Microemulsion-based oxyresveratrol for topical treatment of herpes simplex virus (HSV) infection: physicochemical properties and efficacy in cutaneous HSV-1 infection in mice

Secondary metabolites in topical infectious diseases and nanomedicine applications

Topical infection affects nearly one-third of the world's population; it may result from poor sanitation, hygienic conditions and crowded living and working conditions that accelerate the spread of topical infectious diseases. The problems associated with the anti-infective agents are drug resistance and long-term therapy. Secondary metabolites are obtained from plants, microorganisms and animals, but they are metabolized inside the human body. The integration of nanotechnology into secondary metabolites is gaining attention due to their interaction at the subatomic and skin-tissue levels. Hydrogel, liposomes, lipidic nanoparticles, polymeric nanoparticles and metallic nanoparticles are the most suitable carriers for secondary metabolite delivery. Therefore, the present review article extensively discusses the topical applications of nanomedicines for the effective delivery of secondary metabolites.

Novel nano-drug delivery system for natural products and their application

The development of natural products for potential new drugs faces obstacles such as unknown mechanisms, poor solubility, and limited bioavailability, which limit the broadened applicability of natural products. Therefore, there is a need for advanced pharmaceutical formulations of active compounds or natural products. In recent years, novel nano-drug delivery systems (NDDS) for natural products, including nanosuspensions, nanoliposomes, micelle, microemulsions/self-microemulsions, nanocapsules, and solid lipid nanoparticles, have been developed to improve solubility, bioavailability, and tissue distribution as well as for prolonged retention and enhanced permeation. Here, we updated the NDDS delivery systems used for natural products with the potential enhancement in therapeutic efficiency observed with nano-delivery systems.

Investigating the influence of excipient batch variation on the structure, consistency and physical stability of polysorbate 60-based topical vehicles

Fatty alcohol-polysorbate 60-water ternary systems were used as models to represent the continuous phases of the respective semisolid oil-in-water emulsions for topical delivery of cosmetic and medicinal agents. The influence of batch variation of polysorbate 60 and fatty alcohol on structure and consistency of these systems was investigated using microscopy, rheology, differential scanning calorimetry and X-ray scattering techniques. The polysorbate 60 : cetostearyl alcohol mixed emulsifying wax showed swelling in water, that is, the lamellar repeat distance continually augmented from 93 to 125 Å with water percentage 20-90%. Cetostearyl alcohol ternary systems were thicker than cetyl alcohol ones independently of polysorbate 60 batches used. All the ternary systems showed an initial increase in consistency over the first 2 weeks of storage, which was followed by slight changes in consistency (cetostearyl alcohol systems) due to the re-allocation of polysorbate 60 molecules in the gel network or significant breakdown of structure (cetyl alcohol systems) due to the transformation of swollen α-lamellar gel phase into β, γ crystals on 25°C storage. With all fatty alcohols, the consistency of polysorbate 60 ternary system was directly dependent upon interlamellar water thickness as governed by the length and distribution of polyoxyethylene groups within polysorbate 60 molecules. In relation with the composition of polysorbate 60 batches used, the consistency of ternary systems was higher when prepared with the polysorbate 60 batch containing a greater amount of sorbitan polyoxyethylene monoesters. It was proposed that the swollen α-crystalline gel phase could be better formed by sorbitan polyoxyethylene monoesters rather than sorbitan polyoxyethylene diesters.

