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Chakraborty J, Mahali K, Henaish AMA, Ahmed J, Alshehri SM, Hossain A, Roy S. Exploring the solubility and intermolecular interactions of biologically significant amino acids l-serine and L-cysteine in binary mixtures of H 2O + DMF, H 2O + DMSO and H 2O + ACN in temperature range from T = 288.15 K to 308.15 K. Biophys Chem 2024; 311:107272. [PMID: 38824845 DOI: 10.1016/j.bpc.2024.107272] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2024] [Revised: 05/14/2024] [Accepted: 05/26/2024] [Indexed: 06/04/2024]
Abstract
In the presented work, a study on the solubility and intermolecular interactions of l-serine and L-cysteine was carried out in binary mixtures of H2O + dimethylformamide (DMF), H2O + dimethylsulfoxide (DMSO), and H2O + acetonitrile (ACN) in the temperature range of T = 288.15 K to 308.15 K. l-serine exhibited the highest solubility in water, while L-cysteine was more soluble in water-DMF. The solvation process was assessed through standard Gibbs energy calculations, indicating the solvation stability order: water-ACN > water-DMSO > water-DMF for l-serine, and water-DMF > water-DMSO > water-ACN for L-cysteine. This study also explored the influence of these amino acids on solvent-solvent interactions, revealing changes in chemical entropies and self-association patterns within the binary solvent mixtures.
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Affiliation(s)
- Jit Chakraborty
- Department of Chemistry, University of Kalyani, Kalyani 741235, Nadia, India; Department of Chemistry, JIS College of Engineering, Kalyani 741235, Nadia, India
| | - Kalachand Mahali
- Department of Chemistry, University of Kalyani, Kalyani 741235, Nadia, India.
| | - A M A Henaish
- Physics Department, Faculty of Science, Tanta University, Tanta 31527, Egypt; NANOTECH Center, Ural Federal University, Ekaterinburg 620002, Russia
| | - Jahangeer Ahmed
- Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
| | - Saad M Alshehri
- Department of Chemistry, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
| | - Aslam Hossain
- Smart Materials Research Institute, Southern Federal University, Sladkova 178/24, 344090 Rostov-on-Don, Russian Federation
| | - Sanjay Roy
- Department of Chemistry, School of Sciences, Netaji Subhas Open University, Kolkata, West Bengal, India.
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Nainwal N, Jawla S, Singh R, Banerjee S, Saharan VA. Solubility-permeability interplay of hydrotropic solubilization of piroxicam. Drug Dev Ind Pharm 2024; 50:481-494. [PMID: 38717346 DOI: 10.1080/03639045.2024.2349576] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2024] [Accepted: 04/25/2024] [Indexed: 05/15/2024]
Abstract
OBJECTIVES In this research paper, an investigation has been made to assess the simultaneous effect of a solubility enhancement approach, i.e., hydrotropy on the solubility and apparent permeability of piroxicam. The solubility of piroxicam (PRX) a BCS (biopharmaceutics classification system) class II drug has been increased using a mixed hydrotropy approach. This study is based on identifying the pattern of solubility-permeability interplay and confirming whether every solubility gain results in a concomitant decrease in permeability or permeability remains unaffected. METHOD Solid dispersions of PRX were formulated using two hydrotropes, viz., sodium benzoate (SB) and piperazine (PP) by solvent evaporation method. A comprehensive 32factorial design was employed to study the effect of hydrotropes on the solubility and permeability of PRX. Subsequently, PRX tablets containing these solid dispersions were formulated and evaluated. KEY FINDINGS SB and PP displayed a significant increase in the solubility of PRX ranging from 0.99 to 2.21 mg/mL for F1-F9 batches attributed to the synergistic effect of hydrotropes. However, there is a reduction in PRX permeability with increasing hydrotrope levels. The decline in permeability was notably less pronounced compared to the simultaneous rise in aqueous solubility of PRX. CONCLUSION An evident tradeoff between permeability and solubility emerged through the mixed hydrotropic solubilization for PRX. As PRX has generally higher intrinsic permeability, it has been assumed that this permeability loss will not affect the overall absorption of PRX. However, it may affect the absorption of drugs with limited permeability. Therefore, solubility permeability interplay should be investigated during solubility enhancement.
