Influence of phloretin and 6-ketocholestanol on the skin permeation of sodium-fluorescein

Synthesis, Molecular Docking, biological potentials, and Structure-Activity Relationship of new quinazoline & quinazoline-4-one derivatives

CONTEXT

Quinazolines are a common class of nitrogen-containing heterocyclic scaffolds exhibiting a broad spectrum of pharmacological activities.

OBJECTIVE

In the present study, quinazoline and quinazolin-4-one derivatives were prepared, characterized to evaluate their biological which may pave the way for possible therapeutic applications.

MATERIALS & METHODS

A new derivative of quinazoline and quinazolin-4-one derivatives was prepared and tested for antiulcerogenic, anti-inflammatory and hepatoprotective activity.

RESULTS

The synthesized compounds were characterized by elemental analysis and spectral data. Also, the median lethal doses (LD_50s) of compounds 1-3 in rats were 1125, 835 and 1785 mg/kg b.w., respectively. IC₅₀ values of compounds (1-3) as measured by ABTS⁺ radical method was 0.8, 0.92 and 0.08 mg/mL, respectively. Antiulcerogenic activities at dose 1/20 LD₅₀ in albino rats were 47.94, 24.60 and 56.45%, respectively. Anti-inflammatory effect at dose 1/20 LD₅₀ of compounds (1-3) induced edema model after 120 min. The prepared compounds possess hepato gastric mucosa protective activity against ibuprofen-induced ulceration and LPS-induced liver toxicity, respectively in rats via normalization of oxidative stress biomarkers and inflammatory mediators were inhibited in peritoneal macrophage cells at concentration of 100 µg/L. Molecular docking suggested that the most active compounds 1 and 2 can be positioned within the active sites of COX-2 at Arg121 & Tyr356 similar to ibuprofen (Arg-120, Glu-524, and Tyr-355). The compound 3-COX-2 complex generated by docking revealed intricate interactions with a COX-2 channel.

CONCLUSION

These findings suggest that compounds 1-3 exhibited good antioxidant, antiulcer, anti-inflammatory activity and safe on liver enzymes in rats.

Dermatological applications of the flavonoid phloretin

Botanical molecules are known to have the ability to counteract ultraviolet radiation-induced skin damage. The interest in the development of natural compound-based products for the prevention of solar ultraviolet radiation-induced skin photoaging, melasma, and photocarcinogenesis has been increasing. Recently, the flavonoid phloretin has attracted the attention of researchers in the dermatological field for application in cosmetics and therapeutics. In addition to its antioxidant activity, phloretin has been shown to have properties such as anti-aging and depigmenting effects. In this study, we review the dermatological treatments with phloretin for conditions such as melasma, photoaging, acne, and melanoma. Phloretin has been shown to inhibit elastase and matrix metalloproteinase-1 activity, to reduce cellular tyrosinase activity and melanin content, and induce apoptosis in B16 mouse melanoma 4A5 cells. An in vivo study showed that phloretin, applied topically to the dorsal skin of mice, suppressed the 12-O-tetradecanoylphorbol 13-acetate-induced expression of COX-2, a critical molecular target of many chemopreventive, as well as anti-inflammatory agents. Phloretin can penetrate the skin; nevertheless, its penetration profile in different skin layers has not yet been evaluated. Despite its health benefits, phloretin application has been limited because of its photoinstability and poor aqueous solubility, among other limitations. Therefore, we reviewed the recent advances in pharmaceutical applications such as the use of nanotechnology, in order to improve the cutaneous availability of phloretin. In this review, we also focus on the oral application, product development challenges, and recent progress and future research directions on phloretin.

Electrogenetic cellular insulin release for real-time glycemic control in type 1 diabetic mice

Sophisticated devices for remote-controlled medical interventions require an electrogenetic interface that uses digital electronic input to directly program cellular behavior. We present a cofactor-free bioelectronic interface that directly links wireless-powered electrical stimulation of human cells to either synthetic promoter–driven transgene expression or rapid secretion of constitutively expressed protein therapeutics from vesicular stores. Electrogenetic control was achieved by coupling ectopic expression of the L-type voltage-gated channel CaV1.2 and the inwardly rectifying potassium channel Kir2.1 to the desired output through endogenous calcium signaling. Focusing on type 1 diabetes, we engineered electrosensitive human β cells (Electroβ cells). Wireless electrical stimulation of Electroβ cells inside a custom-built bioelectronic device provided real-time control of vesicular insulin release; insulin levels peaked within 10 minutes. When subcutaneously implanted, this electrotriggered vesicular release system restored normoglycemia in type 1 diabetic mice.

