Exploring the Chemical Properties and Biological Activity of Four New Zealand Monofloral Honeys to Support the Maori Vision and Aspirations.

Honey production and export are significant contributors to the Aotearoa New Zealand economy, generating over 400 million dollars in revenue. Its main export is manuka (Leptospermum scoparium) honey, which has a high commercial value due to its medicinal properties that are linked to its unique chemical composition. The compound methylglyoxal (MGO) has been identified as the main floral marker and is used as a quality indicator, often labelled as unique manuka factor (UMF). However, the high demand for manuka honey creates pressure on beekeepers and may have negative ecological consequences by favouring extensive manuka monocultures to the detriment of other native species. There are other honeys native to New Zealand, such as kamahi (Weinmannia racemosa), kanuka (Kunzea ericoides), rata (Metrosideros robusta) and rewarewa (Knightia excelsa), that also have medicinal properties; however, they are less well known in the local and global market. Indigenous Maori communities envision the production and commercialization (locally and internationally) of these honeys as an opportunity to generate income and secure a sustainable future in alignment with their worldview (Te Ao Maori) and values (tikanga Maori). Diversifying the market could lead to a more sustainable income for beekeepers and reduce pressure on Maori and the conservation land, while supporting indigenous communities to realize their vision and aspirations. This manuscript provides an extensive review of the scientific literature, technical literature and traditional knowledge databases describing the plants of interest and their traditional medicinal uses (rongoa) and the chemical properties of each honey, potential floral markers and their biological activity. For each honey type, we also identify knowledge gaps and potential research avenues. This information will assist Maori beekeepers, researchers, consumers and other stakeholders in making informed decisions regarding future research and the production, marketing and consumption of these native monofloral honeys.

Leptospermum petersonii as a Potential Natural Food Preservative.

Leptospermum petersonii (family Myrtaceae) is often cultivated for ornamental purposes but also serves as a rich source of bioactive essential oils. While several studies focused on the activities of the essential oils, this study analysed the potential of spent L. petersonii leaves as a natural food preservative. METHOD: We investigated the in vitro antioxidant and antimicrobial activities of crude L. petersonii extracts against activities of the purified isolated flavonoid, 6-methyltectochrysin, which was characterized using spectroscopic methods. The antioxidant assays followed ORAC, FRAP and TEAC tests. The antimicrobial activities of the extract and purified flavonoid were analysed against six multi-drug resistant microbial strains in broth dilution assays. RESULT: The results revealed that both the crude extracts and isolated 6-methyltectochrysin exhibited positive radical ion scavenging antioxidant potential, however the crude extract was about 6-fold more potent antioxidant than the purified 6-methyltectochrysin. The crude extract also showed strong antimicrobial activities against Bacillus cereus, and even more potent antimicrobial agent than the reference ampicillin antibiotic against Klebsiella pneumoniae subsp. pneumoniae. A higher resistance was observed for the tested Gram-negative strains than for the Gram-positive ones. 6-methyltectochrysin was generally inactive in the antimicrobial assays. CONCLUSION: The crude methanolic extract showed significant bioactivity which validates the medicinal relevance of the plant. The observed biological activities, especially against a notorious strain of B. cereus, suggest that L. petersonii could be a promising natural source of food preservatives.

Effect of a formulated eye drop with Leptospermum spp honey on tear film properties.