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Affiliation(s)
- Nidhi Nainwal
- Uttaranchal Institute of Pharmaceutical Sciences, Uttaranchal University, Dehradun, Uttarakhand, India
- Adarsh Vijendra Institute of Pharmaceutical Sciences, Shobhit University, Saharanpur, Uttar Pradesh, India
- Department of Pharmaceutics, School of Pharmaceutical Sciences and Technology, Sardar Bhagwan Singh University, Dehradun, Uttarakhand, India
| | - Sunil Jawla
- Adarsh Vijendra Institute of Pharmaceutical Sciences, Shobhit University, Saharanpur, Uttar Pradesh, India
- Geeta Institute of Pharmacy, Geeta University, Panipat, Haryana, India
| | - Ranjit Singh
- Adarsh Vijendra Institute of Pharmaceutical Sciences, Shobhit University, Saharanpur, Uttar Pradesh, India
| | - Surojit Banerjee
- Department of Pharmaceutics, School of Pharmaceutical Sciences and Technology, Sardar Bhagwan Singh University, Dehradun, Uttarakhand, India
| | - Vikas Anand Saharan
- Department of Pharmaceutics, School of Pharmaceutical Sciences and Technology, Sardar Bhagwan Singh University, Dehradun, Uttarakhand, India
- Department of Pharmaceutical Technology (Formulations), National Institute of Pharmaceutical Education and Research, Guwahati (NIPER-G), Guwahati, Assam, India
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Hou J, Zhao P, Wang Y, Jiang X, Fu Q. Co-Amorphization of Acemetacin with Basic Amino Acids as Co-Formers for Solubility Improvement and Gastric Ulcer Mitigation. Pharmaceutics 2024; 16:745. [PMID: 38931867 PMCID: PMC11206560 DOI: 10.3390/pharmaceutics16060745] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2024] [Revised: 05/22/2024] [Accepted: 05/29/2024] [Indexed: 06/28/2024] Open
Abstract
Acemetacin (ACM) is a new non-steroidal anti-inflammatory drug with anti-inflammatory, analgesic, and antipyretic effects. However, the poor water solubility and gastrointestinal side effects limit its use. Recently, the co-amorphous (CAM) strategy has attracted great interest to improve solubility for poorly water-soluble drugs, and basic amino acids have the potential to protect the gastrointestinal tract. In order to develop a highly efficient and low-toxic ACM formulation, we prepared ACM CAM systems, with basic amino acids (lysine, arginine, and histidine) as co-formers, using a cryo-milling method. The solid-state behaviors of the ACM CAM systems were characterized by polarizing light microscopy, differential scanning calorimetry, and powder X-ray diffraction. Fourier transform infrared spectroscopy and molecular docking were carried out to understand the formation mechanism. Moreover, the gastro-protective effects of ACM CAM systems were evaluated in a rat gastric ulcer model. The results demonstrated that the CAM systems improved the dissolution rates of ACM compared with the neat amorphous counterpart. Furthermore, ACM CAM systems are significantly effective in mitigating the ACM-induced gastric ulcer in rats, and the ulcer inhibition rates were almost 90%. More importantly, this study provided a useful method for mitigating drug-induced gastrointestinal damage and broadened the applications of drug-amino acid CAM systems.
