Chemical diversity of kānuka: Inter- and intraspecific variation of foliage terpenes and flavanones of Kunzea (Myrtaceae) in Aotearoa/New Zealand. | LitMetric
Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand; The New Zealand Institute for Plant and Food Research Limited, Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand. Electronic address:
Published: April 2022
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Article Abstract
Kunzea (Myrtaceae) trees and shrubs, generally called kānuka, grow across most of Aotearoa/New Zealand (NZ). With the exception of K. sinclairii, an offshore island endemic, kānuka had been treated as an Australasian species K. ericoides. However, a 2014 taxonomic revision recognized ten species, all endemic to NZ. Kānuka chemistry is less studied than that of its closest relative in NZ, mānuka (Leptospermum scoparium), which shows very distinct regional foliage chemotypes. We have used a miniaturized method with GC and H NMR to analyze foliage chemistry of voucher specimens from across the geographic ranges of the ten NZ Kunzea species. We found common mono- and sesquiterpenes, with α-pinene dominant in all samples, but only traces of antimicrobial triketones. Two unusual flavanones, with unsubstituted B-rings and known bioactivity against Phytophthora, did distinguish some of the samples. 5,7-Dihydroxy-6,8-dimethyl flavanone was only found at high concentrations in the three K. sinclairii samples in this study's sample set, but this compound has separately been reported in K. robusta samples from a nearby region. Therefore none of the NZ Kunzea species was distinguished by the chemistry analyzed in this study, but there is a possibility of regional flavonoid chemotypes cutting across the species boundaries.
Honey from the nectar of the Manuka tree () grown in New Zealand contains high amounts of antibacterial methylglyoxal (MGO). MGO can react with proteins to form peptide-bound Maillard reaction products (MRPs) such as -carboxyethyllysine (CEL) and "methylglyoxal-derived hydroimidazolone 1" (MG-H1). To study the reactions of MGO with honey proteins during storage, three manuka honeys with varying amounts of MGO and a kanuka honey () spiked with various MGO concentrations up to 700 mg/kg have been stored at 37 °C for 10 weeks, and the formation of protein-bound MRPs has been analyzed via high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS) following isolation of the protein fraction and enzymatic hydrolysis.
The use of native plants in land application systems for treated municipal wastewater (TMW) can contribute to ecological restoration. However, research on the potential of native species to manage the nutrients and contaminants contained in TMW is scarce. At a 10-hectare field site irrigated with TMW at >4000 mm yr, we investigated the distribution of nutrients and trace elements in the soil-plant system, comparing the New Zealand native Myrtaceae species and with pasture.
Ma̅nuka honey is known for its strong bioactivity, which arises from the autocatalytic conversion of 1,3-dihydroxyacetone (dihydroxyacetone, DHA) in the floral nectar of (Myrtaceae) to the non-peroxide antibacterial compound methylglyoxal during honey maturation. DHA is also a minor constituent of the nectar of several other species. This study used high-performance liquid chromatography to test whether DHA was present in the floral nectar of five species in other genera of the family Myrtaceae: (Turcz.
is a small shrub belonging to the family and the leaves are steam-distilled to produce a therapeutically active essential oil. With production moving from wild-harvested to orchardised stands, there is a need for harvest management of kunzea oil. This study compared the regrowth, essential oil content and composition of plants after harvesting vegetative material to a depth of 0.
