Synthesis and Antifungal Activities of Novel Griseofulvin Derivatives as Potential Anti-Phytopathogenic Fungi Agents.

The extensive and repeated application of chemical fungicides results in the rapid development of fungicide resistance. Novel antifungal pesticides are urgently required. Natural products have been considered precious sources of pesticides. It is necessary to discover antifungal pesticides by using natural products. Herein, 42 various griseofulvin derivatives were synthesized. Their antifungal activities were evaluated in vitro. Most of them showed good antifungal activity, especially 3d exhibited a very broad antifungal spectrum and the most significant activities against 7 phytopathogenic fungi. In vivo activity results suggested that 3d protected apples and tomatoes from serious infection by phytopathogenic fungi. These proved that 3d had the potential to be a natural product-derived antiphytopathogenic fungi agent. Furthermore, docking analysis suggested that tubulin might be one of the action sites of 3d. It is reasonable to believe that griseofulvin derivatives are worth further development for the discovery of new pesticides.

Synthetic peptides against Trichophyton mentagrophytes and T. rubrum: Mechanisms of action and efficiency compared to griseofulvin and itraconazole.

AIMS: According to the WHO, 20-25% of people worldwide are affected by skin infections caused by dermatophytes, such as those of the Trichophyton genus. Additionally, several dermatophytes have developed resistance to drugs such as griseofulvin and itraconazole. This study tested 2S albumins-derived antimicrobial peptides (AMPs) as alternative antidermatophytic molecules. MAIN METHODS: Membrane pore formation assays, tests to detect overproduction of ROS, scanning electron microscopy (SEM) and fluorescence microscopy (FM) were carried out to provide insight into the mechanisms of antidermatophytic action. KEY FINDINGS: All AMPs (at 50 µg mL-1) tested reduced the mycelial growth of T. mentagrophytes and T. rubrum by up to 95%. In contrast, using a concentration 20-fold higher, griseofulvin only inhibited T. mentagrophytes by 35%, while itraconazole was not active against both dermatophytes. Scanning electron and fluorescence microscopies revealed that the six AMPs caused severe damage to hyphal morphology by inducing cell wall rupture, hyphal content leakage, and death. Peptides also induced membrane pore formation and oxidative stress by overproduction of ROS. Based on the stronger activity of peptides than the commercial drugs and the mechanism of action, all six peptides have the potential to be either employed as models to develop new antidermatophytic drugs or as adjuvants to existing ones. SIGNIFICANCE: The synthetic peptides are more efficient than conventional drug to treat infection caused by dermatophytes being potential molecules to develop new drugs.

Direct incorporation of nano graphene oxide (nGO) into hydrophobic drug crystals for enhanced aqueous dissolution.

This paper reports the development of a successful anti-solvent method that incorporates colloidal nano scale graphene oxide (nGO) directly into hydrophobic drug crystals. The nGO dispersed in solution acted as nucleating sites for crystallization and were embedded into the drug crystals without altering its structure or physical properties such as melting point. Several composites of drugs Sulfamethoxazole and Griseofulvin were synthesized with nGO concentration ranging between 0.2 and 1.0 %. The presence of nGO dramatically enhanced the dissolution rate. The time needed to reach a 50 % release (T50) reduced from 42-14 min with the integration of 0.8 % nGO in SMZ, while in GF the reduction was from 44-27 min with 0.5 % nGO. Increased release rates are attributed to the presence of the hydrophilic nGO which hydrogen bond more so with the aqueous mediums. Therefore, the incorporation of nGO into poorly soluble drugs is an effective approach towards drug delivery and bioavailability improvement and opens a new approach to high performance drug delivery.

Griseofulvin Derivatives: Synthesis, Molecular Docking and Biological Evaluation.

BACKGROUND: Griseofulvin - a mold metabolite produced by Penisilium griseofulvum is known as an antifungal drug. OBJECTIVE: Thus, the goal of this paper is the design and synthesis of new griseofulvin derivatives and evaluation of their antifungal activity. METHODS: Forty-two new compounds were synthesized using classical methods of organic synthesis and evaluated for their antimicrobial activity by microdilution method. RESULTS: All forty-two new compounds exhibited very good activity against eight tested micromycetes with MIC ranging from 0.0075-0.055 mg/ml and MFC from 0.02-024 mg/ml. All compounds exhibited better activity than reference drugs ketoconazole (7-42 times) and bifonazole (3-16 fold). The most promising was compound 15. The most sensitive fungal was found to be T. viride, while the most resistant, as was expected, was A. fumigatus. It should be mentioned that most of compounds exhibited better activity than griseofulvin. The molecular docking studies revealed that the most active compound have the same hydrophobic and H-bonding interactions with Thr276 residue observed for griseofulvin forming 3 hydrogen bonds while griseofulvin only one. In general, the molecular docking results coincide with experimental. CONCLUSION: Forty-two giseofulvin derivatives were designed, synthesized and evaluated for antimicrobial activity. These derivatives revealed good antifungal activity, better than reference drugs ketoconazole, bifonazole, and griseofulvin as well.

