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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.

Three compounds were isolated from alcoholic extracts of Gentiana tizuensis Franch.. On the basis of spectroscopic methods. Their structures were identified as ursolic acid (1), isooreintin (2), swertiajaponin (3). Among them,compound 2 was isolated from the plant for the first time,compound 3 was isolated from Gentiana for the first time.

The contents of four iridoids ( loganic acid, swertiamarin, gentiopicroside, sweroside) in Gentiana tizuensis Franch. and Gentiana farreri were analyzed by HPLC. The analysis was performed on Econosphere C18 (250 x 4.6 mm, 5 µm) column, with the solution of 0.5 % acetic acid and methanol as mobile phase, at a flow rate of 1.0 mL/min. The detection wavelength was 254 nm. The results indicated that swertiamarin was not detected in Gentiana tizuensis Franch., and the contents of four iridoids in these two plants were different.

Amino acids are indispensable components of living organisms. The high amino acid content in Nitraria tangutorum Bobr. fruit distinguishes it from other berry plants and is of great significance to its nutritional value. Herein, using 10-ethyl-acridine-3-sulfonyl chloride as a fluorescent pre-column labeling reagent, a method for the efficient and rapid determination of amino acid content in N. tangutorum by pre-column fluorescence derivatization and on-line mass spectrometry was established and further validated. The limits of detection (signal-to-noise ratio = 3) were between 0.13 and 1.13 nmol/L, with a linear coefficient greater than 0.997 and a relative standard deviation between 1.37% and 2.64%. In addition, the method required a short analysis time, separating 19 amino acids within 20 min. Subsequently, the method was used to analyze the amino acid content of Nitraria tangutorum Bobr. from tissues retrieved from seven regions of the Qinghai-Tibet Plateau. Nitraria tangutorum Bobr. was shown to contain a large amount of amino acids, with the total content and main amino acid varying between the different tissues. This research supports the nutritional evaluation, quality control, and development and utilization of Nitraria tangutorum Bobr.