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Affiliation(s)
- Jiayue Hou
- Wuya College of Innovation, Shenyang Pharmaceutical University, No. 103, Wenhua Road, Shenyang 110016, China
| | - Peixu Zhao
- Wuya College of Innovation, Shenyang Pharmaceutical University, No. 103, Wenhua Road, Shenyang 110016, China
| | - Yanfei Wang
- Wuya College of Innovation, Shenyang Pharmaceutical University, No. 103, Wenhua Road, Shenyang 110016, China
| | - Xiwei Jiang
- College of Medical Equipment, Shenyang Pharmaceutical University, No. 103, Wenhua Road, Shenyang 110016, China
| | - Qiang Fu
- Wuya College of Innovation, Shenyang Pharmaceutical University, No. 103, Wenhua Road, Shenyang 110016, China
- Joint International Research Laboratory of Intelligent Drug Delivery Systems, Ministry of Education, Shenyang 110016, China
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Tian L, Cao C, Ho J, Stenzel MH. Maximizing Aqueous Drug Encapsulation: Small Nanoparticles Formation Enabled by Glycopolymers Combining Glucose and Tyrosine. J Am Chem Soc 2024; 146:8120-8130. [PMID: 38477486 DOI: 10.1021/jacs.3c12502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/14/2024]
Abstract
Highly potent heterocyclic drugs are frequently poorly water soluble, leading to limited or abandoned further drug development. Nanoparticle technology offers a powerful delivery approach by enhancing the solubility and bioavailability of hydrophobic therapeutics. However, the common usage of organic solvents causes unwanted toxicity and process complexity, therefore limiting the scale-up of nanomedicine technology for clinical translation. Here, we show that an organic-solvent-free methodology for hydrophobic drug encapsulation can be obtained using polymers based on glucose and tyrosine. An aqueous solution based on a tyrosine-containing glycopolymer is able to dissolve solid dasatinib directly without adding an organic solvent, resulting in the formation of very small nanoparticles of around 10 nm loaded with up to 16 wt % of drug. This polymer is observed to function as both a drug solubilizer and a nanocarrier at the same time, offering a simple route for the delivery of insoluble drugs.
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Hasegawa K, Goto S, Kataoka H, Chatani H, Kinoshita T, Yokoyama H, Tsuchida T. Quantification of crystallinity during indomethacin crystalline transformation from α- to γ-polymorphic forms and of the thermodynamic contribution to dissolution in aqueous buffer and solutions of solubilizer. RSC Adv 2024; 14:4129-4141. [PMID: 38292264 PMCID: PMC10825737 DOI: 10.1039/d3ra08481g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Accepted: 01/19/2024] [Indexed: 02/01/2024] Open
Abstract
The thermodynamic properties and dissolution of indomethacin (INM) were analyzed as models for poorly water-soluble drugs. Physical mixtures of the most stable γ-form and metastable α-form of INM at various proportions were prepared, and their individual signal intensities proportional to their mole fractions were observed using X-ray powder diffraction and Fourier transform infrared spectrometry at standard temperature. The endothermic signals of the α-form, with a melting point of 426 K, and that of the γ-form, with a melting point of 433 K, were obtained by differential scanning calorimetry (DSC). Furthermore, an exothermic DSC peak of the α/γ-phase transition at approximately 428 K was obtained. As we computed the melting entropy of the α-form and that of its transformation, the frequency of the transition was quantitatively determined, which indicated the maximum of the α/γ-phase transition at an α-form proportion of 68%. Subsequently, the thermodynamic contributions of the α- and γ-forms were analyzed using a Van't Hoff plot for solubility in aqueous solutions at pH 6.8. The dissolution enthalpies for α- and γ-forms were 28.2 and 31.2 kJ mol-1, respectively, which are in agreement with the quantitative contribution predicted by the product of the temperature and melting entropy. The contribution of melting entropy was conserved in different dissolution processes with aqueous solvents containing lidocaine, diltiazem, l-carnosine, and aspartame as solubilizers; their γ-form Setschenow coefficients were -39.6, +82.9, -17.3, and +23.2, whereas those of the α-form were -39.7, +80.4, -16.7, and +22.7, respectively. We conclude that the dissolution ability of the solid state and solubilizers indicate their additivity independently.
