dichroism data were used to define the (6aS,12aR) absolute configuration of the 12a-hydroxyrotenoids. Compounds 2-7 were screened for their radioligand binding affinities toward the opioid (δ, κ, and μ) and cannabinoid (CB1 and CB2) receptor subtypes. The 6-methoxy-substituted rotenoids 3, 4, and 7 showed the highest receptor binding affinity with moderate selectivity toward the δ-opioid receptor subtype, with negligible binding affinities for CB1 and CB2. Their binding affinities toward the δ-opioid receptor were 64.5% (4), 58.7% (7), and 55.3% (3) at 10 μM, respectively.

Identification of Potential SARS-CoV-2 Main Protease and Spike Protein Inhibitors from the Genus Aloe: An In Silico Study for Drug Development

Severe acute respiratory syndrome coronavirus (SARS-CoV-2) disease is a global rapidly spreading virus showing very high rates of complications and mortality. Till now, there is no effective specific treatment for the disease. Aloe is a rich source of isolated phytoconstituents that have an enormous range of biological activities. Since there are no available experimental techniques to examine these compounds for antiviral activity against SARS-CoV-2, we employed an in silico approach involving molecular docking, dynamics simulation, and binding free energy calculation using SARS-CoV-2 essential proteins as main protease and spike protein to identify lead compounds from Aloe that may help in novel drug discovery. Results retrieved from docking and molecular dynamics simulation suggested a number of promising inhibitors from Aloe. Root mean square deviation (RMSD) and root mean square fluctuation (RMSF) calculations indicated that compounds 132, 134, and 159 were the best scoring compounds against main protease, while compounds 115, 120, and 131 were the best scoring ones against spike glycoprotein. Compounds 120 and 131 were able to achieve significant stability and binding free energies during molecular dynamics simulation. In addition, the highest scoring compounds were investigated for their pharmacokinetic properties and drug-likeness. The Aloe compounds are promising active phytoconstituents for drug development for SARS-CoV-2.