AIM: To evaluate the effects of a proprietary formulated eye drop with Leptospermum spp honey versus a conventional lubricant eye drop on tear film properties in subjects with symptoms related to dry eye disease after 28 days of treatment. METHODS: Forty-six subjects with symptoms related to dry eye (Ocular Surface Disease Index (OSDI) score >12) were enrolled and randomly assigned to receive either the test formulated eye drop (Optimel by Melcare Biomedical Pty Ltd) or control eye drops (Alcon, USA) in this double-masked study. Inferior lipid layer thickness (LLT), tear film evaporation rate (TER), fluorescein tear film break-up time (TBUT), corneal staining and subjective symptoms (OSDI and visual analogue scales (VAS)) were measured before and after 28 days of instilling the eye drops. RESULTS: Forty-two subjects completed the study (21 subjects in each group). After 28 days of treatment, TER showed a significantly greater reduction with the formulated eye drop compared with the control (p=0.01). TBUT showed a slight but not statistically significant increase with the formulated eye drop compared with the control (p=0.06), and a significantly greater reduction (improvement) in OSDI scores was observed with the formulated eye drop compared with the control (p=0.01). No significant differences were found between the two groups for inferior LLT, corneal staining and any of the VAS scores. CONCLUSIONS: The formulated eye drops were effective in reducing tear film evaporation rate and were more effective for improving symptoms of dry eye compared with the control eye drops after 28 days of treatment. TRIAL REGISTRATION NUMBER: NCT03622619.

Comparative effect of manuka honey on anaerobic parasitic protozoans with standard drug therapy under in vitro conditions: A preliminary study.

BACKGROUND: From the past five decades, metronidazole and tinidazole have been used for treating nonresistant and resistant giardiasis and trichomoniasis. However, due to the occurrence of drug resistance to standard therapy idealizes us to explore some additional therapies which is cost-effective, easy accessibility, and natural which has least side effects. Manuka honey obtained from Leptospermum scoparium is well known for its antibacterial and wound healing properties and is thought to be a better option as an additional therapy. OBJECTIVE: The present study was conducted to find out the effect of manuka honey on anaerobic protozoans that includes Giardia and Trichomonas under in vitro conditions in comparison to metronidazole and tinidazole. MATERIALS AND METHODS: Axenic culture of Giardia lamblia strain Portland 1 and Trichomonas vaginalis strain 413 was used for drug sensitivity assay to tinidazole, metronidazole, and manuka honey with the highest concentration of 17.1 µg/ml, 24.7 µg/ml, and 50%v/v by using (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, a tetrazole). For this, head-to-head comparison has been done and IC 50 of the standard drug as well as manuka honey was calculated. RESULTS: The result showed that percentage inhibition on the growth of both the parasites is dependent on concentration as well as exposure time of the drug. The calculated IC 50 was found to be 5.6%v/v and 1.5%v/v for manuka honey with respect to G. lamblia and T. vaginalis. CONCLUSION: The present study suggests that manuka honey can be used as an additional therapy for the patient with giardiasis or trichomoniasis. However, in vivo study in the near future will elucidate more about the effectiveness of honey in treating parasitic infections.

Brachyanins A-C, pinene-derived meroterpenoids and phloroglucinol derivative from Leptospermum brachyandrum.

A pair of epimer brachyanins A (1) and B (2), along with a new phloroglucinol brachyanin C (3), were isolated from the leaves of Leptospermum brachyandrum. Brachyanins A (1) and B (2) were the first example of novel meroterpenoid with a unique skeleton that combined a synacrpic acid and a pinene units via a benzyl moiety. Their structures were elucidated through the application of extensive spectroscopic measurements and single-crystal X-ray diffraction analysis and with the absolute configurations of 1 and 2 were confirmed by the quantum chemical CD calculation. The hetero Diels-Alder as the key biotransformation was proposed to account for the biosynthesis of brachyanins A and B sheding light by the potential procursor brachyanin C.

Manuka honey synergistically enhances the chemopreventive effect of 5-fluorouracil on human colon cancer cells by inducing oxidative stress and apoptosis, altering metabolic phenotypes and suppressing metastasis ability.