Oxyresveratrol: Sources, Productions, Biological Activities, Pharmacokinetics, and Delivery Systems

Oxyresveratrol has recently attracted much research attention due to its simple chemical structure and diverse therapeutic potentials. Previous reviews describe the chemistry and biological activities of this phytoalexin, but additional coverage and greater accessibility are still needed. The current review provides a more comprehensive summary, covering research from 1955 to the present year. Oxyresveratrol occurs in both gymnosperms and angiosperms. However, it has never been reported in plants in the subclass Sympetalae, and this point might be of both chemotaxonomic and biosynthetic importance. Oxyresveratrol can be easily obtained from plant materials by conventional methods, and several systems for both qualitative and quantitative analysis of oxyresveratrol contents in plant materials and plant products are available. Oxyresveratrol possesses diverse biological and pharmacological activities such as the inhibition of tyrosinase and melanogenesis, antioxidant and anti-inflammatory activities, and protective effects against neurological disorders and digestive ailments. However, the unfavorable pharmacokinetic properties of oxyresveratrol, including low water solubility and poor oral availability and stability, have posed challenges to its development as a useful therapeutic agent. Recently, several delivery systems have emerged, with promising outcomes that may improve chances for the clinical study of oxyresveratrol.

Formulation and evaluation of a α-linolenic acid and vitamin E succinate microemulsion with low surfactant content and free of co-surfactant for use as a nutritional supplement

Herein, we have designed an alcohol-free and low-surfactant microemulsion to safely and effectively supply α-linolenic acid (ALA) and vitamin E (VE). Ternary phase diagrams show that the use of medium- or short-chain alcohols as the co-surfactant (CoS) was unfavorable for the formation of the ALA microemulsion due to the competitive hydrogen bonding effect and vitamin E succinate (VES) significantly increased the ALA microemulsion region by improving the hydrophilicity of the oil phase. The optimal microemulsion formulation (M_av) was 6.86% ALA, 1.14% VES, 12% surfactant and 80% water, with uniformly dispersed spherical particles with diameters of ~ 25.41 nm and viscosity of 35.17 mPa·s. The M_av was stable to high temperature, ionic strength and pH, and exhibited good physical and anti-oxidation stability. The M_av facilitated the release and hydrolysis of VES, indicating that the CoS-free microemulsion with low surfactant content is promising for the safe and effective supply of ALA and VE.

Role of Resveratrol in Regulating Cutaneous Functions

Protective role of the skin is against external insults and maintenance of electrolyte homeostasis of the body. Cutaneous dysfunction can account for the development of both cutaneous and systemic disorders. Thus, improvements in cutaneous functions can benefit a number of extracutaneous and cutaneous functions. Resveratrol, a natural ingredient, displays multiple benefits for various systems/organs, including the skin. The benefits of resveratrol for cutaneous functions include stimulation of keratinocyte differentiation and antimicrobial peptide expression, inhibition of keratinocyte proliferation and cutaneous inflammation, UV protection, anticancer, antiaging, and inhibition of melanogenesis. The mechanisms of action of resveratrol include activation of sirtuin 1 and nuclear factor erythroid 2-related factor 2, and inhibition of mitogen-activated protein kinase signaling. Evidence suggests that topical resveratrol could be a valuable alternative not only for daily skin care, but also for the prevention and treatment of various cutaneous disorders. This review summarizes the benefits of resveratrol for cutaneous functions.

Formation and stability of Eucommia ulmoides Oliver seed oil-loaded inverse microemulsion formed by food-grade ingredients and its antioxidant activities

Eucommia ulmoides Oliver seed oil (E.u oil) as a functional oil is rich in many natural active components such as α-linolenic acid (56% to 63%), vitamin E, aucubin, and so on. In this study, water-in-oil (W/O) microemulsions composed of Eucommia ulmoides Oliver seed oil, distilled water, a blend of Sorbitan monooleate 80 (Span 80) and Polysorbate (20) sorbitan monooleate (Tween 80), and propylene glycol were prepared for improving the compatibility of Eucommia ulmoides Oliver seed oil. Pseudoternary phase diagrams were built to illustrate the phase behavior of the microemulsions, based on hydrophilic-lipophilic balance values, cosurfactant type, the proportion of cosurfactant, and the changing environmental stress. Dynamic light scattering, transmission electron microscopy, and electrical conductivity measurements were performed to characterize the microstructural aspects. The optimum process conditions at which the Eucommia ulmoides Oliver seed oil-loaded microemulsion had good tolerance to pH and salinity were: Propylene glycol served as cosurfactant, water-Propylene glycol, and Span 80-Tween 80 ratios separately kept constant at 1:1 and 6:4. These microemulsions with narrow size distribution, nanoscale particle size (below 60 nm), transparent appearance had a wide range of oil phase content and free-radical scavenging capacity toward DPPH and ABTS radicals with half-maximal inhibitory concentration (IC₅₀ ) values of 49.20 and 33.43 mg/mL, respectively. PRACTICAL APPLICATION: This nanostructure, environmental stability, and antioxidant activity of microemulsions containing Eucommia ulmoides Oliver seed oil is a potential delivery system as an alternative to α-linolenic acid and can be used for the delivery of peptides, proteins, antioxidants, and water-soluble nutrients.

