A supercritical CO2 based workflow for the fast extraction, isolation, and quantification of polar styrax constituents

Recent instrumental advances of CO₂ based supercritical fluid (SFx) technology have heralded a new era in natural product labs [1]. Despite the technology's poor reputation of being only suitable for non-polar compounds, the number of studies corroborating its suitability for a large variety of compound classes is increasing. However, so far, the polarity limit has not been reached.

Hence, the aim of this study was to develop the first SFx based protocol for the extraction, analysis, and isolation of six polar compounds including o-vanillin (1), styracin (2), vanillin (3), trans-cinnamic acid (4), vanillic acid (5), and shikimic acid (6)[2].

After initial method optimisation on an analytical SFC device (UPC²), the compounds were successfully baseline separated within 4 min. A supercritical fluid extraction (SFE) protocol was established for eight authentic styrax products (R1-R8) known to contain compounds 2-6. The compounds were quantified and the method was validated according to current ICH guidelines. Scaling up to preparative SFC allowed for a fast separation and isolation of the selected constituents 2 and 4 from R6 within 7 min.

In sum, this is the first report of a complete SFx workflow for a rapid and green chemistry based extraction, analysis, and isolation of polar compounds from styrax resin products. The protocol is easily adaptable to compounds of similar polarity and offers an environmental friendly alternative to conventional set-ups. Striking advantages of SFx technologies, which will have a lasting impact on future applications, include low solvent consumption, easy solvent removal, as well as high efficiency and selectivity.

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This work was supported by the Austrian Science Fund (FWF: P24587).

[1] Hartmann A, Ganzera M. Planta Med 2015; 81: 1570 – 1581

[2] Scheuba J, Wronski V-K, Rollinger JM, Grienke U. Planta Med 2017; http://dx.doi.org/10.1055/s-0043 – 105499