Article pubs.acs.org/JAFC
Cite This: J. Agric. Food Chem. 2019, 67, 7050−7059
Zea mays L. Grain: Increase in Nutraceutical and Antioxidant Properties Due to Se Fortification in Low and High Water Regimes Roberto D’Amato,* Mauro De Feudis, Marcello Guiducci, and Daniela Businelli
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Department of Agricultural, Environmental and Food Science, University of Perugia, 06121 Perugia, Italy ABSTRACT: This work aimed to investigate the effect of selenium (Se) and irrigation on the grain yield, on the forms of Se, phenols, and carotenes, and on some antioxidant activities of maize (Zea mays L.) grains. To reach this goal, a 2 year experiment was undertaken. Maize was fertigated with sodium selenite at the rate of 200 g of Se ha−1 and grown under two water regimes. While the irrigation did not show a clear effect on the selected parameters, Se fertigation increased the contents of inorganic and organic Se forms, xanthophyll, and salicylic acid. Furthermore, while Se fertigation decreased the hydroxycinnamic acid content, generally higher antioxidant activities were found in Se-treated grains than in the control. These findings suggest that Se fertigation increases most of the nutraceutical values of maize grains, which therefore might improve human and livestock health and could increase the maize grain shelf life and its byproducts. KEYWORDS: maize flour, water availability, phenolic acids, carotenes, Se-amino acids
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sorghum,10 and maize,11 Se acts as an antioxidant against reactive oxygen species (ROS) which could be harmful to plant cells. Indeed, abiotic stresses, such as low water availability, lead to the overproduction of ROS in plants, which significantly damages proteins, lipids, chlorophyll, and nucleic acids.12 Furthermore, Se promotes the synthesis of nutraceuticals in plants such as phenolic compounds,13 SeMet, and Se(methyl)selenocysteine.14 However, the bioavailability of Se for humans and animals depends on the form of occurrence.15 For example, foods rich in low-molecular-weight proteins and certain vitamins such as vitamins B, C, and D promote Se intake by humans.16 The presence of Se in plants and animal tissues is correlated with the soil Se content,17 which usually ranges between 0.01 and 2 mg kg−1. In order to obtain an increase in Se content in edible crops, a current technology is to apply Se fertilizer as a seed dressing, and seed soaking, soil application, and foliar spray have been used.18,19 Because of their simplicity, the last two techniques represent those used most often. Selenite and selenate are the main forms used for Se fertilizer. Moreover, selenite has been recognized to be far less mobile than selenate when it is applied to the soil, because it shows a greater affinity for adsorption onto soil particle surfaces in comparison selenite, as it forms strongly bonded inner-sphere complexes on metal oxide surfaces.20 From an environmental point of view, it is possible to foresee a lower leaching of the selenite into deep soil by the water from irrigation and rainfall in comparison to what happens to the selenate and therefore selenite has a lower environmental impact.21 Moreover, when selenate is applied to substrates, higher amounts of organic forms of Se appeared in the edible parts of the crop in comparison to those when
INTRODUCTION Maize (Zea mays L.) is an important cereal crop throughout the world and is ranked as the third major cereal crop after wheat and rice. With regard to the human diet, maize provides at least 30% of food calories to more than 4.5 billion people, particularly in developing countries, showing it to be a basic staple food.1 Maize has a high starch content, and it is rich in antioxidant compounds such as phenolic compounds (e.g., phenolic acids), carotenoids (e.g., β-carotene), and xantophylls (e.g., lutein and zeaxanthin).2 Despite the fact that maize grain is itself a food with high nutritional properties, in some areas of the world with low levels of selenium (Se) in the soil (such as some African countries and China)3 experimental tests have been carried out in order to promote the practice of Se fortification of maize crops.4 For example, in Malawi, where subsistence agriculture is widespread, there is evidence of suboptimal dietary Se intake.5 Wang et al.6 analyzed the Se content in maize grain in China and classified most of the samples as Se deficient. In human and animal diets, habitual suboptimal Se intake leads to reduced Se status. In humans, this may be associated with cardiovascular disorders, impaired immune functions, and some forms of cancer. In animals, Se deficiency may be associated with Keshan disease, Kashin−Beck disease, Behcet’s disease, and immune system disease.6 For these reasons, Se fortification of a widely consumed food such as maize could be a valid means of countering the spread of these diseases. In contrast to humans and animals, Se is not considered to be essential in plants7 and it occurs in organic (i.e., selenocystine, selenomethionine, and Se-methylselenocysteine), and inorganic (selenite and selenate) forms. Drought is an abiotic factor affecting the growth and yield of crop plants, and it is one of the most important constraints for maize growth and productivity, because it causes significant losses in grain yield.8 Fertilization with Se can be a valid aid for plants subjected to periods of drought stress. In fact, as observed in olive trees,9 © 2019 American Chemical Society
Received: Revised: Accepted: Published: 7050
April 19, 2019 May 31, 2019 June 3, 2019 June 3, 2019 DOI: 10.1021/acs.jafc.9b02446 J. Agric. Food Chem. 2019, 67, 7050−7059
Article
Journal of Agricultural and Food Chemistry Table 1. Chemical Determination in Soil Sample of Two Field Experiments year
total organic C (g kg−1)
total Se (μg kg−1)
CaCO3 (g 100 g−1)
pH
available K (mg kg−1)
available P (mg kg−1)
cation exchange capacity (cmol(+) kg−1)
2016 2017
10.3 10.1
250 289
