**1. Introduction**

Sprouts and microgreens are popular and trendy foods [1]. The wide variety, available even in a relatively small surface area, o ffers the opportunity to practice urban gardening under space-limited conditions in houses and apartments. The popularity of sprouts and microgreens is related to their high aesthetic potential and intense taste. The sensory and nutritional properties depend on the content of secondary metabolites [2]. The results of various studies have shown that the content of many bioactive compounds increases significantly during sprouting and in the microgreens [3]. High contents of polyphenols, anthocyanins, and other redox-active compounds, i.e., vitamins, glucosinolates, and minerals, have been found [4–7]. Modulation of the light regime [8] and the composition of the growth solution for microgreens have shown a high potential for biofortification with minerals [9] and secondary metabolites [10].

Polyamines, such as agmatine (AGM), putrescine (PUT), cadaverine (CAD), spermine (SPM), and spermidine (SPD) are secondary metabolites with two or more amino groups that are closely related to plant growth and development, stabilization of cellular structures, and stress resistance [11]. Increased endogenous synthesis as well as the exogenous application of polyamines, improve seed germination and growth [12]. The results of several studies show that germination leads to a change in the content

and profile of polyamines. In the soybean, germination leads to an accumulation of all analyzed polyamines. Maximum values were determined after 48 h, followed by slightly lower values after 96 h of germination. These are still three-fold higher than in ungerminated seeds [13]. The content of all analyzed polyamines increased during germination in lupin sprouts whereas, in fenugreek, only PUT and CAD accumulated, while SPM and SPD remained constant [14]. There are some other reports of changes in polyamine content during germination of legume seeds, where a larger increase of PUT and CAD, compared to SPM and SPD, was observed when dry weight is assumed [15,16]. Accumulation of all polyamines was observed in germinated corn [17] and a large increase in agmatine content in radish [16] and flaxseed sprouts [18]. Reports related to the polyamine transformation in microgreens are rare. In lettuce, a gradual decrease in free SPM and SPD was observed from the microgreens stage (2 weeks) to commercial maturity (10 weeks) [19].

The polyamines, which accumulate in the germinating seeds, not only have intracellular functions but can also serve as a substrate for diamine oxidases. The enzymatic oxidation of predominantly PUT and CAD produces H2O2, which is involved in cell wall di fferentiation and programmed cell death and has direct antimicrobial activity when tissue integrity is broken [20,21]. Copper amine oxidases (CuAO) are diamine oxidases with copper ion in the active site and are expressed at high levels in legumes [22]. They are localized either in the apoplasts, in the intercellular spaces, or loosely bound to the cell walls [23,24]. Diamine oxidases are expressed in various tissues of germinated seeds of the *Leguminosae* family. In soybean sprouts, the enzyme is predominantly expressed in the hypocotyl and root system. The activity in bean sprouts has been found mainly in the cotyledons [25], and, in fava beans, in all parts except the cotyledons [26]. The higher enzyme activities were found to be correlated with higher contents of CAD or PUT [27] in the hypocotyl and root of chickpeas. Enzymes that catalyze the oxidative deamination of biogenic amines can be used as dietary supplements. Diamine oxidases of animal origin, incorporated in capsules, can be consumed in the intestinal tract for more e fficient oxidation of undesirable dietary biogenic amines. Such treatment e ffectively reduces the severity of migraine episodes [28]. On the other hand, excessive oxidation of polyamines in the digestive tract is problematic, as the H2O2 generated is toxic to the intestinal cells. A dietary supplement with a combination of white pea diamine oxidase with catalase, which catalyzes the decomposition of H2O2 generated by diamine oxidase, resulting in reduced toxicity [29]. The direct oxidation of biogenic amines in the food matrix, prior to ingestion, could be a viable alternative to the use of amine oxidases as dietary supplements.

From the published results, it can be concluded that the content of polyamines generally increases during sprouting. From a nutritional point of view, there is no simple answer to whether this is beneficial or not. Large contents of PUT and CAD that accumulate as a result of endogenous synthesis in plants or by microbial decarboxylation of amino acids [30] are certainly not desirable. These foul-smelling compounds are slightly toxic to the intestinal cells [31] and, mainly interfere with the enzymatic oxidation of tyramine (TYR) and histamine (HIS) in the digestive tract [32], which increases their negative e ffects. Dietary intake of AGM, SPM, and SPD may be desirable. SPM and SPD, in particular, appear to have cardioprotective and neuroprotective e ffects [33]. AGM, which can cross the blood–brain barrier, can be consumed in large quantities without adverse health e ffects and can relieve the symptoms of central nervous system disorders, including major depression [34]. Endogenous synthesis of polyamines in mammals decreases with age [35], and dietary intake of polyamines, particularly SPD, is directly related to lower mortality, as has been found in a prospective population-based study [36]. However, dietary polyamines are a double-edged sword, as they can potentiate the growth of certain cancers, most probably due to the stabilizing of DNA [37]. Dietary intake of polyamines is therefore generally desirable, but should also be controlled because of the possible adverse e ffects. The content of SPM, SPD [38], and AGM [39] in the diet is becoming an important issue. Di fferent seeds and meats are quantitatively the main sources of SPM and SPD, while certain types of fermented foods are rich in AGM (Table 1).



**Animal**/**human studies**

[44]

• Potentiation of histamine and tyramine toxicity [32]

tumors in mice [56]

The objectives of the present study are (I) to determine the polyamine content in seeds, sprouts and microgreens of three legumes and one cruciferous plant, (II) to evaluate whether microgreens are nutritionally superior to sprouts in terms of polyamine content, and (III) to evaluate the enzymatic potential of sprouts to degrade undesirable biogenic amines.

#### **2. Materials and Methods**
