## 4 Discussion
### Antioxidant Activity and Total Polyphenic Compound Content  
Compounds contained in plant foods, accumulating in plants before harvest, affect the quality of products obtained from them and have a beneficial effect on reducing oxidative stress ([PERSON] et al., 2017). For the best knowledge of authors in the published literature there are not many data concerning the antioxidant activity and polyphenolic compound content, including polyphenolic profile in young green parts of white mustard. In the presented results, it was noticed that the highest amount of polyphenols was observed after 38 days of sowing (8246 mg/100 g), in which also, the maximum antioxidant capacity was obtained by ABTS and FRAP tests. This is an important finding of our study. The maximum antioxidant values using the ABTS method were obtained for the Bamberka cultivar (224.53 umol Trolox/1 g DM). [PERSON] et al. (2017) suggested that the antioxidant activity of _Brassica_ vegetables may be differentiated by genotype. In a similar study, in which the research material was young shoots of buckwheat, the ability to scavenge free radicals was determined at the level of 277.62 umol Trolox/1 g ([PERSON] et al., 2017). This value was similar to the result of the Borowska mustard from the harvest in the second harvest time and allows us to conclude that the green parts of the plants have a high antioxidant capacity. [PERSON] et al. (2017), in their research on Brussels sprouts, determined that fresh leaves of this plant have the ability to neutralize free radicals ABTS at the level of 61.6 umol Trolox/g. On the other hand, in a study carried out on cabbage of the Dolsan cultivar using the ABTS method, 50.07% of RSA was determined ([PERSON] et al., 2017). Results of both analyses confirmed that the plants reached their maximum antioxidant capacity after the 38 days of sowing, obtaining 234.37 umol Trolox/1 g DM in the ABTS method, and 1801 umol Trolox/1 g DM in the FRAP method. Plants harvested a week later obtained values lower in the ABTS method by about 21%, and FRAP by 29%, in relation to the most favorable result. Similarly, the results of research by [PERSON] et al. (2017) showed that the antioxidant activity of red cabbage decreases with growing time. In these studies, young red cabbage leaves had an antioxidant activity determined by the ABTS method by about 100% higher, and by about 35% by the FRAP method, compared to mature ones. It is believed that sprouts of Brassica vegetables are characterized by high biological activity ([PERSON] et al., 2017). The results of research by various authors indicate a high content of phenolic compounds in the _Brassicaceae_ family ([PERSON] et al., 2017; [PERSON] et al., 2017) emphasizing that cabbage leaves are particularly rich in polyphenolic compounds. The variable content of polyphenols depending on the time of harvest is pointed out by [PERSON] et al. (2017) and [PERSON] et al. (2017). According to the study by [PERSON] et al. (2017), the average content of polyphenols in green _Brassica junca_ mustard leaves was 1228.48 mg/100 g of raw material and the total amount of phenols correlated with antioxidant activity. There is a lot of scientific evidence indicating the strong antioxidant effect of polyphenolic compounds ([PERSON] et al., 2017; [PERSON] et al., 2017). For comparison, according to [PERSON] et al. (2017), young buckwheat leaves contained 497 mg/100 g of polyphenols. Blackcurrant fruit is considered to be one of the richest sources of polyphenols ([PERSON] et al., 2017). It contained an average of 1300 mg/100 g of total polyphenols. Comparing the content of polyphenols in mustard and blackcurrant, the high potential of mustard leaves as a source of polyphenols in a balanced diet was noticed. Based on the results of the HPLC analysis (available standards for phenolic compounds) it can be suggested that rutin was the compound with a higher amount in all cultivars and in terms of harvest of plant of mustard.