Polymorphism of l-Tryptophan.

A new polymorph of l-tryptophan was prepared through crystallization from the gas phase, with structure determination carried out directly from powder XRD data augmented by periodic DFT-D calculations. The new polymorph (denoted ß) and the previously reported polymorph (denoted α) are both based on alternating hydrophilic and hydrophobic layers, but with substantially different hydrogen-bonding arrangements. The ß polymorph exhibits the energetically favourable l2-l2 hydrogen-bonding arrangement, which is unprecedented for amino acids with aromatic side chains. The specific molecular conformations adopted in the ß polymorph facilitate this hydrogen-bonding scheme while avoiding steric conflict of the side chains.

Colonic targeting insulin-loaded trimethyl chitosan nanoparticles coated pectin for oral delivery: In vitro and In vivo studies.

Colon-targeted delivery offers several benefits for oral protein delivery, such as low proteolytic enzyme activity, natural pH, and extended residence time, which improve the bioavailability of the encapsulated protein. Therefore, we hypothesize that developing a novel colonic nanocarrier system based on modified chitosan, which enhances solubility at natural pH and is coated with a colon-degradable polymer, will provide an effective delivery system for oral insulin. This study aims to synthesize insulin-loaded pectin-trimethyl chitosan nanoparticles (Ins-P-TMC-NPs) as an oral insulin delivery system and evaluate their efficacy both in vitro and in streptozotocin-induced diabetic male rats. N-trimethyl chitosan (TMC), synthesized via a methylation method, was used to prepare insulin-TMC nanoparticles coated with pectin via the ionic gelation method. The nanoparticles were characterized for their physicochemical properties, cumulative release profile, and surface morphology. In vitro biological cytotoxicity and cellular uptake of the nanoparticles were evaluated against HT-29 cells using an MTT assay and fluorescent microscopy, respectively. The in vivo blood glucose-lowering effect was assessed in diabetic male Sprague-Dawley rats, with in vivo toxicity evaluated in the liver, spleen, duodenum, pancreas, and kidney through histological studies (H&E staining). The results showed that Ins-P-TMC-NPs were spherical, with an average size of 379.40 ±â€¯40.26 nm, a polydispersity index of 24.10 ±â€¯1.03 %, a zeta potential of +17.20 ±â€¯0.52 mV, and a loading efficiency of 83.21 ±â€¯1.23 %. Compared to uncoated TMC nanoparticles, Ins-P-TMC-NPs reduced insulin loss in simulated gastrointestinal fluid by approximately 67.23 ±â€¯0.97 % and provided controlled insulin release in simulated colonic fluid. In vitro bioactivity studies revealed that Ins-P-TMC-NPs were non-toxic, with cell viability of 91.12 ±â€¯0.91 %, and exhibited high cellular uptake in the HT-29 cell line with a fluorescence intensity of 37.80 ±â€¯2.40. Furthermore, in vivo studies demonstrated a sustained reduction in blood glucose levels after oral administration, peaking after 8 h with a glucose reduction of 87 ±â€¯1.03 %. Histological sections showed no signs of toxicity. Overall, the developed colon-targeted oral insulin delivery system shows great potential as a candidate for oral insulin administration.

Structure of the caffeine-pyrogallol complex: revisiting a pioneering structural analysis of a model pharmaceutical cocrystal.

The 1967 attempt of structural analysis of the solid-state complex of caffeine and pyrogallol was a pioneering structural investigation in the supramolecular chemistry of caffeine, of what today would easily be considered an archetype of a model pharmaceutical cocrystal. Re-investigating this historically important system demonstrates that this long overlooked complex is most likely a tetrahydrate with a different structure and composition than initially proposed, and provides the crystal structure of the anhydrous cocrystal.

Unraveling the Complex Solid-State Phase Transition Behavior of 1-Iodoadamantane, a Material for Which Ostensibly Identical Crystals Undergo Different Transformation Pathways.

Phase transitions in crystalline molecular solids have important implications in the fundamental understanding of materials properties and in the development of materials applications. Herein, we report the solid-state phase transition behavior of 1-iodoadamantane (1-IA) investigated using a multi-technique strategy [synchrotron powder X-ray diffraction (XRD), single-crystal XRD, solid-state NMR, and differential scanning calorimetry (DSC)], which reveals complex phase transition behavior on cooling from ambient temperature to ca. 123 K and on subsequent heating to the melting temperature (348 K). Starting from the known phase of 1-IA at ambient temperature (phase A), three low-temperature phases are identified (phases B, C, and D); the crystal structures of phases B and C are reported, together with a re-determination of the structure of phase A. Remarkably, single-crystal XRD shows that some individual crystals of phase A transform to phase B, while other crystals of phase A transform instead to phase C. Results (from powder XRD and DSC) on cooling a powder sample of phase A are fully consistent with this behavior while also revealing an additional transformation pathway from phase A to phase D. Thus, on cooling, a powder sample of phase A transforms partially to phase C (at 229 K), partially to phase D (at 226 K) and partially to phase B (at 211 K). During the cooling process, each of the phases B, C, and D is formed directly from phase A, and no transformations are observed between phases B, C, and D. On heating the resulting triphasic powder sample of phases B, C, and D from 123 K, phase B transforms to phase D (at 211 K), followed by the transformation of phase D to phase C (at 255 K), and finally, phase C transforms to phase A (at 284 K). From these observations, it is apparent that different crystals of phase A, which are ostensibly identical at the level of information revealed by XRD, must actually differ in other aspects that significantly influence their low-temperature phase transition pathways. This unusual behavior will stimulate future studies to gain deeper insights into the specific properties that control the phase transition pathways in individual crystals of this material.

Structural and in vitro in vivo evaluation for taste masking.

INTRODUCTION: Although many techniques, such as complexation and microencapsulation, are used to mask the unpleasant taste of drugs, the success of all masking processes is evaluated in the same way. To evaluate the success of a masking process, a masked formulation must pass two tests: a structural test and an in vitro in vivo test. AREAS COVERED: This review article highlights structural evaluation and in vitro in vivo evaluation of a taste-masking process. The structural evaluation has two criteria: the absence of any chemical interaction between the drug and the masking agent and the molecular distribution of drug in the network of masking agent. The in vitro in vivo section can be verified by electronic tongues, dissolution test, and volunteers and it should confirm that the final product, after applying the masking process, will have a lower rank in terms of taste. EXPERT OPINION: This critical review helps researchers and industrial partners to evaluate a taste-masking process in a systematic way, leading to better understanding of taste-masking process and consequently improving the efficiency of masked dosage forms while hindering the unpleasant taste of drugs. This will ultimately improve the quality of life of many patients.