Antioxidant properties of pea (Pisum sativum L.) seeds

Abstract

Antioxidants play an important role in regulating free radical transformations in plants during ontogenesis, conspicuously affecting their state. In addition to the plant resistance to abiotic factors, antioxidants contained in plant products can have a positive effect on human health and thus make food physiologically valuable. Unlike systematic studies of antioxidant properties of different crops (cereals, vegetables, legumes, odoriferous plants, medicinal plants, etc.) conducted in leading research institutions of the world, domestic investigations on this subject are extremely scarce.

The aim and tasks of the study. The objective of our study was to assess the content and isomeric composition of tocopherols (hydrophobic antioxidant) as well as to determine the total antioxidant activity of ethanol-soluble (hydrophilic) components from seeds of pea accessions of the working collection of the Laboratory of Pea Breeding of the Plant Production Institute named after VYa Yuryev.

Materials and methods. The content and isomeric composition of tocopherols were determined in compliance with the National Standard of Ukraine DSTU EN 12822: 2005. The total antioxidant activity (AOA) in pea seeds was evaluated with stable radical DPPH • (2,2-diphenyl-1-picrylhydrazyl). All the experiments were carried out in triplicate. The test material was 30 pea accessions of different eco-geographical origin (varieties bred in the Plant Production Institute as well as varieties of other originators) harvested in 2011-2012 and 2015-2016.

Results and discussion. The evaluation of the total AOA of 28 grain pea accessions showed the variability range in the range of 39.89% -50.34% in 2015 (equivalent of chlorogenic acid (AChGA) 374.6-473.1 μg/g), and in 2016 the range was 41.56% - 61.46% (AChGA 559.5-829.1 μg/g). The average AOA across the experiment was 47.33% (AChGA – 443.7 μg/g) and 52.39% (AChGA - 706.1 μg/g) in 2015 and 2016, respectively. In this sample, the range of phenotypic variability of the total AOA was 39.89% - 61.46%, of the environmental variability - 47.33% - 52.39%, and of the genotypic variability - 44.32% -55.69%. Basing on the results obtained, we assume that the eco-geographical origin of pea accessions does not influence the total AOA. The correlations between the total AOA (equivalent of chlorogenic acid) and the yield capacity as well as between the total AOA and protein content in pea seeds were weak and insignificant, Analysis of the content and isomeric composition of tocopherols in pea seeds with different states of the R and Rb genes showed that over 90% of tocopherols are represented by γ-isomer. The total amount of tocopherols was higher in accession ‘Violena’ (RRrbrb) - 10.94 mg/%. .

Conclusions.Thus, the evaluation of pea accessions for the total antioxidant activity showed the range of variability across grain pea accessions of 44.32% to 55.69%. To confirm the assumption abput absence of effect of the eco-geographical origin of pea accessions on the total AOA, further investigations should be carried out in a larger sample. No significant relationships between the total AOA and the yield capacity or the protein content in pea seeds were noted. It was shown that over 90% of pea tocopherols were represented by γ-isomer. To confirm significant differences in the total AOA of the pea accession - the rb gene carrier, it is necessary to analyze the sample of national collection accessions of the Pisum sativum L. species