Artocarpus lakoocha Extract Inhibits LPS-Induced Inflammatory Response in RAW 264.7 Macrophage Cells

Artocarpus lakoocha Roxb. (AL) has been known for its high content of stilbenoids, especially oxyresveratrol. AL has been used in Thai traditional medicine for centuries. However, the role of AL in regulating inflammation has not been elucidated. Here we investigated the molecular mechanisms underlying the anti-inflammation of AL ethanolic extract in RAW 264.7 murine macrophage cell line. The HPLC results revealed that this plant was rich in oxyresveratrol, and AL ethanolic extract exhibited anti-inflammatory properties. In particular, AL extract decreased lipopolysaccharide (LPS)-mediated production and secretion of cytokines and chemokine, including IL-6, TNF-α, and MCP-1. Consistently, the extract inhibited the production of nitric oxide (NO) in the supernatants of LPS-stimulated cells. Data from the immunofluorescence study showed that AL extract suppressed nuclear translocation of nuclear factor-kappa B (NF-κB) upon LPS induction. Results from Western blot analysis further confirmed that AL extract strongly prevented the LPS-induced degradation of IκB which is normally required for the activation of NF-κB. The protein expression of iNOS and COX-2 in response to LPS stimulation was significantly decreased with the presence of AL extract. AL extract was found to play an anti-inflammatory role, in part through inhibiting LPS-induced activation of Akt. The extract had negligible impact on the activation of mitogen-activated protein kinase (MAPK) pathways. Specifically, incubation of cells with the extract for only 3 h demonstrated the rapid action of AL extract on inhibiting the phosphorylation of Akt, but not ERK1/2. Longer exposure (24 h) to AL extract was required to mildly reduce the phosphorylation of ERK1/2, p38, and JNK MAPKs. These results indicate that AL extract manipulates its anti-inflammatory effects mainly through blocking the PI3K/Akt and NF-κB signal transduction pathways. Collectively, we believe that AL could be a potential alternative agent for alleviating excessive inflammation in many inflammation-associated diseases.

Biomedical applications of microemulsion through dermal and transdermal route

Microemulsions are thermodynamically stable, transparent, colloidal drug carrier system extensively used by the scientists for effective drug delivery across the skin. It is a spontaneous isotropic mixture of lipophilic and hydrophilic substances stabilized by suitable surfactant and co-surfactant. The easy fabrication, long-term stability, enhanced solubilization, biocompatibility, skin-friendly appearance and affinity for both the hydrophilic and lipophilic drug substances make it superior for skin drug delivery over the other carrier systems. The topical administration of most of the active compounds is impaired by limited skin permeability due to the presence of skin barriers. In this sequence, the microemulsion represents a cost-effective and convenient drug carrier system which successfully delivers the drug to and across the skin. In the present review work, we compiled various attempts made in last 20 years, utilizing the microemulsion for dermal and transdermal delivery of various drugs. The review emphasizes the potency of microemulsion for topical and transdermal drug delivery and its effect on drug permeability.