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Affiliation(s)
- Kanji Hasegawa
- Faculty of Pharmaceutical Sciences, Tokyo University of Science 2641 Yamazaki, Noda Chiba 278-8510 Japan
| | - Satoru Goto
- Faculty of Pharmaceutical Sciences, Tokyo University of Science 2641 Yamazaki, Noda Chiba 278-8510 Japan
| | - Hikaru Kataoka
- Faculty of Pharmaceutical Sciences, Tokyo University of Science 2641 Yamazaki, Noda Chiba 278-8510 Japan
| | - Hitoshi Chatani
- Faculty of Pharmaceutical Sciences, Tokyo University of Science 2641 Yamazaki, Noda Chiba 278-8510 Japan
| | - Takatoshi Kinoshita
- Faculty of Pharmaceutical Sciences, Tokyo University of Science 2641 Yamazaki, Noda Chiba 278-8510 Japan
| | - Hideshi Yokoyama
- Faculty of Pharmaceutical Sciences, Tokyo University of Science 2641 Yamazaki, Noda Chiba 278-8510 Japan
| | - Tomohiro Tsuchida
- Faculty of Pharmaceutical Sciences, Tokyo University of Science 2641 Yamazaki, Noda Chiba 278-8510 Japan
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Suleiman Alsalhi M, Royall PG, Al-Obaidi H, Alsalhi A, Cilibrizzi A, Chan KLA. Non-salt based co-amorphous formulation produced by freeze-drying. Int J Pharm 2023; 645:123404. [PMID: 37714312 DOI: 10.1016/j.ijpharm.2023.123404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2023] [Revised: 09/08/2023] [Accepted: 09/09/2023] [Indexed: 09/17/2023]
Abstract
Amino acids-based co-amorphous system (CAM) has shown to be a promising approach to overcome the dissolution challenge of biopharmaceutics classification system class II drugs. To date, most CAM formulations are based on salt formation at a 1:1 M ratio and are prepared by mechanical activation. However, its use in medicinal products is still limited due to the lack of in-depth understanding of non-ionic based molecular interactions. There are also limited studies on the effect of drug-to-co-former ratio, the development of more scalable, less aggressive, manufacturing processes such as freeze drying and its dissolution benefits. This work aims to investigate the effect of the ratio of tryptophan (a model non-ionic amino acid) to indomethacin (a model drug) on a non-salt-based CAM prepared via freeze-drying with the tert-butyl alcohol-water cosolvent system. The CAM material was systemically characterized at various stages of the freeze-drying process using DSC, UV-Vis, FT-IR, NMR, TGA and XRPD. Dissolution performance and physical stability upon storage were also investigated. Freeze-drying using the cosolvent system has been successfully shown to produce CAMs. The molecular interactions involving H-bonding, H/π and π-π between compounds have been confirmed by FT-IR and NMR. The drug release rate for formulations with a 1.5:1 drug: amino acid molar ratio (or 1:0.42 wt ratio) or below is found to be significantly improved compared to the pure crystalline drug. Furthermore, formulation with a 2.3:1 drug:amino acid molar ratio (or 1:0.25 wt ratio) or below have shown to be physically stable for at least 9 months when stored at dry condition (5% relative humidity, 25 °C) compared to the pure amorphous indomethacin. We have demonstrated the potential of freeze-drying using tert-butyl alcohol-water cosolvent system to produce an optimal non-salt-based class II drug-amino acid CAM.
