GC-MS Profile, Antimicrobial Properties and Spectra Characterization of the Ethanol Extract of Theobroma cacao Beans Grown in Nigeria
E. G. Adeyeni
*
Industrial Chemistry Department, University of Ilesa, Ilesa, Osun Sate, Nigeria and Chemistry Department, Hallmark University, Ijebu-Itele, Ogun Sate, Nigeria.
G. M. Taiwo
Chemistry Department, National Open University, Osogbo Study Center, Osun Sate, Nigeria.
A. E. Ariwoola
Chemistry Department, Hallmark University, Ijebu-Itele, Ogun Sate, Nigeria.
O. A. Tawose
Department of Microbiology, Hallmark University, Ijebu-Itele, Ogun Sate, Nigeria.
*Author to whom correspondence should be addressed.
Abstract
Cocoa (Theobroma cacao) contains several classes of bioactive compounds that may contribute to biological activity. This study characterised an ethanol extract of cocoa bean powder sourced from Nigeria and evaluated its antimicrobial activity against Klebsiella pneumoniae and Escherichia coli. Qualitative phytochemical screening was used to assess secondary metabolites, while Fourier transform infrared spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC-MS) were applied for chemical characterisation. Alkaloids, tannins, and phenols were detected, whereas saponins, flavonoids, glycosides, terpenoids, steroids, anthraquinones, and phlobatannins were not detected. FT-IR analysis showed prominent absorption bands at 3398.67, 2920.32, 2850.88, 1689.70, and 1288.49 cm⁻¹, corresponding to functional groups associated with O-H, C-H, carbonyl, and C-O vibrations. GC-MS analysis indicated multiple chemical constituents in the ethanol extract. In the antimicrobial assay, the extract produced inhibition zones of 10.50 ± 0.5 mm and 8.00 ± 1.0 mm against K. pneumoniae at 100 and 50 mg/mL, respectively, while no inhibition was observed against E. coli at the tested concentrations. Ceftriaxone showed greater activity than the extract. Overall, the findings indicate that Nigerian cocoa bean ethanol extract contains several phytochemical constituents and exhibits measurable antimicrobial activity against K. pneumoniae under the conditions of this study. The study therefore provides a combined chemical and biological profile of the locally sourced cocoa material.
Keywords: Theobroma cacao, cocoa beans, ethanol extract, phytochemical screening, antimicrobial activity, Klebsiella pneumoniae, Escherichia coli, FTIR, GC-MS