Oxyresveratrol prevents murine H22 hepatocellular carcinoma growth and lymph node metastasis via inhibiting tumor angiogenesis and lymphangiogenesis

The purpose of this study was to investigate the effects and mechanisms of oxyresveratrol (Oxyres) on hepatocellular carcinoma (HCC) in vitro and in vivo. The MTT and Transwell assays were performed to investigate the effects of Oxyres on cell proliferation and migration of two HCC cell lines, QGY-7701 and SMMC-7721 cells. H22 cells were subcutaneously injected into hind foot pads of 70 male mice to establish a lymph node metastasis model. These mice were randomly divided into seven groups as follows, control group, HCC group, Oxyres 20 mg/kg group, Oxyres 40 mg/kg group, Oxyres 60 mg/kg group, Resveratrol (Res) group, and Adriamycin (ADM) group. Oxyres, Res, and ADM were intraperitoneally injected daily for consecutive 21 days. Tumors and popliteal lymph node were isolated and embedded for histology analysis. Expressions of CD31 and vascular endothelial growth factor receptor-3 (VEGFR3) in tumors were detected by immunohistocehmistry. Expressions of vascular endothelial growth factor C (VEGF-C) were measured by Western blot. Oxyres significantly inhibited the proliferation and migration of QGY-7701 and SMMC-7721 cells. Oxyres significantly inhibited tumor growth (p < 0.001) and metastasis to sentinel lymph nodes (70%) in a dose-dependent manner. Oxyres showed a similar inhibition rate as Res. Oxyres also significantly decreased micro-blood vessel density and micro-lymphatic vessel density in tumors (p < 0.05). Expressions of CD31, VEGFR3, and VEGF-C of tumors were also inhibited by Oxyres (p < 0.05). Oxyres exerts anti-tumor effects against HCC through inhibiting both angiogenesis and lymph node metastasis, which suggests Oxyres be a potential therapeutic agent.

The effects of oxyresveratrol abrogates inflammation and oxidative stress in rat model of spinal cord injury

Oxyresveratrol and its glycoside are important natural active materials. As an effective tyrosine kinase inhibitor, oxyresveratrol may prevent herpes virus infection, inflammation and oxidative stress, as well as protect nerves. In addition, it is known to inhibit cell apoptosis following cerebral ischemia. In recent years, oxyresveratrol and its glycoside have been widely investigated, and their useful biological activities have been explored, indicating that they may be worthy of further comprehensive research. The aim of the present study was to evaluate the photoprotective effects of oxyresveratrol and its ability to abrogate inflammation and oxidative stress in a rat model of spinal cord injury (SCI). The authors identified that oxyresveratrol significantly reversed the SCI‑induced inhibition of Basso, Beattie, and Bresnahan scores, inhibited the SCI‑mediated increase in spinal cord water content, significantly suppressed SCI‑induced nuclear factor‑κB/p65, tumor necrosis factor‑α, interleukin (IL)‑1β and IL‑6 activities and reversed the malondialdehyde, superoxide dismutase, glutathione (GSH) and GSH peroxidase activities in SCI rats. SCI‑induced granulocyte‑macrophage colony‑stimulating factor (GM‑CSF), inducible nitric oxide synthase (iNOS) and cyclo‑oxygenase‑2 (COX‑2) protein expression was significantly suppressed by oxyresveratrol, and SCI‑mediated inhibition of nuclear factor (erythroid‑derived 2)‑like 2 (Nrf2) protein expression was significantly increased by oxyresveratrol. In conclusion, these results suggest that the effects of oxyresveratrol restores SCI, and abrogates inflammation and oxidative stress in rat model of SCI via the GM‑CSF, iNOS, COX‑2 and Nrf2 signaling pathway.