The development of chemo-sensitizers is urgently needed to overcome 5-fluorouracil (5-FU) therapeutic resistance and adverse toxicity in colorectal cancer. This work aims to evaluate the synergic effects of 5-FU and Manuka honey (MH), a rich source of bioactive compounds, in enhancing the anticancer effects of this drug on human colon cancer HCT-116 and LoVo cells. Compared to 5-FU alone, MH synergistically enhanced the chemotherapeutic effects of 5-FU, by reducing cell proliferation through the suppression of EGFR, HER2, p-Akt and p-mTOR expression, and promoting apoptosis by the modulation pro-apoptotic (p53, Bax, Cyto c, FasL caspase-3, -8, -9 and cleave-PARP) and anti-apoptotic (Bcl-2) markers. The activations of p-p38MAPK and p-Erk1/2 pathways and ROS production were also involved in this process. Downregulation of transcription factor (NF-κB and Nrf2) and antioxidant enzyme activity (SOD, catalase, glutathione peroxidase and glutathione reductase) and expression (SOD, catalase and HO-1) were more evident after the combined treatment, leading to more cell death by oxidative stress. Moreover, additive effects were also observed by increasing lipid and protein oxidation and arresting cell cycle. All the parameters of mitochondrial respiration and glycolysis function decreased and both cells entered the quiescent stage after the combined treatments. MH also influenced the anti-metastasis effects of 5-FU by decreasing migration ability, suppressing the expression of MMP-2, MMP-9 and increasing N-cadherin and E-cadherin. In conclusion, MH could be a useful preventive or adjuvant agent in the treatment of colorectal cancer with 5-FU.

Sub-inhibitory stress with essential oil affects enterotoxins production and essential oil susceptibility in Staphylococcus aureus.

Fourteen wild strains of Staphylococcus aureus positive for gene sea were tested for enterotoxins production and the minimum inhibitory concentration of Leptospermum scoparium, Origanum majorana, Origanum vulgare, Satureja montana and Thymus vulgaris essential oils (EOs) were determined. After this trial, bacteria stressed with sub-inhibitory concentration of each EO were tested for enterotoxins production by an immunoenzymatic assay and resistance to the same EO. Oregano oil exhibited the highest antibacterial activity followed by manuka and thyme oils. After the exposure to a sub-inhibitory concentration of EOs, strains displayed an increased sensitivity in more than 95% of the cases. After treatment with oregano and marjoram EOs, few strains showed a modified enterotoxins production, while 43% of the strains were no longer able to produce enterotoxins after treatment with manuka EO. The results obtained in this study highlight that exposure to sub-inhibitory concentration of EO modifies strains enterotoxins production and EOs susceptibility profile.

Combined Toxicity of Three Essential Oils Against Aedes aegypti (Diptera: Culicidae) Larvae.

Essential oils are potential alternatives to synthetic insecticides because they have low mammalian toxicity, degrade rapidly in the environment, and possess complex mixtures of bioactive constituents with multi-modal activity against the target insect populations. Twenty-one essential oils were initially screened for their toxicity against Aedes aegypti (L.) larvae and three out of the seven most toxic essential oils (Manuka, oregano, and clove bud essential oils) were examined for their chemical composition and combined toxicity against Ae. aegypti larvae. Manuka essential oil interacted synergistically with oregano essential oil and antagonistically with clove bud essential oil. GC-MS analysis revealed the presence of 21 components in Manuka essential oil and three components each in oregano and clove bud essential oils. Eugenol (84.9%) and eugenol acetate (9.6%) were the principal constituents in clove bud essential oil while carvacrol (75.8%) and m-isopropyltoluene (15.5%) were the major constituents in oregano essential oil. The major constituents in Manuka essential oil were calamenene (20%) and 3-dodecyl-furandione (11.4%). Manuka essential oil interacted synergistically with eugenol acetate and antagonistically with eugenol, suggesting that eugenol was a major contributor to the antagonistic interaction between Manuka and clove bud essential oils. In addition, Manuka interacted synergistically with carvacrol suggesting its contribution to the synergistic interaction between Manuka and oregano essential oils. These findings provide novel insights that can be used to develop new and safer alternatives to synthetic insecticides.

Hydrogel film loaded with new formula from manuka honey for treatment of chronic wound infections.

