Acetal derivatives as prodrugs of resveratrol

Therapeutic Potential of Resveratrol and Lignans in the Management of Tuberculosis

This study aims to investigate the therapeutic potential of herbal remedies, specifically resveratrol and lignans, as alternative treatments for tuberculosis (TB), given the challenges posed by drug-resistant strains and adverse effects of conventional therapies. A comprehensive review of the literature was conducted to analyze the mechanisms of action, safety profiles, and efficacy of resveratrol and lignans in the context of TB management. This review focused on the bactericidal and bacteriostatic effects of these compounds, examining their interaction with Mycobacterium tuberculosis within macrophages. Resveratrol and lignans were found to exhibit significant antibacterial properties through mechanisms such as SIRT1 modulation, coenzyme A transferase inhibition, suppression of intracellular bacterial proliferation in macrophages, and induction of autophagy. These mechanisms contribute to their effectiveness in combating TB and highlight their potential as alternative therapeutic agents.

Single Mutation on Trastuzumab Modulates the Stability of Antibody-Drug Conjugates Built Using Acetal-Based Linkers and Thiol-Maleimide Chemistry

Antibody-drug conjugates (ADCs) are a class of targeted therapeutics used to selectively kill cancer cells. It is important that they remain intact in the bloodstream and release their payload in the target cancer cell for maximum efficacy and minimum toxicity. The development of effective ADCs requires the study of factors that can alter the stability of these therapeutics at the atomic level. Here, we present a general strategy that combines synthesis, bioconjugation, linker technology, site-directed mutagenesis, and modeling to investigate the influence of the site and microenvironment of the trastuzumab antibody on the stability of the conjugation and linkers. Trastuzumab is widely used to produce targeted ADCs because it can target with high specificity a receptor that is overexpressed in certain breast cancer cells (HER2). We show that the chemical environment of the conjugation site of trastuzumab plays a key role in the stability of linkers featuring acid-sensitive groups such as acetals. More specifically, Lys-207, located near the reactive Cys-205 of a thiomab variant of the antibody, may act as an acid catalyst and promote the hydrolysis of acetals. Mutation of Lys-207 into an alanine or using a longer linker that separates this residue from the acetal group stabilizes the conjugates. Analogously, Lys-207 promotes the beneficial hydrolysis of the succinimide ring when maleimide reagents are used for conjugation, thus stabilizing the subsequent ADCs by impairing the undesired retro-Michael reactions. This work provides new insights for the design of novel ADCs with improved stability properties.

Outstanding flame retardancy for poly(vinyl alcohol) achieved using a resveratrol/tannic acid complex

Resveratrol/tannic acid-poly(vinyl alcohol) (RETA-PVA) blends have been prepared by compression molding using poly(vinyl alcohol), tannic acid and resveratrol as raw materials. The effects of different resveratrol/tannic acid ratios on the flammability of RETA-PVA blends have been studied. The flammability of the RETA-PVA blends was assessed using cone calorimetry, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Results indicate that RETA-PVA molecules occur through hydrogen bonding and RETA-PVA blends are amorphous. The glass transition temperature for RETA-PVA-2 is the highest among all blends and the peak of heat release rate and smoke production rate for RETA-PVA is 38.4% and 43.9% lower than that for PVA, respectively. With the addition of resveratrol, the residual amount of RETA-PVA after complete combustion is greatly increased, to 30 times that for PVA, indicating that RETA-PVA blends display excellent flame retardant properties.

The rigid molecular structure of biobased resveratrol/tannic acid (RETA) complex increases the residual amount of RETA-poly(vinyl alcohol) after complete combustion.

Modular ketal-linked prodrugs and biomaterials enabled by organocatalytic transisopropenylation of alcohols

Isopropenyl ethers are critical intermediates for accessing medicinally valuable ketal-based prodrugs and biomaterials, but traditional approaches for the synthesis of isopropenyl ethers suffer from poor functional group compatibility and harsh reaction conditions. Here, we develop an organocatalytic transisopropenylation approach to solve these challenges, enabling the synthesis of isopropenyl ethers from various hydroxyl-group-containing small-molecule drugs, polymers, and functional building blocks. The method provides a straightforward and versatile synthesis of isopropenyl ethers, features excellent tolerance of diverse functional groups, applies to a wide range of substrates, and allows scalable synthesis. The development of this organocatalytic transisopropenylation approach enables access to modular preparation of various acid-sensitive ketal-linked prodrugs and functionalized ketalated biomaterials. We expect our syntheses and transformations of isopropenyl ethers will find utility in several diverse fields, including medicinal chemistry, drug delivery, and biomaterials.

