Karrikinolide – where there’s smoke, there’s germination

What does it look like?

Image generated by the VESTA (Visualisation for Electronic and STructual analysis) software http://jp-minerals.org/vesta/en/

Image generated by the VESTA (Visualisation for Electronic and STructual analysis) software http://jp-minerals.org/vesta/en/

What is it?

Karrikinolide is a bicyclic, heteroatomic organic compound found in smoke. It is created in the combustion of cellulosic materials like plants and promotes seed germination, particularly following a bushfire.

It had long been known that bushfires stimulated germination in many plant species, but the particular molecule responsible for this effect was not confirmed until 2004 by Flematti et al. The karrikinolide was isolated from smoke bubbled through deionised water by a series of purification steps starting with solvent extraction, followed by high performance liquid chromatographic separations and culminating with gas chromatography-mass spectrometry. Once the target compound was isolated and the structure determined by nuclear magnetic resonance spectroscopy, it was also synthesised in the laboratory and applied to seeds to confirm that it was in fact the bioactive compound with germination-promoting qualities. It was found to be active at very low concentrations, well below 1 part per billion.

The class of pyran-fused butenolides to which karrikinolide belongs were named karrikins in 2009, from the indigenous Noongar word ‘karrik’, meaning ‘smoke’. The Noongar people have lived in the area around the university where karrikinolide was discovered for over 45,000 years. In the intervening years between the compound’s discovery and it’s designation as karrikinolide, it was informally known by the eponymous moniker ‘Gavinone’.

Where did the structure come from?

The crystal structure of karrikinolide was determined in 2014 by Nair et al., from the product they obtained using the original synthetic route of Flematti et al. It crystallises with a monoclinic unit cell, space group P 21/c. It is entry 961473 in the Cambridge Crystallographic Data Centre.

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