Issue 39, 2021

Molecular salts of quinine: a crystal engineering route to enhance the aqueous solubility

Abstract

The antimalarial drug quinine (QUN) has poor aqueous solubility and belongs to Biopharmaceutical Classification System (BCS) Class-II. We report 12 novel molecular salts of QUN with α,ω-aliphatic dicarboxylic acids and aromatic coformers. The high basicity of QUN and ΔpKa of ∼5 make the complexes ionic, and most of them are hydrates. The solid forms showed enhanced aqueous solubility compared to the pristine QUN. The single-crystal and powder X-ray diffraction, thermal, and microscopy data provide structural, compositional, and stability profiles of the salts. The calculated Full Interaction Maps (FIMs) provide statistical insights into the salt formation and high probability of hydration in QUN. Though with prospective torsional freedom, QUN in most complexes adopts a unique conformation; this indicates that the structure class has a higher statistical probability and belongs to a relatively deep potential energy trough in the vast crystal landscape.

Graphical abstract: Molecular salts of quinine: a crystal engineering route to enhance the aqueous solubility

Supplementary files

Article information

Article type
Paper
Submitted
15 Kho 2021
Accepted
22 Mha 2021
First published
24 Mha 2021

CrystEngComm, 2021,23, 6942-6951

Molecular salts of quinine: a crystal engineering route to enhance the aqueous solubility

I. S. Divya, S. Amrutha, S. SeethaLekshmi and S. Varughese, CrystEngComm, 2021, 23, 6942 DOI: 10.1039/D1CE00791B

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