OBJECTIVES: Chronic wound infections can be effectively treated using hydrogel loaded with an extract from manuka honey. METHODS: This study was performed on bacterial isolates from patients with infected wounds at Alexandria Main University Hospital (Alexandria, Egypt). Isolates were exposed to hydrogel sheets composed of chitosan and gelatin and loaded with a new formula from manuka honey. RESULTS: The results illustrate the antibacterial activity of the formula extracted from manuka honey against Staphylococcus aureus, Streptococcus pyogenes, Acinetobacter baumannii, Pseudomonas aeruginosa and Proteus mirabilis. Screening of the hydrogel by electron microscopy showed the ultrastructure of the gel. CONCLUSIONS: A hydrogel sheet composed of chitosan and gelatin loaded with a new formula extracted from manuka honey can be used as a dressing for chronic infected wounds.

Myrtaceae Plant Essential Oils and their ß-Triketone Components as Insecticides against Drosophila suzukii.

Spotted wing drosophila (SWD, Drosophila suzukii (Matsumura), Diptera: Drosophilidae) is recognized as an economically important pest in North America and Europe as well as in Asia. Assessments were made for fumigant and contact toxicities of six Myrtaceae plant essential oils (EOs) and their components to find new alternative types of insecticides active against SWD. Among the EOs tested, Leptospermum citratum EO, consisting mainly of geranial and neral, exhibited effective fumigant activity. Median lethal dose (LD50; mg/L) values of L. citratum were 2.39 and 3.24 for males and females, respectively. All tested EOs except Kunzea ambigua EO exhibited effective contact toxicity. LD50 (µg/fly) values for contact toxicity of manuka and kanuka were 0.60 and 0.71, respectively, for males and 1.10 and 1.23, respectively, for females. The LD50 values of the other 3 EOs-L. citratum, allspice and clove bud were 2.11-3.31 and 3.53-5.22 for males and females, respectively. The non-polar fraction of manuka and kanuka did not show significant contact toxicity, whereas the polar and triketone fractions, composed of flavesone, isoleptospermone and leptospermone, exhibited efficient activity with the LD50 values of 0.13-0.37 and 0.22-0.57 µg/fly for males and females, respectively. Our results indicate that Myrtaceae plant EOs and their triketone components can be used as alternatives to conventional insecticides.

Randomised controlled trial of topical antibacterial Manuka (Leptospermum species) honey for evaporative dry eye due to meibomian gland dysfunction.

BACKGROUND: The aim was to evaluate the efficacy of standardised Manuka (Leptospermum species) antibacterial honey as adjunctive twice daily treatment to conventional therapy (warm compresses, lid massage and preservative-free lubricant), in participants with evaporative dry eye due to moderate to advanced meibomian gland dysfunction. METHODS: This prospective, open-label study involved 114 participants. After two weeks of conventional therapy participants were randomised to one of three treatment groups: Optimel Antibacterial Manuka Eye Gel (98 per cent Leptospermum species honey) plus conventional therapy (n = 37), Optimel Manuka plus Lubricant Eye Drops (16 per cent Leptospermum species honey) plus conventional therapy (n = 37) and a control (conventional therapy) (n = 40). Clinical evaluations performed at baseline and Week 8 included: symptom scores (Ocular Surface Disease Index, Ocular Comfort Index), daily lubricant use, tear assessments (break-up time, secretion, osmolarity and InflammaDry), corneal sensation, ocular surface staining, meibomian gland secretion quality and expressibility, bulbar conjunctival, limbal and lid marginal redness and eyelid marginal bacterial cultures and colony counts. RESULTS: Significant improvements (p ≤ 0.05) occurred at Week 8 in symptoms, tear break-up time, staining, tear osmolarity, meibum quality and bulbar, limbal and lid margin redness for all treatments. Improvement in staining was significantly greater with Optimel 16 per cent drops (p = 0.035). Significant improvements (p < 0.05) in meibomian gland expressibility and InflammaDry occurred for both Optimel treatments. Optimel 98 per cent gel was significantly more effective in improving meibum quality (p = 0.005) and gland expressibility (p = 0.042). Total eyelid marginal bacterial colony counts reduced significantly with Optimel 16 per cent drops (p = 0.03) but not the other treatments. Staphylococcus epidermidis counts reduced significantly with Optimel 16 per cent drops (p = 0.041) and Optimel 98 per cent gel (p = 0.027). Both Optimel treatments significantly reduced the need for lubricants, with Optimel 16 per cent drops decreasing lubricant use most (p = 0.001). Temporary redness and stinging were the only adverse effects of Optimel use. CONCLUSIONS: Optimel antibacterial honey treatments are effective as adjunctive therapies for meibomian gland dysfunction.