Improved transdermal delivery of cetirizine hydrochloride using polymeric microneedles

PURPOSE

The aim of this study was to design and characterize microneedle patch formulation containing cetirizine hydrochloride.

METHODS

Chitosan was co-formulated with cetirizine hydrochloride. Transdermal patches were prepared by casting this solution to microneedle molds. Control patches were formulated by casting this solution to a plain cuvet of same area as mold but lacking microneedles. An array of methods namely; differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) were employed for the characterization of the films and the microneedles accordingly whereas in vitro permeation studies were conducted across rat skin. Light microscopy was performed to assess any histological changes upon microneedles application onto the rat skin.

RESULTS

The patches had a reproducible thickness (0.86 ± 0.06 mm) and folding endurance. Both the blank and drug loaded patches had 100 microneedles each of 300 micrometre length. In addition, the microneedle patches were ascribed with a two-fold increase in drug permeation across rat skin in the presence of microneedles as compared to the control formulations. Histological examination confirms a minimal invasion of the skin conferred by the microneedles.

CONCLUSION

The microneedle patches serve as an alternate route of drug administration in patients with nausea and swelling difficulties. Graphical abstract Microneedle patch manifest a two-fold increase in the skin permeation of Cetirizine Hydrochloride as compared to the control that is drug loaded patch without microneedles.

Antidiabetic and antiparasitic potentials: Inhibition effects of some natural antioxidant compounds on α-glycosidase, α-amylase and human glutathione S-transferase enzymes

The glutathione S-transferase (GST) was purified from fresh blood erythrocytes using affinity column chromatography. Also, α-amylase from porcine pancreas and α-glycosidase from Saccharomyces cerevisiae were used as target enzymes. In this study, these compounds were tested on α-amylase, α-glycosidase, and GST enzymes and demonstrated effective inhibitor compounds with K_i values in the range of 8.34-40.78 μM against GST, and 120.53-892.36 nM against α-glycosidase. Additionally, the phenolic molecules were tested for the inhibition of α-amylase enzyme which determined effective inhibition profile with IC₅₀ values in the range of 175.01-626.58 nM. Indeed, these molecules can be elective inhibitors of GST, α-glycosidase and α-amylase enzymes as antidiabetic and antiparasitic agents.

LdtR is a master regulator of gene expression in Liberibacter asiaticus

Huanglongbing or citrus greening disease is causing devastation to the citrus industry. Liberibacter asiaticus, an obligate intracellular pathogen of citrus, is one the causative agents of the disease. Most of the knowledge about this bacterium has been deduced from the in silico exploration of its genomic sequence. L. asiaticus differentially expresses genes during its transmission from the psyllid vector, Diaphorina citri, to the plant. However, the regulatory mechanisms for the adaptation of the bacterium into either hosts remain unknown. Here we show that LdtR, a MarR family transcriptional regulator, activates or represses transcription genome-wide. We performed a double approach to identify the components of the LdtR regulon: a transcriptome analysis in both the related bacterium Liberibacter crescens and citrus-infected leaves, strengthened with an in silico prediction of LdtR regulatory sites. Our results demonstrated that LdtR controls the expression of nearly 180 genes in L. asiaticus, distributed in processes such as cell motility, cell wall biogenesis, energy production, and transcription. These results provide new evidence about the regulatory network of L. asiaticus, where the differential expression of genes from these functional categories could be of great importance during the adaptation of the bacterium to either hosts.

