The Impact of Air or Nitrogen Non-Thermal Plasma on Variations of Natural Bioactive Compounds in Djulis (Chenopodium formosanum Koidz.) Seed and the Potential Effects for Human Health

Non-thermal plasma (NTP) has been widely applied in the food and agricultural industries. It is still unknown whether natural bioactive compounds in seeds are affected by NTP treatment. Our goal was to examine whether the bioactive compounds in djulis (Chenopodium formosanum Koidz.) seed are changed after NTP treatment. The betacyanin, anthocyanin, total phenolic content (TPCs), total flavonoids (TFs), 2,2-diphenyl-1-picrylhydrazyl radical scavenging effects (DPPH), gallic acid, and rutin were compared in NTP-treated seed and an untreated control. Levels of betacyanin, anthocyanin, and TPCs in the seed were found to be significantly increased after the nitrogen (N2)-NTP treatment compared with the control (p < 0.001). Inversely, the air-NTP treatment significantly weakened the performance of these bioactive compounds in the seed as compared to the control. Levels of TFs in both the air- and N2-NTP treated seed were significantly lower than those in the control (p < 0.001). After the NTP treatment, DPPH was still at high levels, similar to those in the control. The djulis seed extract had antioxidant and anti-inflammatory effects on THP-1 (human-monocyte-cell line) cells. N2-NTP generated nitrogen reactive species that activated the bioactive compounds in the seed. In contrast, air-NTP produced oxygen and nitrogen reactive species inhibited the expression of these bioactive compounds.