Physicochemical Analysis of the Aqueous Extracts of Six Nigerian Medicinal Plants

Purpose: Extracts of Picralima nitida seeds, Detarium microcarpum stem bark, Aframomum melagueta seeds, Terminalia catappa leaves, Acacia nilotica pods, and Morinda lucida stem bark, are under consideration for development into suitable dosage forms for treating diabetes mellitus, sickle cell anemia and malaria. This study aimed at evaluating the extracts for features that would influence decisions on them in the course of the project. Methods: Physicochemical determinations, including proximate analysis, were done by sensory examination, and gravimetric and electrochemical techniques. Thin layer chromatography was carried out with normal silica plates using various solvent systems. Metallic content analyses were carried out by atomic absorption spectroscopy. Results: The extracts were dry but hygroscopic, with a loss on drying range of 0.26 – 12.00 %w/w. The pH of the 5 - 10 % solutions ranged 5 - 7. No harsh sensory effects, such as lacrimation, were detected in any of the extracts. Total ash ranged from 3.79 – 20.68 %w/w, while acid insoluble ash values were below detection. The extracts yielded reproducible chromatograms on normal silica plates developed with various solvent systems. Copper, present at 0.16 - 0.58 mg/100g, was the lowest occurring microelement while calcium content was highest, at 41 - 216 mg/100g. The level of lead, a heavy metal, was 0.05 - 0.22 mg/100g. Conclusion: The results confirm that the extracts require no special handling, possess characteristics that would allow their possible development into solid dosage forms, and that their lead contents complied with official limits. Keywords: Aqueous extract, Picralima nitida, Detarium microcarpum, Aframomum melagueta, Terminalia catappa, Acacia nilotica, Morinda lucida.