Iontophoretic drug delivery for the treatment of scars

Topical treatment of hypertrophic scars is challenging because of poor penetrability of drugs into the scar tissue. The objective of the study was to investigate the effectiveness of iontophoresis to deliver medicaments across the scar epidermis. Initially, biophysical studies were performed to investigate the differences between scar and normal skin epidermis obtained from cadaver. In case of scar skin epidermis, the transepidermal water loss was not significantly different from the normal skin epidermis, whereas the electrical resistivity was significantly higher. The passive permeation flux of sodium fluorescein was approximately one-third of that across the normal skin epidermis. Scanning electron microscopy studies revealed that the two membranes were alike except that the scar skin epidermis lacked follicles. Cathodal iontophoresis enhanced the delivery of sodium fluorescein across the scar skin epidermis by approximately 46 folds [51.90 ± 8.82 ng/(cm(2) h)]. However, the transport of sodium fluorescein across the scar skin epidermis was about an order of magnitude less than the normal skin epidermis. Overall, the studies suggest that iontophoresis could be utilized to overcome the barrier resistance of scar skin epidermis and treat the scar regionally.

Elongate microparticles for enhanced drug delivery to ex vivo and in vivo pig skin

The delivery of therapeutics and cosmaceuticals into and/or through the skin is hindered by epidermal barriers. To overcome the skin's barriers we have developed a novel cutaneous delivery method using high aspect ratio elongate microparticles (EMPs). Using ex vivo and in vivo pig skin we assess the penetration and delivery characteristics of the elongate microparticles. With reflectance confocal microscopy we observed that the elongate microparticles successfully penetrated the epidermis and upper dermis. Delivery was then assessed using two different length populations of EMPs, comparing their delivery profile to topical alone using sodium fluorescein and confocal microscopy. We observed a relatively uniform and continuous delivery profile in the EMP treated area within the upper layers of the skin--up to seven times greater than topical alone. Finally, we delivered two therapeutically relevant compounds (Vitamins A and B3), showing enhanced delivery using the EMPs. To our knowledge this is the first report using high aspect ratio elongate microparticles in this manner for enhanced topical delivery to the skin.

Fluorescein derivatives in intravital fluorescence imaging

Intravital fluorescence microscopy enables the direct imaging of fluorophores in vivo and advanced techniques such as fluorescence lifetime imaging (FLIM) enable the simultaneous detection of multiple fluorophores. Consequently, it is now possible to record distribution and metabolism of a chemical in vivo and to optimise the delivery of fluorophores in vivo. Recent clinical applications with fluorescein and other intravital fluorescent stains have occurred in neurosurgery, dermatology [including photodynamic therapy (PDT)] and endomicroscopy. Potential uses have been identified in periodontal disease, skin graft and cancer surgery. Animal studies have demonstrated that diseased tissue can be specifically stained with fluorophore conjugates. This review focuses on the fluorescein derived fluorophores in common clinical use and provides examples of novel applications from studies in tissue samples.

Fully embeddable chitosan microneedles as a sustained release depot for intradermal vaccination

This study introduces a microneedle transdermal delivery system, composed of embeddable chitosan microneedles and a poly(L-lactide-co-D,L-lactide) (PLA) supporting array, for complete and sustained delivery of encapsulated antigens to the skin. Chitosan microneedles were mounted to the top of a strong PLA supporting array, providing mechanical strength to fully insert the microneedles into the skin. When inserted into rat skin in vivo, chitosan microneedles successfully separated from the supporting array and were left within the skin for sustained drug delivery without requiring a transdermal patch. The microneedle penetration depth was approximately 600 μm (i.e. the total length of the microneedle), which is beneficial for targeted delivery of antigens to antigen-presenting cells in the epidermis and dermis. To evaluate the utility of chitosan microneedles for intradermal vaccination, ovalbumin (OVA; MW = 44.3 kDa) was used as a model antigen. When the OVA-loaded microneedles were embedded in rat skin in vivo, histological examination showed that the microneedles gradually degraded and prolonged OVA exposure at the insertion sites for up to 14 days. Compared to traditional intramuscular immunization, rats immunized by a single microneedle dose of OVA showed a significantly higher OVA-specific antibody response which lasted for at least 6 weeks. These results suggest that embeddable chitosan microneedles are a promising depot for extended delivery of encapsulated antigens to provide sustained immune stimulation and improve immunogenicity.

