Why Mānuka isn't the only healing honey from New Zealand anymore

Move over Mānuka—scientists uncover the surprising health powers of New Zealand's lesser-known native honeys, packed with antioxidants, polyphenols, and natural antibacterial strength.

Study: Antibacterial Properties, Arabinogalactan Proteins, and Bioactivities of New Zealand Honey. Image Credit: Janice Chen / Shutterstock

In a recent study in the journal Antioxidants, researchers at the Auckland University of Technology conducted several assays and experiments to determine the health benefits of eight native varieties of New Zealand honey. Their assays determined the antibacterial effects, arabinogalactan proteins (AGPs), polyphenolic content, and antioxidant activities of these kinds of honey, many of which, except mānuka, had been relatively understudied until now.

Study findings revealed that all varieties of honey exhibited antibacterial properties and AGPs. Thyme honey was the richest source of antioxidants and Total Phenolic Content (TPC), while beech honeydew honey was the richest source of Total Flavonoid Content (TFC). Polyphenol concentrations varied across all the evaluated honeys. Notably, thyme and beech honeydew honey contained significant amounts of Vitamin C, a nutrient not found in the other six honey types. Artificial honey was included as a control, and results confirmed that the antibacterial properties of the natural honeys were not solely due to sugar content. Together, these findings underscore the health benefits of native New Zealand honey and its potential to naturally enhance human well-being.

Background

Honey is a sweet, sticky, and viscous food made by several species of bees using floral nectar or honeydew secretions. It has constituted a staple dietary component of several cultures for thousands of years, revered for its benefits to human health and well-being as a food source and an antibacterial agent (wound cleansing).

While honey is being increasingly researched for its health benefits, particularly as a sugar substitute, and its antibacterial properties, most studies focus on only a few of the hundreds of honey varieties known. A notable example is native New Zealand honey – while more than ten honey varieties are known, most literature focuses on only the mānuka variety. Since the source (raw material – nectar or honeydew) and bee species can significantly alter the honey composition and, in turn, properties, the understudied honey types may be treasure troves waiting to be unlocked.

About the study

The present study addresses knowledge gaps by evaluating the antibacterial effects, polyphenolic constituents, antioxidant properties, and arabinogalactan proteins (AGPs) in eight native New Zealand honey varieties. Honey samples used in the study were collected across New Zealand between 2018 and 2020 and were stored under controlled settings to preserve their nutritional properties.

Map of New Zealand indicating the locations of honey sample collection. Source: Google Earth Pro accessed October 2024.

The Australia New Zealand Food Standards Code Standard 2.8.2 was used to identify and classify honey types into two categories: 1. Clover (obtained from Trifolium repens), and 2. Beech honeydew (Nothofagus solandri), 3. Mānuka (Leptospermum scoparium), 4. Pōhutukawa (Metrosideros excelsa), 5. Rewarewa (Knightia excelsa), 6. Kānuka (Kunzea ericoides), 7. Thyme (Thymus vulgaris), and 8. Kamahi (Weinmannia racemosa).

“These specific floral varieties were chosen for their prevalence in New Zealand and their importance in the honey industry. Known for their unique properties and potential health benefits, each variety holds value for both commercial and research applications.”

All samples were subjected to nine assays and experiments aimed at estimating their antibacterial properties (broth assay, growth inhibition assay), AGP content (radial gel diffusion assay), antioxidant power (Ferric Reducing Antioxidant Power Assay [FRAP], Cupric Ion Reducing Antioxidant Capacity [CUPRAC] assay, and 2,2-diphenyl-1-picrylhydrazyl [DPPH] radical scavenging capacity assay), phenolic content (Folin–Ciocalteau Total Phenolic Content (TPC) assay), flavonoid content (aluminum chloride colorimetric method) and vitamin C content (high-performance liquid chromatography [HPLC]).

Liquid Chromatography-Mass Spectrometry (LC-MS) was used to identify and quantify the different polyphenols in these honey varieties. Analysis of Variance (ANOVA), Analysis of Covariance (ANCOVA), and partial least squares discriminant analysis (PLS-DA) were used to compare the different variable concentrations and potential health benefits between the analyzed honey types.

Study findings

Antibacterial assays were conducted using eight bacterial species: Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923, Bacillus subtilis, Staphylococcus epidermidis ATCC 12228, Enterococcus faecalis ATCC 29212, Salmonella typhimurium, Lactobacillus plantarum, and Pseudomonas aeruginosa ATCC 27853. Encouragingly, all honey varieties exhibited significant antibacterial properties against these bacterial strains, with mānuka, kānuka, and pōhutukawa demonstrating potent antibacterial effects against several strains even at low concentrations such as 3.125%, and rewarewa at higher concentrations (25.0%). Clover honey demonstrated the least significant impact of the tested honeys.

Radial gel diffusion assays revealed the presence of AGPs in all tested honeys, with pōhutukawa having the highest concentration, followed by kamahi. Beech honeydew and thyme honey were found to have the lowest concentrations. In contrast, thyme honey, followed by beech honeydew, demonstrated the highest antioxidant activity of the tested varieties, with clover and kāmahi honey showing the least significant antioxidant effects.

Surprisingly, only thyme and beech honeydew were found to contain trace amounts of vitamin C, while all other honey varieties were devoid of the vitamin. Polyphenol analysis revealed 13 different polyphenols in the tested honey, including quinic acid, hydroxybenzoic acid, p-coumaric acid, caffeic acid, rutin, benzoic acid, luteolin, kaempferol, quercetin, pinobanksin, chrysin, gallic acid, and pinocembrin. Pinocembrin was consistently the primary polyphenol of all honey types, with its highest concentration found in clover honey. Clover honey also exhibited high levels of caffeic acid and quercetin, while mānuka honey was distinguished by its significantly higher luteolin content.

Conclusions

The present study found an abundance of beneficial nutrients, antioxidants, and antibacterial components across all tested native New Zealand honeys. Notably, the concentration of these components varied substantially from honey to honey, highlighting their individual importance in the honey industry and potential human health benefits. Each honey variety exhibited a unique polyphenolic fingerprint, reinforcing their value not just in nutrition, but also for medicinal and commercial applications.