Isopropenyl ethers (IPPEs) are essential intermediates for obtaining ketal-based prodrugs and biomaterials, but traditional approaches for their synthesis are limited by poor functional group compatibility and harsh reaction conditions. Here, the authors report an organocatalytic transisopropenylation approach for IPPE synthesis in mild reaction conditions and with wide range of substrates, and use it to prepare acid-sensitive ketal-linked prodrugs and biomaterials.

C=C Bond Oxidative Cleavage of BODIPY Photocages by Visible Light

Photocages for protection and the controlled release of bioactive compounds have been widely investigated. However, the vast majority of these photocages employ the cleavage of single bonds and high-energy ultraviolet light. The construction of a photoactivation system that uses visible light to cleave unsaturated bonds still remains a challenge. Herein, we report a regioselective oxidative cleavage of C=C bonds from a boron-dipyrrolemethene (BODIPY)-based photocage by illumination at 630 nm, resulting in a free aldehyde and a thiol fluorescent probe. This strategy was demonstrated in live HeLa cells, and the generated α-formyl-BODIPY allowed real-time monitoring of aldehyde release in the cells. In particular, it is shown that a mannose-functionalized photocage can target HepG2 cells.

An Overview on Dietary Polyphenols and Their Biopharmaceutical Classification System (BCS)

Polyphenols are natural organic compounds produced by plants, acting as antioxidants by reacting with ROS. These compounds are widely consumed in daily diet and many studies report several benefits to human health thanks to their bioavailability in humans. However, the digestion process of phenolic compounds is still not completely clear. Moreover, bioavailability is dependent on the metabolic phase of these compounds. The LogP value can be managed as a simplified measure of the lipophilicity of a substance ingested within the human body, which affects resultant absorption. The biopharmaceutical classification system (BCS), a method used to classify drugs intended for gastrointestinal absorption, correlates the solubility and permeability of the drug with both the rate and extent of oral absorption. BCS may be helpful to measure the bioactive constituents of foods, such as polyphenols, in order to understand their nutraceutical potential. There are many literature studies that focus on permeability, absorption, and bioavailability of polyphenols and their resultant metabolic byproducts, but there is still confusion about their respective LogP values and BCS classification. This review will provide an overview of the information regarding 10 dietarypolyphenols (ferulic acid, chlorogenic acid, rutin, quercetin, apigenin, cirsimaritin, daidzein, resveratrol, ellagic acid, and curcumin) and their association with the BCS classification.

Stimulus-cleavable chemistry in the field of controlled drug delivery

This review comprehensively summarises stimulus-cleavable linkers from various research areas and their cleavage mechanisms, thus provides an insightful guideline to extend their potential applications to controlled drug release from nanomaterials.

Acid-sensitive PEGylated paclitaxel prodrug nanoparticles for cancer therapy: Effect of PEG length on antitumor efficacy

Paclitaxel is one of the most widely used anticancer agents, but strong side effects and low bioavailability limit its clinical efficacy. The use of tumor microenvironment-responsive prodrugs is promising to solve these problems, and a smart linkage is crucial to achieve the efficient release of paclitaxel from such prodrugs in tumor. Herein, an acid-responsive acetone-based acyclic ketal linkage is used to construct paclitaxel prodrugs with different length of poly(ethylene glycol) (PEG). The PEGylated acetone-based acyclic-ketal-linked prodrugs of paclitaxel (PKPs) self-assembled into nanoparticles that were stable in normal physiological environment but released paclitaxel rapidly in mildly acidic environment in tumor. The length of PEG had considerable impact on size and critical micelle concentration of PKP nanoparticles, thereby affecting prodrug hydrolysis kinetics, pharmacokinetics, biodistribution, and antitumor activity for PKP nanoparticles. In an A2780 xenograft mouse model, PKP nanoparticles displayed improved pharmacokinetics and superior antitumor efficacy against Taxol. Our results demonstrate that acyclic-ketal-based prodrugs are useful for the development of acid-responsive anticancer nanomedicines.

Application of nano/microencapsulated phenolic compounds against cancer

Nowadays, polyphenols as bioactive compounds are being used in producing anti-cancer drugs. Low stability against harsh environmental conditions, untargeted release, low solubility, and low absorption of pure phenolic molecules are significant barriers, which decrease the functions of polyphenols. Recently, the nanoencapsulation processes have been applied to overcome these restrictions, in which the anti-cancer activity of polyphenols has been noticeably increased. This review will focus on the anti-cancer activity of polyphenols, and the effect of loading polyphenolics into various micro/nanoencapsulation systems on their anti-cancer activity. Different encapsulation systems such as lipid and polymer based nanoparticles, and solid form of encapsulated phenolic molecules by nano-spray dryer and electrospinnig have been used for loading of polyphenols. Incorporation of phenolic molecules into various carriers inevitably increases their anti-cancer activity. Because, in this way, encapsulated cargos can provide a targeted release, which will increase the bioavailability of phenolic molecules and their functions such as absorption into cancer cell.