Enhancement of the solubility and antioxidant capacity of α-linolenic acid using an oil in water microemulsion

The applications of α-linolenic acid (ALA) in the food industry are restricted due to its poor water solubility and antioxidant stability. This study concentrates on developing an ALA-loaded microemulsion (ALA-ME) to enhance its solubility and antioxidant capacity. The formulation of the microemulsion was investigated based on pseudoternary phase diagrams. The ALA-ME was characterized by using electrical conductivity, viscosity and transmission electron microscopy (TEM). The microstructure of the ALA-ME was probed using nuclear magnetic resonance (¹H-NMR). The results proved that ALA-ME consisted of spheroidal droplets with 20-40 nm diameter. A structural transformation from water in oil (W/O) to oil in water (O/W) occurred, as seen from the electrical conductivity determination. The ¹H-NMR results revealed a transition of the ALA position encapsulated from the core area of the microemulsion to the lipophilic layer of the surfactant. Furthermore, two microstructural models of ALA-ME were proposed. The antioxidant evaluation demonstrated that the ALA antioxidant capacity in microemulsions was enhanced to about 80% compared with that of ALA in oil solution.

Testing of resveratrol microemulsion photostability and protective effect against UV induced oxidative stress

Resveratrol is well known for its antioxidant activity and susceptibility to ultraviolet radiation. Development of formulations providing improved stability and relevant drug delivery of resveratrol is still a challenging task. The aim of this study was to determine protective characteristics of formulated microemulsions by evaluating photoisomerization of resveratrol and to investigate the effects of resveratrol on human keratinocyte cells under oxidative stress caused by ultraviolet radiation. Incorporation of resveratrol into microemulsions resulted in increased photostability of active compounds and the results demonstrated that photodegradation of resveratrol was significantly delayed. Results of biopharmaceutical evaluation in vitro demonstrated that up to 60 % of resveratrol was released from microemulsions within 6 hours under a constant release rate profile. In vivo biological testing confirmed the ability of resveratrol to protect cells from oxidative stress and to increase cell viability. It was concluded that microemulsions might be considered in the development of UV light sensitive compounds.

Oxyresveratrol and ascorbic acid O/W microemulsion: Preparation, characterization, anti-isomerization and potential application as antibrowning agent on fresh-cut lotus root slices

The purpose of this study is to prepare an oxyresveratrol (Oxy) microemulsion (ME) with improved Oxy's solubility and stability and to investigate its antibrowning effects on fresh-cut lotus root slices. The formula of OxyME consisted of ethyl butyrate, Tween 80, PEG400, and water with w/w of 4%, 10.67%, 5.33%, and 80%, respectively. Encapsulating Oxy into OxyME greatly increased its solubility and stability compared with that of in water. Strong antibrowning effects were observed on fresh-cut lotus root slices treated with OxyME, even better than 4-hexylresorcinol. The addition of ascorbic acid (VC) into OxyME greatly improved the Oxy stability in long-term storage and antibrowning effects on fresh-cut lotus root slices. However, the simultaneous addition of calcium chloride and VC did not obviously improve the antibrowning effects compared with the addition of VC alone. These results indicated that Oxy+VCME may be suitable as an antibrowning agent for fresh-cut vegetables.

Influence of surfactants in self-microemulsifying formulations on enhancing oral bioavailability of oxyresveratrol: Studies in Caco-2 cells and in vivo

Self-microemulsifying drug delivery systems (SMEDDS) containing two types (Tween80 and Labrasol) and two levels (low; 5% and high; 15%) of co-surfactants were formulated to evaluate the impact of surfactant phase on physical properties and oral absorption of oxyresveratrol (OXY). All formulations showed a very rapid release in the simulated gastric fluid (SGF) pH 1.2. After dilution with different media, the microemulsion droplet sizes of the Tween80-based (∼26 to 36 nm) were smaller than that of the Labrasol-based systems (∼34 to 45 nm). Both systems with high levels of surfactant increased the Caco-2 cells permeability of OXY compared to those with low levels of surfactant (1.4-1.7 folds) and the unformulated OXY (1.9-2.0 folds). It was of interest, that there was a reduction (4.4-5.3 folds) in the efflux transport of OXY from both systems compared to the unformulated OXY. The results were in good agreement with the in vivo absorption studies of such OXY-formulations in rats. Significantly greater values of Cmax and AUC(0-10h) (p<0.05) were obtained from the high levels of Tween80-based (F(r,0-10h) 786.32%) compared to those from the Labrasol-based system (F(r,0-10h) 218.32%). These finding indicate the importance of formulation variables such as type and quantity of surfactant in the SMEDDS to enhance oral drug bioavailability.

