Design, synthesis, and neuroprotective effects of novel hybrid compounds containing edaravone analogue and 3-n-butylphthalide ring-opened derivatives

Recent developments in the design of functional derivatives of edaravone and exploration of their antioxidant activities

Edaravone, a pyrazalone derivative, is an antioxidant and free radical scavenger used to treat oxidative stress-related diseases. It is a proven drug to mitigate conditions prevailing to oxidative stress by inhibiting lipid peroxidation, reducing inflammation, and thereby preventing endothelial cell death. In recent years, considerable interest has been given by researchers in the derivatization of edaravone by adding varieties of substituents of versatile steric and functional properties to improve its antioxidant and pharmacological activity. This review accounts all the important methods developed for the derivatization of edaravone and the impacts of the structural modifications on the antioxidant activity of the motif.

Synthesis, Characterization and Assessment of Antioxidant and Melanogenic Inhibitory Properties of Edaravone Derivatives

A series of edaravone derivatives and the corresponding Cu(II) complexes were synthesized and characterized using spectroscopic and analytical techniques such as IR, UV, NMR and elemental analysis. Antioxidant activities of all compounds were examined using free radical scavenging methods such as hydrogen peroxide scavenging activity (HPSA), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2-2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonate) (ABTS) assays. All of the tested compounds exhibited good antioxidant activity. Further, the frontier orbital energy levels, as well as various chemical properties, were determined using the density functional theory (DFT) calculations. The MEP maps of all of the derivatives were plotted to identify the nucleophilic and electrophilic reactive sites. Further, binding energies of all of the organic compounds with the protein tyrosinase was investigated to determine their potential anti-melanogenic applications. The selected ligand, L6 was subjected to molecular dynamics simulation analysis to determine the stability of the ligand-protein complex. The MD simulation was performed (150 ns) to estimate the stability of the tyrosinase-L6 complex. Other key parameters, such as, RMSD, RMSF, Rg, hydrogen bonds, SASA and MMPBSA were also analyzed to understand the interaction of L6 with the tyrosinase protein.

Design, synthesis, and evaluation of n-butylphthalide and ligustrazine hybrids as potent neuroprotective agents for the treatment of ischemic stroke in vitro and in vivo

A series of novel NBP-TMP hybrids with neuroprotective effects were designed and synthesized for the treatment of ischemic stroke. The anti-cerebral ischemic activity of these compounds was screened by evaluating their neuroprotective effects on the oxygen glucose deprivation/reperfusion (OGD/R)-induced SH-SY5Y cell injury model in vitro. Nine compounds 7e, 7h-7i, 7k, 7m-7p and 7r showed better activities on cell viability and LDH levels compared to NBP at the concentration of 6.25 μM. Among them, compound 7m showed the best potency with a percentage of protection 90.2 % compared to NBP (69.2 %) and other compounds. Preliminary structure-activity analysis revealed that the introduction of iodine and N-methylpiperazine groups could significantly improve the neuroprotective effect. Further mechanism research showed that compound 7m could reduce the damage to neuronal mitochondria caused by OGD/R by reducing ROS and increasing mitochondrial membrane potential (MMP), and reduce the apoptosis and necrosis of neurons to play a neuroprotective role. In addition, 7m could regulate the levels of mitochondrial apoptosis pathway-related proteins Bcl-2, Bax, and caspase 3. Finally, in vivo experiments showed that the compound 7m significantly inhibited ischemia-reperfusion injury and cerebral blood flow in rats, and showed a more significant neuroprotective effect than the positive drug NBP at a dose concentration of 20 mg/kg. In conclusion, our results suggest that 7m may be used as a novel lead compound for the future development of anti-cerebral ischemic agents.