Microencapsulation as a tool to counteract the typical low bioavailability of polyphenols in the management of diabetes

Polyphenols are secondary metabolites widely distributed in many plant foods, such a tea, coffee, chocolate and fruits. The consumption of these compounds is related to the improvement or amelioration of many diseases, including diabetes. Nevertheless, the great barrier to the therapeutic use of polyphenols is the low bioavailability of these compounds once ingested. For that reason, the encapsulation of polyphenols in different matrices may protect them from digestion and improve their release and subsequent absorption to obtain target-specific health effects. Some studies have reported the beneficial effect of encapsulation to increase both bioavailability and bioaccessibility. However, these works have mostly been carried out in vitro and few studies are specifically addressed at improving diabetes. In the current work, an overview of the knowledge related to nanoparticles and their use in the diabetic condition has been reviewed.

Strategies to Improve Resveratrol Systemic and Topical Bioavailability: An Update

In recent years, a great deal of attention has been paid to natural compounds due to their many biological effects. Polyphenols are a class of plant derivatives that have been widely investigated for preventing and treating many oxidative stress-related pathological conditions, such as neurodegenerative and cardiovascular diseases, cancer, diabetes mellitus and inflammation. Among these polyphenols, resveratrol (RSV) has attracted considerable interest owing to its high antioxidant and free radical scavenging activities. However, the poor water solubility and rapid metabolism of RSV lead to low bioavailability, thus limiting its clinical efficacy. After discussing the main biochemical mechanisms involved in RSV biological activities, this review will focus on the strategies attempted to improve RSV effectiveness, both for systemic and for topical administration. In particular, technological approaches involving RSV incorporation into different delivery systems such as liposomes, polymeric and lipid nanoparticles, microemulsions and cyclodextrins will be illustrated, highlighting their potential clinical applications. In addition, chemical modifications of this antioxidant aimed at improving its physicochemical properties will be described along with the results of in vitro and in vivo studies.

Folic acid functionalized nanoparticles as pharmaceutical carriers in drug delivery systems

Conventional chemotherapeutic approaches in cancer therapy such as surgery, chemotherapy, and radiotherapy have several disadvantages due to their nontargeted distributions in the whole body. On the other hand, nanoparticles (NPs) based therapies are remarkably progressing to solve several limitations of conventional drug delivery systems (DDSs) including nonspecific biodistribution and targeting, poor water solubility, weak bioavailability and biodegradability, low pharmacokinetic properties, and so forth. The enhanced permeability and retention effect escape from P-glycoprotein trap in cancer cells as a passive targeting mechanism, and active targeting strategies are also other most important advantages of NPs in cancer diagnosis and therapy. Folic acid (FA) is one of the biologic molecules which has been targeted overexpressed-folic acid receptor (FR) on the surface of cancer cells. Therefore, conjugation of FA to NPs most easily enhances the FR-mediated targeting delivery of therapeutic agents. Here, the recent works in FA which have been decorated NPs-based DDSs are discussed and cancer therapy potency of these NPs in clinical trials are presented.

Preparation and in vitro performance evaluation of resveratrol for oral self-microemulsion

The purpose of this study was to improve the solubility of resveratrol (Res) by a self-microemulsifying drug-delivery system (SMEDDS). Through a solubility experiment, the pseudoternary phase diagram and ternary phase diagram were used to optimize the Res SMEDDS formula. The optimum formulation consisted of 5% IPM, 20% PEG400, and 65% Cremophor RH40. The water solubility, stability, in vitro release and antioxidant activity of the Res SMEDDS were characterized. The Res solubility in the SMEDDS was at least 1,000 times compared to that in water. The average droplet size of the microemulsion was 28.00±1.67 nm and uniform distribution. The Res SMEDDS should be stored at low temperature and in the dark to avoid light conditions. Res SMEDDS was able to improve the in vitro release rate of Res, and the in vitro release of Res from Res SMEDDS was significantly faster that of Res powder and unaffected by pH value of media. Antioxidant assays showed that antioxidant activities of Res in Res SMEDDS were unaffected compared to Res powder. Cytotoxicity study indicated that Res SMEDDS at the concentration of less than 100 μM was safe. These results demonstrated the potential use of Res SMEDDS for oral administration of Res.

