Extraction, Characterization, and Chemical Modification of Ricinine Isolated from Castor Seeds: Formation of Metal Complexes and Evaluation of Antibacterial Activity

Background: Ricinine is a castor alkaloid. Its significance is due to its chemical properties, biological potential and prospects of its antibacterial complexes. Objectives: To extracted and characterized from its castor garden origin, complexes were formed with Platinum, Copper, Cobalt, Nickel and Zinc and the same were tested for their antibacterial activity. Methodology: Seeds were shade dried and sequentially extracted with diethyl ether, acid, base and chloroform. The characterization of the compounds was carried out by FTIR, UV–Vis, ¹H NMR spectroscopy, melting point determination, and mass spectrometry. The antibacterial activity was determined by agar diffusion technique using Escherichia coli and Staphylococcus aureus bacteria. Results: Ricinine crystals weighing 311mg which had a slightly yellowish colour were obtained. The nitrile band at 2219.92 cm⁻¹, maximum absorption at 322 nm, resonance signals at 8.11, 6.43, 3.98, and 3.60 ppm, and melting range of 198.8–199.5 °C supported ricinine identity and purity. The changes in the complexes UV–Vis and infrared spectra with low frequency bands suggest coordination. The platinum complex showed the greatest inhibitory potential (22 & 24 mm), followed by copper (18 & 20 mm), cobalt (14 & 15 mm), nickel (11 & 12 mm) and zinc (8 & 9 mm) against E. coli and S. aureus, respectively. Ciprofloxacin produced 31- and 33 mm, while dimethyl sulfoxide exhibited no inhibition. Conclusion: The metal co-ordinated complex can be found to be more effective for its antibacterial activity, but to confirm structure, activity and safety, MIC test, elemental analysis, stability study and cellular toxicity should be done.