Particulate systems based on pectin/chitosan association for the delivery of manuka honey components and platelet lysate in chronic skin ulcers.

The aim of the present work was the development of a powder formulation for the delivery of manuka honey (MH) bioactive components and platelet lysate (PL) in chronic skin ulcers. In particular pectin (PEC)/chitosan (CS) particles were prepared by ionotropic gelation in the presence of calcium chloride and subsequently characterized for particle size, hydration properties and mechanical resistance. Different experimental conditions (calcium chloride and CS concentrations; rest time in the cationic solution) were considered in order to obtain particles characterized by optimal size, hydration properties and mechanical resistance. Two different fractions of MH were examined: one (Fr1), rich in methylglyoxal and the other (Fr2), rich in polyphenols. Particles were loaded with Fr1, fraction able to enhance in vitro proliferation of human fibroblasts, and with PL. The presence of CS in Fr1-loaded particles produced an improvement in cell proliferation. Moreover, PL loading into particles did not affect the biological activity of the hemoderivative. In vivo efficacy of PL- and Fr1-loaded particles was evaluated on a rat wound model. Both treatments markedly increased wound healing to the same extent.

Investigations of kanuka and manuka essential oils for in vitro treatment of disease and cellular inflammation caused by infectious microorganisms.

BACKGROUND: Diseases caused by infectious and inflammatory microorganisms are among the most common and most severe nosocomial diseases worldwide. Therefore, developing effective agents for treating these illnesses is critical. In this study, essential oils from two tea tree species, kanuka (Kunzea ericoides) and manuka (Leptospermum scoparium), were evaluated for use in treating diseases and inflammation caused by microorganism infection. METHODS: Isolates of clinically common bacteria and fungi were obtained from American Type Culture Collection and from Kaohsiung Veterans General Hospital. Minimum inhibitory concentrations for Trichosporon mucoides, Malassezia furfur, Candida albicans, and Candida tropicalis were determined by the broth microdilution method with Sabouraud dextrose broth. The antibacterial susceptibility of Staphylococcus aureus, Streptococcus sobrinus, Streptococcus mutans, and Escherichia coli were determined by the broth microdilution method. A human acute monocytic leukemia cell line (THP-1) was cultured to test the effects of the essential oils on the release of the two inflammatory cytokines, tumor necrosis factor-α and interleukin-4. RESULTS: Multiple analyses of microorganism growth confirmed that both essential oils significantly inhibited four fungi and the four bacteria. The potent fungicidal properties of the oils were confirmed by minimum inhibitory concentrations ranging from 0.78% to 3.13%. The oils also showed excellent bactericidal qualities with 100% inhibition of the examined bacteria. In THP-1 cells, both oils lowered tumor necrosis factor-α released after lipopolysaccharide stimulation. Finally, the antimicrobial and anti-inflammatory effects of the oils were obtained without adversely affecting the immune system. CONCLUSION: These results indicate that the potent antimicroorganism and anti-inflammation properties of kanuka and manuka essential oils make them strong candidates for use in treating infections and immune-related disease. The data confirm the potential use of kanuka and manuka extracts as pharmaceutical antibiotics, medical cosmetology agents, and food supplements.

Regional, annual, and individual variations in the dihydroxyacetone content of the nectar of maÌ nuka (Leptospermum scoparium) in New Zealand.

