Inclusion Complexation of Artemisinin with α-, β-, andγ-Cyclodextrins

α-Mangostin/γ-Cyclodextrin Inclusion Complex: Formation and Thermodynamic Study

α-Mangostin (α-M) has various biological activities, such as anti-cancer, antibacterial, anti-fungal, anti-tyrosin, anti-tuberculosis, anti-inflammatory, and antioxidant. However, it has very low solubility in water. The formulation of this compound requires high amounts of solubilizers, which limits its clinical application. In addition, its low solubility in water is a barrier to the distribution of this drug, thus affecting its potency. Cyclodextrin (CD) is widely used as a solubility enhancer of poorly soluble drugs. This study aimed to increase the solubility of α-M in water through complex formation with CD. The complex of α-Mangostin and γ-Cyclodextrin (α-M/γ-CD CX) was prepared by the solubilization method, resulting in a solubility improvement of α-M in water. Characterization of α-M/γ-CD CX by using FTIR-Spectrometry, XRD, H-, C-, and HMBC-NMR showed that α-M was able to form an inclusion complex with γ-CD. The complex yielded an entrapment efficiency of 84.25 and the thermodynamic study showed that the α-M/γ-CD CX was formed spontaneously, based on the negative values of Gibbs energy and ΔH. Interestingly, the solubility of α-M/γ-CD CX significantly increased by 31.74-fold compared with α-M. These results suggest that α-M/γ-CD CX has the potential in the formulation of water-based preparation for clinical applications.

13-Weeks subchronic toxicity of isoquercitrin-γ-cyclodextrin (IQC-γCD) molecular inclusion complex in Sprague-Dawley rats

Flavonoids such as quercetin and its glycoside Isoquercitrin and are abundantly present in the diet and have various pharmacological effects. However, limited data about its potential toxicity is available. In this study, we aim to evaluate the subchronic toxicity of the isoquercitrin-γ-cyclodextrin (IQC-γCD) molecular inclusion complex (SunActive® QCD/EN) in Sprague-Dawley (SD) rats. The IQC-γCD was administrated orally to 40 male and 40 female SD rats at dietary doses up to 5.0 % for 13 consecutive weeks. During the experiment periods, the general clinical signs, mortality, hematological, urinalysis values, biochemical, and histopathological parameters were examined. All animals survived until the scheduled necropsy, and no statistically significant or clinical sign of toxicologically relevant differences including pathology parameters, and histopathological endpoints were observed in any of the IQC-γCD treatment groups, compared with the control group. However, certain observations were noted in the male rats treated with the highest concentration (5.0 %), but these were not seen in female rats. A slight inhibition of weight gain was observed, probably linked to a fall in red blood cells, and hematocrit index in female rats. Statistically significant changes were noted in some clinical measures, such as plasma bilirubin level, alkaline phosphatase total bile acid without evidence of systemic clinical toxicity. The results support no observed adverse effect level (NOAEL) of IQC-γCD of 5.0 % in the diet for males (3338.55 mg/kg/day), and 3.0 % in the diet for females (2177.33 mg/kg/day) SD rats. Therefore, in this 13 weeks repeated-dose SD rat study there were no treatment-related adverse clinical or pathological findings for IQC-γCD of 5.0 % in the diet for males, and 3.0 % in the diet for females SD rats. The results of the present study support the safe use of IQC-γCD as a functional food, food additive, and natural ingredient.

Pre-clinical study of iron oxide nanoparticles fortified artesunate for efficient targeting of malarial parasite

BACKGROUND

Artesunate the most potent antimalarial is widely used for the treatment of multidrug-resistant malaria. The antimalarial cytotoxicity of artesunate has been mainly attributed to its selective, irreversible and iron- radical-mediated damage of parasite biomolecules. In the present research, iron oxide nanoparticle fortified artesunate was tested in P. falciparum and in an experimental malaria mouse model for enhancement in the selectivity and toxicity of artesunate towards parasite. Artesunate was fortified with nontoxic biocompatible surface modified iron oxide nanoparticle which is specially designed and synthesized for the sustained pH-dependent release of Fe2+ within the parasitic food vacuole for enhanced ROS spurt.