Ultradeformable liposomes with terpenes for delivery of hydrophilic compound

Ultradeformable liposomes containing penetration enhancers were created to deliver NaFl. Vesicles were investigated for their particle size, zeta potential, NaFl entrapment efficiency (%EE), loading efficiency, and in vitro skin penetration. The vesicles obtained were spherical in shape, with a particle size of less than 100 nm and a negative surface charge (-6 to -11 mV). The %EE of NaFl loaded in vesicles ranged from 37 to 48%. Ultradeformable liposomes with monoterpenes (d-limonene, 1,8-cineole and geraniol) significantly improved NaFl penetration through the skin. Confocal laser scanning microscopy analysis confirmed skin-penetration results and was used to evaluate the behavior of hydrophilic compounds penetrating through the skin.

Interaction of 1-dodecyl-azacycloheptan-2-one with mouse stratum corneum

The interactions of 1-dodecyl-azacycloheptan-2-one (Azone), a penetration enhancer, with mouse skin were analyzed by fluorescence microscopy, solid-state 13C-CP/MAS-NMR spectroscopy and Attenuated Total Reflectance Fourier-transform infrared (ATR-FT-IR) spectroscopy. Ferulic acid was employed as fluorescent probe to observe the delivery pathway in the stratum corneum (SC) after treatment with Azone. Results suggested that the interaction between Azone and the SC occurs in the lipid domains as well as the protein domains. FT-IR measurements show that treatment with Azone results in significant shifts toward larger wavenumbers at v(as)CH2 and v(s)CH2, indicating an increased gauche conformational isomer content of lipid CH2. Further, a decrease of (13C)T1 values and a shift of the SC protein amide-II band to a short wavenumber were found when the SC was pretreated with Azone. It is concluded that Azone can partially convert the SC protein from an alpha-helix conformation to a beta-sheet conformation and loosen the aggregating SC keratins at room temperature.

Controlling transgene expression in subcutaneous implants using a skin lotion containing the apple metabolite phloretin

Adjustable control of therapeutic transgenes in engineered cell implants after transdermal and topical delivery of nontoxic trigger molecules would increase convenience, patient compliance, and elimination of hepatic first-pass effect in future therapies. Pseudomonas putida DOT-T1E has evolved the flavonoid-triggered TtgR operon, which controls expression of a multisubstrate-specific efflux pump (TtgABC) to resist plant-derived defense metabolites in its rhizosphere habitat. Taking advantage of the TtgR operon, we have engineered a hybrid P. putida-mammalian genetic unit responsive to phloretin. This flavonoid is contained in apples, and, as such, or as dietary supplement, regularly consumed by humans. The engineered mammalian phloretin-adjustable control element (PEACE) enabled adjustable and reversible transgene expression in different mammalian cell lines and primary cells. Due to the short half-life of phloretin in culture, PEACE could also be used to program expression of difficult-to-produce protein therapeutics during standard bioreactor operation. When formulated in skin lotions and applied to the skin of mice harboring transgenic cell implants, phloretin was able to fine-tune target genes and adjust heterologous protein levels in the bloodstream of treated mice. PEACE-controlled target gene expression could foster advances in biopharmaceutical manufacturing as well as gene- and cell-based therapies.

Enhancement of skin permeation of docetaxel: a novel approach combining microneedle and elastic liposomes

A combination method of using microneedle pretreatment and elastic liposomes was developed to increase skin permeation of drugs with high molecular weight and poor water solubility. Docetaxel (DTX, MW=807.9) was chosen as a model drug. DTX liposomal systems with and without elastic properties were prepared and characterized. The effect of the developed formulations on the permeation of DTX across both rat and porcine skin was investigated in vitro. The combination effect of microneedle pretreatment and elastic liposomes on the permeability of DTX was evaluated using porcine skin in vitro. The following results were obtained: (1) Elastic liposomes loaded with DTX can enhance transdermal delivery of DTX without microneedle treatment. (2) An enhanced transdermal flux (1.3-1.4 microg/cm(2)/h) for DTX from all liposomal formulations was observed after microneedle treatment. Importantly, the lag time obtained following the application of elastic liposomes through microneedle-treated skin was decreased by nearly 70% compared with that obtained from conventional liposomes. These results suggest that the combination of elastic liposomes with microneedle pretreatment can be a useful method to increase skin permeation of drugs with high molecular weight and poor water solubility.

