Total antioxidant capacity as an important element in the assessment of soil properties for the production of high-quality agricultural and horticultural raw materials with health-promoting properties

Abstract

Soil is one of the most important elements of the natural environment, it is characterized by the highest resistance to degradation. It is the first element in the trophic chain and may have different effects on the health condition of people, primarily through the consumption of plant raw materials. One of the effects of soil contamination is the formation of excess free radicals in cells, which leads to oxidative stress. Free radicals contribute to the damage of lipids, proteins, mitochondrial and nuclear DNA and also to disorders in the signalling pathways responsible for the broad spectrum of cellular responses. The result of this is the emergence of many diseases, such as cancer, cardiovascular disorders, osteoporosis, inflammation, Alzheimer's disease, Parkinson's disease. However, it is possible for people to protect themselves from the excess of free radicals found in soils and cultivate plants in the best quality soils. The best way to assess soil quality is to determine its total antioxidant capacity using the different methods available (FRAP method, CUPRAC method, FOLIN-CIOCALTE method, ABTS + method, DPPH + method). Such designations make it possible to assess the soil in terms of its suitability for the production of high-quality food or the possible need for reclamation. It should be noted that soil quality may be improved by adding antioxidant compounds to it, which in turn will increase the amount of antioxidants in agricultural raw materials. One of the ways to achieve this is balanced fertilization, especially organic, but also mineral.

Antioxidant capacity sources of soils under different land uses

“…2 ). Although the studies on the phenolic profiles of soil are still limited, the results obtained here are in accordance with the available literature findings 14 , 18 , 19 , where the same or similar compounds belonging to the three PCs groups were reported.

Figure 2 The mean percentage share of individual compounds identified in AAH extracts from investigated abandoned fallows ( a ), farmlands ( b ), and forest soils ( c ).

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“…Humic substances (humic acids—HA, fulvic acids—FA and humins—HU), present in the soil are the most reactive part of organic matter 41 . They are complex and heterogeneous mixtures of polydispersed materials formed by biochemical and chemical reactions during the decay and transformation of plant and microbial remains 18 . These organic molecules contain phenolic electron-donating moieties, due to which they may act as antioxidants 42 , thus significantly contributing to TAC and influencing soil quality.…”

“…In parallel, these processes lead to the formation of humic substances (HS) in soil, containing stable semiquinone radicals 13 in their structure, most likely to be derived from the reaction of phenolic compounds with reactive radicals 14 . Several studies imply that most of the antioxidants in soil can be found among the humic substances 15 – 18 . This was evaluated by Ziółkowska et al 19 ., who determined the important role of phenolic compounds in the processes of organic matter transformations in meadow soils, leading to the formation of humic substances.…”

“…It was found to be an efficient extraction method for insoluble-bound forms of polyphenols from plant and soil material, although up to date only meadow soils have been tested. Meanwhile, in the literature several methods have been suggested to determine the phenolics content or antioxidant capacity of various extracts, based on either reduction of metal ions using a tested antioxidant or scavenging of stable radicals 17 , 18 , 20 . Among them, the Folin–Ciocâlteu (FC) colorimetric assay has been commonly proposed to determine the total phenolics mainly in various plant-derived materials 6 , 18 , 25 .…”

“…Meanwhile, in the literature several methods have been suggested to determine the phenolics content or antioxidant capacity of various extracts, based on either reduction of metal ions using a tested antioxidant or scavenging of stable radicals 17 , 18 , 20 . Among them, the Folin–Ciocâlteu (FC) colorimetric assay has been commonly proposed to determine the total phenolics mainly in various plant-derived materials 6 , 18 , 25 . The FC reaction is based on single electron transfer, and measures the reductive capacity of a mixture containing redox-active phenolic compounds 26 .…”