METHODS

Antimalarial efficacy of Iron oxide nanoparticle fortified artesunate was evaluated in wild type and artemisinin-resistant Plasmodium falciparum (R539T) grown in O + ve human blood and in Plasmodium berghei ANKA infected swiss albino mice. Internalization of nanoparticles, the pH-dependent release of Fe2+, production of reactive oxygen species and parasite biomolecule damage by iron oxide nanoparticle fortified artesunate was studied using various biochemical, biophysical, ultra-structural and fluorescence microscopy. For determining the efficacy of ATA-IONP+ART on resistant parasite ring survival assay was performed.

RESULTS

The nanoparticle fortified artesunate was highly efficient in the 1/8th concentration of artesunate IC50 and led to retarded growth of P. falciparum with significant damage to macromolecules mediated via enhanced ROS production. Similarly, preclinical In vivo studies also signified a radical reduction in parasitemia with ~8-10-fold reduced dosage of artesunate when fortified with iron oxide nanoparticles. Importantly, the ATA-IONP combination was efficacious against artemisinin-resistant parasites.

INTERPRETATION

Surface coated iron-oxide nanoparticle fortified artesunate can be developed into a potent therapeutic agent towards multidrug-resistant and artemisinin-resistant malaria in humans. FUND: This study is supported by the Centre for Study of Complex Malaria in India funded by the National Institute of Health, USA.

Inclusion of terpenes in cyclodextrins: Preparation, characterization and pharmacological approaches

Terpenes constitute the largest class of natural products and are important resources for the pharmaceutical, food and cosmetics industries. However, due to their low water solubility and poor bioavailability there has been a search for compounds that could improve their physicochemical properties. Cyclodextrins (natural and derived) have been proposed for this role and have been complexed with different types of terpenes. This complexation has been demonstrated by using analytical techniques for characterizing complexes such as DSC, NMR, XRD, FTIR, and TGA. The formation of inclusion complexes has been able to improve drug characteristics such as bioavailability, solubility and stability; and to enhance biological activity and efficacy. This review shows strong experimental evidence that cyclodextrins improve the pharmacological properties of terpenes, and therefore need to be recognized as being possible targets for clinical use.

Development of a myricetin/hydroxypropyl-β-cyclodextrin inclusion complex: preparation, characterization, and evaluation

Myricetin shows low oral bioavailability (<10%) in rats due to poor aqueous solubility, though it has various pharmacological activities. Complexation with cyclodextrins (CDs) is a potent pharmaceutical method to enhance the bioavailability of poorly soluble compounds. The myricetin/HP-β-CD inclusion complex was prepared and confirmed by DSC, PXRD, and SEM. Here, the inclusion mode is described in detail with regard to structural and energetic aspects using a phase solubility diagram and 1H NMR, NOESY, and FT-IR spectra. The water solubility and dissolution rate of myricetin were greatly enhanced by forming the myricetin/HP-β-CD inclusion complex. Consequently, the oral bioavailability of the myricetin/HP-β-CD inclusion complex in rats was effectively increased 9.4-fold over free myricetin, and its antioxidant activity was also improved. The present study provides useful information for the potential application of complexation with myricetin, a naturally occurring hydrophobic phenolic compound in herbal medicine.

Advances in nanomedicines for malaria treatment

Malaria is an infectious disease that mainly affects children and pregnant women from tropical countries. The mortality rate of people infected with malaria per year is enormous and became a public health concern. The main factor that has contributed to the success of malaria proliferation is the increased number of drug resistant parasites. To counteract this trend, research has been done in nanotechnology and nanomedicine, for the development of new biocompatible systems capable of incorporating drugs, lowering the resistance progress, contributing for diagnosis, control and treatment of malaria by target delivery. In this review, we discussed the main problems associated with the spread of malaria and the most recent developments in nanomedicine for anti-malarial drug delivery.

Agglomerated oral dosage forms of artemisinin/β-cyclodextrin spray-dried primary microparticles showing increased dissolution rate and bioavailability

