Exploring South African honey: a focus on chemical composition and antimicrobial activity against pathogenic organisms

Abstract

Honey has been used as an alternative medicinal agent for many years. Several factors give honey its antimicrobial ability including the presence of hydrogen peroxide, phenolic compounds, low moisture content, low pH, and high sugar concentrations. In South Africa, data on the antimicrobial activity of indigenous honey is limited, as there are many floral sources that are still underexplored. Additionally, very few studies highlight the influence that antimicrobial properties may have on the honey’s antimicrobial activity. The aim of this study was to investigate whether ten honey samples collected from different regions within South Africa possess antibacterial activity against clinically relevant pathogenic bacteria, namely Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli and Pseudomonas aeruginosa, and to determine whether the physicochemical properties of the honey samples collected influenced their antimicrobial activity. Samples were mainly collected from regions within the Western Cape and Northern Cape. The phenol equivalence assay was employed to assess antibacterial activity at honey concentrations ranging from 5 – 50% (w/v). Physicochemical properties were assessed, including moisture content, colour intensity, pH, and chemical composition. Results of this study revealed that S. aureus was the most susceptible bacterium and P. aeruginosa the least. Honey obtained from the Succulent Karoo region exhibited exceptional antibacterial activity, whereas most Graafwater region samples exhibited poor or no activity. Despite no statistical correlation being observed between the physicochemical properties and the antibacterial activity of the honey samples, all Succulent Karoo samples (Niewoudtville – Loeriesfontein and Vanrhynsdorp – Niewoudtville) possessed a high pH (4.36 and 4.59) and moisture content (4.42% and 8.39%) and were darkest in colour (211.89 mm and 323.27 mm) compared to other samples. Furthermore, 1H NMR analysis revealed that Succulent Karoo samples are chemically unique compared with other honeys, with unidentified resonances that could correspond to bioactive compounds. In conclusion, this study revealed that honey derived from the Succulent Karoo region in South Africa has the potential to be used therapeutically and provides insight on the chemical composition of South African honeys, contributing towards the chemical profile of South African flora