Antimicrobial Activity of Cu, Ni Carboxylates of Castor (Ricinus communis) Seed Oil and Their Calcinated Derivatives

Copper and nickel carboxylates of castor seed oil were prepared by metathesis in aqueous ethanol. The FTIR spectra of the carboxylates are characterized by two asymmetric vibrations of the carbox ylate group and two symmetric vibrations. For Cu carboxylate, the values are 1594 1532 cm^-1 and 1458 1409 cm^-1 while those of Ni carboxylate were observed at 1561 1513 cm^-1 and 1469 1412 cm^-1 respectively indicating that the carboxylates existed as bridging bidentate structure and confirmed their formation. The carboxylates were calcinated in muffle furnace at 400°C to obtain blackish derivatives. Antimicrobial activities of the carboxylates and their calcinated derivatives were assayed using modified Kirby Bauer disc diffusion method against two groups of medically implicated bacterial species, viz: Gram positive organisms (Staphylococcus aureus and Streptococcus faecalis,) and Gram negative organisms (Pseudomonas fluorescence, Salmonella thypii, Klebsiella pneumonia and Proteus mirabilis). It was observed that the antimicrobial potencies of the carboxylates and their derivatives compared favourably with the standard antibiotics used for the assay. However, calcinated derivative of Ni carboxylate showed a quite significant increase in the antimicrobial potency against both gram negative and gram positive microorganisms when compared with its carboxylate.