Synthesis of Novel 3-Butylphthalide Derivatives Containing Isopentenylphenol Moiety as Potential Antiplatelet Agents for the Treatment of Ischemic Stroke

In order to find novel antiplatelet drugs for the treatment of ischemic stroke, a series of 3-butylphthalide derivatives containing isopentenylphenol moiety were designed, synthesized and characterized with spectroscopic analyses. The in vitro antiplatelet activity results indicated that compound 3 better inhibited the arachidonic acid (AA) induced platelet aggregation than aspirin (ASP) and 3-butylphthalide (NBP). Additionally, compared with precursor NBP, compound 3 possessed outstanding antithrombotic activity in the animal experiment model, which could effectively alleviate the formation of tail thrombus and carotid artery thrombus in mice. More importantly, intraperitoneal administration of compound 3 can well protected the rats against ischemia/reperfusion-induced brain injury. Further pharmacokinetic (PK) assay indicated that compound 3 had good absorption characteristics and metabolic stability in vivo. Overall, the present research provides a new candidate compound for the treatment of ischemic stroke caused by platelet aggregation.

Sesquiterpenoids from Ixeris sonchifolia and their neuroprotective activities

The phytochemical investigation of the methanol extract of Ixeris sonchifolia led to the isolation and identification of nine analogs, including one new guaiane-type sesquiterpenoid, named ixerinoid A (1). The structure of 1 was determined by extensive analysis of the 1 D and 2 D nuclear magnetic resonance spectroscopic data, as well as quantum chemical calculations. Additionally, all the isolates were tested for their neuroprotective activity using the oxygen-glucose deprivation/reperfusion-induced SH-SY5Y cell injury model. Compounds 3, 5, 6, 8, and 9 displayed remarkable protective effects at concentrations of 1, 5, and 10 μM, respectively.

Synergic Effect of Phthalide Lactones and Fluconazole and Its New Analogues as a Factor Limiting the Use of Azole Drugs against Candidiasis

The resistance of Candida albicans and other pathogenic yeasts to azole antifungal drugs has increased rapidly in recent years and is a significant problem in clinical therapy. The current state of pharmacological knowledge precludes the withdrawal of azole drugs, as no other active substances have yet been developed that could effectively replace them. Therefore, one of the anti-yeast strategies may be therapies that can rely on the synergistic action of natural compounds and azoles, limiting the use of azole drugs against candidiasis. Synergy assays performed in vitro were used to assess drug interactions Fractional Inhibitory Concentration Index. The synergistic effect of fluconazole (1) and three synthetic lactones identical to those naturally occurring in celery plants-3-n-butylphthalide (2), 3-n-butylidenephthalide (3), 3-n-butyl-4,5,6,7-tetrahydrophthalide (4)-against Candida albicans ATCC 10231, C. albicans ATCC 2091, and C. guilliermondii KKP 3390 was compared with the performance of the individual compounds separately. MIC90 (the amount of fungistatic substance (in µg/mL) inhibiting yeast growth by 90%) was determined as 5.96-6.25 µg/mL for fluconazole (1) and 92-150 µg/mL for lactones 2-4. With the simultaneous administration of fluconazole (1) and one of the lactones 2-4, it was found that they act synergistically, and to achieve the same effect it is sufficient to use 0.58-6.73 µg/mL fluconazole (1) and 1.26-20.18 µg/mL of lactones 2-4. As fluconazole and phthalide lactones show synergy, 11 new fluconazole analogues with lower toxicity and lower inhibitory activity for CYP2C19, CYP1A2, and CYP2C9, were designed after in silico testing. The lipophilicity was also analyzed. A three-carbon alcohol with two rings was preserved. In all compounds 5-15, the 1,2,4-triazole rings were replaced with 1,2,3-triazole or tetrazole rings. The hydroxyl group was free or esterified with phenylacetic acid or thiophene-2-carboxylic acid chlorides or with adipic acid. In structures 11 and 12 the hydroxyl group was replaced with the fragment -CH2Cl or = CH2. Additionally, the difluorophenyl ring was replaced with unsubstituted phenyl. The structures of the obtained compounds were determined by 1H NMR, and 13C NMR spectroscopy. Molecular masses were established by GC-MS or elemental analysis. The MIC50 and MIC90 of all compounds 1-15 were determined against Candida albicans ATCC 10231, C. albicans ATCC 2091, AM 38/20, C. guilliermondii KKP 3390, and C. zeylanoides KKP 3528. The MIC50 values for the newly prepared compounds ranged from 38.45 to 260.81 µg/mL. The 90% inhibitory dose was at least twice as high. Large differences in the effect of fluconazole analogues 5-15 on individual strains were observed. A synergistic effect on three strains-Candida albicans ATCC 10231, C. albicans ATCC 2091, C. guilliermondii KKP 339-was observed. Fractional inhibitory concentrations FIC50 and FIC90 were tested for the most active lactone, 3-n-butylphthalide, and seven fluconazole analogues. The strongest synergistic effect was observed for the strain C. albicans ATCC 10231, FIC 0.04-0.48. The growth inhibitory amount of azole is from 25 to 55 µg/mL and from 3.13 to 25.3 µg/mL for 3-n-butylphthalide. Based on biological research, the influence of the structure on the fungistatic activity and the synergistic effect were determined.