Artemisinin, a poorly water-soluble antimalarial drug, presents a low and erratic bioavailability upon oral administration. The aim of this work was to study an agglomerated powder dosage form for oral administration of artemisinin based on the artemisinin/β-cyclodextrin primary microparticles. These primary microparticles were prepared by spray-drying a water-methanol solution of artemisinin/β-cyclodextrin. β-Cyclodextrin in spray-dried microparticles increased artemisinin water apparent solubility approximately sixfold. The thermal analysis evidenced a reduction in the enthalpy value associated with drug melting, due to the decrease in drug crystallinity. The latter was also evidenced by powder X-ray diffraction analysis, while (13)C-NMR analysis indicated the partial complexation with β-cyclodextrin. Agglomerates obtained by sieve vibration of spray-dried artemisinin/β-cyclodextrin primary microparticles exhibited free flowing and close packing properties compared with the non-flowing microparticulate powder. The in vitro dissolution rate determination of artemisinin from the agglomerates showed that in 10 min about 70% of drug was released from the agglomerates, whereas less than 10% of artemisinin was dissolved from raw material powder. Oral administration of agglomerates in rats yielded higher artemisinin plasma levels compared to those of pure drug. In the case of the agglomerated powder, a 3.2-fold increase in drug fraction absorbed was obtained.

Preparation and characterization of pioglitazone cyclodextrin inclusion complexes

Pioglitazone, a class II Biopharmaceutical Classification System drug having poor water solubility and slow dissolution rate may have a negative impact on its subtherapeutic plasma drug levels leading to therapeutic failure. In order to improve its water solubility and thus dissolution, cyclodextrin complexation technique was followed. The phase solubility studies were carried using three different types of cyclodextrins viz., β, methyl-β and γ-cyclodextrins. The Gibbs free energy was calculated in order to determine ease of the complexation. Binary systems of pioglitazone with cyclodextrins were prepared by kneading method and spray drying method. The phase solubility profiles with all the three cyclodextrins were classified as A_L-type, indicating the formation of 1:1 stoichiometric inclusion complexes. The complexation capability of cyclodextrins with pioglitazone increased in the order of methyl-β > β > γ-cyclodextrin. The Gibbs free energy was found to be in the order γ > methyl-β > β cyclodextrin. Characterization of inclusion complexes was done by solubility studies, in vitro dissolution studies, Fourier transformation-infrared spectroscopy, scanning electron microscopy, differential scanning calorimetry and X-ray powder diffractometry studies. Inclusion complexes exhibited higher rates of dissolution than the corresponding physical mixtures and pure drug. Greater solubility was observed with spray-dried methyl-β cyclodextrin complexes (2.29 ± 0.001 mg/ml) in comparison to the kneaded methyl-β cyclodextrin complexes (1.584 ± 0.053 mg/ml) and pure drug (0.0714 ± 0.0018 mg/ml).

β-Cyclodextrin polymer nanoparticles as carriers for doxorubicin and artemisinin: a spectroscopic and photophysical study

The association of doxorubicin (DOX) and artemisinin (ART) to a β-CyD-epichlorohydrin crosslinked polymer (pβ-CyD), organized in nanoparticles of ca. 15 nm size, was investigated in neutral aqueous medium by circular dichroism (CD), UV-vis absorption and fluorescence. The stability constants and the absolute CD spectra of the drug complexes were determined by global analysis of multiwavelength data from spectroscopic titrations. The polymer pβ-CyD proved able to disrupt the DOX dimer when the latter is the predominant form of DOX in solution. The spectroscopic and photophysical properties of the complexes evidenced an alcohol-like environment for ART and an improved inherent emission ability for DOX in the nanoparticle frame.

Bioavailability Enhancement of Poorly Water Soluble and Weakly Acidic New Chemical Entity with 2-Hydroxy Propyl-β-Cyclodextrin: Selection of Meglumine, a Polyhydroxy Base, as a Novel Ternary Component

The purpose of the present study was to investigate the influence of a polyhydroxy base, N-acetyl glucamine (also know as Meglumine), as a ternary component on the complexation of DRF-4367, a poorly water-soluble and weakly acidic anti-inflammatory molecule, with 2-hydroxypropyl-beta-cyclodextrin (HPbetaCD). The molecular inclusion of DRF-4367 with HPbetaCD alone and in combination with ternary component was aimed at improvement in solubility and, subsequently, dissolution rate-limited oral bioavailability. The solid complexes of DRF-4367 and HPbetaCD with or without meglumine (binary and ternary systems, respectively) were prepared as coevaporated product in different stoichiometric ratios and compared against physical mixture. The formation of inclusion complexes was confirmed by using classical instrumental techniques. Phase solubility studies suggested that meglumine was responsible for solubility improvement via multiple factors rather than just providing a favorable pH. Mechanisms and factors governing solubility enhancement were investigated by using phase solubility and thermodynamic parameters. The complexation of DRF-4367 with HPbetaCD is thermodynamically favored because the Gibbs free energies of transfer of the drug to the cyclodextrin cavity are negative. The solubilization efficiency and stability were further improved while retaining the favorable Gibbs free energies of transfer with the addition of meglumine. Inclusion ternary complex of DRF-4367 with HPbetaCD and meglumine showed significant improvement in dissolution compared with uncomplexed drug and binary system. Moreover, the phenomena of reprecipitation observed with binary system during dissolution could be avoided with meglumine as an enabling ternary component. This improved physicochemical behavior of ternary complex with the novel inclusion of a polyhydroxy base translated into an enhanced oral bioavailability of DRF-4367 compared with either uncomplexed drug or nanosuspension.

