Preparation and evaluation of microemulsion‑based transdermal delivery of Cistanche tubulosa phenylethanoid glycosides

Preparing a novel baicalin-loaded microemulsion-based gel for transdermal delivery and testing its anti-gout effect

We previously demonstrated that baicalin had efficacy against gouty arthritis (GA) by oral administration. In this paper, a novel baicalin-loaded microemulsion-based gel (B-MEG) was prepared and assessed for the transdermal delivery of baicalin against GA. The preparation method and transdermal capability of B-MEG was screened and optimized using the central composite design, Franz diffusion cell experiments, and the split-split plot design. Skin irritation tests were performed in guinea pigs. The anti-gout effects were evaluated using mice. The optimized B-MEG comprised of 50 % pH 7.4 phosphate buffered saline, 4.48 % ethyl oleate, 31.64 % tween 80, 13.88 % glycerin, 2 % borneol, 0.5 % clove oil and 0.5 % xanthan gum, with a baicalin content of (10.42 ± 0.08) mg/g and particle size of (15.71 ± 0.41) nm. After 12 h, the cumulative amount of baicalin permeated from B-MEG was (672.14 ± 44.11) μg·cm-2. No significant skin irritation was observed following B-MEG application. Compared to the model group, B-MEG groups significantly decreased the rate of auricular swelling (P < 0.01) and number of twists observed in mice (P < 0.01); and also reduced the rate of paw swelling (P < 0.01) and inflammatory cell infiltration in a mouse model of GA. In conclusion, B-MEG represents a promising transdermal carrier for baicalin delivery and can be used as a potential therapy for GA.

In vitro diffusion of plant phenolics through the skin: A review update

OBJECTIVE

Excessive skin exposure to deleterious environmental variables results in inflammation as well as molecular and cellular impairments that compromise its functionality, aesthetic qualities, and overall well-being. The implementation of topical administration of antioxidants and other compounds as a method for preventing or reversing damage is a rational approach. Numerous phenolic compounds derived from plants have demonstrated capabilities such as scavenging free radicals and promoting tissue healing. However, the primary obstacle lies in effectively delivering these compounds to the specific place on the skin, and accurately forecasting their diffusion through the skin can assist in determining the most effective tactics. Hence, this article provides a comprehensive analysis of recent literature pertaining to the in vitro skin diffusion characteristics of plant phenolics. The aim is to gain a deeper understanding of their behaviour when present in various forms such as solutions, suspensions, and formulations.

METHOD

The data on plant extracts and isolated plant phenolic compounds in vitro skin diffusion assays published over the last six years were compiled and discussed.

RESULTS

Even though the gold standard Franz diffusion cell is the most commonly used in the assessment of in vitro plant phenolic skin diffusion profiles, a plethora of skin models and assay conditions are reported for a variety of compounds and extracts in different vehicles.

CONCLUSION

The presence of numerous models and vehicles poses a challenge in creating correlations among the existing data on plant phenolic compounds. However, it is possible to draw some general conclusions regarding molecular, vehicle, and skin characteristics based on the gathered information.

Development of the Forskolin Microemulsion Formula and its Irritation Test on Rabbits

Objectives

This study aimed to develop a microemulsion formula that can increase the solubility and stability of forskolin and its safety for topical use.

Materials and Methods

The materials used for the development of the microemulsion formula were triglyceride oil, non-ionic surfactants, and polyethylene glycol (PEG) for cosurfactants, which were selected on the basis of the results of the forskolin solubility test using high performance liquid chromatography (HPLC). The microemulsion was formulated by the phase titration method. Formula stability was determined by storage for 90 days in a refrigerator at room temperature, and an accelerated stability test was performed by determining globule size, forskolin concentration, and pH. The safety of using microemulsions was determined by skin irritation tests on albino rabbits.

Results

The optimum microemulsion formula consisted of Maisine® CC, polyoxyethylene sorbitan 20 (POE 20), and PEG 400 with a ratio of 4:25:5 w/v, which increased the solubility of forskolin the most, namely 2.19 mg mL-1. Based on globule size (<50 nm), forskolin concentration (2 mg.mL-1), and pH (6.0-6.35), the formula was stable in refrigerator storage and room temperature but unstable in the accelerated stability test (40 °C) starting on day 21. This optimum formula exhibits a primary irritation index (PII) of 0.11, which is categorized as feeble irritation and can be ignored.