Interaction of phloretin and 6-ketocholestanol with DPPC-liposomes as phospholipid model membranes

Phloretin and 6-ketocholestanol are penetration enhancers for percutaneous delivery of certain topically applied drugs. In the present study some physicochemical experiments have been performed to elucidate the mechanism of action of phloretin and 6-ketocholestanol. The penetration enhancing effect of phloretin and 6-ketocholestanol is believed to be due to their increase of the fluidity of the intercellular lipid bilayers of the stratum corneum. Phospholipid vesicles were chosen as a simple model to represent these bilayers. The effect of phloretin and 6-ketocholestanol on phase transition temperature and enthalpy was studied using differential scanning calorimetry. Beside of that the size of liposomes was monitored when the amount of penetration enhancer in the liposome preparation was changed. Addition of increasing amounts of phloretin and 6-ketocholestanol to the bilayer resulted in lowering of phase transition temperatures and increasing the enthalpy. Additionally the size of the liposomes was increased when penetration enhancer was added. The results suggest that phloretin as well as 6-ketocholestanol would interact with stratum corneum lipids in a similar manner, both reduce the diffusional resistance of the stratum corneum to drugs with balanced hydrophilic-lipophilic characteristics.

Influence of 6-Ketocholestanol on Skin Permeation of 5-Aminolevulinic Acid and Evaluation of Chemical Stability

The ability of 6-ketocholestanol to increase the skin permeation of the prodrug aminolevulinic acid (5-ALA) was investigated. 6-Ketocholestanol was incorporated together with 5-ALA in four different formulations. Preparations used were a liquid solution/suspension of 5-ALA in buffer, 5-ALA in phospholipid liposomal formulations with and without gelating agent, and finally, a complex cream formulation also including phospholipids. Standard diffusion experiments of 5-ALA using Franz-type diffusion cells and porcine skin were performed. Drug stability was monitored by analyzing the 5-ALA content in the different formulations over time and viewing the preparation for microbial contamination. The analysis of 5-ALA as a nonfluorescent probe was performed after chemical reaction, leading to a fluorescent derivative. The 5-ALA permeation through porcine skin was increased threefold by 6-ketocholestanol in the cream formulation. The chemical stability of 5-ALA in the tested formulations was in the range of about 33 to 72% after an observation period of 28 days. After that time point microbial stability was no longer evident for formulations 2 and 3. Formulation 1 could be observed until day 34, and only formulation 4 showed a microbial stability over the whole observation period of 42 days.

Influence of phloretin on the skin permeation of lidocaine from semisolid preparations

The purpose of the present study was to determine the significance of phloretin on the topical permeation of lidocaine using different semisolid preparations as delivery systems. One hydrophilic and three lipophilic formulations were used. After estimation of the solubility of phloretin and lidocaine in the vehicles and analysis of the viscoelastic properties, standard diffusion experiments with Franz type diffusion cells through porcine skin were performed. Results indicate a general lidocaine enhancement by phloretin in the tested vehicles. The permeation was enhanced 1.39-fold in the hydrophilic formulation and between 1.25- and 1.76-fold in the lipophilic formulations.

Phloretin and 6-ketocholestanol: membrane interactions studied by a phospholipid/polydiacetylene colorimetric assay and differential scanning calorimetry

The aim of this study was to investigate membrane interactions of phloretin and 6-ketocholestanol using different methods. A previously reported colorimetric assay with phospholipid/polydiacetylene (PDA) vesicles was used to examine a possible interaction of phloretin and 6-ketocholestanol with this target. During this interaction the used aggregates of lipids and conjugated PDA undergo a visible and quantifiable blue to red color transition. A positive result is indicative for a reaction response with membrane lipids of a simplified bilayer structure instead of the complex bilayer system of the stratum corneum. Results of this test confirm previous proposed membrane interactions by skin diffusion studies. Additional differential scanning calorimetry studies with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) liposomes confirm a membrane interaction and indicates that phloretin and 6-ketocholestanol interact with the lipid layer and change structural parameters. They strongly decrease the lipid phase transition temperature of DMPC and DPPC liposomes by at least about 6.6 degrees C and maximally about 13.9 degrees C which refers to a higher fluidity of the membrane.