DL-Arginine

Reinvestigating the Preferential Enrichment of DL-Arginine Fumarate: New Thoughts on the Mechanism of This Far from Equilibrium Crystallization Phenomenon

Preferential enrichment (PE) is a crystallization process, starting from either a racemic of slightly enantio-enriched solution (ca. +5%) that results in a high enantiomeric excess in the liquid phase (>+90%ee) and a slight opposite excess in the deposited crystals (-2 to -5%ee). The mechanism(s) of this symmetry-breaking phenomenon is (are) still a matter of debate since it eludes rationalization by phase diagram formalism. In this publication, we thoroughly reinvestigate the PE phenomenon of arginine fumarate by using a new approach: the process is monitored by introducing isotopically labeled arginine enantiomers into the crystallization medium to better understand the mass exchanges during crystallization. These experiments are supported by chiral HPLC-MS/MS. This study permits re-evaluating the criteria that were thought mandatory to perform PE. In particular, we show that PE occurs by a continuous exchange between the solution and the crystals and does not require the occurrence of a solvent-mediated solid-solid phase transition.

X-ray studies on crystalline complexes involving amino acids and peptides. XLI. Commonalities in aggregation and conformation revealed by the crystal structures of the pimelic acid complexes of L-arginine and DL-lysine

The complexes of L-arginine and DL-lysine with pimelic acid are made up of singly positively charged zwitterionic amino acid cations and doubly negatively charged pimelate ions in a 2:1 ratio. In both structures, the amino acid molecules form twofold symmetric or centrosymmetric pairs that are stabilized by hydrogen bonds involving alpha-amino and alpha-carboxylate groups. In the L-arginine complex, these pairs form columns along the shortest cell dimension, stabilized by intermolecular hydrogen bonds involving alpha-amino and alpha-carboxylate groups. The columns are connected by hydrogen bonds and water bridges to give rise to an amino acid layer. Adjacent layers are then connected by pimelate ions. Unlike molecular ions aggregate into alternating distinct layers in the DL-lysine complex. In the amino acid layer, hydrogen-bonded lysinium dimers related by a glide plane are connected by hydrogen bonds involving alpha-amino and alpha-carboxylate groups into head-to-tail sequences. Interestingly, the aggregation pattern observed in L-arginine hemipimelate monohydrate is very similar to those in DL-arginine formate dihydrate, DL-arginine acetate monohydrate and L-arginine hemiglutarate monohydrate. Similarly, the aggregation of amino acid molecules is very similar in DL-lysine hemipimelate 0.53-hydrate, DL-lysine formate and DL-lysine hydrochloride. The complexes thus demonstrate how, in related structures, the effects of a change in composition, and sometimes even those of reversal in chirality, can be accommodated by minor adjustments in essentially the same aggregation pattern. It also transpires that the conformation of the argininium ion is the same in the four argininium complexes; the same is true about the conformation of the lysinium ion in the three lysinium complexes. This result indicates a relation between, and mutual dependence of, conformation and aggregation.

Highly efficient chiral resolution of DL-arginine by cocrystal formation followed by recrystallization under preferential-enrichment conditions

An excellent chiral symmetry-breaking spontaneous enantiomeric resolution phenomenon, denoted preferential enrichment, was observed on recrystallization of the 1:1 cocrystal of dl-arginine and fumaric acid, which is classified as a racemic compound crystal with a high eutectic ee value (>95 %), under non-equilibrium crystallization conditions. On the basis of temperature-controlled video microscopy and in situ time-resolved solid-state (13) C NMR spectroscopic studies on the crystallization process, a new mechanism of phase transition that can induce preferential enrichment is proposed.