Protective effect of 3-n-butylphthalide against intrastriatal injection of malonic acid-induced neurotoxicity and biochemical alteration in rats

Mitochondrial abnormalities and a defective expression of neurotrophic factors contribute to neuronal damage in Huntington's disease (HD). HD patients showed a reduction in transforming growth factor-β1 (TGF-β1) levels in the peripheral blood and in cortical neurons. 3-n-butylphthalide (NBP) is first isolated from the seeds of celery, treats ischemic stroke in China. NBP could attenuate cognitive and motor impairments in the experimental models of Parkinson's disease and Alzheimer's disease, reduce mitochondrial oxidative stress and increase the expression of TGF-β1 in rats with focal cerebral ischemia. To our knowledge, the effect of NBP on Huntington's disease has not been reported. We proposed the hypothesis that whether NBP could protect mitochondria and regulate TGF-β1 and its downstream signaling in a HD animal model, further prevents motor dysfunction. Malonic acid is a reversible inhibitor of mitochondrial enzyme complex-II, induces energy crisis and free radical generation. In this study, we used intrastriatal injections of malonic acid in rats to mimic mitochondrial abnormalities and the other HD like symptoms. We found that treatment with NBP significantly attenuated malonic acid-induced motor and cognitive dysfunction in locomotor behaviour test, rotarod test, novel object recognition test and morris water maze test, prevented neurotoxicity and mitochondrial damage, activated TGF-β1/Akt/Wnt/β-Catenin pathway in striatum, but didn't regulate mitochondrial fusion and fission. The above effect was partly reversed by a PI3K/Akt inhibitor. Our data support NBP as a potential candidate for the treatment of HD.

Rapid and improved oral absorption of N-butylphthalide by sodium cholate-appended liposomes for efficient ischemic stroke therapy

As a multi-target drug to treat ischemic stroke, N-butylphthalide (NBP) is extremely water-insoluble and exhibits limited oral bioavailability, impeding its wide oral application. Effective treatment of ischemic stroke by NBP requires timely and efficient drug exposure, necessitating the development of new oral formulations. Herein, liposomes containing biosurfactant sodium cholate (CA-liposomes) were systemically investigated as an oral NBP delivery platform because of its high biocompatibility and great potential for clinical applications. The optimized liposomes have a uniform hydrodynamic size of 104.30 ± 1.60 nm and excellent encapsulation efficiency (93.91 ± 1.10%). Intriguingly, NBP-loaded CA-liposomes produced rapid drug release and the cumulative release was up to 88.09 ± 4.04% during 12 h while that for NBP group was only 6.79 ± 0.99%. Caco-2 cell monolayer assay demonstrated the superior cell uptake and transport efficiency of NBP-loaded CA-liposomes than free NBP, which was mediated by passive diffusion via transcellular and paracellular routes. After oral administration to rats, NBP-loaded CA-liposomes exhibited rapid and almost complete drug absorption, with a t_max of 0.70 ± 0.14 h and an absolute bioavailability of 92.65% while NBP suspension demonstrated relatively low bioavailability (21.7%). Meanwhile, NBP-loaded CA-liposomes produced 18.30-fold drug concentration in the brain at 5 min compared with NBP suspension, and the brain bioavailability increased by 2.48-fold. As expected, NBP-loaded CA-liposomes demonstrated significant therapeutic efficacy in a middle cerebral artery occlusion rat model. Our study provides new insights for engineering oral formulations of NBP with fast and sufficient drug exposure against ischemic stroke in the clinic.