A comparative assessment of nanocomposites vs. amorphous solid dispersions prepared via nanoextrusion for drug dissolution enhancement.

Nanoextrusion was used to produce extrudates of griseofulvin, a poorly water-soluble drug, with the objective of examining the impact of drug particle size and polymeric matrix type-size of the extrudates on drug dissolution enhancement. Hydroxypropyl cellulose (HPC) and Soluplus® were used to stabilize wet-milled drug suspensions and form matrices of the extrudates. The wet-milled suspensions along with additional polymer (HPC/Soluplus®) were fed to a co-rotating twin-screw extruder, which dried the suspensions and formed various extrudates. The extrudates were dry-milled and sieved into samples with two different sizes. A wet-milled suspension was also spray-dried in comparison to nanoextrusion. Due to differences in polymer-drug miscibility, two forms of the drug were prepared: extrudates with nano/micro-crystalline drug particles dispersed in the HPC matrix as a secondary phase (nano/microcomposites) and extrudates with amorphous drug molecularly dispersed within the Soluplus® matrix (amorphous solid dispersion, ASD). Under non-supersaturating conditions in the dissolution medium, drug nanocrystals in the HPC-based nanocomposites dissolved faster than the amorphous drug in Soluplus®-based ASD. While smaller extrudate particles led to faster drug release for the ASD, such matrix size effect was weaker for the nanocomposites. These findings suggest that nanocrystal-based formulations could outperform ASDs for fast dissolution of low-dose drugs.

Synthesis and formulation studies of griseofulvin analogues with improved solubility and metabolic stability.

Griseofulvin (1) is an important antifungal agent that has recently received attention due to its antiproliferative activity in mammalian cancer cells. Comprehensive SAR studies have led to the identification of 2'-benzyloxy griseofulvin 2, a more potent analogue with low micromolar anticancer potency in vitro. Analogue 2 was also shown to retard tumor growth through inhibition of centrosomal clustering in murine xenograft models of colon cancer and multiple myeloma. However, similar to griseofulvin, compound 2 exhibited poor metabolic stability and aqueous solubility. In order to improve the poor pharmacokinetic properties, 11 griseofulvin analogues were synthesized and evaluated for biological activity and physiological stabilities including SGF, plasma, and metabolic stability. Finally, the most promising compounds were investigated in respect to thermodynamic solubility and formulation studies. The 2'-benzylamine analogue 10 proved to be the most promising compound with low µM in vitro anticancer potency, a 200-fold increase in PBS solubility over compound 2, and with improved metabolic stability. Furthermore, this analogue proved compatible with formulations suitable for both oral and intravenous administration. Finally, 2'-benzylamine analogue 10 was confirmed to induce G2/M cell cycle arrest in vitro.

Strategies for improving the solubility and metabolic stability of griseofulvin analogues.

We report two types of modifications to the natural product griseofulvin as strategies to improve solubility and metabolic stability: the conversion of aryl methyl ethers into aryl difluoromethyl ethers at metabolic hotspots and the conversion of the C-ring ketone into polar oximes. The syntheses of the analogues are described together with their solubility, metabolic half-life in vitro and antiproliferative effect in two cancer cell lines. We conclude that on balance, the formation of polar oximes is the most promising strategy for improving the properties of the analogues.

Synthesis and activities towards resistant cancer cells of sulfone and sulfoxide griseofulvin derivatives.

Griseofulvin, an antifungal drug, has been shown in recent years to have anti-proliferative activities. We report here the synthesis of new analogs of griseofulvin, substituted in 2' by a sulfonyl group or in 3' by a sulfinyl or sulfonyl group. These compounds exhibit good anti-proliferative activities against SCC114 cells, an oral squamous carcinoma cell line showing pronounced centrosome amplification, and unexpected cytotoxic activities on HCC1937 cells, a triple negative breast cancer cell line resistant to microtubule inhibitors.

Asymmetric Michael-aldol tandem reaction of 2-substituted benzofuran-3-ones and enones: a facile synthesis of griseofulvin analogues.

A highly enantioselective Michael-aldol tandem reaction with respect to prochiral 2-substituted benzofuran-3-ones and enones by a facile primary amine catalyst was investigated. The approach provides rapid access to the desired pharmaceutically active griseofulvin analogues.

Synthesis of 4'-thiosemicarbazonegriseofulvin and its effects on the control of enzymatic browning and postharvest disease of fruits.