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Affiliation(s)
- Mohammed Suleiman Alsalhi
- Institute of Pharmaceutical Science, King's College London, SE1 9NH, UK; College of pharmacy, King Saud University, Riyadh, Saudi Arabia.
| | - Paul G Royall
- Institute of Pharmaceutical Science, King's College London, SE1 9NH, UK
| | - Hisham Al-Obaidi
- School of Chemistry, Food and Pharmacy (SCFP), University of Reading, Whiteknights, Reading RG6 6AP, UK
| | - Alyaa Alsalhi
- College of pharmacy, King Saud University, Riyadh, Saudi Arabia
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Yu Y, Tong D, Yu Y, Tian D, Zhou W, Zhang X, Shi W, Liu G. Toxic effects of four emerging pollutants on cardiac performance and associated physiological parameters of the thick-shell mussel (Mytilus coruscus). ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2023; 334:122244. [PMID: 37482340 DOI: 10.1016/j.envpol.2023.122244] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Revised: 07/01/2023] [Accepted: 07/20/2023] [Indexed: 07/25/2023]
Abstract
Robust cardiac performance is critical for the health and even survival of an animal; however, it is sensitive to environmental stressors. At present, little is known about the cardiotoxicity of emerging pollutants to bivalve mollusks. Thus, in this study, the cardiotoxic effects of four emergent pollutants, carbamazepine (CBZ), bisphenol A (BPA), tetrabromobisphenol A (TBBPA), and tris(2-chloroethyl) phosphate (TCEP), on the thick-shell mussel, Mytilus coruscus, were evaluated by heartbeat monitoring and histological examinations. In addition, the impacts of these pollutants on parameters that closely related to cardiac function including neurotransmitters, calcium homeostasis, energy supply, and oxidative status were assessed. Our results demonstrated that 28-day exposure of the thick-shell mussel to these pollutants resulted in evident heart tissue lesions (indicated by hemocyte infiltration and myocardial fibrosis) and disruptions of cardiac performance (characterized by bradyrhythmia and arrhythmia). In addition to obstructing neurotransmitters and calcium homeostasis, exposure to pollutants also led to constrained energy supply and induced oxidative stress in mussel hearts. These findings indicate that although do differ somehow in their effects, these four pollutants may exert cardiotoxic impacts on mussels, which could pose severe threats to this important species and therefore deserves more attention.
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Affiliation(s)
- Yingying Yu
- College of Animal Sciences, Zhejiang University, Hangzhou, PR China
| | - Difei Tong
- College of Animal Sciences, Zhejiang University, Hangzhou, PR China
| | - Yihan Yu
- College of Animal Sciences, Zhejiang University, Hangzhou, PR China
| | - Dandan Tian
- College of Animal Sciences, Zhejiang University, Hangzhou, PR China
| | - Weishang Zhou
- College of Animal Sciences, Zhejiang University, Hangzhou, PR China
| | - Xunyi Zhang
- College of Animal Sciences, Zhejiang University, Hangzhou, PR China
| | - Wei Shi
- College of Animal Sciences, Zhejiang University, Hangzhou, PR China
| | - Guangxu Liu
- College of Animal Sciences, Zhejiang University, Hangzhou, PR China.
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Fatease AA, Shoman ME, Abourehab MAS, Abou-Taleb HA, Abdelkader H. A Novel Curcumin Arginine Salt: A Solution for Poor Solubility and Potential Anticancer Activities. Molecules 2022; 28:262. [PMID: 36615455 PMCID: PMC9822184 DOI: 10.3390/molecules28010262] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 12/22/2022] [Accepted: 12/24/2022] [Indexed: 12/30/2022] Open
Abstract
Curcumin is a natural polyphenolic compound with well-known anticancer properties. Poor solubility and permeability hamper its use as an anticancer pharmaceutical product. In this study, L-arginine, a basic amino acid and a small hydrophilic molecule, was utilized to form a salt with the weak acid curcumin to enhance its solubility and potentiate the anticancer activities of curcumin. Two methods were adopted for the preparation of curcumin: L-arginine salt, namely, physical mixing and coprecipitation. The ion pair or salt was characterized for docking, solubility, DSC, FTIR, XRD, in vitro dissolution, and anticancer activities using MCF7 cell lines. The molecular docking suggested a salt/ion-pair complex between curcumin and L-arginine. Curcumin solubility was increased 335- and 440-fold by curcumin in L-arginine, physical, and co-precipitated mixtures, respectively. Thermal and spectral analyses supported the molecular docking and formation of a salt/ion pair between curcumin and L-arginine. The cytotoxicity of curcumin L-arginine salt significantly improved (p < 0.05) by 1.4-fold, as evidenced by the calculated IC50%, which was comparable to Taxol (the standard anticancer drug but with common side effects).