Studies of the Catalytic Activity of Iron (III) Porphyrins for the Protection of Carbonyl Groups in Homogeneous Media

The protection of carbonyl groups that produce acetal products is a key reaction in fine chemistry due to the high reactivity of aldehydes and ketones in certain media. This process can be catalyzed by protic or Lewis acids. Since metalloporphyrins often possess free axial positions in the central metal, they can be applied as Lewis acid catalysts, allowing the additional coordination of substrates. Therefore, three ferric complexes were selected to be evaluated as catalysts for the acetalization of benzaldehyde with ethanol and triethyl orthoformate (TEOF) in the homogeneous phase: (i) 5,10,15,20-tetrakis(phenylporphyrin) iron (III) chloride (Fe0F); (ii) 5,10,15,20-tetrakis(2,6-difluorphenylporphyrin) iron (III) chloride (Fe2F); and (iii) 5,10,15,20-tetrakis(pentafluorphenylporphyrin) iron (III) chloride (Fe5F). The complex Fe5F showed the highest catalytic activity, and kinetic parameters were evaluated for this reaction, exhibiting an increasing rate of reaction of about 550-fold in comparison with the non-catalyzed reaction. The reaction scope was also investigated, and Fe5F was found to be active for the acetalization of benzaldehyde and acetophenone, with different protective agents such as alcohols, glycols, glycerol, and epoxide being selective for the formation of cyclic acetals. The protection of benzaldehyde with ethylene glycol and propylene glycol were also studied at different temperatures, and turnover frequency (TOF) values of up to 360 h−1 were determined at 40 °C in homogenous media without the need for solvent or drying agents.

SULFATION PATHWAYS: Potential benefits of a sulfated resveratrol derivative for topical application

Resveratrol (RSV) is a polyphenolic compound with antioxidant, anti-inflammatory and anti-aging properties partly associated with sirtuin 1 (SIRT1)-activation in the skin. However, poor water solubility may limit RSV efficacy. This work aimed to clarify the interest of a new synthetic water-soluble RSV derivative (resveratrol glucoside sulfate, RSV-GS) for topical application. Resveratrol glucoside sulfate was synthesized using microwave-assisted sulfation. Cytotoxicity assays were performed with the keratinocyte HaCaT cell line, using MTT reduction, neutral red uptake, Alamar Blue/resazurin reduction, trypan blue exclusion and measurement of ATP concentration. Western blotting was used to evaluate SIRT1 protein content. Regarding SIRT1 binding, an in silico docking study was performed, using AutoDock Vina. Our results showed that the synthetic derivative RSV-GS was 1000 times more soluble in water than RSV and its non-sulfated glucoside. No relevant decrease in HaCaT cell viability was observed for concentrations up to 5 mM for RSV-GS, and up to 500 μM for resveratrol glucoside, while a significant decrease in HaCaT viability occurred from 100 μM for RSV. RSV-GS and RSV showed a similar behavior regarding protective effect against oxidative stress-induced cytotoxicity. SIRT1 protein content increased after treatment with 500 μM of RSV-GS and 100 μM of RSV. Moreover, in silico studies predicted that RSV-GS binds more stably to SIRT1 with a lower binding free energy than RSV. Although these results support the possible use of RSV-GS in topical formulations, in vivo safety and efficacy studies are needed before considering the use of RSV-GS in commercial products.

Rationale for assessing the therapeutic potential of resveratrol in hematological malignancies

Promising results from pre-clinical studies on the naturally-occurring polyphenol resveratrol have generated considerable interest and somewhat excessive expectations regarding the therapeutic potential of this compound for treating or preventing various diseases, including cardiovascular and neurodegenerative disorders and cancer. Resveratrol has potent inhibitory activity in vitro against various tumor types, including cell lines derived from virtually all blood malignancies. Pharmacological studies have shown that resveratrol is safe for humans but has poor bioavailability, due to its extensive hepatic metabolism. Curiously, a substantial proportion of the orally administered resveratrol can reach the bone marrow compartment. Notably, various pathways dysregulated in blood cancers are known to be molecular targets of resveratrol, thus substantiating the potential utility of this agent in blood malignancies. In this review, we primarily focus on the scientific evidence that supports the potential utility of resveratrol for the management of select hematological malignancies. In addition, potential clinical trials with resveratrol are suggested.

Oral delivery system enhanced the bioavailability of stilbenes: Resveratrol and pterostilbene

Stilbenes are a large group of compounds with the C₆ C₂ C₆ skeleton, in which two aromatic rings are connected by an ethylene bridge. Resveratrol and its structural analog, pterostilbene, are by far the two most widely researched stilbenes in terms of their beneficial bioactivities. However, the bioefficacy of these compounds is greatly reduced when consumed orally due to their poor aqueous solubility, which leads to poor bioavailability. To overcome the limitation, strategies improving their solubility, absorption, and systemic concentration were applied when designing a suitable edible delivery system. This review will summarize the findings from the studies evaluating the oral bioavailability of stilbenes with emphasize on the resveratrol and pterostilbene. It will also include the edible delivery systems currently available and their effect on the oral bioavailability. © 2018 BioFactors, 44(1):5-15, 2018.