4'-Thiosemicarbazonegriseofulvin, a new thiosemicarbazide derivative of griseofulvin, was synthesized and evaluated for its potential in the control of enzymatic browning and postharvest disease of fruits. Browning on fruits is mainly due to the enzymatic oxidation of phenolic compounds catalyzed by tyrosinase. 4'-Thiosemicarbazonegriseofulvin could effectively inhibit the activity of tyrosinase, and its 50% inhibitory concentration (IC(50)) against tyrosinase was determined to be 37.8 µM. It was a reversible and noncompetitive inhibitor of tyrosinase, and its inhibition constant (K(I)) was determined to be 38.42 µM. The antifungal activity of 4'-thiosemicarbazonegriseofulvin was studied against four fungi (Fusarium oxysporum, Fusarium moniliforme, Fusarium solani, and Colletotrichum truncatum) that often cause postharvest diseases of fruits. The results showed that 4'-thiosemicarbazonegriseofulvin could also strongly inhibit the mycelial growth of the four target fungi; the 50% lethal concentration (LC(50)) values were 5.4, 7.0, 15.3, and 1.5 mM, respectively.

Transformations of griseofulvin in strong acidic conditions--crystal structures of 2'-demethylgriseofulvin and dimerized griseofulvin.

The structure of griseofulvic acid, C16H15ClO6, at 100 K has orthorhombic (P2(1)2(1)2) symmetry. It is of interest with respect to biological activity. The structure displays intermolecular O-H...O, C-H...O hydrogen bonding as well as week C-H...pi and pi...pi interactions. In strong acidic conditions the griseofulvin undergoes dimerization. The structure of dimerized griseofulvin, C34H32C12O12 x C2H6O x H2O, at 100 K has monoclinic (P2(1)) symmetry. The molecule crystallized as a solvate with one ethanol and one water molecule. The dimeric molecules form intermolecular O-H...O hydrogen bonds to solvents molecules only but they interact via week C-H...O, C-H...pi, C-Cl...pi and pi...pi interactions with other dimerized molecules.

Synthesis and immobilization of micro-scale drug particles in presence of ß-cyclodextrins.

The anti-solvent synthesis in presence of cyclodextrins (CDs) of the drug Griseofulvin (GF) is presented. This was followed by immobilization into cellulosic polymer films suitable for drug delivery. The results show that 72% of the GF precipitated in presence of CD, while the rest led to the formation of a water soluble GF/CD complex. The cyclodextrins were effective in inhibiting particle growth and stabilizing the drug suspensions. Among the CDs tested here, hydroxypropyl-ß-cyclodextrin (HPBCD) was found to be most effective in reducing the particle size. The release profiles from the cyclodextrin stabilized GF particles showed improvement in release rate, which indicated effective drug/cyclodextrin interactions.

Disparate SAR data of griseofulvin analogues for the dermatophytes Trichophyton mentagrophytes, T. rubrum, and MDA-MB-231 cancer cells.

Griseofulvin and 53 analogues of this compound have been tested against the pathogenic dermatophytes Trichophyton rubrum and Trichophyton mentagrophytes as well as against the breast cancer cell line MDA-MB-231. The modifications to griseofulvin include the 4, 5, 6, 2', 3', and 4' positions. The SAR of the griseofulvin analogues toward the two fungi followed the same trend with the majority being less active than griseofulvin and none had more than twice the potency of the parent compound. A comparison of the antifungal and the anticancer SAR revealed distinct differences, as the majority of analogues showed increased activity against the cancer cell line MDA-MB-231, highlighted by 2'-benzyloxy-2'-demethoxy-griseofulvin, which showed low activity against both fungi but was among the most potent compounds against MDA-MB-231 cancer cells. Tubulin has been proposed as the target of griseofulvin in both fungal and mammalian cells, but the differences revealed by this SAR study strongly suggest that the mode-of-action of the compound class toward fungi and mammalian cancer cells is different.

Preparation and evaluation of dermal delivery system of griseofulvin containing vitamin E-TPGS as penetration enhancer.

Griseofulvin, an antifungal agent, is a BCS class II drug slowly, erratically, and incompletely absorbed from the gastrointestinal tract in humans. The clinical failure of the conventional oral therapy of griseofulvin is most likely attributed to its poor solubility and appreciable inter- and intra-subject variation in bioavailability from different commercial products. Moreover, the conventional oral therapy is associated with numerous adverse effects and interactions with other drugs. The purpose of the study was to formulate a topical application of griseofulvin which would deliver the drug locally in a therapeutically effective concentration. Griseofulvin was solubilized in ethanol, D-α-tocopheryl polyethylene glycol 1000 succinate (TPGS), and combinations of ethanol with varying amounts of TPGS; then, it was incorporated in the Carbopol (980 NF) base. The formulations were characterized and evaluated ex vivo using Laca mice skin, microbiologically against Microsporum gypseum and Microsporum canis and clinically in a small group of patients. The current study suggested that TPGS and ethanol synergistically enhanced the drug permeation and drug retention in the skin. The selected formulation F VII was found to be effective against M. gypseum and M. canis, non-sensitizing, histopathologically safe, stable at 4°C, 25°C, and 40°C with respect to percent drug content, permeation characteristics, pH, transparency, feel, viscosity, and clinically effective in a small group of subjects. The proposed topical formulation of griseofulvin may be an effective and convenient alternative to the currently available oral therapy for the treatment of superficial fungal infections.

