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Optimized on-line HPLC-DPPH method for evaluation and identification of the antioxidants in <b>Limonium aureum</b> (Linn.)<br><br>Display Omitted<br>• On-line HPLC-DPPH method was used for evaluate and identify of the antioxidants in <b>Limonium aureum</b> (Linn.) extract. • The optimum conditions of the method were obtained by response surface methodology. • Antioxidants were identified by MS.<br><b>Limonium aureum</b> (Linn.) is a traditional Chinese medicine with strong antioxidant activity. To search for antioxidants in <b>L. aureum</b>, an optimized, on-line high performance liquid chromatography (HPLC) method with DPPH (1,1-diphenyl-2-picrylhydrazyl) for the detection of radical scavenging ability was developed. Response surface methodology (RSM) was used to determine the best combination of experimental conditions, such as DPPH concentration, DPPH velocity and the reaction tank length. The optimized method uses a DPPH concentration of 25.0 μg/mL, DPPH velocity of 0.45 mL/min and a 15.0 m long reaction tank. The highly sensitive, optimized method can not only be used for the detection of antioxidants in plants, but can also be coupled with mass spectrometry (MS) to obtain the mass-to-charge ratios of chemical species corresponding to the different peaks in the HPLC profiles. Seven antioxidants were identified in <b>L. aureum</b> using the optimized method, including myricetin-3-<b>O</b>-β-d-(6”-<b>O</b>-galloyl)-glucopyranoside, myricetin-3-<b>O</b>-glucoside, myricitrin, eriodictyol-7-<b>O</b>-glucoside, myricetin, eriodictyol and homoeridictyol.

<br>Display Omitted<br>• Response surface methodology was applied to optimize supercritical fluid extraction conditions of alantolactone and isoalantolactone. • The optimized extraction conditions were pressure 20 MPa, extraction temperature 50 °C, carbon dioxide flow rate of 17 × 10−5 kg/s and extraction time of 40 min. • Freezing purification greatly improve the content of the target compounds by 30.7 wt.%.<br><b>Inula racemose</b> Hook.f. (<b>I</b>. <b>racemosa</b>) is a traditional herbal medicine with strong anti-fungal and anti-inflammation activity while alantolactone (AL) and isoalantolactone (IAL) are the major active compounds of this plant. The aim of this paper was obtaining AL and IAL from the radix of <b>I</b>. <b>racemosa</b> by supercritical fluid extraction (SFE) which was optimized by response surface methodology (RSM). Our results showed that, the optimal conditions for maximum extraction efficiency were as follows: pressure 20 MPa, extraction temperature 50 °C, carbon dioxide (CO2) flow rate of 17.0 × 10−5 kg/s and extraction time of 40 min. Subsequently, an efficient freezing method was developed for purification of AL and IAL in the crude extract obtained from SFE. After purification by freezing, the total content of the target compounds was greatly improved by 30.7%. The results demonstrate that SFE coupled with freezing would be a powerful technique for extraction and purification of AL and IAL from the radix of <b>I</b>. <b>racemosa</b>.