Gnetin-C and other resveratrol oligomers with cancer chemopreventive potential

Resveratrol has been extensively studied to investigate its biological effects, including its chemopreventive potential against cancer. Over the past decade, various resveratrol oligomers, both naturally occurring and synthetic, have been described. These resveratrol oligomers result from the polymerization of two or more resveratrol units to form dimers, trimers, tetramers, or even more complex derivatives. Some oligomers appear to have antitumor activities that are similar or superior to monomeric resveratrol. In this review, we discuss resveratrol oligomers with anticancer potential, with emphasis on well-characterized compounds, such as the dimer gnetin-C and other oligomers from Gnetum gnemon, whose safety, pharmacokinetic, and biological activities have been studied in humans.

Resveratrol derivatives as a pharmacological tool

Prodrugs of resveratrol are under development. Among the long-term goals, still largely elusive, are (1) modulating physical properties (e.g., water-soluble derivatives bearing polyethylene glycol chains), (2) changing distribution in the body (e.g., galactosyl derivatives restricted to the intestinal lumen), (3) increasing absorption from the gastrointestinal tract (e.g., derivatives imitating the natural substrates of endogenous transporters), and (4) hindering phase II metabolism (e.g., temporarily blocking the hydroxyls), all contributing to (5) increasing bioavailability. The chemical bonds that have been tested for functionalization include carboxyester, acetal, and carbamate groups. A second approach, which can be combined with the first, seeks to reinforce or modify the biochemical activities of resveratrol by concentrating the compound at specific subcellular sites. An example is provided by mitochondria-targeted derivatives. These proved to be pro-oxidant and cytotoxic in vitro, selectively killing fast-growing and tumor cells when supplied in the low micromolar range. This suggests the possibility of anticancer applications.

Nanoparticle formulations to enhance tumor targeting of poorly soluble polyphenols with potential anticancer properties

Polyphenols have been extensively studied for their relevant anticancer activity. Quite often however their instability, extensive metabolization, low bioavailability and poor solubility limit their application in cancer prevention and therapy. Formulation in nanoparticles has been widely proposed as a means to overcome these limits, maximize localization and specific activity at tumor site. The present review is intended as an update of literature regarding nanoparticulate carriers aimed to deliver polyphenols to the cancer site. Three molecules were chosen, all of which were hydrophobic and poorly soluble, representative of different polyphenol classes: quercetin (QT) among the flavonoid group, curcumin (CUR) as representative of curcuminoids, and resveratrol (RSV) among the stilbenes. In particular, nanoparticulate systems suitable for poorly soluble drugs will be described and attention will be paid to characteristics designed to improve tumor targeting, specific delivery and interaction with tumor cells.

Semisynthesis and biological evaluation of prenylated resveratrol derivatives as multi-targeted agents for Alzheimer's disease

A series of prenylated resveratrol derivatives were designed, semisynthesized and biologically evaluated for inhibition of β-secretase (BACE1) and amyloid-β (Aβ) aggregation as well as free radical scavenging and neuroprotective and neuritogenic activities, as potential novel multifunctional agents against Alzheimer's disease (AD). The results showed that compound 4b exhibited good anti-Aβ aggregation (IC₅₀ = 4.78 µM) and antioxidant activity (IC₅₀ = 41.22 µM) and moderate anti-BACE1 inhibitory activity (23.70% at 50 µM), and could be a lead compound. Moreover, this compound showed no neurotoxicity along with a greater ability to inhibit oxidative stress on P19-derived neuronal cells (50.59% cell viability at 1 nM). The neuritogenic activity presented more branching numbers (9.33) and longer neurites (109.74 µm) than the control, and was comparable to the quercetin positive control. Taken together, these results suggest compound 4b had the greatest multifunctional activities and might be a very promising lead compound for the further development of drugs for AD.

New natural amino acid-bearing prodrugs boost pterostilbene's oral pharmacokinetic and distribution profile

The biomedical effects of the natural phenol pterostilbene are of great interest but its bioavailability is negatively affected by the phenolic group in position 4' which is an ideal target for the conjugative enzymes of phase II metabolism. We report the synthesis and characterization of prodrugs in which the hydroxyl moiety is reversibly protected as a carbamate ester linked to the N-terminus of a natural amino acid. Prodrugs comprising amino acids with hydrophobic side chains were readily absorbed after intragastric administration to rats. The Area Under the Curve for pterostilbene in blood was optimal when prodrugs with isoleucine or β-alanine were used. The prodrug incorporating isoleucine was used for further studies to map distribution into major organs. When compared to pterostilbene itself, administration of the isoleucine prodrug afforded increased absorption, reduced metabolism and higher concentrations of pterostilbene, sustained for several hours, in most of the organs examined. Experiments using Caco-2 cells as an in vitro model for human intestinal absorption suggest that the prodrug could have promising absorption profiles also in humans; its uptake is partly due to passive diffusion, and partly mediated by H⁺-dependent transporters expressed on the apical membrane of enterocytes, such as PepT1 and OATP.

