Synthesis and DFT Calculations of Novel Vanillin-Chalcones and Their 3-Aryl-5-(4-(2-(dimethylamino)-ethoxy)-3-methoxyphenyl)-4,5-dihydro-1H-pyrazole-1-carbaldehyde Derivatives as Antifungal Agents

Development of natural perfume as potential fungicide candidates: construction and biological evaluation of vanillin analogs bearing the 1,3,4-oxadiazole/1,3-thiazolidin-4-one fragments

Two series of vanillin derivatives containing 1,3,4-oxadiazole and 1,3-thiazolidin-4-one scaffolds were prepared and evaluated for their antifungal activity. The results revealed that compounds 6j (29.73 μg/ml) and 7a (38.15 μg/ml) displayed excellent inhibitory activity against the spore of Fusarium solani. The inhibitory activity of compound 7d (10.53 μg/ml) against the spore of Alternaria solani was more than 42-fold that of vanillin. Compound 7a (37.54 μg/ml) showed better antifungal activity against the spore of B. cinerea than positive controls. The cytotoxicity assay confirmed that compounds 6k, 7a, and 7d showed good selectivity and less toxicity to normal mammalian cells.

Synthesis of vanillin derivatives with 1,2,3-triazole fragments and evaluation of their fungicide and fungistatic activities

Vanillin is the main component of natural vanilla extract and is responsible for its flavoring properties. Besides its well-known applications as an additive in food and cosmetics, it has also been reported that vanillin can inhibit fungi of clinical interest, such as Candida spp., Cryptococcus spp., Aspergillus spp., as well as dermatophytes. Thus, the present work approaches the synthesis of a series of vanillin derivatives with 1,2,3-triazole fragments and the evaluation of their antifungal activities against Candida albicans, Candida glabrata, Candida parapsilosis, Candida tropicalis, Cryptococcus neoformans, Cryptococcus gattii, Trichophyton rubrum, and Trichophyton interdigitale strains. Twenty-two vanillin derivatives were obtained, with yields in the range of 60%-91%, from copper(I)-catalyzed alkyne-azide cycloaddition (CuAAC) click reaction between two terminal alkynes prepared from vanillin and different benzyl azides. In general, the evaluated compounds showed moderate activity against the microorganisms tested, with minimum inhibitory concentration (MIC) values ranging from 32 to >512 µg mL^-1 . Except for compound 3b against the C. gattii R265 strain, all vanillin derivatives showed fungicidal activity for the yeasts tested. The predicted physicochemical and ADMET (absorption, distribution, metabolism, excretion, and toxicity) properties for the compounds indicated favorable profiles for drug development. In addition, a four-dimensional structure-activity relationship (4D-SAR) analysis was carried out and provided useful insights concerning the structures of the compounds and their biological profile. Finally, molecular docking calculations showed that all compounds bind favorably at the lanosterol 14α-demethylase enzyme active site with binding energies ranging from -9.1 to -12.2 kcal/mol.

Synthesis, Antibacterial, and Antioxidant Activities of Thiazolyl-Pyrazoline Schiff Base Hybrids: A Combined Experimental and Computational Study

Thiazole-pyrazoline Schiff base hybrids have a broad range of pharmacological potential with an ability to control the activity of numerous metabolic enzymes. In this work, a greener and more efficient approach has been developed to synthesize a novel series of thiazole-pyrazoline Schiff base hybrids using ZnO nanoparticle-assisted protocol in good to excellent yields (78.3–96.9%) and examined their antibacterial activity against Gram-positive and Gram-negative bacteria, as well as their antioxidant activity. Compound 24 (IZD = 18.67 ± 0.58) displayed better activity against P. aeruginosa compared with amoxicillin (IZD = 14.33 ± 2.52) at 250 μg/mL, whereas compounds 22 and 24 (IZD = 13.33 ± 0.58 mm and 17.00 ± 1.00 mm, respectively) showed better activity against E. coli compared with amoxicillin (IZD = 14.67 ± 0.58 mm) at 500 μg/mL. The remaining compounds showed moderate to weak activity against the tested bacterial strains. Compound 21 displayed significant inhibition of DPPH (IC50 = 4.63 μg/mL) compared with ascorbic acid (IC50 = 3.21 μg/mL). Compound 21 displayed 80.01 ± 0.07% inhibition of peroxide formation, suggesting its potential in preventing the formation of lipid peroxides. The results of the ADMET study showed that all synthesized compounds obeyed Lipinski's rule of five. In silico pharmacokinetic study demonstrated that compound 24 had superior intestinal absorption compared with amoxicillin. In silico molecular docking analysis revealed a binding affinity of −9.9 Kcal/mol for compound 24 against PqsA compared with amoxicillin (−7.3 Kcal/mol), whereas compounds 22 and 24 displayed higher binding affinity (−8.5 and −7.9 Kcal/mol, respectively) with DNA gyrase B compared with amoxicillin (-7.1 Kcal/mol), in good agreement with in vitro antibacterial activity against P. aeruginosa and E. coli. In silico toxicity study showed that all synthesized compounds had LD50 (mg/kg) values ranging from 800 to 1,000 putting them in ProTox-II class 4. The in vitro antibacterial activity and molecular docking analysis showed that compound 24 is a promising antibacterial therapeutic agent against P. aeruginosa and E. coli and compound 22 is a promising antibacterial agent against E. coli, whereas compound 21 is found to be a potential natural antioxidant agent. Moreover, the green synthesis approach using ZnO nanoparticle as catalyst was found to be a very efficient method to synthesize biologically active thiazole-pyrazoline Schiff base hybrids compared with the conventional method.