Conclusion

The microemulsion prepared by the phase titration method containing Maisine® CC, POE 20, and PEG 400 (4:25:5, w/v) as a base and 0.2% forskolin was stable in refrigerator storage and at room temperature. This microemulsion is mild or negligible irritant with a PII: 0.11.

Effect of Penetration Enhancers on Transdermal Delivery of Oxcarbazepine, an Antiepileptic Drug Using Microemulsions

Oxcarbazepine (OXC) is an anticonvulsant drug, indicated for the treatment of the neurological disorder, epilepsy. The objective of the present study was to evaluate the transdermal delivery of OXC from microemulsions using different penetration enhancers. Transcutol® P (TRC), oleic acid (OA), cineole (cin), Labrasol (LS), Tween 80 (T80) and N-Methyl-Pyrrolidone (NMP) were used as penetration enhancers as well as microemulsion components. Simple formulations of OXC in propylene glycol (PG) incorporating various penetration enhancers and combination of penetration enhancers were also evaluated for transdermal delivery. Drug delivery and penetration enhancement were studied using human cadaver skin on Franz diffusion cells. The results showed that all penetration enhancers improved the rate of permeation of OXC compared to the control. The flux of drug delivery from the various formulations was found to be, in decreasing order, cin > OA + TRC > NMP > TRC > OA. Overall, microemulsions prepared using cineole, Tween 80 and Transcutol® P (TRC) were shown to be provide the best penetration enhancement for OXC.

Solid lipid nanoformulation of berberine attenuates Doxorubicin triggered in vitro inflammation in H9c2 rat cardiomyocytes

AIM

To evaluate berberine solid lipid nanoparticles' efficacy against doxorubicin-induced cardiotoxicity.

BACKGROUND

Berberine (Ber) is cardioprotective, but its oral bioavailability is low and its effect in chemotherapy-induced cardiotoxicity has not been studied.

OBJECTIVE

Solid lipid nanoparticles (SLNs) of berberine chloride were prepared, characterized and evaluated in vitro against Doxorubicin induced cardiomyocyte injury.

METHODOLOGY

Berberine loaded SLNs (Ber-SLNs) were synthesized using water-in-oil microemulsion technique with tripalmitin, Tween 80 and poloxamer 407. Ber-SLNs were evaluated for preventive effect against toxicity of Doxorubicin in H9c2 cells. The culture was pre-treated (24 h) with Ber (10 µM) and Ber-SLNs (1 and 10 µM) and exposed to 1 µM of Doxorubicin (Dox) was added for 3 h. The cell viability (LDH (Lactate dehydrogenase) assay and MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)), levels of Creatine kinase-MB (CK-MB), Nitrite, MDA (Malondialdehyde), ROS (Reactive oxygen species) generation and apoptotic DNA (Deoxyribonucleic acid) content were assessed.

RESULTS

Ber-SLNs had a mean particle size of 13.12±1.188 nm, zeta potential of -1.05 ± 0.08 mV, poly-dispersity index (PDI) of 0.317 ± 0.05 and entrapment efficiency of 50 ± 4.8%. Cell viability was 81  0.17% for Ber-SLNs (10 µM) and 73.22  0.83% for Ber (10 µM) treated cells in MTT assay. Percentage cytotoxicity calculated from LDH release was 58.91  0.54% after Dox, 40.3  1.3% with Ber (10 µM) and 40.7  1.3% with Ber-SLNs (1 µM) (p<0.001). Inflammation and oxidative stress markers were lower with Ber and Ber-SLNs. Attenuation of ROS generation and apoptosis of cardiomyocytes were noted on fluorescence microscopy.

CONCLUSION

Ber loaded SLNs effectively prevented Doxorubicin-induced inflammation and oxidative stress in rat cardiomyocytes. The results demonstrate that microemulsion is a simple, cost-effective technique to prepare Ber-SLNs and may be considered as a drug delivery vehicle for berberine.

