Antioxidative activities and phenolic compounds of pumpkin (Cucurbita pepo) seeds and amaranth (Amaranthus caudatus) grain extracts

Phenolic compounds were extracted from pumpkin (Cucurbita pepo) seed and amaranth (Amaranthus caudatus) grain into 80% (v/v) methanol. The extracts obtained were characterized by the contents of total phenolic compounds (TPC), trolox equivalent antioxidant capacity (TEAC), ferric-reducing antioxidant power (FRAP) and antiradical activity against 2,2-diphenyl-1-picrylhydrazyl (DPPHo) radical. The content of individual phenolic compounds was determined by HPLC-DAD method. Pumpkin seeds showed the higher content of TPC than that from amaranth. The TEAC values of both extracts were similar each other. The lower value of FRAP was observed for pumpkin seed. Phenolic compound present in amaranth grain exhibited strongest antiradical properties against DPPH radical. Several peaks were present on the HPLC chromatograms of two extracts. The UV-DAD spectra confirmed the presence of vanillic acid derivatives in the amaranth grain. The three main phenolic compound present in pumpkin seed were characterized by UV-DAD spectra with maximum at 258, 266, and 278 nm.