Colour, smell and taste – the beautiful world of plants and chemistry

1. Colour, smell and taste – the beautiful world of plants and chemistry Dubrovnik, Croatia, 2012 Alison Foster, University of Oxford Botanic Garden

3. Plants and Chemistry • Colour • Smell • Taste

4. Colour • Main pigment types • Porphyrins (nitrogen containing) • Flavonoids (incl. anthocyanins) • Carotenoids (terpenes) • Betalains (nitrogen containing)

5. Colour cyanidin-3-glucoside β-carotene betanidin

6. Colour • Anthocyanins: • Found in many plant families – except those in Caryophyllales • Found in all plant tissues • 109 tonnes produced per year in nature • 2% of all carbon fixed via photosynthesis is converted to anthocyanins

7. Ferns (and Fern allies) Gymnosperms Angiosperms

8. Colour • Functions of anthocyanins: • Pollinator attractant • Sunscreen – succulents and autumn leaf colouration • Anti-feedants – bitter tasting

9. Colour Anthocyanins as pollinator attractant? Bromeliaceae

10. Colour Anthocyanins as sunscreen or antifeedant or both?

11. Colour Anthocyanins as antifeedant ?

12. Colour Metasequoia glyptostroboides dawn redwood Rhodoxanthin:

13. Colour Daucus carrota carrot beta-carotene

14. Colour Solanum lycopersicon tomato lycopene:

15. Colour • Betalains: • Amino-acid derived • Nitrogen containing – metabolically more expensive • Yellow to red pigments (betaxanthins and betacyanins) • Only present in plants in order Caryophyllales

16. Caryophyllales

17. Colour • Betalains: • Caryophyllales: • Beetroot (Amaranthaceae) • Bougainvillea (Nyctaginaceae) • Pokeweed (Phytolaccaceae) • Carnations (Caryophyllaceae)

18. Smell • Nicotianaattenuatafrom the SW United States • Releases benzyl acetone when flower opens at night • Attracts hawkmothpollinators • Pollinators are also herbivores (larval stage) • Upon herbivore attack, flowers no longer produce benzyl acetone nor open at night • Day opening flowers are then hummingbird pollinated

19. Smell • Lavandula angustifolia camphor cineole linalyl acetate linalool

20. Smell • Amorphophallus titanum • Spadix emits smell of rotting flesh • Pollinators are attracted • Carrion-eating beetles • Flesh flies • Smell made up of amines and disulfides putrescine cadaverine

22. Smell • Cercidiphyllum japonicum • Senescing and abscising leaves • Green leaves contain maltol glucosides • Yellow brown/fallen leaves contain maltol

23. Taste • Chilli peppers (Capsicum species) contain capsaicin • “Hotness” measured on the Scoville scale • Test method devised in 1912 by Wilbur Scoville • Now measured by HPLC

24. Taste • Sweet pepper 0 • Jalapeño pepper 5,000 • Scotch Bonnet 100,000 • Naga jolokia 1,040,000 Scoville Heat Units Chilli pepper

25. Taste • Euphorbia resiniferatoxin • Resiniferatoxin 16 Billion SHU

27. Taste • Ginger – Zingiber officinalis, Zingiberaceae • Active constituent of fresh ginger is gingerol • Cooking ginger transforms it into zingerone

28. Taste • Ginger – Zingiber officinalis, Zingiberaceae • Dried ginger contains more of another molecule, shogaol • The Japanese name for ginger is shōga

29. Taste • Ginger – Zingiberofficinalis, Zingiberaceae • Dried ginger contains more of another molecule, shogaol • The Japanese name for ginger is shōga

30. Taste • Vanilla– Vanilla planifolia, Orchidaceae

31. Taste

32. Taste theophylline theobromine caffeine

33. Taste theophylline theobromine caffeine

34. Conclusions