Optimization of extraction process and analysis of active components of water-soluble antioxidant substances from Goji

The water-soluble substances in Goji was extracted by aqueous extraction method. Using half maximal inhibitory concentration (IC₅₀) value of scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals as response value, the extraction process was optimized by response surface tests on the basis of single factor tests. The water-soluble antioxidant components in Goji were analyzed by ultra performance liquid chromatography coupled with quadrupole-time of flight-mass spectrometry (UPLC-QTOF-MS). The results showed that the optimal extraction conditions were as follows: solid-liquid ratio 1∶180 (g∶ml), extraction temperature 80 ℃ and time 2 h. The IC₅₀ value of scavenging DPPH radicals of the extracting solution was 1.34 g/L under these optimized conditions. The analysis by UPLC-QTOF-MS indicated that a total of 6 substances capable of scavenging DPPH radicals were detected in the aqueous extracting solution of Goji, which were beriberic acid, betaine, kaempferol-3-O-sophorodisaccharide-7-O-glucoside, proline, L-arginine and rutin, respectively.