Evaluation of ex vivo human skin permeation of genistein and daidzein

The anti-inflammatory activity of flavonoids and alkaloids from Sophora flavescens alleviates psoriasiform lesions: Prenylation and methoxylation beneficially enhance bioactivity and skin targeting

The herb Sophora flavescens displays anti-inflammatory activity and can provide a source of antipsoriatic medications. We aimed to evaluate whether S. flavescens extracts and compounds can relieve psoriasiform inflammation. The ability of flavonoids (maackiain, sophoraflavanone G, leachianone A) and alkaloids (matrine, oxymatrine) isolated from S. flavescens to inhibit production of cytokine/chemokines was examined in keratinocytes and macrophages. Physicochemical properties and skin absorption were determined by in silico molecular modeling and the in vitro permeation test (IVPT) to establish the structure-permeation relationship (SPR). The ethyl acetate extract exhibited higher inhibition of interleukin (IL)-6, IL-8, and CXCL1 production in tumor necrosis factor-α-stimulated keratinocytes compared to the ethanol and water extracts. The flavonoids demonstrated higher cytokine/chemokine inhibition than alkaloids, with the prenylated flavanones (sophoraflavanone G, leachianone A) led to the highest suppression. Flavonoids exerted anti-inflammatory effects via the extracellular signal-regulated kinase, p38, activator protein-1, and nuclear factor-κB signaling pathways. In the IVPT, prenylation of the flavanone skeleton significantly promoted skin absorption from 0.01 to 0.22 nmol/mg (sophoraflavanone G vs. eriodictyol). Further methoxylation of a prenylated flavanone (leachianone A) elevated skin absorption to 2.65 nmol/mg. Topical leachianone A reduced the epidermal thickness in IMQ-treated mice by 47%, and inhibited cutaneous scaling and cytokine/chemokine overexpression at comparable levels to a commercial betamethasone product. Thus, prenylation and methoxylation of S. flavescens flavanones may enable the design of novel antipsoriatic agents.

Flavonoids in the Spotlight: Bridging the Gap between Physicochemical Properties and Formulation Strategies

Flavonoids are hydroxylated polyphenols that are widely distributed in plants with diverse health benefits. Despite their popularity, the bioavailability of flavonoids is often overlooked, impacting their efficacy and the comparison of products. The study discusses the bioavailability-related physicochemical properties of flavonoids, with a focus on the poorly soluble compounds commonly found in dietary supplements and herbal products. This review sums up the values of pKa, log P, solubility, permeability, and melting temperature of flavonoids. Experimental and calculated data were compiled for various flavonoid subclasses, revealing variations in their physicochemical properties. The investigation highlights the challenges posed by poorly soluble flavonoids and underscores the need for enabling formulation approaches to enhance their bioavailability and therapeutic potential. Compared to aglycones, flavonoid glycosides (with sugar moieties) tend to be more hydrophilic. Most of the reviewed aglycones and glycosides exhibit relatively low log P and high melting points, making them "brick dust" candidates. To improve solubility and absorption, strategies like size reduction, the potential use of solid dispersions and carriers, as well as lipid-based formulations have been discussed.

In Vitro, Ex Vivo, and In Vivo Evaluation of Nanoparticle-Based Topical Formulation Against Candida albicans Infection

Ketoconazole is commonly used in the treatment of topical fungal infections. The therapy requires frequent application for several weeks. Systemic side effects, allergic reactions, and prolonged treatment are often associated with non-compliance and therapy failure. Hence, we developed an optimized topical antifungal gel that can prolong the release of drug, reduce systemic absorption, enhance its therapeutic effect, and improve patient compliance. Ketoconazole-loaded PLGA nanoparticles were prepared by the emulsion/solvent evaporation method and were characterized with respect to colloidal properties, surface morphology, and drug entrapment efficiency. The optimized ketoconazole-loaded PLGA nanoparticles and commercially available silver nanoparticles were incorporated into a Carbopol 934P-NF gel base. This arrangement was characterized and compared with commercially available 2% ketoconazole cream to assess physical characteristics of the gel, in vitro drug release, ex vivo skin permeation and retention, and in vivo studies on Wister male albino rats. The results showed that polymeric PLGA nanoparticles were very effective in extending the release of ketoconazole in our optimized formulation. Nanoparticles were smooth, spherical in shape, and below 200 nm in size which is consistent with the data obtained from light scattering and SEM images. The ex vivo data showed that our gel formulation could strongly reduce drug permeation through the skin, and more than 60% of the drug was retained on the upper surface of the skin in contrast to 38.42% of the commercial cream. The in vivo studies showed that gel formulation could effectively treat the infection. This study demonstrates that our topical gel could be effective in sustaining the release of drug and suggests its potential use as a possible strategy to combat antifungal-resistant Candida albicans.