Identification of Kaempferol as viral entry inhibitor and DL-Arginine as viral replication inhibitor from selected plants of Indian traditional medicine against COVID-19: An in silico guided in vitro approach

Background: Indian traditional medicinal plants are known for their great potential in tackling viral diseases. Previously, we reported a systematic review approach of seven plausible traditional Indian medicinal plants against SARS CoV 2.
Methods: Molecular docking was conducted with Biovia Discovery Studio. Three binding domains for Spike glycoprotein (PDB IDs: 6LZG, 6M17, 6M0J) and one binding domain of RdRp (PDB ID: 7BTF) were used. Among 100 phytoconstituents listed from seven plants by IMPPAT Database used for virtual screening, the best six compounds were again filtered using Swiss ADME prediction and Lipinski's rule. Additionally, a Pseudovirion assay was performed to study the interaction of SARS CoV 2 S1-protein with the ACE 2 receptor for further confirming the effect.
Results: Chebulagic acid (52.06 Kcal/mol) and Kaempferol (48.84 Kcal/mol) showed an increased interaction energy compared to Umifenovir (33.68 Kcal/mol) for the 6LZG binding domain of Spike glycoprotein. Epicatechin gallate (36.95 Kcal/mol) and Arachidic acid (26.09 Kcal/mol) showed equally comparable interaction energy compared to Umifenovir (38.20 Kcal/mol) for 6M17 binding domain of Spike glycoprotein. Trihydroxychalcone (35.23 Kcal/mol) and Kaempferol (36.96 Kcal/mol) showed equally comparable interaction energy with Umifenovir (36.60 Kcal/mol) for 6M0J binding domain of Spike glycoprotein. On analyzing the phytoconstituents against RdRp binding domain, DL-Arginine (41.78 Kcal/mol) showed comparable results with the positive control Remdesivir (47.61 Kcal/mol). ADME analysis performed using Swiss ADME revealed that Kaempferol and DL Arginine show drug-like properties with appropriate pharmacokinetic parameters. Further in vitro analysis of Kaempferol by Pseudo virion assay confirmed an acceptable decrease of the lentiviral particles on transfected HEK293T-hACE2 cells.
Conclusion: The study highlights that Kaempferol and DL-Arginine could be the significant molecules to exhibit potent action against SARS CoV 2 and its variants.

A Qualitative Analysis of Periodontal Pathogens in Chronic Periodontitis Patients after Nonsurgical Periodontal Therapy with and without Diode Laser Disinfection Using Benzoyl-DL Arginine-2-Naphthylamide Test: A Randomized Clinical Trial

Introduction: Periodontal diseases are caused by pathogenic bacteria locally colonized in the dental biofilm creating infection; the main etiological factor is represented by dental plaque and in particular by anaerobic Gram-negative bacilli. For that reason, the first phase of periodontal treatment is always represented by the initial preparation which primarily aims at the elimination or reduction of bacterial infection and the control of periodontal plaque-associated inflammation. Yet, another innovative causal therapy is represented by the irradiation of periodontal pockets with LASER. The aim of this randomized clinical study is to compare and to detect the presence of periodontal pathogens in chronic periodontitis patients after nonsurgical periodontal therapy with and without diode LASER disinfection using BANA test.
Materials and methods: This randomized clinical trial includes 20 patients having chronic periodontitis. From each patient, one test site and one control site were selected and assessed for gingival index (GI), oral hygiene index (OHI), pocket probing depth and clinical attachment level (CAL), and presence of BANA pathogens. The test site underwent scaling and root planning along with diode LASER therapy as an adjuvant while the control site received scaling and root planning alone. Patients were recalled for review after 2 weeks and 2 months where periodontal parameters were assessed and plaque samples were collected and analyzed for BANA pathogens.
Results: The test site where LASER was used as an adjuvant showed significant reduction in pocket probing depth, CAL, OHI, GI, and periodontal pathogens which shows that the amount of recolonization of microbes is less when LASER is used as an adjuvant to conventional therapy.
Conclusion: Diode LASER as an adjuvant to SRP has shown additional benefits over conventional therapy in all the clinical parameters evaluated and this can be associated in the treatment of periodontal therapy. BANA-enzymatic kit is a simple chair side kit which can be reliable indicator of BANA positive species in dental plaque.