Influence of a Selenium Biofortification on Antioxidant Properties and Phenolic Compounds of Apples (Malus domestica)

Abstract

Biofortified apples seem to be a suitable produce. In this study, different selenium forms and application levels were applied to the two apple varieties ‘Golden Delicious’ and ‘Jonagold’, grown in the years 2017 and 2018 in order to increase the selenium uptake within a typical Western diet. It was shown that the biofortification, which was performed as a foliar application implemented in usual calcium fertilization, led to significantly increased selenium contents in the fruits. Furthermore, biofortification affected the total phenolic content (TPC), the polyphenol oxidase activity (PPO), as well as the antioxidant activity (AOA), the latter measured with the two well-known assays Trolox Equivalent Antioxidant Capacity Assay (TEAC) and Oxygen Radical Absorbance Capacity Assays (ORAC). The varying selenium forms and application levels showed a differing influence on the parameters mentioned before. Higher fertilizer levels resulted in higher selenium accumulation. It was found that PPO activity fluctuates less in biofortified apples. With regard to TPC, selenate led to higher amounts when compared to the untreated controls and selenite resulted in lower TPC. AOA analysis showed no clear tendencies as a result of the selenium biofortification. In the case of ‘Jonagold’, a higher AOA was generally measured when being biofortified, whereas, in the case of ‘Golden Delicious’, only one form of application led to higher AOA. Additionally, differences in the amount of major phenolic compounds, measured with High Performance Liquid Chromatography Mass Spectrometry (HPLC-DAD-ESI-MSn), were observed, depending on the conditions of the biofortification and the variety.

Relationship between Phenolic Compounds, Antioxidant Properties, and the Allergenic Protein Mal d 1 in Different Selenium-Biofortified Apple Cultivars (Malus domestica)

“…It is hypothesized that the application of selenium-containing fertilizers leads to the better protection of the fruits against certain stress factors, whereby only a lower synthesis rate of the Mal d 1 protein is required. The induction of further plant-protective substances, such as phenolic compounds, resulting from biofortification with selenium in apples [ 48 ] and other crops [ 49 , 50 , 51 , 52 , 53 , 54 , 55 ] has also been determined in previous studies. Furthermore, it has already been shown that selenium can protect plants from a range of abiotic stresses such as cold, drought, radiation, salinity, and heavy metals [ 56 , 57 ].…”

“…In a previous study, the influence of the biofortification of apples with selenium by foliar fertilization was investigated. There, it was found that the content and composition of phenolic compounds were significantly influenced by selenium [ 48 ]. In other experiments it was found that even the Mal d 1 content was reduced, in most cases, when the fruits were biofortified with selenate, while apple cultivar and ecophysiological conditions (e.g., climate) were identified as further influencing factors [ 34 ].…”

Iodine Biofortification of Apples and Pears in an Orchard Using Foliar Sprays of Different Composition

“…For example, at a content of 50 μg I (100 g FM) –1 , the target value for Se would be 5.2 μg (100 g FM) –1 . In a study by Groth et al (2020) , Se content of this level was achieved in apples by a foliar spray of 150 g Se (ha ⋅ m CH) –1 , regardless of whether SeO 3 2– or SeO 4 2– was applied. Further field experiments are needed to examine the effects of appropriately increased Se fertilization rate in combination with I.…”

Content of selenoaminoacids and catechins in Chinese green teas

“…Generally, the effect of chemical stress induced by selenium treatment can enhance the antioxidant activity of plant extracts [38,43]. However, the opposite results are also reported [44]. The two studied varieties of apples were differently affected: one of them mostly showed a higher antioxidant activity (measured with TEAC) resulting from the biofortification and independently of the selenium form and the level of application, whereas the values for the second was only slightly influenced by the biofortification.…”