Scientists show how Manuka and Ohia Lehua honey differ in their antioxidant potential, showing that while Manuka honey boasts higher phenolic content, Ohia Lehua honey excels in reducing oxidative stress and promoting antioxidant defenses.
Study: Phytochemical Composition and Antioxidant Activity of Manuka Honey and Ohia Lehua Honey. Image Credit: Valentyn Volkov / Shuttersotck.com
The use of honey as medicine is widespread across cultures, mainly due to its antioxidant and anti-inflammatory properties, which protect tissues from oxidative stress. A recent study published in the journal Nutrients investigated the different components in Manuka honey (MH) and ohia lehua honey (OLH) that contribute to their anti-inflammatory properties.
The damaging effects of oxidative stress
Oxidative stress arises from an imbalance between reactive oxygen species (ROS) and the body’s antioxidant defenses. During the inflammatory response to injury or infection, immune cells like macrophages and neutrophils release ROS.
Excessive ROS can oxidize and damage cell proteins, lipids, and nucleic acids, subsequently inducing a cycle of immunologic inflammatory responses. Unlike acute inflammation, which underlies the healing response, long-term inflammation amplifies tissue damage and contributes to chronic disease.
Inflammatory pathways like the nuclear factor-kappa B (NF-κB), cyclooxygenase (COX), and mitogen-activated protein kinase (MAPK) pathways lead to the increased production of pro-inflammatory cytokines like interleukin-6 (IL-6). These cytokines induce inflammation, oxidative stress, and the activation of the NLRP3 inflammasome. NLRP3 increases inflammation and may trigger chronic inflammatory conditions like type 2 diabetes and atherosclerosis.
The components of honey
Honey is a natural product primarily composed of fructose, glucose, and water. It also contains numerous phenolic plant compounds, enzymes, and organic acids, as well as hydrogen peroxide (H2O2) and methylglyoxal (MG), both of which are bioactive compounds.
Honey is a traditional medicine used to reduce inflammation and oxidative stress. Its antioxidant properties are key to preventing cardiovascular risk factors, disease, and cancer.
MH is pure honey produced by honeybees in New Zealand that primarily feed on the Manuka shrub (Leptospermum scoparium), whereas OLH honey is produced in the Ka’u district of Hawaii’s Big Island from honeybees feeding on Metrosiderospolymorpha blossoms.
Both MH and Kanuka honey inhibits inflammation in immune and cancer cell cultures. Honey's phenolic acids and flavonoids also have antioxidant activity.
Previous studies have established that honey can inhibit multi-drug-resistant bacteria like Staphylococcus aureus and Pseudomonas aeruginosa. With its high sugar concentrations, acidic pH, and bioactive content, honey prevents microbial growth and wound infection and promotes tissue repair.
Antimicrobial mechanisms in honey are either peroxide- or non-peroxide-based. Peroxide-based honey converts glucose to gluconic acid and hydrogen peroxide by glucose oxidase. Comparatively, non-peroxide-based honey like MH relies on polyphenols and the formation of methylglyoxal, which suppresses glucose peroxidase activity.
About the study
The current study examined the composition of MH and OLH, particularly the concentrations of polyphenolic plant compounds present within these types of honey. Additional in vitro experiments were performed to assess their antioxidant activity by determining the free radical scavenging capacity of the extracts.
The current study performed various in vitro assays, including ferric ion-reducing antioxidant power (FRAP), 1,1-diphenyl-2-picrylhydrazyl (DPPH), and H2O2 and nitric oxide (NO) scavenging assays. Trolox, a synthetic vitamin E analog, was also used to measure the antioxidant capacity of foods, beverages, and supplements.
In vivo testing examined total oxidative stress (TOS), total antioxidant capacity (TAC), and the oxidative stress index (OSI), which reflects the ratio between TOS and TAC in a rat inflammation model. The levels of advanced oxidation protein products (AOPP), total thiols, malondialdehyde (MDA), which indicates lipid peroxidation levels, and NO, an endothelium, nerve, and immune-derived signaling molecule, were also measured in vivo.
Phenolic profile
MH had ten times as much phenolic content as OLH. Both honey products contained a wide range of phenolic compounds, with non-flavonoids like hydroxybenzoic acid comprising about 90% and 68% of phenolics like 2,4-dihydroxybenzoic acid and gallic acid in MH and OLH, respectively.
Flavonoids include anti-inflammatory and free radical-scavenging apigenin-glucoside, quercetin-glucoside, and quercetin, all of which were only present in MH. Pinocembrin-glucoside was present in both MH and OLH.
Antioxidant properties
OLH had high in vivo antioxidant activity, primarily achieved by reducing serum oxidant activity. Furthermore, OLH reduced TOS, OSI, and MDA more than diclofenac, a non-steroidal anti-inflammatory drug (NSAID), in addition to increasing TAC and SH.
OLH prevents lipid peroxidation, reduces oxidative stress, and increases antioxidant capacity rather than inhibiting NO and protein oxidation pathways. At the lowest concentration of OLH, antioxidant activity was greatest. Conversely, TOS and OSI inhibition was most potent at higher dilutions while exceeding the observed effects of diclofenac.
MH exhibited limited antioxidant activity at all dilutions compared to its potent antibacterial activity. MH reduced NO and AOPP and increased SH levels, exceeding the effects of diclofenac.
TOS and OSI were moderately reduced. Higher dilutions were less effective than diclofenac or Trolox. Notably, the composition and concentration of phenolic compounds in MH are variable, which may alter its antioxidant properties.
Syringic acid inhibits pro-inflammatory pathways and scavenges free radicals. MH has a high content of methyl-syringic acid, which protects DNA from oxidative damage.
Conclusions
MH was associated with a tenfold higher phenolic content than OLH, attributed to its antioxidant capacity; however, these effects were concentration-dependent. Conversely, OLH significantly reduces oxidative stress by scavenging free radicals and increases serum antioxidant capacity.
Honey is an essential and traditional functional food; therefore, the components present within honey should be identified and investigated for their potential impact on human health. Such natural foods must be explored as promising sources of antioxidant activity through the diet.
Journal reference:
- Morar, I. I., Pop, R. M., Peitzner, E., et al. (2025). Phytochemical Composition and Antioxidant Activity of Manuka Honey and Ohia Lehua Honey. Nutrients. doi:10.3390/nu17020276.