The effectiveness of synthetic methoxylated isoflavones in delivering to the skin and alleviating psoriasiform lesions via topical absorption

This study was conducted to appraise the possible potential of synthetic isoflavones (SIFs) on psoriasis treatment. A practical and easy-to-operate approach was employed in synthesizing a series of SIFs, considering that acquiring flavonoids from natural resources is usually expensive, time-consuming, and non-eco-friendly. Seven SIFs derived from daidzein were produced with differences in the location of the hydroxyl groups and degree of methoxylation. The in vitro and in vivo skin absorption of topically applied SIFs was estimated. Further, keratinocytes (HaCaT) were employed as the model to investigate the anti-inflammatory activity of the isoflavones. The lipophilicity was increased from SIF-1 to -7. Noteworthily, there was a parabolic relationship between lipophilicity and skin absorption, with SIF-5 (4',7-dihydroxyisoflavone, daidzein) and SIF-6 (7-hydroxy-3',4'-dimethoxyisoflavone, cladrin) demonstrating the highest retention in pig skin. The methoxylated isoflavone SIF-5 showed the greatest permeation into barrier-deficient skin among the compounds tested, with a 6- and 8-fold increase after lipid and protein removal. The cell-based study exhibited the capability of SIFs to restrain the overexpressed IL-6, IL-8, and CXCL1 in stimulated HaCaT. The therapeutic index (TI) predicted the potential candidates of SIF-5 and SIF-6 for topical application to treat psoriatic inflammation. The imiquimod (IMQ)-driven psoriasiform murine model manifested the inhibition of hyperplasia and immune cell infiltration by topically administered SIF-5 and SIF-6. The epidermal thickness of IMQ-treated skin was decreased from 172 to 40 μm by both isoflavones. This effect was comparable with that of betamethasone, the positive control. The topical treatment of SIF-6 significantly reduced cytokine/chemokine upregulation by IMQ. The methoxylated isoflavone with dramatic anti-inflammatory activity is promising for the development of an antipsoriatic agent.

Echinacea angustifolia DC. Lipophilic Extract Patch for Skin Application: Preparation, In Vitro and In Vivo Studies

Dodeca-2E,4E,8Z,10E/Z-tetraenoic isobutylamide (tetraene) is the main component of Echinacea angustifolia DC. lipophilic extract, the bioavailability and immunomodulatory effect after oral administration in soft gel capsules in healthy volunteers of which we have already demonstrated. In the present work, we assessed the transdermal administration as an alternative route of administration of such an alkamide. The first step, therefore, encompassed the preparation of a drug-in-adhesive patch with an area of 868 mm² and containing a dose of 0.64 mg of tetraene. In vitro skin permeation studies in Franz-type diffusion chambers resulted in a tetraene flux of (103 ± 10) ng × cm⁻² × h⁻¹ with a very good linearity (r = 0.99). The relatively low lag time of just 13 min indicates low binding and the accumulation of tetraene in the skin. Finally, the patch was administered to six healthy volunteers, and the pharmacokinetic analysis was performed by nonlinear mixed effects modelling with soft gel oral capsules serving as the reference formulation. The in vivo results correlated well with the in vitro permeation and indicated an initial burst tetraene absorption from the patch that was in parallel with the zero-order kinetics of absorption. The rate of the latter process was in good agreement with the one estimated in vitro. The tetraene absorption rate was therefore slow and prolonged with time, resulting in a bioavailability of 39% relative to the soft gel capsules and a very flat plasma concentration profile.

