Study of Supercritical CO2 Extraction from Tunisian Psidium guava leaves. Antioxidant activity of the extracts

International audienceGuava (Psidium guajava L.) is a fruit cultivated in all warm regions of the globe for tasty sweet yellow fruit. In this work the extraction of biologically active constituents of Tunisian guava was performed by supercritical fluid extraction (SFE). The SFE with carbon dioxide (CO2) and ethanol as co-solvent was explored using two modes of extraction. The SFED (supercritical fluid extraction direct mode) at 20MPa and 333K, and the SFEbS (supercritical fluid extraction by step) mode in six steps using a gradual variation pressure (15- 20 MPa) and temperature (313, 323 to 333K). The obtained results were compared to two traditional extraction methods, the Soxhlet and maceration extractions. All extracts were subjected to the scavenging tests of DPPH and ABTS radicals. The total phenolics and flavonoid contents were measured using standard methods. The obtained results showed that SFE was very rapid compared other used extraction methods. The higher global yield was observed with SFED at 20MPa and 333K (6.92%). However the highest levels of polyphenols (8.19 and 4.30 mg GAE.g-1) and flavonoid (10.8 and 6.55 mg EQ.g-1DW) were observed in the extracts E1 and E2 obtained with SFEbS at 10MPa. The highest radical scavenging effect by DPPH (IC50 = 12 mg mL–1) and ABTS (TEAC= 1.860 mM.mg–1) was observed in maceration extract. Compared to the traditional extraction, SFE method provides low extraction yield, but a best quality of extract in terms of antioxidant compounds. The SFE with progressive variation of pressure and temperature was shown to be the most efficient method based on the extraction selectivity