Solids Turn into Liquids—Liquid Eutectic Systems of Pharmaceutics to Improve Drug Solubility

The low solubility of active pharmaceutical ingredients (APIs) is a problem in pharmaceutical development. Several methodologies can be used to improve API solubility, including the use of eutectic systems in which one of the constituents is the API. This class of compounds is commonly called Therapeutic Deep Eutectic Systems (THEDES). THEDES has been gaining attention due to their properties such as non-toxicity, biodegradability, and being non-expensive and easy to prepare. Since the knowledge of the solid liquid diagram of the mixture and the ideal eutectic point is necessary to ascertain if a mixture is a deep eutectic or just a eutectic mixture that is liquid at ambient temperature, the systems studied in this work are called Therapeutic Liquid Eutectic Systems (THELES). Therefore, the strategy proposed in this work is to improve the solubility of chlorpropamide and tolbutamide by preparing THELES. Both APIs are sulfonylurea compounds used for the treatment of type 2 diabetes mellitus and have low solubility in water. To prepare the THELES, several coformers were tested, namely, tromethamine, L(+)-arginine, L-tryptophan, citric acid, malic acid, ascorbic acid, and p-aminobenzoic acid, in molar ratios of 1:1 and 1:2. To improve viscosity, water was added in different molar ratios to all systems. THELES were characterized by mid-infrared spectroscopy (MIR), and differential scanning calorimetry. Their viscosity, solubility, and permeability were also determined. Their stability at room temperature and 40 °C was accessed by MIR. Cytocompatibility was performed by metabolic activity and cell lysis evaluation, according to ISO10993-5:2009, and compared with the crystalline APIs. THELES with TRIS were successfully synthesized for both APIs. Results showed an increased solubility without a decrease in the permeability of the APIs in the THELES when compared with the pure APIs. The THELES were also considered stable for 8 weeks at ambient temperature. The cells studied showed that the THELES were not toxic for the cell lines used.

Recent Advances in Nanomaterials for Dermal and Transdermal Applications

The stratum corneum, the most superficial layer of the skin, protects the body against environmental hazards and presents a highly selective barrier for the passage of drugs and cosmetic products deeper into the skin and across the skin. Nanomaterials can effectively increase the permeation of active molecules across the stratum corneum and enable their penetration into deeper skin layers, often by interacting with the skin and creating the distinct sites with elevated local concentration, acting as reservoirs. The flux of the molecules from these reservoirs can be either limited to the underlying skin layers (for topical drug and cosmeceutical delivery) or extended across all the sublayers of the epidermis to the blood vessels of the dermis (for transdermal delivery). The type of the nanocarrier and the physicochemical nature of the active substance are among the factors that determine the final skin permeation pattern and the stability of the penetrant in the cutaneous environment. The most widely employed types of nanomaterials for dermal and transdermal applications include solid lipid nanoparticles, nanovesicular carriers, microemulsions, nanoemulsions, and polymeric nanoparticles. The recent advances in the area of nanomaterial-assisted dermal and transdermal delivery are highlighted in this review.

Preparation and quality evaluation of a volatile oil microemulsion from Flos magnoliae and Centipeda minima

In order to improve the water solubility of the volatile oils extracted from Flos magnoliae (FM) and Centipeda minima (CM), they were prepared as a microemulsion (ME), which were then used in the development of an FM and CM volatile oil ME for the treatment of allergic rhinitis (AR). ME was prepared by phase inversion emulsification, and the prescription factors such as emulsifier, co‑emulsifier, oil phase, Km, which represents the ratio of the mass of emulsifier to that of the co‑emulsifier, and preparation factors such as temperature affecting the formation of the ME were selected according to the formation area of ME in a pseudo‑ternary phase diagram. The quality of the ME was evaluated based on its appearance, particle size, Zeta potential and stability. The content of eucalyptol in ME was determined by gas chromatography‑mass spectrometry (GC‑MS). The cumulative permeability of the ME within 24 h was measured with a transdermal diffusion tester. The results revealed that the best formula for preparation of the ME was as follows: Castor oil polyoxyethylene ether (EL‑40) was the emulsifier; the co‑emulsifier was anhydrous ethanol; the Km was 2:1; the mixed phase of volatile oil and isopropyl myristate with mass ratio of 1:1 was used as oil phase; and the preparation temperature was 25˚C. The content of eucalyptol in the ME was 2.57 mg/g, and the cumulative permeability of the ME in 24 h was significantly increased compared with that of the reference oil solution. The appearance of the ME was uniform, and the solution was transparent. In conclusion, compared with traditional preparations, FM and CM volatile oil ME is a novel, improved and more effective preparation for the treatment of AR.

