Images of Petalostigma and chemical structures

Does the Quinine berry (Petalostigma pubescens) contain Quinine?

Because of persistent rumours that Petalostigma pubescens , a dioecious shrub or small tree in the Picrodendraceae (alt. Euphorbiaceae), contained the anti-malarial drug Quinine it was decided to investigate the chemistry of the berries. The extractions resulted in the isolation of Shikimic acid, Betulinic acid, Oleanolic acid, 3β-Hydroxy-13(28)-epoxy-ursan-11-ene, 3βHydroxyurs-11-en-13β28)-olide, Ursolic aldehyde, Oleanolic aldehyde, Betulinic aldehyde and Canophyllol. Structural elucidation was achieved through the use of a variety of NMR techniques.

Shikimic acid was isolated in yields of 12-16%. This represents the greatest concentration of Shikimic acid recorded for a plant. The high concentration of Shikimic acid is of interest as a world shortage Shikimic acid represents the bottleneck in the synthesis of the anti-viral drug Tamiflu. Therefore P. pubescens could represent an economic crop for the production of Shikimic acid.

Since P. pubescens does not contain Quinine, what is the source of the overwhelmingly bitter taste of the berries? It is most likely caused by a Shikimate salt of an amino sugar. Evidence to support this was derived from taste testing, NMR spectroscopy and mass spectrometry.

The chemistry of two species of Strychnos (S. lucida and S. psilosperma), Loganiaceae were also investigated. Seven known Strychnos alkaloids were isolated from S. lucida , including Strychnine and Brucine, and two from S. psilosperma, including Strychnospermine. Diaboline was the only alkaloid found to occur in both species. This investigation has shown that there are chemotaxonomic differences between the two species.

Contact persons: Lachlan.mcintyre@jcu.edu.au and bruce.bowden@jcu.edu.au

Images of Strychnos and chemical structures