Chemical time capsules: bioactive volatiles in eighteenth century herbarium samples of mānuka, Leptospermum scoparium

• Published in: New Zealand journal of crop and horticultural science Vol. 47; no. 4; pp. 297 - 309
• Main Authors: Sansom, Catherine E., van Klink, John W., Perry, Nigel B.
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 02-10-2019; Taylor & Francis Ltd
• Subjects: antimicrobial; Botanists; Chemotaxonomy; Foliage; Gas chromatography; Glands; Headspace; Islands; Leaves; Leptospermum scoparium; monoterpene; Myrtaceae; mānuka; New Zealand; Organic chemistry; sesquiterpene; Solid phase methods; Solid phases; SPME; Time capsules; triketone; Volatile compounds; Volatiles; New Zealand
• ISSN: 0114-0671; 1175-8783
• DOI: 10.1080/01140671.2019.1576745

Leptospermum scoparium J. R. et G. Forst. (Myrtaceae), called mānuka or kahikātoa by Māori, shows distinct foliage chemotypes in different regions of Aotearoa New Zealand, including one with rare antimicrobial triketones. To extend knowledge of mānuka chemotypes geographically and historically, we have developed a miniaturised method for analyses of herbarium samples needing just a few small leaves analysed by headspace solid phase microextraction gas chromatography (HS-SPME-GC). This method was validated on herbarium samples of known chemotypes. Geographical knowledge was extended by analysing herbarium samples collected on New Zealand's offshore islands, ranging from the Manawa/Three Kings in the North to Rakiura/Stewart Island in the South. The chemotypes were generally similar to the nearest populations on the main North or South islands. Historically, volatiles were identified from herbarium samples collected by the first botanists from Europe in 1769, showing that the oil glands in mānuka leaves act as 'chemical time capsules'.