Development of Microemulsions Containing Glochidion wallichianum Leaf Extract and Potential for Transdermal and Topical Skin Delivery of Gallic Acid

Glochidion wallichianum (GW) is a good source of antioxidants, including gallic acid, promoting its development as a microemulsion. We constructed five pseudo-ternary phase diagrams comprising isopropyl myristate (IPM), water, and surfactant mixture (Smix)—i.e., Labrasol®:HCO-40® (1:1) with Transcutol® (1:1, 2:1, 3:1), and Tween80:Span80 (3:2) with Transcutol® or propylene glycol:ethanol (1:1). Additionally, blank and GW extract-loaded microemulsions were prepared at an IPM:Water:Smix ratio of 10:30:60 (high water content) and 30:10:60 (high oil content) from each Smix. The physical characteristics, skin permeation, and disposition were evaluated. The formulations with high water content and conductivities provided higher gallic acid permeation and disposition than those with high oil content. The Smix of Labrasol®:HCO-40® (1:1) and Transcutol® (1:1) promoted the highest gallic acid permeation (enhancement ratio 1.78 ± 0.12) and was suitable for transdermal delivery. However, the 1% hydroxypropyl methylcellulose control gel, the microemulsion with Smix of Labrasol®:HCO-40® (1:1) with Transcutol® (2:1), and Smix of Tween80:Span80 (3:2) with propylene glycol:ethanol (1:1) could provide higher skin accumulation of gallic acid than that with other formulations. The microstructures, ratio of surfactant:cosurfactant, and compositions of microemulsions were found to affect the skin permeation and disposition of gallic acid and require optimization to act as transdermal or topical delivery carriers.

Antifungal Activity and the Chemical and Physical Stability of Microemulsions Containing Citrus hystrix DC Leaf Oil

Citrus hystrix DC (kaffir lime) leaf oil exhibited antifungal activities against Aspergillus niger and Candida albicans. This study aimed to evaluate the antifungal activity of kaffir lime leaf oil and microemulsions containing kaffir lime oil against Trichophyton mentagrophytes var. interdigitale. The chemical components of kaffir lime leaf oil were analyzed by gas chromatography coupled with mass spectrometry. Microemulsions containing kaffir lime oil were formulated using Tween 80, propylene glycol, and water using a phase titration method. The microemulsion of kaffir lime leaf oil was evaluated for droplet size, polydispersity index, and zeta potential using a dynamic light scattering technique. The antifungal activities of kaffir lime oil and its microemulsion were investigated through macrodilution and agar well diffusion methods, respectively. The degradation of citronellal in the microemulsion was analyzed by validated UV-Visible spectrophotometry. The minimum inhibitory concentration value of kaffir lime oil was 1.08 ± 0.00 mg/mL. The microemulsion of kaffir lime leaf oil exhibited potent antifungal activity against T. mentagrophytes var. interdigitale. The size, polydispersity index, and zeta potential of freshly prepared microemulsion were 12.82 ± 0.40 nm, 0.183 ± 0.072, and −7.87 ± 0.06 mV, respectively. The microemulsion of kaffir lime leaf oil also demonstrated good physical and chemical stability at specific temperatures. The kaffir lime oil microemulsion was highly stable when stored at 4 °C and 30 °C for 1 month but was unstable at 45 °C. The microemulsion of kaffir lime leaf oil may be an alternative therapeutic against tinea pedis caused by T. mentagrophytes var. interdigitale.