Synthesis and structure-activity relationship of griseofulvin analogues as inhibitors of centrosomal clustering in cancer cells.

Griseofulvin was identified as an inhibitor of centrosomal clustering in a recently developed assay. Centrosomal clustering is an important cellular event that enables bipolar mitosis for cancer cell lines harboring supernumerary centrosomes. We report herein the synthesis and SAR of 34 griseofulvin analogues as inhibitors of centrosomal clustering. The variations in the griseofulvin structure cover five positions, namely the 4, 5, 2', 3', and 4' positions. Modification of the 4 and 5 positions affords inactive molecules. The enol ether must be at the 2' position, and the 4' position needs to be sp(2) hybridized. The most active analogues were the 2'-benzyloxy and 2'-(4-methylbenzyloxy) analogues as well as the oxime of the former with a 25-fold increase of activity compared to griseofulvin. Comparison of the results obtained in this work with prior reported growth inhibition data for dermatophytic fungi showed both similarities and differences.

Preparation and characterization of poly-epsilon-caprolactone nanoparticles containing griseofulvin.

Griseofulvin is an antifungal agent with poor solubility and low bioavailability. The aim of this work was to prepare poly-epsilon-caprolactone nanospheres and nanocapsules of griseofulvin by nanoprecipitation and to characterize them. Nanoparticles of griseofulvin were obtained with high encapsulation efficiency. The particle size was about 250-326 nm for nanospheres and 390-400 nm for nanocapsules. The dissolution rate of griseofulvin nanoparticles was higher than that of micronized griseofulvin therefore recourse to nanoencapsulation of griseofulvin should enhance its bioavailability and possibly its efficiency for the treatment of dermatomycosis.

Preparation and dissolution characteristics of griseofulvin solid dispersions with saccharides.

To improve the solubility of poorly water-soluble drugs, we studied physical characteristics of griseofulvin (GF) solid dispersions with saccharides as the dispersion carrier using a roll mixing method. In all carriers tested, roll mixtures of GF and saccharides gradually became amorphous, and the solubility of GF increased. The solubility of GF was higher in the mixtures with higher molecular weight carriers such as corn starch and processed starch. The dissolution of GF was markedly improved by the GF-Britishgum roll mixture. The initial dissolution rate of these mixtures was 170-fold higher than GF alone. The surface tension of carrier aqueous solutions was low in the processed starch with branched sugar chains. The initial dissolution rate of GF in physical mixtures was correlated with the surface tension of carrier aqueous solutions. The stability of the amorphous state of GF at a high humidity was maintained in the mixtures with carriers with a high molecular weight. These results indicated that the solubility of GF was markedly improved in the roll mixtures. It was suggested that the saccharides with a high molecular weight are useful carriers for solid dispersions.

Syntheses and antifungal activity of dl-griseofulvin and its congeners. II.

Griseofulvin derivatives, dl-6'-demethyl-6'-ethylgriseofulvin (dl-5) and dl-6'demethyl-6'phenylgriseofulvin (dl-6) were prepared by application of a synthetic method developed by us. Antifungal activity of these derivatives decreased in the order of dl-griseofulvin (dl-1) >> dl-6(inactive). The reaction of these derivatives with ethanethiol gave two types of compounds, 2'-(ethylthio)griseofulvin (15) and 4'-(ethylthio)isogriseofulvin (16). The relationship between the ratios of isolated yield of 15 and 16 and antifungal the activity of griseofulvin derivatives is discussed.

Synthesis and biological activities of griseofulvin analogs.

In order to elucidate the structure-activity relationship of griseofulvin (1), (+/-)-6-demethyl analog (3), 2-demethoxy-6-demethyldihydro analog (4), (+/-)-dechloro-6-ethyl analog (5), (+/-)-dechloro-6-epi-ethyl analog (6), (+/-)6-ethyl analog (7) and (+/-)-6-epi-ethyl analog (8) were synthesized by a Diels-Alder cycloaddition of alkylidene ketones (16, 17 18, 19 and 20) with modified 1,3-butadienes (21 or 22). Their biological activities were examined against fungi.