A Novel Polymorph of 5-Chloro-8-Hydroxyquinoline with Improved Water Solubility and Faster Dissolution Rate

Abstract

The active pharmaceutical ingredient 5-chloro-8-hydroxyquinoline, which has shown potential antituberculosis activities, crystallizes in two different polymorphic forms, denoted Form I (Banerjee et al. Acta Crystallogr, Sect C: Cryst Struct Commun C42:1408–11, 1986) and Form II. In this present work, we have succeeded in crystallization of Form II. The cell dimensions of the monoclinic P2(1)/c Form II are a = 13.132(3) Å, b = 3.7632(8) Å, c = 15.459(3) Å and β = 99.69(3)°. Characterizations for Form II have been conducted in details. Finally the solubilities and dissolution kinetics of both polymorphs have been measured in various media at different temperature. The measurement results highlight the fact that Form II has higher water solubility and faster dissolution rate than Form I.

Index Abstract

5-chloro-8-hydroxyquinoline has been well known for its antifungal, antibacterial and antiamebic activities for decades. Recently, 5-chloro-8-hydroxyquinoline was reported to exhibit good antituberculosis activity even for multidrug-resistant isolates as well. The first crystalline form (Form I) of 5-chloro-8-hydroxyquinoline was reported in 1986 by Banerjee and Saha. Then there has been no new crystalline form of 5-chloro-8-hydroxyquinoline discovered from then on. In this work, we primarily reported the crystal structure of a novel polymorph (Form II) of 5-chloro-8-hydroxyquinoline. Solubility and dissolution kinetic measurements of both polymorphs were performed as well.