Design and Evaluation of Cryptolepine Hydrochloride-Loaded Gelatine Nanoparticles Intended for Parenteral Administration

Abstract

Background and aim: Malaria is a protozoa disease caused by the genus plasmodium. WHO statistics indicate that the disease affects more than 216 million people annually, killing about 655000. The parasites have developed resistance to most antimalarial compounds, necessitating the search for new drugs. Cryptolepine is one of such new compounds under study. The main objective of this thesis is to answer the question of whether or not pharmaceutical nanotechnology can be used as a formulation technique to improve the efficacy and safety of cryptolepine hydrochloride. Methods: Cryptolepine hydrochloride was isolated from Cryptolepis sanguinolenta and identified by NMR, mass, and melting point. An HPLC method was developed and validated for the detection and quantification of cryptolepine hydrochloride. Preformulation studies included compatibility, solubility, acid dissociation constant, FTIR, Raman and stability. Cryptolepine hydrochloride-loaded gelatine nanoparticles were formulated by a double desolvation method and characterized in vitro. Pharmacokinetics and in vivo chemosuppressive activity of the formulation in relation to the aqueous solution of the compound were investigated in Wistar rats by using a four-day suppressive test. Results: NMR, mass, and melting point of the isolate were consistent with the compound. The HPLC method was precise, accurate reproducible and stability indicating. Cryptolepine constitutes about 1.2% of the root content. Cryptolepine hydrochloride was slightly soluble over wide pH range with maximum around pH 4. This solubility profile was supported by a high pKa value around 11.2. There is little interaction between cryptolepine hydrochloride and gelatine (A). Both FTIR and RAMAN scattering agreed with theoretical vibrations and also confirmed presence of functional groups of the compound. The nanoparticles have size range, mostly under 250 nm. Products were stable under refrigeration but less so at room temperature signified by reduced zeta potential and increased particle size. The nanoformulations were less haemolytic compared to the compound, an indication of improved safety. Pharmacokinetic data showed an improved profile depicted by higher AUC (400.47 μg-hr/ml), longer elimination halflife (21.85 hr), reduced distribution rate (1.06 1/hr), reduced clearance (2.90 ml/hr), and increased mean residence time (29.47 hr) compared to the respective values of 88.30 μg-hr/ml, 11.70 hr, 2.03 1/hr, 19.83 ml/hr and 8.57 hr obtained with aqueous drug injection. These observations were confirmed by enhanced chemosuppressive activity by the nanoformulation in relation to the compound. Conclusion: The findings in this work answered in the affirmative the question of whether or not pharmaceutical nanotechnology can be used as a formulation technique to improve the efficacy and safety of cryptolepine hydrochloride.