A method was designed and validated for the analysis of dihydroxyacetone in the floral nectar of ma̅nuka (Leptospermum scoparium). The method was applied to samples collected from different regions of the North Island and the Nelson region of the upper South Island of New Zealand during the period 2009-2012 as well as to nectar samples from some Australian Leptospermum species. The ratio of dihydroxyacetone to total sugar (DHA/Tsugar) was classified as low (<0.001 mg/mg), moderate (0.001-0.002 mg/mg), or high (>0.002 mg/mg). Inter- and intraregional variation were observed as well as interannual variation with variation from low to high classification occurring within one region and from low to moderate between years. Australian species also demonstrated elevated levels of dihydroxyacetone in the nectar. Some garden cultivars were shown to produce very high nectar DHA/Tsugar, and a survey of cultivars was undertaken; cultivars with single-flowered red or pink flowers were the most common producers of very high nectar DHA/Tsugar.

Anti-biofilm effects of honey against wound pathogens Proteus mirabilis and Enterobacter cloacae.

Biofilm growth and its persistence within wounds have recently been suggested as contributing factors to impaired healing. The goal of this study was to investigate the anti-biofilm effects of several honey samples of different botanical origin, including manuka honey against Proteus mirabilis and Enterobacter cloacae wound isolates. Quantification of biofilm formation was carried out using a microtiter plate assay. All honeys at a sub-inhibitory concentration of 10% (w/v) significantly reduced the biofilm development of both isolates. Similarly, at a concentration of 50% (w/v), each of the honeys caused significant partial detachment of Pr. mirabilis biofilm after 24 h. On the other hand, no honey was able to significantly detach Ent. cloacae biofilm. In addition, treatment of Ent. cloacae and Pr. mirabilis biofilms with all honeys resulted in a significant decrease in colony-forming units per well values in a range of 0.35-1.16 and 1.2-7.5 log units, respectively. Of the tested honeys, manuka honey possessed the most potent anti-biofilm properties. Furthermore, methylglyoxal, an antibacterial compound of manuka honey, was shown to be responsible for killing biofilm-embedded wound bacteria. These findings suggest that manuka honey could be used as a potential therapy for the treatment of wounds containing Pr. mirabilis or Ent. cloacae.

Manuka honey protects middle-aged rats from oxidative damage.

OBJECTIVE: This study aimed to determine the effect of manuka honey on the oxidative status of middle-aged rats. METHOD: Twenty-four male Sprague-Dawley rats were divided into young (2 months) and middle-aged (9 months) groups. They were further divided into two groups each, which were either fed with plain water (control) or supplemented with 2.5 g/kg body weight of manuka honey for 30 days. The DNA damage level was determined via the comet assay, the plasma malondialdehyde level was determined using high performance liquid chromatography, and the antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase, glutathione peroxidase and catalase) were determined spectrophotometrically in the erythrocytes and liver. The antioxidant activities were measured using 1,1-diphenyl-2-picrylhydrazyl and ferric reducing/antioxidant power assays, and the total phenolic content of the manuka was analyzed using UV spectrophotometry and the Folin-Ciocalteu method, respectively. RESULTS: Supplementation with manuka honey reduced the level of DNA damage, the malondialdehyde level and the glutathione peroxidase activity in the liver of both the young and middle-aged groups. However, the glutathione peroxidase activity was increased in the erythrocytes of middle-aged rats given manuka honey supplementation. The catalase activity was reduced in the liver and erythrocytes of both young and middle-aged rats given supplementation. Manuka honey was found to have antioxidant activity and to have a high total phenolic content. These findings showed a strong correlation between the total phenolic content and antioxidant activity. CONCLUSIONS: Manuka honey reduces oxidative damage in young and middle-aged rats; this effect could be mediated through the modulation of its antioxidant enzyme activities and its high total phenolic content. Manuka honey can be used as an alternative supplement at an early age to improve the oxidative status.