Novel Galactosyl Moiety-Conjugated Furylchalcones Synthesized Facilely Display Significant Regulatory Effect on Plant Growth

The expansion of weed infestation has increased the demand on new herbicides. A series of novel galactosyl moiety-conjugated furylchalcones was facilely synthesized in which the furyl group (A ring) was combined with the substituted benzene group (B ring), and a galactosyl moiety was introduced. All these galactosyl furylchalcones were predicted to be phloem-mobile. Most of the galactosyl furylchalcones significantly promoted early seedling growth of sorghum and barnyardgrass under dark conditions, but all of them revealed considerable anti-growth ability on illuminated pot plants; especially, 1-(3'-(4″-O-β-d-galactopyranosyl)furyl)-3-(4″-nitrophenyl)-2-en-1-one (B₁₁) had a better herbicidal activity against rapeseed and Chinese amaranth than haloxyfop-R-methyl. The median efficient concentrations (EC₅₀) of compound B₁₁ against cucumber and wheat were 9.55 and 26.97 mg/L, respectively, also showing a stronger suppressing capacity than 2,4-D. Molecular docking with phosphoenolpyruvate carboxylase protein showed a stable binding conformation in which the galactosyl group interacted with LYS363 and GLU369, the furan ring and carbonyl bound with ARG184, and the crosslink of the nitro group with GLU240 formed a salt bridge. The results demonstrate that galactosyl furylchalcones possess the great potential as new herbicides for weed management, and further evaluations on more weeds are required for practical application.

The Antibacterial Synthetic Flavonoid BrCl-Flav Exhibits Important Anti-Candida Activity by Damaging Cell Membrane Integrity

Infections caused by Candida are very difficult to treat due to increasing antifungal resistance. Recent studies showed that patients with Candida infections resistant to fluconazole have very few treatment options. Therefore, finding new efficient antifungal agents is a matter of medical high priority. The aim of this study was to explore the antifungal potential of BrCl-flav-a representative of a new class of synthetic flavonoids with bromine as halogen substituent at the benzopyran core against four Candida clinical strains. Determination of minimum inhibitory concentration and minimum fungicidal concentration along with the time kill assay indicated a strong antifungal effect of BrCl-flav against C. albicans, C. parapsilosis, C. krusei and C. glabrata. The investigation of anti-Candida mechanism of action using fluorescence microscopy and scanning electron microscopy revealed that Br-Cl flav could inhibit fungal growth by impairing the membrane integrity, the resulting structural damages leading to cell lysis. BrCl-flav also showed important anti-virulence properties against Candida spp., inhibiting biofilm formation and yeast to hyphal transition. A strong synergistic antifungal effect against C. albicans strain was observed when BrCl-flav was used in combination with fluconazole. BrCl-flav has a good potential to develop new effective antifungal agents in the context of Candida spp. multidrug resistance phenomenon.

2-Hydroxychalcone as a Potent Compound and Photosensitizer Against Dermatophyte Biofilms

Dermatophytes, fungi that cause dermatophytosis, can invade keratinized tissues in humans and animals. The biofilm-forming ability of these fungi was described recently, and it may be correlated with the long treatment period and common recurrences of this mycosis. In this study, we evaluated the anti-dermatophytic and anti-biofilm activity of 2-hydroxychalcone (2-chalcone) in the dark and photodynamic therapy (PDT)-mediated and to determine its mechanism of action. Trichophyton rubrum and Trichophyton mentagrophytes strains were used in the study. The antifungal susceptibility test of planktonic cells, early-stage biofilms, and mature biofilms were performed using colorimetric methods. Topographies were visualized by scanning electron microscopy (SEM). Human skin keratinocyte (HaCat) monolayers were also used in the cytotoxicity assays. The mechanisms of action of 2-chalcone in the dark and under photoexcitation were investigated using confocal microscopy and the quantification of ergosterol, reactive oxygen species (ROS), and death induction by apoptosis/necrosis. All strains, in the planktonic form, were inhibited after treatment with 2-chalcone (minimum inhibitory concentration (MIC) = 7.8-15.6 mg/L), terbinafine (TRB) (MIC = 0.008–0.03 mg/L), and fluconazole (FLZ) (1–512 mg/L). Early-stage biofilm and mature biofilms were inhibited by 2-chalcone at concentrations of 15.6 mg/L and 31.2 mg/L in all tested strains. However, mature biofilms were resistant to all the antifungal drugs tested. When planktonic cells and biofilms (early-stage and mature) were treated with 2-chalcone-mediated PDT, the inhibitory concentrations were reduced by four times (2–7.8 mg/L). SEM images of biofilms treated with 2-chalcone showed cell wall collapse, resulting from a probable extravasation of cytoplasmic content. The toxicity of 2-chalcone in HaCat cells showed higher IC₅₀ values in the dark than under photoexcitation. Further, 2-chalcone targets ergosterol in the cell and promotes the generation of ROS, resulting in cell death by apoptosis and necrosis. Overall, 2-chalcone-mediated PDT is a promising and safe drug candidate against dermatophytes, particularly in anti-biofilm treatment.