Dietary Management of Skin Health: The Role of Genistein

In women, aging and declining estrogen levels are associated with several cutaneous changes, many of which can be reversed or improved by estrogen supplementation. Two estrogen receptors—α and β—have been cloned and found in various tissue types. Epidermal thinning, declining dermal collagen content, diminished skin moisture, decreased laxity, and impaired wound healing have been reported in postmenopausal women. Experimental and clinical studies in postmenopausal conditions indicate that estrogen deprivation is associated with dryness, atrophy, fine wrinkling, and poor wound healing. The isoflavone genistein binds to estrogen receptor β and has been reported to improve skin changes. This review article will focus on the effects of genistein on skin health.

Formulation study of a patch containing propranolol by design of experiments

OBJECTIVE

To evaluate the feasibility of a transdermal patch containing propranolol (PR).

METHOD

Skin penetration enhancers (SPEs) able to improve the skin permeability of PR were selected and a quality by design approach was applied to the development of the patch by a 2(4) full factorial design. The permeation profile of PR from the formulations was assessed in in vitro permeation studies performed by using Franz diffusion cells and human epidermis as membrane. Finally, skin irritation was evaluated by the Draize test.

RESULTS

N-methyl pyrrolidone (NMP) resulted as the best SPE: in addition, the critical factors influencing the PR diffusion through the human epidermis when loaded in the patch resulted in the matrix thickness (X1, p = 0.0957) and PR content (X3, p = 0.0004) which improved the flux; conversely, NMP lacked its enhancement effect when loaded in the patch and the increase in its concentration (X4, p = 0.006) affected the drug permeation through human epidermis. The flux of optimal formulation was 12.7 μg/cm(2)/h. On the basis of the steady-state concentration and clearance of PR, the estimated patch surface was 100-120 cm(2), since the activity of PR is related to its Senantiomer and no in vivo bioconversion occurs.

CONCLUSION

A patch containing (S)-PR was prepared and the (S)-PR flux (13.3 μg/cm(2)/h) permitted to confirm the suitability of a transdermal administration of PR. In particular, the use of a 50 μm thick methacrylic matrix containing 8% (S)-PR and 15% NMP can allow to develop a patch non-irritating to the skin, in order to ensure a constant permeation flux of PR over 48 h.

A comparative analysis of the photo-protective effects of soy isoflavones in their aglycone and glucoside forms

Isoflavones exist in nature predominantly as glucosides such as daidzin or genistin and are rarely found in their corresponding aglycone forms daidzein and genistein. The metabolism and absorption of isoflavones ingested with food is well documented, but little is known about their use as topical photo-protective agents. The aim of this study was to investigate in a comparative analysis the photo-protective effects of isoflavones in both their aglycone and glucoside forms. In human skin fibroblasts irradiated with 60 mJ/cm2 ultraviolet B (UVB), we measured the expression levels of COX-2 and Gadd45, which are involved in inflammation and DNA repair, respectively. We also determined the cellular response to UVB-induced DNA damage using the comet assay. Our findings suggest that both the isoflavone glucosides at a specific concentration and combination with an aglycone mixture exerted an anti-inflammatory and photo-protective effect that prevented 41% and 71% of UVB-induced DNA damage, respectively. The advantages of using either isoflavone glucosides or an aglycone mixture in applications in the field of dermatology will depend on their properties and their different potential uses.

Development and validation of a simple and rapid liquid chromatography method for the determination of genistein in skin permeation studies

Genistein (GEN) has potential advantages for topical skin delivery, but no literature data are available for its quantitation in different skin layers, such as the stratum corneum (SC). Therefore, a simple, rapid, selective and sensitive bioanalytical method was developed and validated for GEN quantitation in porcine skin samples following in vitro permeation studies. GEN was assayed by HPLC with UV-Vis detection (270 nm) using 0.5% acetic acid in water-n-propanol-acetonitrile (50 : 2 : 48, v/v/v) as mobile phase (flow-rate of 1.0 mL/min). Specificity was demonstrated since endogenous skin components did not interfere with GEN peak. Standard analytical curve was linear over the concentration range (0.1-60 µg/mL) and the lower limit of quantitation was determined for different skin layers (100 ng/mL). GEN recovery from skin layers ranged from 95.57 to 97.57%. Permeation studies were carried out using an automated vertical diffusion cell apparatus. No fluctuation on the amount of GEN retained in the SC was observed over time, but increasing amounts of the drug were found in deeper layers of the skin. The method was reliable and reproducible for the quantitation GEN in skin samples enabling the determination of the cutaneous penetration profile of this drug in permeation experiments.

