Comparison of antioxidant activity and phenolic compounds of amaranth (Amaranthus caudatus) grain and pumpkin (Cucurbita pepo) seed extracts

Abstract

The aim of this study was to compare the antioxidant activities of methanolic extracts of amaranth grain and pumpkin seed. Samples were extracted with methanol and evaluated for their radical scavenging activities against ferric reducing antioxidant power (FRAP), Trolox equivalent antioxidant capacity (TEAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH·) radical. The total phenolic contents (TPC) was determined by using Folin-Ciocalteu’s phenol reagent on the extracts from the ground samples using 80:20 methanol:water at a solids to solvent ratio of 1:10 [1]. All chemical determinations were performed in triplicate. Data were analyzed by one-way analysis of variance (ANOVA). The lowest value of FRAP was observed in pumpkin seeds. TEAC and antiradical activity against DPPH radical did not differ among these two plants, even if the IC50 was slightly higher in pumpkin seeds than amaranth grain. Finally, extracts obtained from pumpkin seeds were characterized by the highest content of TPC. Moreover, the phenolic compounds (PCs) contained in extracts were separated using DAD-HPLC system [2]. HPLC analysis of amaranth extract confirmed the presence of the vanillic acid derivatives. Several peaks were present on the HPLC chromatogram of pumpkin seed. The three main PCs exhibited UV-DAD spectra with maxima at 266, 258, and 278 nm.