Get more out star anise

13 May 2015 - Expresso technology

The compound shikimic acid is a natural precursor in the production of the synthetic (and supposedly) anti-influenza drug oseltamivir (Tamiflu). See Oseltamivir total synthesis and previous blog episodes here, here, here, here and here. Nice to know that researchers from the School of Physical Sciences in Australia report on an improved method to isolate the acid from star anise here.

Current commercial isolation of shikimic acid is based on soxhlet extraction with a publicised yield of between 2.4 and 7%. The Australian researchers opted for pressurized hot water extraction (PHWE) using a regular espresso machine (this one). Here are the details: operation pressure: 9 bar, solvent: a 30% ethanol/water solution, rate: 2 minutes per 20 gram sample of star anise, workup: silica gel added and mixture dried, then product extracted with acetic acid/ethyl acetate solution. Yield: 5.5% and no chromatography!.