The binding interaction of synthetic ozonide antimalarials with natural and modified β-cyclodextrins

The current studies were undertaken to explore the potential basis for a significant difference in the pharmacokinetic parameters after intravenous administration of a synthetic ozonide (OZ) antimalarial drug candidate (1) to rats when formulated in either Captisol (a sulfobutylether substituted beta-cyclodextrin derivative ((SBE)(7)-beta-CD)) or a buffered aqueous vehicle. It was suspected that the differences may have been due to failure of 1 to rapidly dissociate from the cyclodextrin complex in vivo, perhaps due to an unusually tight binding within the cyclodextrin cavity. To address this hypothesis, the binding of representative synthetic OZ antimalarial drug candidates (including 1) with beta-cyclodextrin and (SBE)(7)-beta-CD was investigated by isothermal titration calorimetry and phase solubility analysis. It was found that each of the OZ compounds exhibited an exceptionally high binding constant ( approximately 10(6)/M) with both Cyclodextrins (CD). The nature of the complexation was investigated by molecular dynamics simulations and NMR to explore the mechanisms, which generated such high binding constants. The data suggested that the most probable cause of the unusually high binding constants was a very close fit within the cyclodextrin cavity that resulted in more favourable changes in both the enthalpy and entropy of the binding interaction, compared to published data for other drugs.

Solubility of (+/-)-ibuprofen and S (+)-ibuprofen in the presence of cosolvents and cyclodextrins

Aqueous solubility is an important parameter for the development of liquid formulations and in the determination of bioavailability of oral dosage forms. Ibuprofen (IB), a nonsteroidal anti-inflammatory drug, is a chiral molecule and is currently used clinically as a racemate (racIB). However, the S form of ibuprofen or S(+)-ibuprofen (SIB) is the biologically active isomer and is primarily responsible for the antiinflammatory activity. Phase solubility studies were carried out to compare the saturation solubilities of racIB and SIB in the presence of common pharmaceutical solvents such as glycerol, sorbitol solution, propylene glycol (PG), and polyethylene glycol (PEG 300) over the range of 20% to 80% v/v in aqueous based systems. The solubilities of the two compounds were also compared in the presence of cyclodextrins such as beta cyclodextrin (CD), hydroxypropyl beta cyclodextrin (HPCD), and beta cyclodextrin sulfobutyl ether sodium salt (CDSB) over the range of 5% to 25% w/v. Solubility determinations were carried at 25 degrees C and 37 degrees C. Cosolvents exponentially increased the solubility of both SIB and racIB, especially in the presence of PG and PEG 300. Glycerol was not very effective in increasing the aqueous solubilities of both compounds, whereas sorbitol solution had a minimal effect on their solubility. PG and PEG 300 increased the solubility of SIB by 400-fold and 1500-fold, respectively, whereas the rise in solubility for racIB was 193-fold and 700-fold, respectively, at 25 degrees C for the highest concentration of the cosolvents used (80% v/v). Of the two compounds studied, higher equilibrium solubilities were observed for SIB as compared with racIB. The derivatized cyclodextrins increased the aqueous solubility of racIB and SIB in a concentration-dependent manner giving AL type of phase diagrams. The phase solubility diagrams indicated the formation of soluble inclusion complexes between the drugs and HPCD and CDSB, which was of 1:1 stoichiometry. The addition of underivatized CD reduced the solubility of racIB and SIB via the formation of an insoluble complex. The S form formed more stable complexes with HPCD and CDSB as compared with raclB. The solubilization process is discussed in terms of solvent polarity and differential solid-state structure of raclB and SIB. The thermodynamic parameters for the solubilization process are presented.