Validation of an LC method to determine skin retention profile of genistein from nanoemulsions incorporated in hydrogels

Recent studies have shown the effect of soy isoflavones in preventing skin photoaging and photocarcinogenesis, especially for genistein (GEN). Nanoemulsions have been proposed as a delivery system for GEN administration due to the low water solubility of this isoflavone. This article describes the validation of an isocratic liquid chromatography method to determine GEN in porcine ear skin layers from nanoemulsions before and after incorporation into hydrogels. The analyses are performed on a reversed-phase C18 column using a mobile phase composed of methanol-water (70:30, v/v) under acid conditions (at pH 3.0) and UV detection at 270 nm. The method is linear in the range of 0.1-10 µg/mL (r(2) > 0.999) in the presence of skin extracts. The low limit of quantitation is estimated as 0.1 µg/mL. No interferences from formulation excipients or skin layer compounds are detected. The RSD values for intra- and inter-day precision are lower than 15%. Recovery ranged from approximately 90% to 110%. The method is applied to estimate GEN retention in the skin from formulations using Franz diffusion cells. The highest amount of GEN is detected in the epidermis (185 µg/cm(2)). In conclusion, the method proved to be specific, precise, and accurate in determining GEN amounts from formulations in skin retention studies.

Daidzein/cyclodextrin/hydrophilic polymer ternary systems

OBJECTIVE

To evaluate the effect of different cyclodextrins (β-cyclodextrin [β-CD], methyl-β-cyclodextrin [Mβ-CD], or hydroxypropyl-β-cyclodextrin [HPβ-CD]) and/or hydrophilic polymers (carboxymethylcellulose, hydroxypropylmethylcellulose [HPMC], polyethyleneglycol, or polyvinylpyrrolidone [PVP]) on daidzein solubility in water.

MATERIALS AND METHODS

The corresponding associations were characterized in aqueous media using phase-solubility studies. The morphology of daidzein/cyclodextrin freeze-dried complexes was characterized using scanning electron microscopy, and their spatial configuration was proposed by means of nuclear magnetic resonance spectroscopy.

RESULTS AND DISCUSSION

In the presence of 6 mM of cyclodextrins, the solubility of daidzein in water was significantly enhanced: 5.7-fold (β-CD), 7.2-fold (Mβ-CD), and 9.4-fold (HPβ-CD). The analysis of the three solid complexes proved that the formation of inclusion complexes occurred through the insertion of the B and C rings of daidzein molecule into the cyclodextrins cavity. The association of daidzein/cyclodextrin complexes to the hydrophilic polymers HPMC or PVP (1%, w/w) was able to improve the solubility of daidzein even further.

CONCLUSION

The highest solubilizing effect was obtained for daidzein/HPβ-CD/PVP ternary system (12.7-fold).

In vitro and in vivo evaluation of topical delivery and potential dermal use of soy isoflavones genistein and daidzein

Genistein, daidzein, and glycitein are soy isoflavones. These compounds can be used to protect the skin from oxidative stress induced by UVB radiation. To this end, the feasibility of skin absorption of soy isoflavones was evaluated in the present study. As assayed by flow cytometry, UVB-induced H(2)O(2) production in keratinocytes was inhibited by genistein and daidzein, confirming that these two compounds can act as free radical scavengers when keratinocytes are photodamaged. Glycitein showed no protective activity against photodamage. The effects of vehicles on the in vitro topical delivery from saturated solutions such as aqueous buffers and soybean oil were investigated. The isoflavones in a non-ionized form (pH 6) showed higher skin deposition compared to the ionized form (pH 10.8). Soybean oil reduced the isoflavone amount retained in the skin, especially for genistein. Genistein generally exhibited greater skin absorption than did daidzein. However, daidzein permeation was enhanced when an aglycone mixture was used as the active ingredient. An eutectic effect was proposed as the enhancing mechanism. In vivo skin deposition showed a linear correlation with the in vitro results. The safety profiles suggested no or only negligible stratum corneum disruption and skin erythema by topical application of soy isoflavones. It was concluded that topical delivery may serve as a potent route for soy isoflavones against photoaging and photodamage.