Camellia oleifera seeds cake: Polyphenol profile and in vitro antioxidant activities as determined by different harvest periods

Camellia oleifera seed oil is widely recognized for its high nutritional value. And a large amount of seed cake is produced as a by-product of oil extraction. Studies have shown that the polyphenol content of oil obtained from materials at different harvesting stages varies, but no study has examined changes in the polyphenols of seed cake (CP). In our study, the composition profiles of 44 polyphenols contained in CP were identified and 8 of them were quantified by UPLC-QTOF-MS/MS and HPLC-QQQ-MS/MS, respectively. The antioxidant activity of CP was evaluated by ABTS and FRAP methods in combination with the H2O2-induced oxidative damage model of RAW264.7 cells. The results showed that although the content of CPs in the four stages showed different trends, they all had good ABTS+ scavenging and FRAP-reducing abilities. Moreover, CP attenuated oxidative damage in cells by enhancing cell viability, increasing SOD activity, decreasing the contents of MDA and ROS, decreasing apoptosis, and inhibiting the activation of the NF-κB signaling pathway. Correlation results from Grey relational degree analysis and Pearson analysis showed that chlorogenic acid, 5, 7-dimethoxy-4'-hydroxyflavanone, and kaempferol-3-O-rutinoside contributed significantly to antioxidant activity. The results would provide a theoretical basis for the development and utilization of the added value of Camellia oleifera seed cake.