Manuka honey protects middle-aged rats from oxidative damage

OBJECTIVE: This study aimed to determine the effect of manuka honey on the oxidative status of middle-aged rats. METHOD: Twenty-four male Sprague-Dawley rats were divided into young (2 months) and middle-aged (9 months) groups. They were further divided into two groups each, which were either fed with plain water (control) or supplemented with 2.5 g/kg body weight of manuka honey for 30 days. The DNA damage level was determined via the comet assay, the plasma malondialdehyde level was determined using high performance liquid chromatography, and the antioxidant enzyme activities (superoxide dismutase, glutathione peroxidase, glutathione peroxidase and catalase) were determined spectrophotometrically in the erythrocytes and liver. The antioxidant activities were measured using 1,1-diphenyl-2-picrylhydrazyl and ferric reducing/antioxidant power assays, and the total phenolic content of the manuka was analyzed using UV spectrophotometry and the Folin-Ciocalteu method, respectively. RESULTS: Supplementation with manuka honey reduced the level of DNA damage, the malondialdehyde level and the glutathione peroxidase activity in the liver of both the young and middle-aged groups. However, the glutathione peroxidase activity was increased in the erythrocytes of middle-aged rats given manuka honey supplementation. The catalase activity was reduced in the liver and erythrocytes of both young and middle-aged rats given supplementation. Manuka honey was found to have antioxidant activity and to have a high total phenolic content. These findings showed a strong correlation between the total phenolic content and antioxidant activity. CONCLUSIONS: Manuka honey reduces oxidative damage in young and middle-aged rats; this effect could be mediated through the modulation of its antioxidant enzyme activities and its high total phenolic content. Manuka honey can be used as an alternative supplement at an early age to improve the oxidative status. .

Modified sugar adulteration test applied to New Zealand honey.

The carbon isotope method (AOAC 998.12) compares the bulk honey carbon isotope value with that of the extracted protein; a difference greater than 1‰ suggesting that the protein and the bulk carbohydrate have different origins. New Zealand Manuka honey is a high value product and often fails this test. It has been suggested such failures are due to the pollen in the Manuka honey and an adaptation of the method to remove pollen prior to testing has been proposed. Here we test 64 authentic honey samples collected directly from the hives and find that a large proportion (37%) of Manuka honeys fail the test. Of these 60% still fail the adapted method. These honey samples were collected and processed under stringent conditions and have not been adulterated post-harvest. More work is required to ascertain the cause of these test failures.

In vitro efficacy of the essential oil from Leptospermum scoparium (manuka) on antimicrobial susceptibility and biofilm formation in Staphylococcus pseudintermedius isolates from dogs.

BACKGROUND: Staphylococcus pseudintermedius is a common pathogen of skin and ear infections in dogs. The widespread and rapid emergence of meticillin-resistant S. pseudintermedius (MRSP) has created therapeutic challenges in veterinary medicine and the need for alternative treatments. HYPOTHESIS/OBJECTIVES: We aimed to evaluate the in vitro antimicrobial activity of the essential oil manuka (Leptospermum scoparium) against S. pseudintermedius. METHODS: This study was performed using S. pseudintermedius strains isolated from dogs with skin and ear infections collected throughout Korea between 2009 and 2011. The in vitro antimicrobial activity of manuka oil against 39 MRSP and 11 meticillin-susceptible S. pseudintermedius (MSSP) strains was analysed by measuring minimal inhibitory concentrations (MICs) using the agar dilution method and biofilm inhibition activity as assessed by the colorimetric microtitre plate assay. RESULTS: Our results indicated that manuka oil had excellent activity against all bacterial isolates. The MICs for MRSP and MSSP to manuka oil were in the range of 2(-9) to 2(-6) and 2(-9) to 2(-7) % (v/v), respectively. Manuka oil was a potent inhibitor of S. pseudintermedius biofilm formation, and the majority of bacteria decreased by >50%. No significant differences were observed in the MICs or biofilm formation between the MRSP and MSSP strains. CONCLUSIONS AND CLINICAL IMPORTANCE: These results suggest that manuka oil has the potential to be a useful therapeutic option for treating superficial infections caused by MRSP and MSSP; further clinical investigations are required.