Optimized flash extraction and UPLC-MS analysis on antioxidant compositions of Nitraria sibirica fruit

The fruit of Nitraria sibirica Pall. (N. sibirica) is a common folk medicine in the Northwest China and contains plentiful antioxidant compositions. In the study, a rapid flash extraction method (extracting for 3.3 min with 53% ethanol at the solvent-sample ratio of 34 mL/g) for the antioxidant compositions in N. sibirica fruit was optimized by response surface methodology. Twenty-seven compounds of the extract were recognized by ultra-high performance liquid chromatography combined with ion trap mass spectrometry (UPLC-IT/MS), including twelve flavonoids, twelve alkaloids and three phenolic acids. Four compounds among them were first reported in Nitraria genus. Moreover, eight main antioxidant compounds in eight batches of N. sibirica fruit collected from different regions were quantified by a rapid and reliable method of ultra-high performance liquid chromatography combined with triple quadrupole tandem mass spectrometry (UPLC-QQQ/MS). Chemometric study further revealed that the contents of two compounds, tryptophan and alcesefoliside, were highly correlated with the antioxidant activity, which provided a reference for the quality evaluation of N. sibirica fruit.