Abstract
Kānuka (Kunzea ericoides) is an Aotearoa New Zealand endemic species, widely distributed across the North and South Islands. It has a rich history of traditional uses by Māori to treat illness and infections but is chemically understudied. Previous reports indicate that it contains rare non-volatile hybrid compounds (compounds composed of units from different biosynthetic backgrounds), including several with one report in the literature, from kānuka. Most work on the natural products of this plant has focussed on steam-distilled essential oils, which do not extract these hybrid compounds.
This research aimed to work with Māori partners to isolate and characterize non-volatile hybrid compounds in solvent extracts of kānuka. Following this, the isolated compounds and crude kānuka solvent extracts would be tested for antimicrobial bioactivity against pathogens relevant to rural communities, and in particular, those that affect children. The chemical and biological understanding of kānuka natural products would then be developed into an outreach programme, for use with schools and rural / Māori communities to spark an interest in science through seeing this taonga species in a new light.
Seven compounds were isolated from kānuka by solvent extraction, five of which were hybrid compounds. All of these showed antibacterial activity against Gram-positive pathogens tested, to varying degrees. Interestingly, some compounds performed better against drug resistant isolates of Staphylococcus aureus and Streptococcus pyogenes than susceptible isolates. Hybrid compounds varied between plants and between locations. The profile of hybrid compounds was not strongly heritable, with some seedlings having a hybrid compound profile that did not resemble the mother plant. Non-volatile hybrid compounds survived the steam distillation process and could be extracted from residue foliage, creating a potential secondary product stream for essential oil producers. Within a school environment, the chemical diversity within kānuka was successfully visualised through TLC-based methods, with future work refining school-based biological testing, including development of TLC-Direct Bioautography as a linked chemical and biological screen.