Supercritical fluid extraction of pyrethrins from pyrethrum flowers (Chrysanthemum cinerariifolium) compared to traditional maceration and cyclic pressurization extraction

In this work, a comparison between three extraction processes, including traditional maceration in n-hexane and ethyl alcohol, supercritical fluid extraction (SFE) and cyclically pressurized extraction known as rapid solid-liquid dynamic extraction (RSLDE), has been carried out for the extraction of pyrethrins, predominantly nonpolar natural compounds with insecticidal properties found in pyrethrum, an extract of certain species of chrysanthemums. Pyrethrins are often used in household insecticides and for the control of parasites on pets or livestock. Maceration is the cheapest method, but the values of the percent of extracted material compared to the weight of the dried flowers are lower. The extraction with supercritical CO2 is less efficient than the Naviglio extractor, but it has the advantage of not requiring the use of solvents. Consequently, all three techniques are valid for the extraction of compounds from pyrethrum flowers. The results obtained show that by suitably varying the parameters of the three extraction procedures, it is possible to obtain pyrethrin extracts for use in the production of low toxicity insecticides for warm-blooded animals and low pollution. In particular, extraction with supercritical CO2 presents an additional advantage; although oleoresin is a natural product, its extraction involves the use of solvents, while SFE is a highly efficient extraction process due to the use of CO2 in the supercritical phase without the use of solvents. On the other hand, the Naviglio extractor is an inexpensive technique and requires a minimum energy loss when compared to the extraction with supercritical fluids. Thus, the latter is more convenient on an industrial level but is not universally applicable. Nevertheless, the supercritical extraction can be used as a medium detergent of the oleoresin produced to avoid residues of the solvents left during the extraction process. Therefore, for demonstration purposes, for the SFE CO2 extraction process, numerical simulations have been performed, allowing for helpful results to optimize the process for further tests