Kuthuru Suresh

Novel Furosemide Cocrystals and Selection of High Solubility Drug Forms

Furosemide was screened in cocrystallization experiments with pharmaceutically acceptable coformer molecules to discover cocrystals of improved physicochemical properties, that is high solubility and good stability. Eight novel equimolar cocrystals of furosemide were obtained by liquid-assisted grinding with (i) caffeine, (ii) urea, (iii) p-aminobenzoic acid, (iv) acetamide, (v) nicotinamide, (vi) isonicotinamide, (vii) adenine, and (viii) cytosine. The product crystalline phases were characterized by powder x-ray diffraction, differential scanning calorimetry, infrared, Raman, near IR, and (13) C solid-state NMR spectroscopy. Furosemide-caffeine was characterized as a neutral cocrystal and furosemide-cytosine an ionic salt by single crystal x-ray diffraction. The stability of furosemide-caffeine, furosemide-adenine, and furosemide-cytosine was comparable to the reference drug in 10% ethanol-water slurry; there was no evidence of dissociation of the cocrystal to furosemide for up to 48 h. The other five cocrystals transformed to furosemide within 24 h. The solubility order for the stable forms is furosemide-cytosine > furosemide-adenine > furosemide-caffeine, and their solubilities are approximately 11-, 7-, and 6-fold higher than furosemide. The dissolution rates of furosemide cocrystals were about two times faster than the pure drug. Three novel furosemide compounds of higher solubility and good phase stability were identified in a solid form screen.

Fast dissolving eutectic compositions of curcumin.

The bioactive herbal ingredient curcumin was screened with pharmaceutically acceptable coformers to discover solid-state forms of high solubility. Mechano-chemical grinding of curcumin with cocrystal formers in a fixed stoichiometry ratio resulted in binary eutectic compositions of curcumin-coformer with nicotinamide (1:2), ferulic acid (1:1), hydroquinone (1:1), p-hydroxybenzoic acid (1:1), and l-tartaric acid (1:1). The eutectic nature of the product crystalline solids was established by differential scanning calorimetry, and the absence of hydrogen-bonded crystalline phases such as cocrystals/salts was ascertained by powder X-ray diffraction, IR-Raman, and solid-state NMR spectroscopy. The best case of CUR-NAM eutectic exhibits 10-fold faster IDR and 6-times higher AUC compared to crystalline curcumin.

A novel curcumin–artemisinin coamorphous solid: physical properties and pharmacokinetic profile

Here we report a curcumin–artemisinin coamorphous solid (1 : 1) prepared by rotavaporization and a dramatic increase in the pharmacokinetic profile of curcumin (AUC0–12 2.6 μg h mL−1, Cmax 1 μg mL−1) administered as CUR–ART to SD rats. PXRD and FESEM analysis explains the molecular basis for the solubility enhancement of coamorphous CUR–ART.

Andrographolide: Solving Chemical Instability and Poor Solubility by Means of Cocrystals

The bioactive agent andrographolide was screened with pharmaceutically acceptable coformers to discover a novel solid form that will solve the chemical instability and poor solubility problems of this herbal medicine. Liquid-assisted grinding of andrographolide with GRAS (generally regarded as safe) coformers in a fixed stoichiometry resulted in cocrystals with vanillin (1:1), vanillic acid (1:1), salicylic acid (1:1), resorcinol (1:1), and guaiacol (1:1). All the crystalline products were characterized by thermal, spectroscopic, and diffraction methods. Interestingly, even though the cocrystals are isostructural, their physicochemical properties are quite different. The andrographolide-salicylic acid cocrystal completely inhibited the chemical transformation of andrographolide to its inactive sulfate metabolite, and moreover, the cocrystal exhibited a dissolution rate that was three times faster and a drug release that was two times higher than pure andrographolide.

A furosemide–isonicotinamide cocrystal: an investigation of properties and extensive structural disorder

Furosemide is a loop diuretic drug marketed in solid form which suffers from low solubility and low permeability. The pharmaceutically relevant properties of a recently described furosemide–isonicotinamide 2 : 1 cocrystal (2FS–INA) were investigated and compared with those of other known furosemide cocrystals. The intrinsic dissolution rate of 2FS–INA was found to be very similar to that of commercial FS, while its equilibrium solubility was 5.6 times higher than that of pure FS. The extensive structural disorder in 2FS–INA observed by diffraction methods was also investigated by variable-temperature solid-state NMR in conjunction with first principles calculations. 15N NMR confirmed the absence of proton disorder in the short OH⋯N hydrogen bond. The disordered sulphonamide group was found to be dynamic by variable temperature 2H experiments, involving fast exchange of the sulphonamide NH2 protons combined with a rotation of the whole sulphonamide group about the C–S bond. The disorder of the furan rings of both the unique furosemide molecules was also found to be dynamic by 13C experiments, with approximately the same activation barrier for both rings.