Synthesis and biological evaluation of novel pyrazoline derivatives containing indole skeleton as anti-cancer agents targeting topoisomerase II

In order to develop potent anticaner agents, a novel series of 3-(1H-indol-3-yl)-2,3,3a,4-tetrahydrothiochromeno[4,3-c]pyrazole derivatives were synthesized. Structures of all compounds were confirmed. MTT assay has been employed to study antiproliferative activity of these compounds with four human cancer cell lines (MGC-803, Hela, MCF-7 and Bel-7404) and a normal cell line L929. Most of these compounds showed potential anticancer activity and low cytotoxicity on normal cell in vitro. 7d and 7f showed the best anticancer activity, whose IC₅₀ value is 15.43 μM and 20.54 μM towards MGC-803, respectively. Most of them exhibited topoisomerase II selective inhibitory. Cleavage reaction assay and DNA unwinding assay showed that 7f was a nonintercalative Topo II catalytic inhibitor, which was consistent with the docking results. Laser scanning confocal microscopy system tracks the location of representative compounds 7d and 7f which can be abundantly entering the nucleus. In particular, the most potent compounds 7d and 7f were shown to be able to induce G2/M cell cycle arrest and apoptosis in MGC-803 cells.

Theoretical study of solvent effects on the hyperpolarizabilities of two chalcone derivatives

The use of organic as nonlinear optical materials has been intensively explored in the recent years due to the ease of manipulation of the molecular structure and the synthetic flexibility regarding the change of substituent groups. In the present work, the linear and nonlinear properties of two chalcones derivatives (E)-1-(4-methylphenyl)-3-phenylprop-2-en-1-one (4MP3P) and (E)-1-(4-Nitrophenyl)-3-phenylprop-2-en-1-one (4NP3P), that differ by the substituent position at the phenyl ring, were studied in the presence of protic and aprotic solvents simulated by the Polarizable Continuum Model (PCM) at DFT/B3LYP/6-311+G(d) level. The static and dynamic (1064 nm) molecular parameters as the dipole moment, linear polarizability, first and second hyperpolarizabilities were studied as function of the solvent dielectric constant value. The geometrical behavior as the chemical bond angles, torsion angles, and partial charges distribution of the compounds were studied, including calculations of gap energies in various solvents. The obtained results revealed that the substituent change of CH3 (4MP3P) to NO2 (4NP3P) benefits the nonlinear optical properties of the compounds in the presence of the solvent media, the absolute values of the parallel first hyperpolarizability were the ones that present the greater variation.

Design, Synthesis, and Biological Activities of Novel 1,3,5-Trimethylpyrazole-Containing Malonamide Derivatives

New 1,3,5-trimethylpyrazole-containing malonamide derivatives based on pyflubumide were designed, synthesized, and characterized using ¹H-NMR, ¹³C-NMR, and high-resolution mass spectra (HRMS). The results of preliminary bioassays showed that the target compounds possessed good activities against Tetranychus cinnabarinus, Plutella xylostella, and Aphis craccivora. Most of the target compounds exhibited moderate to good acaricidal activity against Tetranychus cinnabarinus at a concentration of 400 µg/mL, and some showed moderate activity at a concentration of 200 µg/mL; in particular, compounds 8m and 8p exhibited 70.0% mortality. In addition, some of the target compounds exhibited good insecticidal activities against Plutella xylostella at a concentration of 200 µg/mL, especially compounds 8i and 8o, which achieved 100.0% mortality at a concentration of 100 µg/mL. Interestingly, some of the target compounds exhibited potent anti-aphid activity against Aphis craccivora at a concentration of 200 µg/mL; furthermore, compounds 8p and 8q demonstrated 100.0% anti-aphid activity at a concentration of 50 µg/mL. The preliminary analyses of the structure–activity relationships (SAR) indicated that the acaricidal and insecticidal activities varied significantly depending on the type of substituent and substitution pattern, which provides guidance for the further investigation of such structural modifications.