Supercritical CO2 extraction of Tetraclinis articulata: chemical composition, antioxidant activity and mathematical modeling

Abstract

Operating conditions for extraction from the leaves of Tetraclinis articulata using supercritical carbon diox-ide (SCCO2) were studied to focus on the feasibility of obtaining volatile and nonvolatile fractions throughthe use of different extraction pressures (90, 280 and 1000 bar). In addition, influence of temperature,static pretreatment and dynamic extraction durations, particle size and CO2flow rate were investigated.All extracts were analyzed by GC–FID/MS and their antioxidant activity was measured using ABTS•+andDPPH•methods. Conventional hydrodistillation (HD) was also performed for comparison. At high CO2pressure (280 and 1000 bar), the amount of phenolics in the extracts was higher (respectively 102.03and 267.90 GAE mg/g) than for HD and supercritical fluid extraction (SFE) at 90 bar (respectively 8.89 and9.70 GAE mg/g). Correlatively, high antioxidant activity was found for high pressure SFE. Surprisingly, forextracts obtained by SFE at 90 bar, despite very low phenolic content, significant antioxidant activity wasobserved, while essential oil obtained by HD, which presented also low phenolic content, exhibited lowantioxidant activity.Physical aspects were only investigated for the low pressure supercritical extraction (90 bar) process.Qualitative assessment of kinetic curves together with their modeling revealed that the extraction pro-cess was mainly limited by the thermodynamic equilibrium of easily accessible solutes but where axialdispersion was significant. From this result a simple extrapolation procedure was proposed.