Design and Formulation of Optimized Microemulsions for Dermal Delivery of Resveratrol

The objective of this study was to formulate optimal formulations of microemulsions (MEs) and evaluate their feasibility for delivery of resveratrol into human skin ex vivo. Oil-in-water MEs were formulated using surfactant (S) PEG-8 caprylic/capric glycerides and cosurfactant (CoS) polyglyceryl-6-isostearate. Ethyl oleate was used as an oily phase. MEs were formulated using 5 : 1, 6 : 1, and 7 : 1 surfactant and cosurfactant (S : CoS) weight ratios. Pseudoternary phase diagrams were constructed and optimal compositions of MEs were obtained using Design Expert software. Mean droplet size for optimized ME formulations was determined to be 68.54 ± 1.18 nm, 66.08 ± 0.16 nm, and 66.66 ± 0.56 nm for systems with S : CoS weight ratios 5 : 1, 6 : 1, and 7 : 1, respectively. Resveratrol loading resulted in mean droplet size increase. The distribution of droplet size between fractions changed during storage of formulated MEs. Results demonstrated the increase of number of droplets and relative surface area when S : CoS weight ratios were 6 : 1 and 7 : 1 and the decrease when S : CoS weight ratio was 5 : 1. The highest penetration of resveratrol into the skin ex vivo was determined from ME with S : CoS weight ratio 5 : 1. It was demonstrated that all MEs were similar in their ability to deliver resveratrol into the skin ex vivo.

Nanostructures for the Inhibition of Viral Infections

Multivalent interactions are omnipresent in biology and confer biological systems with dramatically enhanced affinities towards different receptors. Such multivalent binding interactions have lately been considered for the development of new therapeutic strategies against bacterial and viral infections. Multivalent polymers, dendrimers, and liposomes have successfully targeted pathogenic interactions. While a high synthetic effort was often needed for the development of such therapeutics, the integration of multiple ligands onto nanostructures turned to be a viable alternative. Particles modified with multiple ligands have the additional advantage of creating a high local concentration of binding molecules. This review article will summarize the different nanoparticle-based approaches currently available for the treatment of viral infections.

Preparation, characterization, and preliminary antibrowning evaluations of norartocarpetin microemulsions

Norartocarpetin is a flavone widely distributed in Moraceae plants with strong tyrosinase inhibitory activity. However, its poor solubility in aqueous systems and in food grade solvents (oils) limits its extensive applications. The aim of this study was to improve the solubility of norartocarpetin by developing an oil-in-water (o/w) microemulsion with food grade components. A microemulsion was developed and characterized, and its chemical and physical stabilities were also evaluated within 8 weeks. Using the construction of pseudoternary phase diagrams, the optimized formulation of 2% w/w of ethyl oleate, 12% w/w of Tween 80, 6% w/w of polyethylene glycol 400, and 80% w/w of water was obtained, with a maximum solubility of norartocarpetin up to 1.73 ± 0.21 mg/mL, at least a 1000-fold increase in solubility. The microemulsion base and norartocarpetin-loaded microemulsion were demonstrated to be stable after accelerated and long-term conditions (8 weeks). The norartocarpetin microemulsion still showed strong tyrosinase inhibitory activity and antibrowning effect on fresh-cut apple slices. These combined results indicated that norartocarpetin microemulsion may be suitable as an antibrowning agent for fresh-cut fruits.