Polymorphism, isostructurality and physicochemical properties of glibenclamide salts

Novel salts of glibenclamide (GBA), namely glibenclamide-sodium (GBA-Na), glibenclamide-potassium (GBA-K) and glibenclamide-ammonium (GBA-NH4) were crystallized under different conditions to obtain their polymorphs, and their aqueous solubility and hydration stability studies are reported. The GBA-Na salt is dimorphic (forms I and II) and also exists as hydrate GBA-Na–H2O (form III). The GBA-K salt exists in anhydrous and hydrate forms (GBA-K, forms I and II). Crystal structure analysis of GBA-Na forms I and II showed differences in geometry of the central metal atom and ligand orientation. This kind of polymorphism of sulfonyl urea salts appears to be novel in the Cambridge Structural Database (CSD). The isostructurality of GBA-Na form I with GBA-NH4 and GBA-K form I salts is discussed. The potassium salts of GBA exhibited higher solubility compared to pure GBA. Specifically GBA-K salt forms I and II showed higher solubility by 77 fold in the water and 33 fold in phosphate buffer (pH 7) compared to the other salts. Dynamic vapor sorption (DVS) showed reversible water sorption without hysteresis for all salts, except for GBA-K form II which transformed to form I after a sorption and desorption cycle as confirmed by PXRD.

Curcumin-Artemisinin Coamorphous Solid: Xenograft Model Preclinical Study

Curcumin is a natural compound present in Indian spice turmeric. It has diverse pharmacological action but low oral solubility and bioavailability continue to limit its use as a drug. With the aim of improving the bioavailability of Curcumin (CUR), we evaluated Curcumin-Pyrogallol (CUR-PYR) cocrystal and Curcumin-Artemisinin (CUR-ART) coamorphous solid. Both of these solid forms exhibited superior dissolution and pharmacokinetic behavior compared to pure CUR, which is practically insoluble in water. CUR-ART coamorphous solid showed two fold higher bioavailability than CUR-PYR cocrystal (at 200 mg/kg oral dose). Moreover, in simulated gastric and intestinal fluids (SGF and SIF), CUR-ART is stable up to 3 and 12 h, respectively. In addition, CUR-PYR and CUR-ART showed no adverse effects in toxicology studies (10 times higher dose at 2000 mg/kg). CUR-ART showed higher therapeutic effect and inhibited approximately 62% of tumor growth at 100 mg/kg oral dosage of CUR in xenograft models, which is equal to the positive control drug, doxorubicin (2 mg/kg) by i.v. administration.

Structure and physicochemical characterization of a naproxen–picolinamide cocrystal

The crystal structure is reported of a new 1:1 cocrystal of naproxen with picolinamide, and the pharmaceutically relevant properties are investigated. An NMR crystallography approach is used to distinguish between two crystallographically unique COOH–CONH hydrogen-bonded dimers and to confirm the location of the H atoms in the two dimers.

Rare Earth Doped Alkali Earth Sulfide Phosphors for White-Light LEDs

CaS:Eu and SrS:Eu phosphors were synthesized by solid-state reaction. The effects of doping concentrations on luminescent properties of phosphors are investigated. The samples are excited using electroluminescent blue light emitting diode (460 nm) to examine them as potential coating phosphors for white-light LEDs. The excitation and emission spectra of these phosphors are broadband which can be viewed as the typical emission of Eu2

Curcumin: pharmaceutical solids as a platform to improve solubility and bioavailability

Curcumin (CUR) is the prime curcuminoid in the Indian dietary spice turmeric, Curcuma longa, a plant of the Zingiberaceae family. CUR has promising and diverse therapeutic benefits, such as antioxidant, anti-inflammatory, antitumor, anti-hyperglycemic, antimalarial, antibacterial, and antiviral activity, including anti-Alzheimers disease. However, CUR is yet to reach the status of a therapeutic drug candidate mainly because a standard solid dosage of curcumin suffers from poor oral bioavailability (0.05 μg mL−1, less than 1%). The reasons behind its low bioavailability include poor solubility (<8 μg mL−1 in water), low permeability and absorption, and rapid metabolism (short elimination half-life of <2 h). A successful CUR therapy requires an appropriate formulation system that will enhance the bioavailability and offer greater therapeutic efficacy. This review covers a comprehensive description of the CUR pharmaceutical solids, such as polymorphs, cocrystals, eutectics, and coamorphous solid-state forms with aim to determine ways to improve its physicochemical properties, including dissolution rate, solubility, physicochemical stability, mechanical strength, compressibility for tablet formation, and oral bioavailability. The cumulative publications in the past decade have forecast a bright future for development of an oral drug formulation of curcumin.