Biorelevant physicochemical profiling of (E)- and (Z)-resveratrol determined from isomeric mixtures

Biorelevant, isomer-specific physicochemical parameters of resveratrol, a multifunctional component in red wines, with cardioprotective, anti-Alzheimer and several other pharmacologic activities were determined. The parameters include site-specific basicities, lipophilicities, solubilities and diffusion constants for the two geometric isomers. The protonation equilibria of (E)- and (Z)-resveratrol were monitored by ¹H NMR-pH titrations. Five closely related auxiliary compounds ((E)-pinostilbene, (Z)-pinostilbene, (E)-pterostilbene, (Z)-pterostilbene and resorcinol) were also studied. Combining the datasets, the group-specific protonation constants of resveratrol isomers were determined. The results show that (Z)-resveratrol is more basic at every protonation site than the (E)-isomer. Lipophilicities are quantified in terms of logP values and were determined by octanol/water partition experiments and quantitative NMR spectroscopy: (E)-resveratrol was found to be more lipophilic. Since the molecular geometries of the isomers differ, diffusion ordered NMR spectroscopy (DOSY) experiments were also carried out to quantify the diffusion capabilities of the isomers: (Z)-resveratrol of bent shape has a slightly higher diffusion coefficient than its extended (E) counterpart. A striking 10-fold difference of water solubility was found in favor of the (Z) isomer, due obviously to the reduced water-repellent character in the more compact molecule. This is so far the greatest recorded solubility difference between geometric isomers of any compounds.

Enhanced colloidal stability, solubility and rapid dissolution of resveratrol by nanocomplexation with soy protein isolate

The polyphenolic compound resveratrol has received significant attention due to its many pharmacological actions such as anti-cancer, anti-inflammatory, antioxidant and antimicrobial activities. However, poor solubility and stability are major impediments for resveratrol's clinical effectiveness. In this work we have encapsulated resveratrol into soy protein isolate nanoparticles using a simple rotary evaporation technique. Resveratrol-loaded nanoparticles were around 100nm in diameter and negatively charged. Nano-encapsulated resveratrol was found to be in amorphous form and showed more than two times higher solubility with significantly increased dissolution when compared to free resveratrol. Finally, an in-vitro NF-κB inhibition assay revealed that encapsulated resveratrol was stable and retained bioactivity. This new formulation of resveratrol has the potential to boost the clinical effectiveness of this drug and could be utilised for other poorly soluble hydrophobic drugs.

Resveratrol cocrystals with enhanced solubility and tabletability

Two new 1:1 cocrystals of resveratrol (RES) with 4-aminobenzamide (RES-4ABZ) and isoniazid (RES-ISN) were synthesized by liquid assisted grinding (LAG) and rapid solvent removal (RSR) methods using ethanol as solvent. Their physiochemical properties were characterized using PXRD, DSC, solid state and solution NMR, FT-IR, and HPLC. Pharmaceutically relevant properties, including tabletability, solubility, intrinsic dissolution rate, and hygroscopicity, were evaluated. Temperature-composition phase diagram for RES-ISN cocrystal system was constructed from DSC data. Both cocrystals show higher solubility than resveratrol over a broad range of pH. They are phase stable and non-hygroscopic even under high humidity conditions. Importantly, both cocrystals exhibit improved solubility and tabletability compared with RES, which make them more suitable candidates for tablet formulation development.

Electrosprayed nanocomposites based on hyaluronic acid derivative and Soluplus for tumor-targeted drug delivery

Nanocomposite (NC) based on hyaluronic acid-ceramide (HACE) and Soluplus (SP) was fabricated by electrospraying for the tumor-targeted delivery of resveratrol (RSV). Amphiphilic property of both HACE and SP has been used to entrap RSV in the internal cavity of NC. Electrospraying with established experimental conditions produced HACE/SP/RSV NC with 230nm mean diameter, narrow size distribution, negative zeta potential, and >80% drug entrapment efficiency. Sustained and pH-dependent drug release profiles were observed in drug release test. Cellular uptake efficiency of HACE/SP NC was higher than that of SP NC, mainly based on HA-CD44 receptor interaction, in MDA-MB-231 (CD44 receptor-positive human breast cancer) cells. Selective tumor targetability of HACE/SP NC, compared to SP NC, was also confirmed in MDA-MB-231 tumor-xenograted mouse model using a near-infrared fluorescence (NIRF) imaging. According to the results of pharmacokinetic study in rats, decreased in vivo clearance and increased half-life of RSV in NC group, compared to drug solution group, were shown. Given that these experimental results, developed HACE/SP NC can be a promising theranostic nanosystem for CD44 receptor-expressed cancers.

