Antioxidant properties and preliminary evaluation of phytochemical composition of different anatomical parts of amaranth

Plant Foods for Human Nutrition

Paulius Kraujalis, Petras R. Venskutonis*, Vaida Kraujalienė, Audrius Pukalskas

Department of Food Technology, Kaunas University of Technology, Radvilėnų pl. 19, LT-50254, Lithuania

*Corresponding author. Tel.+37037456647, E-mail address:

Chemical characterization of amaranth extracts

Preliminary screening of extracts was performed by the on-line HPLC-UV-DPPH• and UPLC-QTOF-MS methods. The typical chromatograms of amaranth FM extracts are shown in Fig. 1, the intensities of peaks in the chromatograms is given in Table 1. It is evident that rutin is dominating compound in amaranth. In total,5 compounds were identified by comparing their spectral properties with literature data. Peak 1 had a retention time of 0.49 min,its MS gave m/z=163.0403, corresponding to molecular ion formula C9H7O3. So far as the peak of this compound was overlapping with other eluting from the column peaks, the extraction of UV data was complicated. Based on its accurate mass compound 1was identified as p-coumaric acid. Peak 2 had a retention time of 2.18 min and gave MS peak at m/z = 137.0246, corresponding to molecular ion formula C7H5O3. UV spectral data for this compound was also not available due to small concentrations and overlapping with other peaks. This compound was identified as 4-hydroxybenzoic acid. Peak 3 had a retention time 5.42 min and gave an m/z = 609.1462, corresponding to molecular ion formula C27H29O16. This compound had UV maxima at 254, 265 (sh) and 354 nm. Based on this data and by comparing it with the standard, this compound was identified as rutin. Peak 4 had a retention time 5.65 min and m/z value 463.0886, corresponding to molecular ion formula C21H19O12. Its UV spectrum had maxima at 254, 266 (sh) and 354 nm, corresponding to quercetin aglycone moiety. This compound was identified as isoquercitrin. Peak 5 had a retention time 6.24 min and m/z value of 593.1518. A molecular ion formula of C27H29O15 was calculated from this accurate mass, whileUV spectral datagave maxima at 167 and 237 nm. Based on literature data this compound was tentatively identified as nicotiflorin.Other constituents are also present in the extracts as it may be observed from the single ion monitoring chromatogram extracted from the total mass range. However, based on the signal, the concentration of these compounds should be many times lower that the concentration of rutin. Therefore, from the practical point of view these compounds are of lower interest, while for the scietific purposes these compounds should be purified for obtaining more comprehensive spectra data, e.g. NMR, FTIR.

Fig. 1. Typical chromatograms of amaranth flower methanol:water extracts: UPLC-Q-TOF (left) and HPLC-UV-DPPH• (right)

Fig. 2. Single ion monitoring chromatogram (extracted from the total mass) of amaranth leaf acetone extract obtained by UPLC-Q-TOF

Table 1. Peak areas (arbitrary units) of identified constituents in different amaranth extracts

Extract / 4-Hydroxybeizoic acid / Rutin / Isoquercitrin / Nicotiflorin
Flowers M / - / 192243 / 23213 / 6088
Flowers A / 4634 / 63255 / 16506 / 4434
Seeds M / - / - / - / -
Seeds A / 3648 / 2610 / - / -
Leaves M / - / 121950 / 4975 / 6309
Leaves A / 2408 / 57317 / 3460 / 6004
Stems M / - / traces / 1117 / -
Stems A / 14300 / traces / 3467 / -

M: methanol/water; A: acetone