Natural products chemistry
Dr Rob Keyzers
We study metabolites from food and wine, and isolate and characterise novel bioactive compounds from New Zealand and the Pacific region.
Isolating bioactive molecules from mixtures can be done in two different ways. The mixture can either be separated on the basis of its behaviour in a biological assay (activity-guided), or by isolating molecules from the mixture that have interesting chemical structures (structure-guided). The aim of both is the same—to find new pharmaceutical leads.
We begin with anti-tuberculosis, anti-inflammatory and anti-bacterial assays for our activity-guided isolation, as well as a number of purification techniques to isolate the compounds of interest.
Structural identification of the active components follows, using mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy. Our premise is that chemical novelty equates to bioactive novelty as irrelevant metabolites are bred out through natural selection.
Finally, we synthesise the target molecules we have isolated. Analogues are also synthesised to help identify potential structure-activity relationships that may prove useful for the development of new pharmaceuticals, to confirm the chemical structure we have determined for the compound and to provide a reliable supply of the compound for testing.
Secondary metabolites are a broad class of compounds that have an important role in the flavour and aroma of plant-derived foods and beverages. Primary metabolites are common to all organisms and are necessary for life, but secondary metabolites are specific to the species of plant and are non-essential, although they do bring some ecological advantage to the plant.
We are working on the metabolic profile of various products, including wine. Current projects involve identifying links between the secondary metabolites of grapes, with the final flavour and aroma of wine. Although the compounds responsible for wine flavour and aroma are relatively well understood, little is known about the links between the metabolites present in grapes and how compounds present after fermentation are formed from them.
Optimising the fermentation process and increasing our knowledge of grape chemistry will allow better control of the product and will enhance the quality of New Zealand wine.
We are also identifying bioactive compounds in other foods such as kiwifruit, boysenberries and native karaka berries.