Doxorubicin-loaded pH-sensitive polymeric blends for synergistic cancer treatment

An intelligentized system that can transport chemotherapeutics to targets in tumors is an attractive strategy to reverse drug resistance in tumor cells.

Dual-responsive star-shaped polypeptides for drug delivery

Core cross-linked star-shaped polypeptides based on poly(l-glutamic acid)-poly(l-phenylalanine-co-l-cystine) copolymer have been successfully synthesized and thoroughly characterized.

Synergistic effect of PEGylated resveratrol on delivery of anticancer drugs

Resveratrol (RES) is a natural polyphenol which can be considered as a nutraceutical because of its benefits such as anticancer and antioxidant activity. In this paper, we designed polymer-RES conjugates as anticancer drug carrier for synergistic therapeutic effect in cancer treatment. Bicalutamide (BIC) was used as a model drug to investigate the drug release behaviors and in vitro anticancer performance. PEG-RES and PEG-Glycine-RES nanoparticles were prepared and characterized. The size of the prepared particles was around 50 nm with RES content of 17.2 and 16.3 wt% for PEG-RES and PEG-Glycine-RES, respectively, and BIC loading efficiency were of 81.6% and 84.5%, separately. Release rate of RES from conjugates depended on the stability of ester group against hydrolysis. BIC release was much faster than RES release. The anticancer activity of BIC loaded PEGylated RES nanoparticles was much better than that of free BIC, indicating the conjugates provided a synergetic cytotoxicity to cancer cells. Confocal laser scanning microscopy observation and flow cytometry analyses indicated that PEGylated RES conjugates were more efficiently internalized into cells, released drug into cytoplasm. These results suggest that PEGylated RES conjugates show great potential for cancer therapy.

Improved Antioxidant Capacity of Optimization of a Self-Microemulsifying Drug Delivery System for Resveratrol

The use of nano-encapsulated resveratrol (RSV) in self-micro-emulsified drug delivery systems (SMEDDS) formulations was investigated. Self-emulsifying grading tests were used to establish the optimal ratio of oil, surfactant, and co-surfactant. The optimized system was further investigated for the droplet size and zeta potential at the different medium pH values by a Malvern Zetasizer and transmission electron microscopy (TEM). The antioxidant capacity and cytotoxicity of the formulation were detected by DCFH-DA and a CCK-8 assays. The results showed that the nano-emulsion based on ethyl oleate, Tween-80, and PEG-400 (35:40:25, w/w/w) was the most stable formulation due to the small droplet size (approximately 50 nm) and high zeta potential in a neutral environment. Furthermore, this formulation also exhibited a greater antioxidant capacity with less toxicity than free RSV. Taken together, considering these results and the simple fabrication process, this formulation could be used to deliver nutritional food supplements in a stable, efficient, and safe manner.

Amino Acid Carbamates As Prodrugs Of Resveratrol

Resveratrol (3, 5, 4′-trihydroxy-trans-stilbene), a plant polyphenol, has important drug-like properties, but its pharmacological exploitation in vivo is hindered by its rapid transformation via phase II conjugative metabolism. One approach to bypass this problem relies on prodrugs. We report here the synthesis, characterization, stability and in vivo pharmacokinetic behaviour of prodrugs of resveratrol in which the OH groups are engaged in an N-monosubstituted carbamate ester (-OC(O)NHR) linkage with a natural amino acid (Leu, Ile, Phe, Thr) to prevent conjugation and modulate the physicochemical properties of the molecule. We also report a convenient, high-yield protocol to obtain derivatives of this type. The new carbamate ester derivatives are stable at pH 1, while they undergo slow hydrolysis at physiological pH and hydrolyse with kinetics suitable for use in prodrugs in whole blood. After administration to rats by oral gavage the isoleucine-containing prodrug was significantly absorbed, and was present in the bloodstream as non-metabolized unaltered or partially deprotected species, demonstrating effective shielding from first-pass metabolism. We conclude that prodrugs based on the N-monosubstituted carbamate ester bond have the appropriate stability profile for the systemic delivery of phenolic compounds.

