Conventional and innovative extraction methods applied on Calligonum azel Maire leaves and roots: a comparative study

Two extraction schemes, conventional and high-pressure extraction methods were applied on Calligonum azel Maire leaves and roots, with purpose to exploit this plant as a source of natural antioxidants. The total phenolic content (TPC), trolox equivalent antioxidant capacity (TEAC) of extracts, and solid materials were determined. Varying yields of active fractions were obtained by consecutive extractions with increasing polarity solvents. In the Soxhlet extraction, the highest antioxidant capacity values were obtained with methanol, while in the pressurized liquid extraction (PLE), the highest TEAC was recorded in acetone extracts for both materials. The changes of antioxidant indicators of solid plant materials during the extraction were studied by the so-called QUENCHER method (QU: quick, E: Easy, N: New, CHE: Cheap, and R: Reproducible). In this case, TPC varied in the range of 2.3–60.5 expressed in mg gallic acid equivalent per gram of dry weight of plant (mg GAE/g DWP), while radical scavenging capacity was 1.7–75.4 micromole Trolox equivalent per gram of dry weight of plant material (µmol TE/g DWP). All extracts were analysed by ultra-high-performance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry and the results showed thirteen compounds including flavonoids. The essential oils extracted by hydrodistillation, were screened by gas chromatography–mass spectrometry and the results showed the presence of 82 and 55 compounds in C. azel leaves and roots, representing 97.6% and 83.4% of the oil, respectively, while in the supercritical fluid extraction using CO2, both materials showed 52 and 50 compounds, representing over 98.7% and 71.5% of the oil.