Influence of the supercritical CO2 extraction in the stability of the coumarins of Pterocaulon lorentzii (Asteraceae)

Coumarins are important especialized metabolites that have potential application in different fields. For the purpose of obtaining fractions enriched with coumarins, extracts from the leaves and inflorescences of Pterocaulon lorentzii Malme (Asteraceae) were obtained by different methods and solvents, i.e. with water at 60 °C, with dichloromethane at room temperature (25 °C) and by means of supercritical CO2 (SC-CO2) extraction at 40 °C with gradual pressure increments (90, 120, 150, 200 and 300 bar). The coumarins content in the extracts was calculated using ultra-fast liquid chromatography analyses, which allowed the characterization of the coumarins. Sabandinol (5-(2′,3′-dihydroxy-3′-methylbutyloxy)-6,7-methylenedioxycoumarin) was the main coumarin found in the aqueous and dichlorometane extracts. The epoxy-derivative 5-(2′,3′-epoxy-3′-methylbutyloxy)-6,7-methylenedioxycoumarin was identified as the major component of all extracts obtained by SC-CO2. The SC-CO2 extract from the inflorescences proved to be richer in coumarins than the extract from the leaves. The results suggest that when the objective is to obtain epoxy-coumarins, the method of choice should be SC-CO2, as this technique was effective for preventing the ring-opening of the epoxy group.