Enhancing delivery and cytotoxicity of resveratrol through a dual nanoencapsulation approach

Despite the known anticancer potential of resveratrol, its clinical applications are often hindered by physicochemical limitations such as poor solubility and stability. The encapsulation of resveratrol in formulations such as polymeric nanoparticles and liposomes has shown limited success. This study aimed to develop and optimize a novel drug carrier by co-encapsulating pristine resveratrol alongside cyclodextrin-resveratrol inclusion complexes in the lipophilic and hydrophilic compartments of liposomes, respectively by using a novel dual carrier approach. The particle size, polydispersity index and zeta potential of the final formulation were 131±1.30nm, 0.089±0.005 and -2.64±0.51mV, respectively. Compared to free resveratrol and conventional liposomal formulations with drug release profile of 40-60%, our novel nanoformulations showed complete (100%) drug release in 24h. The formulation was stable for 14days at 4°C. We also studied the in vitro cytotoxicity of resveratrol encapsulated liposomes in HT-29 colon cancer cell lines. The cytotoxicity profile of our liposomes was observed to be dose dependent and enhanced in comparison to free resveratrol (in DMSO). Our study demonstrates that co-encapsulation of pristine resveratrol along with its cyclodextrin complex in liposomal formulations is a plausible option for the enhanced delivery of the hydrophobic chemotherapeutic agent.

N-Monosubstituted Methoxy-oligo(ethylene glycol) Carbamate Ester Prodrugs of Resveratrol

Resveratrol is a natural polyphenol with many interesting biological activities. Its pharmacological exploitation in vivo is, however, hindered by its rapid elimination via phase II conjugative metabolism at the intestinal and, most importantly, hepatic levels. One approach to bypass this problem relies on prodrugs. We report here the synthesis, characterization, hydrolysis, and in vivo pharmacokinetic behavior of resveratrol prodrugs in which the OH groups are engaged in an N-monosubstituted carbamate ester linkage. As promoiety, methoxy-oligo(ethylene glycol) groups (m-OEG) (CH₃–[OCH₂CH₂]_n–) of defined chain length (n = 3, 4, 6) were used. These are expected to modulate the chemico-physical properties of the resulting derivatives, much like longer poly(ethylene glycol) (PEG) chains, while retaining a relatively low MW and, thus, a favorable drug loading capacity. Intragastric administration to rats resulted in the appearance in the bloodstream of the prodrug and of the products of its partial hydrolysis, confirming protection from first-pass metabolism during absorption.

Resveratrol nanoformulations: challenges and opportunities

Resveratrol, a naturally occurring polyphenol and phytoalexin, has received significant attention in recent years due to its vast therapeutic effects including anticancer, antioxidant and anti-inflammatory effects. However, poor pharmacokinetic properties such as low aqueous solubility, low photostability and extensive first pass metabolism result in poor bioavailability, hindering its immense potential. Conventional dosage forms such as dry powder capsules and injections have met with limited success, demonstrating challenges faced in developing an effective formulation. Recently, nanotechnology-based formulations (nanoformulations) are being looked upon as a novel method for improving the pharmacokinetic properties, as well as enhancing targetability and bioavailability of resveratrol. This review outlines the therapeutic potential of resveratrol, explores its mechanisms of action and pharmacokinetic limitations, and discusses the success and challenges of resveratrol-encapsulated nanoparticles in the last decade. Potential techniques to improve encapsulation of the drug within nanoparticles, thereby enhancing its clinical potential are highlighted.

Synthesis of mevalonate- and fluorinated mevalonate prodrugs and their in vitro human plasma stability

The mevalonate pathway is essential for the production of many important molecules in lipid biosynthesis. Inhibition of this pathway is the mechanism of statin cholesterol-lowering drugs, as well as the target of drugs to treat osteoporosis, to combat parasites, and to inhibit tumor cell growth. Unlike the human mevalonate pathway, the bacterial pathway appears to be regulated by diphosphomevalonate (DPM). Enzymes in the mevalonate pathway act to produce isopentenyl diphosphate, the product of the DPM decarboxylase reaction, utilize phosphorylated (charged) intermediates, which are poorly bioavailable. It has been shown that fluorinated DPMs (6-fluoro- and 6,6,6-trifluoro-5-diphosphomevalonate) are excellent inhibitors of the bacterial pathway; however, highly charged DPM and analogs are not bioavailable. To increase cellular permeability of mevalonate analogs, we have synthesized various prodrugs of mevalonate and 6-fluoro- and 6,6,6-trifluoromevalonate that can be enzymatically transformed to the corresponding DPM or fluorinated DPM analogs by esterases or amidases. To probe the required stabilities as potentially bioavailable prodrugs, we measured the half-lives of esters, amides, carbonates, acetals, and ketal promoieties of mevalonate and the fluorinated mevalonate analogs in human blood plasma. Stability studies showed that the prodrugs are converted to the mevalonates in human plasma with a wide range of half-lives. These studies provide stability data for a variety of prodrug options having varying stabilities and should be very useful in the design of appropriate prodrugs of mevalonate and fluorinated mevalonates.