Chemical compounds, FTIR and <i>in vitro</i> antibacterial analyses of the acetone stem bark extract of <i>Ziziphus mucronata</i> subsp. <i>mucronata</i> (Buffalo Thorn) against potential nosocomial bacterial pathogens

Ziziphus mucronata is a commonly used plant in South Africa for treatment of infections and diseases. The study aimed at determining the antimicrobial activities and the pharmacologically active chemical compounds present in the acetone extract of this plant. The pharmacologically active chemical compounds in this extract were determined using gas chromatography-mass spectrometry (GC-MS). Their antibacterial activity was assayed in vitro by agar well diffusion and macrobroth dilution techniques against different bacterial isolates. Fourier transform infrared (FTIR) spectroscopy was used to determine the functional groups of the chemical compounds in the plant extract. The GC-MS result showed 52 chemical compounds with 29 compounds having reported pharmacological activities (while for 23 compounds they have not been reported), with1,1,6-trimethyl-3-methylene-2-(3,6,9,13-tetramethyl-6-ethenye-10,14-dimethylene-pentadec-4-enyl)cyclohexane, 2,6-β-17-β-Trihydroxy-6-α-pentyl-2,3-seco-5-α-androstan-3-oic acid-γ-lactone, 2,3,4,5-tetrahexyl-dimethyl ester Hexanedioic acid, i-Propyl 9-tetradecenoate, (3-β-22E)-Ergosta-7,22-dien-3-ol, Ergosta-4,22-dien-3-one, 3,4-dimethoxy-methylmonoacetalBenzaldehyde, 6-(acetyloxy)-4-methyl-4-Hexenoic acid and O-α-D-glucopyranosyl-α-D-Glucopyranoside being compounds amounting for ≥1%. The FTIR spectrograph indicated that the identified compounds are amines, amides, alkanes, aldehydes, diketones, nitrosamine, esters, alkyl amine, secondary and primary alcohols and sulfoxide groups which are present in the plant extract. The Minimum Inhibitory Concentrations (MICs) ranged between 0.31 mg/mL and 5.5 mg/mL against the test bacterial isolates. This study shows the biological activities of Ziziphus mucronata extract depend greatly on the varied concentrations of the chemical compounds identified in the acetone extract and indicated the potential importance of this plant as a significant source of novel compounds for the treatment of diseases over synthetic antibiotics.