Antimicrobial Evaluation of Cardol and Cardol-Metal Complexes from the Nut Shell Liquid of <I>Anacardium occidentale</I>

Abstract

Cardol, as one of the major constituents of Cashew Nut Shell Liquids has received little attention in terms of modification and applications. The presence of two hydroxyl groups and an alkyl side chain of 15 carbon length make it a natural compound of interest. The present study is aimed at modification and complexation of cardol, and the antimicrobial investigations of the compound as well as its analogue and complexes. Isolated cardol from cashew nut shell liquid was nitrated, and the compounds were used in the synthesis of metal (II) complexes of Copper, Cobalt, and Zinc. The compounds and complexes were characterised by melting points, UV-Vis spectrophotometry, Fourier Transform Infrared (FTIR) spectrophotometry, and Nuclear Magnetic resonance (NMR) spectroscopy. The antibacterial and antifungal evaluations of both the compounds and complexes were tested in vitro against some selected bacteria and fungi. From the results, Copper complex of nitrocardol produced significantly higher antibacterial zone of inhibition (11.5 ± 2.1 mm) against Pedobacter mendelii than tetracycline while Copper complex of cardol showed significantly higher antifungal activity (13.5 ± 2.1 mm) against Rhizopus stolonifar than clotrimazole (10.0 ± 0.0 mm). It was generally observed that modification and metal complexation enhanced the antimicrobial activity of cardol. Further studies on these complexes could be done to enhance their potencies and potentials for use as antibacterial and antifungal agents.