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Affiliation(s)
- Adel Al Fatease
- Department of Pharmaceutics, College of Pharmacy, King Khalid University, Abha 62529, Saudi Arabia
| | - Mai E. Shoman
- Department of Medicinal Chemistry, Faculty of Pharmacy, Minia University, Minia 61519, Egypt
| | - Mohammed A. S. Abourehab
- Department of Pharmaceutics, College of Pharmacy, Umm Al-Qura University, Makkah 21955, Saudi Arabia
- Department of Pharmaceutics, Faculty of Pharmacy, Minia University, Minia 61519, Egypt
| | - Heba A. Abou-Taleb
- Department of Pharmaceutics and Industrial Pharmacy, Faculty of Pharmacy, Merit University (MUE), Sohag 82755, Egypt
| | - Hamdy Abdelkader
- Department of Pharmaceutics, College of Pharmacy, King Khalid University, Abha 62529, Saudi Arabia
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Ya. Zakharova L, Vasilieva EA, Mirgorodskaya AB, Zakharov SV, Pavlov RV, Kashapova NE, Gaynanova GA. Hydrotropes: solubilization of nonpolar compounds and modification of surfactant solutions. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.120923] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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Effect of ATP and amino acids on the properties of cationic amphiphiles in solution and on the surface. Russ Chem Bull 2022. [DOI: 10.1007/s11172-022-3559-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/15/2022]
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Alsalhi MS, Royall PG, Chan KLA. Mechanistic study of the solubilization effect of basic amino acids on a poorly water-soluble drug. RSC Adv 2022; 12:19040-19053. [PMID: 35865577 PMCID: PMC9240925 DOI: 10.1039/d2ra02870k] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 06/15/2022] [Indexed: 11/21/2022] Open
Abstract
Amino acids have shown promising abilities to form complexes with poorly water-soluble drugs and improve their physicochemical properties for a better dissolution profile through molecular interactions. Salt formation via ionization between acidic drugs and basic amino acids is known as the major contributor to solubility enhancement. However, the mechanism of solubility enhancement due to non-ionic interactions, which is less pH-dependent, remains unclear. The aim of this study is to evaluate non-ionic interactions between a model acidic drug, indomethacin (IND), and basic amino acids, arginine, lysine and histidine, in water. At low concentrations of amino acids, IND-arginine and IND-lysine complexes have shown a linear relationship (AL-type phase solubility diagram) between IND solubility and amino acid concentration, producing ∼1 : 1 stoichiometry of drug-amino acid complexes as expected due to the strong electrostatic interactions. However, IND-histidine complexes have shown a nonlinear relationship with lower improvement in IND solubility due to the weaker electrostatic interactions when compared to arginine and lysine. Interestingly, the results have also shown that at high arginine concentrations, the linearity was lost between IND solubility and amino acid concentration with a negative diversion from linearity, following the type-AN phase solubility. This is indicative that the electrostatic interaction is being interrupted by non-electrostatic interactions, as seen with histidine. The IND-lysine complex, on the other hand, showed a complex curvature phase solubility diagram (type BS) as lysine self-assembles and polymerizes at higher concentrations. The freeze-dried drug-amino acid solids were further characterized using thermal analysis and infrared spectroscopy, with results showing the involvement of weak non-ionic interactions. This study shows that the solubility improvement of an insoluble drug in the presence of basic amino acids was due to both non-ionic and ionic interactions.
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Affiliation(s)
| | - Paul G Royall
- Institute of Pharmaceutical Science, King's College London SE1 9NH UK
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