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Rutin is a flavonoid and has found a wide application in the treatment of various chronic diseases such as cancer, diabetes, hypertension and hypercholesterolemia. The pharmaceutical application of rutin is limited due to its poor water solubility. One of the ways to enhance the solubility and stability is the formation of the inclusion complexes. The purpose of this study was to improve the solubility, antioxidative activity and photostability of rutin by preparation of the inclusion complexes with β-cyclodextrin (β-CD) and (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD). The inclusion complexes were structurally characterized using FT-IR, XRD, 1H NMR methods. The obtained results indicated that the complexation between rutin and cyclodextrins were successfully achieved in the mixture of ethanol and water 2:3 (v/v) at room temperature for 24 h. The study of phase-solubility was showed that the solubility of rutin was linearly increased in the solution of increasing amount of cyclodextrins, i.e. that the molar ratio was 1:1 in the complexes. The calculated values of stability constants were found to be 508.4 and 488.9 M−1 for rutin:β-CD and rutin:HP-β-CD complexes, respectively. After preparation of inclusion complexes, the antioxidant activity of rutin was improved due to the increase of its scavenge capacity. The photostability study indicates that the complexed rutin was a more stable and protected from the effect of irradiation in compared with free rutin. The improvement in the physicochemical properties provide the opportunities to the inclusion complexes of rutin to use for design of the new pharmaceutical products with modified characteristics of active substance.

Carvedilol is one of the most effective antihypertensive drugs used in the treatment of congestive heart failure. A major disadvantage of this pharmaceutical active substance is its limited solubility in water, gastric and intestinal fluids. One way to overcome this problem is the preparation of inclusion complexes. The aim of this study was to prepare the inclusion complexes of carvedilol with β-cyclodextrin (β-CD) and (2-hydroxypropyl)-β-cyclodextrin (HP-β-CD) and to investigate their physical properties. The formation of inclusion complexes with β-CD and HP-β-CD was confirmed using FTIR, 1H-NMR and XRD methods. Phase solubility studies indicate the formation of inclusion complexes in 1:2 molar ratio and the increase of carvedilol solubility. The stability constant (β 2) was found to be 3.4 × 104 and 5.1 × 104 M−2 for inclusion complexes of carvedilol:β-CD and carvedilol:HP-β-CD, respectively. Photostability of carvedilol was increased after preparation of inclusion complexes with β-CD and HP-β-CD. Based on the results of this study, it can be concluded that the prepared complexes of carvedilol improve the solubility and stability of carvedilol and give it an advantage to be applied for the design of new pharmaceutical formulations.

Quercetin is a typical plant flavonoid with a wide variety of pharmacological activities, including anti-inflammatory, anti-oxidative, anti-cancer and anti-age activity. It can be used for treatment of cardiovascular disorders. However, the application of quercetin in pharmacy is limited because of its poor aqueous solubility, low bioavailability, low permeability and instability. In order to overcome the mentioned limitations, an inclusion complex of quercetin with (2-hydroxypropyl)-β-cyclodextrin in a molar ratio of 1:1 have been prepared at room temperature by co-precipitation from ethanol solution. The inclusion complex was prepared at room temperature for 24 h by the co-precipitation method from ethanol solution. The obtained complex were evaporated and dried before the structural characterization. Based on the obtained results of FT-IR, DSC, 1H-NMR and XRD analysis, it can be concluded that the inclusion complex was formed by establishing the interaction between quercetin and (2-hydroxypropyl)-β-cyclodextrin. The phase solubility study indicates that the complexation of quercetin leads to increase the solubility of quercetin in water about 129-fold in the aqueous solution of HP-β-CD (10 mmol dm−3). Also, the photostability of quercetin was improved after its complexation with this cyclodextrin.

Sulfanilamide belongs to the group of drugs that have a bacteriostatic effect on different pathogenic microorganisms. This activity originates from the competitive antagonism with p-aminobenzoic acid, which is an integral part of folic acid. The safe use of sulfanilamide is limited due to poor solubility in the aqueous medium. Therefore, the aim of this paper is the synthesis of sulfanilamide, as well as preparing and structural characterization of its inclusion complexes with cyclodextrins. The crude sulfanilamide was obtained in the synthesis between acetanilide and chlorosulfonic acid according to the standard procedure. The synthesized sulfanilamide was recrystallized from water in order to obtain the satisfactory purity of the substance. Sufanilamide was complexed with beta-cyclodextrin and 2-hydroxypropyl-beta-cyclodextrin by the co-precipitation method. A molecular encapsulation of sulfanilamide was confirmed by using FTIR, H-1-NMR, XRD and DSC methods. Phase-solubility techniques were used to assess the formation of the inclusion complex between sulfanilamide and cyclodextrins. The photostability of sulfanilamide and its inclusion complexes was estimated by UVB irradiation in a photochemical reactor by applying the UV-Vis method. Based on the UV-Vis analysis, sulfanilamide:2-hydroxypropyl-beta-cyclodextrin complex was presented as more photostable than sulfanilamide:beta-cyclodextrin complex and sulfanilamide. The obtained results enable the potential use of these inclusion complexes for the preparation of oral formulations due to the enhanced solubility of sulfanilamide.

Molecular inclusion complexes of usnic acid (UA) with beta-cyclodextrin (beta-CD) and 2-hydroxypropyl beta-cyclodextrin (HP beta-CD) were prepared by the co-precipitation method in the solid state in the molar ratio of 1:1. Structural complexes characterization was based on different methods, FTIR, H-1 NMR, XRD and DSC. Parallel to the complex by the above methods, corresponding physical mixtures of UA with cyclodextrins and complexing agents (beta-CD, HP beta-CD and UA) were analyzed. The results of DSC analysis showed that, at around 200 A degrees C, the endothermal peak in the complexes with cyclodextrins originating from the UA melting has disappeared. Complex diffractogram patterns do not contain peaks characteristic for the pure UA. They are more appropriate to cyclodextrin diffractogram. This fact points to the molecular encapsulation of UA in the cyclodextrin cavity. Chemical shifts in H-1 NMR spectra after the inclusion of UA into the cyclodextrin cavity, especially H-3 protons (0.0012 and 0.0102 ppm in the beta-CD and HP beta-CD, respectively) and H-5 and H-6 (0.0134 ppm) and hydrogen from CH3 (0.0073 ppm) HP beta-CD also points to the formation of molecular inclusion complexes. The improved solubility of UA in water was achieved by molecular incapsulation. In the complex with beta-CD the solubility is 0.3 mg/cm(3), with HP beta-CD 4.2 mg/cm(3) while the uncomplexed UA solubility is 0.06 mg/cm(3). The microbial activity of UA and both complexes was tested against eight bacteria and two fungi and during the test no reduced activity of UA in the complexes was observed.