Antioxidant and cytoprotective properties of seeds and seed by-products from lotus (Nelumbo nucifera)

The seed of Nelumbo nucifera Gaertn., commonly known as Chinese lotus, has been used as an indigenous medicine in Taiwan. The present study aims to evaluate the variable antioxidant activity of Nelumbo nucifera ethanolic extracts (NNEE) collected from different parts of the lotus. The seed epicarp had significantly higher extractable total phenolic content (TPC) and flavonoid content (TFC) than the seed and seed pod. Compared to the seed and seed pod, the seed epicarp also exhibited lower IC50 values of 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid (ABTS), EC50 for reducing power, and hydrogen peroxide (H2O2) scavenging activity. Moreover, DPPH and ABTS radicals, reducing power activity, and H2O2 scavenging activity by NNEE were highly and significantly associated with TPC and TFC. Seed epicarp NNEE at a concentration of 25 μg/mL gave significantly higher protection to Raw 264.7 mouse macrophages against H2O2 induced damage compared with blanks. Seed epicarp NNEE was also found to have the most significant protection effect on oxidative DNA damage. Therefore, the NNEE of seed epicarp exhibited higher in vitro and ex vivo antioxidant activity, and can be used as a functional ingredient representing a potential source of natural antioxidants to prevent and treat oxidative stress-related disorders.