Enhanced Transdermal Delivery of Concentrated Capsaicin from Chili Extract-Loaded Lipid Nanoparticles with Reduced Skin Irritation

The aim of this study was to develop lipid-based nanoparticles that entrapped a high concentration of capsaicin (0.25%) from a capsicum oleoresin extract. The solid lipid nanoparticles (SLNs) and nanostructured lipid carriers (NLCs) were strategically fabricated to entrap capsaicin without a hazardous solvent. Optimized nanosize lipid particles with high capsaicin entrapment and loading capacity were achieved from pair-wise comparison of the solid lipid mixtures consisting of fatty esters and fatty alcohols, representing small and large crystal-structure molecules combined with a compatible liquid lipid and surfactants (crystallinity index = 3%). This report was focused on selectively captured capsaicin from oleoresin in amorphous chili extract-loaded NLCs with 85.27% ± 0.12% entrapment efficiency (EE) and 8.53% ± 0.01% loading capacity (LC). The particle size, polydispersity index, and zeta potential of chili extract-loaded NLCs were 148.50 ± 2.94 nm, 0.12 ± 0.03, and -29.58 ± 1.37 mV, respectively. The favorable zero-order kinetics that prolonged capsaicin release and the significantly faster transdermal penetration of the NLC attributed to the reduction in skin irritation of the concentrated capsaicin NLCs, as illustrated by the in vitro EpiDerm^TM three-dimensional human skin irritation test and hen's egg test chorioallantoic membrane assay (HET-CAM).

Selective Adsorption and Purification of the Acteoside in Cistanche tubulosa by Molecularly Imprinted Polymers

Acteoside (ACT) is the main component of phenylethanoid glycosides in Cistanche tubulosa, and it is extremely desirable for obtaining high purification of ACT by molecularly imprinted polymers (MIPs) from their extracts. In this study, MIPs were designed and synthetized to adsorb selectively the ACT in C. tubulosa. The effects of different functional monomers, cross-linkers, and solvents of MIPs were investigated. MIPs were studied in terms of static adsorption experiments, dynamic adsorption experiments, and selectivity experiments. The optimal functional monomer, cross-linking agent, and solvent are 4-vinylpyridine, ethylene glycol dimethylacrylate, and the mixed solvent (acetonitrile and N,N-dimethylformamide, 1:1.5, v/v), respectively. Under the optimal conditions, the synthesized MIP1 has a high adsorption performance for ACT. The adsorption capacity of MIP1 to ACT reached 112.60 mg/g, and the separation factor of ACT/echinacoside was 4.68. Because the molecularly imprinted cavities of MIP1 resulted from template molecules of ACT, it enables MIP1 to recognize selectively ACT. Moreover, the N–H groups on MIP1 can form hydrogen bonds with the hydroxyl groups on the ACT; this improves the separation factor of MIP1. The dynamic adsorption of ACT accorded with the quasi-second-order kinetics; it indicated that the adsorption process of MIP1 is the process of chemical adsorption to ACT. MIPs can be applied as a potential adsorption material to purify the active ingredients of herbal medicines.

Enhancement of Kidney Invigorating Function in Mouse Model by Cistanches Herba Dried Rapidly at a Medium High Temperature

Cistanches Herba is a popular Traditional Chinese Medicine and functional food that is used to treat kidney yang deficiency (KYD) in China. In this study, we investigated the effects of different drying methods for Cistanches Herba on kidney invigoration and yang strengthening. We established a mouse model of KYD by intraperitoneal injection of hydrocortisone for 8 days. We dried slices of Cistanches Herba in the sun, in the shade, in a microwave, or in an oven at 40°C, 60°C, 80°C or 100°C, then prepared and administered extracts to the mice by gastric gavage. We measured and evaluated the echinacoside (ECH) and acteoside (ACT) contents of the extracts, as well as the mice's body weight; testicular, epididymal, hepatic, and renal coefficients; and semen quality. All the Cistanches Herba extracts, obtained using different drying techniques, improved symptoms of KYD diagnosis in mice. Among them, treatments with Cistanches Herba dried in a microwave and dried in an oven at 100°C had the best therapeutic effects. Our results suggested that the higher the total content of ECH and ACT in Cistanches Herba extracts, the better the effects of kidney invigoration and yang strengthening. In addition, shorter drying times at higher temperatures lead to the highest recoveries of active components, and Cistanche dried in the sun at a medium-high temperature can improve sperm quality in mice.