**1. Introduction**

Wild foods include leaves, flowers, fruits, and seeds gathered from spontaneous plants. In Europe, their consumption, often considered as an emergency practice associated with food shortage periods, has been almost completely neglected in the last decades. Nowadays wild food plants are gaining renewed attention for their nutritional value and their use is promoted by health-oriented people in the healthy lifestyle framework, with special reference to wild-green centered cuisines [1]. The leafy plants, also known as wild greens, have been traditionally consumed as salad, soup or vegetable dishes and have represented an important part of the daily diet in the Mediterranean countries, especially during the early spring and in the autumn [1]. Wild greens are known to be a good source of protein and fat, vitamins, sugars, and minerals [2–4]. A wide variety of phytochemicals with antioxidant e ffects have been also reported in many of these species [5]. Moreover, some studies demonstrated that wild plants often contain molecules showing antimicrobial potential [6] and other biological-pharmacological activities [7]. For this reason, some wild greens have recently attracted considerable attention as

a source of functional foods or fortified food additive powders. On the other hand, most of them grow in anthropogenically disturbed sites such as farmlands (weeds), places of human habitation (ruderals), borders of paths and roads, etc., in soils often rich in nitrate or contaminated by metallic trace elements [8] whose detrimental e ffects on human health are known [9–11]. Considering that, due to the e fficiency in root-to-shoot translocation paths, the synanthropic plants can accumulate high levels of pollutants in the aerial parts [12,13], their use as food may also entail health risks.

More than 600 wild species are used in traditional rural Italian cuisine and, among them, approximately 200 are the leafy plants [14]. We hypothesized that these wild greens could be profitably grown as specialty crops like microgreens or baby greens, with the dual advantage of widening the range of these products and, at the same time, promoting the wild species.

Microgreens are tender immature greens harvested within 10–20 days from seedling emergence and about 5 cm in height, when cotyledons are fully expanded, and the first pair of true leaves are more or less developed. Recently, microgreens have been gaining more and more popularity as a novel culinary ingredient used to enhance salads and other dishes in color, taste or texture [15], and their price may exceed \$100 per kg [16]. Also, baby greens (otherwise known as baby leaves) are harvested and consumed in immature plant size, but they are older and larger than microgreens (about 10 cm in height) [16]. Baby greens are widely requested as a base component of mixed salads, especially for the ready-to-eat ones, whose consumption is constantly growing [17]. Considering both fruits and vegetables, the market for fresh-cut products in Europe has shown a double-digit growth since they began to be commercialized in the early 1980s [18]. In the United States, ready-to-eat salad mixes went through a five-fold increase in supermarket sales over a period of 20 years [19].

As reviewed by di fferent authors [20–22], several studies have recently shown that plants at the microgreen stage are particularly rich in antioxidants and other health-promoting compounds, which is a reason why microgreens have started to be appreciated also as functional food. However, literature on the chemical composition of microgreens [23–27], as well as of baby greens [17,28], is by far focused on cultivated species, while very few studies have been carried out on wild edible plants [29–31]. Furthermore, the concentration of minerals and organic bioactive compounds of micro/baby greens has often been compared with that of the mature counterparts [30,32–35], while to our knowledge only one study is available about the di fferences in the mineral composition between microgreens and baby greens of the same species [36].

Based on this background, the aim of the present study was to evaluate three wild leafy species (*Sanguisorba minor* Scop., *Sinapis arvensis* L., and *Taraxacum o*ffi*cinale* Weber ex F. H. Wigg.) as possible candidates as microgreens and baby greens. Plants were grown hydroponically until they reached the microgreen or baby leaf stage, and yield, some antioxidants, nitrate, and mineral content were analyzed. The possible contribution of the di fferent products to human mineral requirements was calculated and the health risk due to the ingestion of heavy metals possibly resulting from their consumption was also estimated.

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

#### *2.1. Plant Material and Growth Conditions*

Seeds of *S. minor* (small burnet), *S. arvensis* (wild mustard), and *T. o*ffi*cinale* (common dandelion) were used as starting material. *S. minor* and *S. arvensis* seeds were provided by "B & T World Seeds" (Aigues-vives, France), while seeds of *T. o*ffi*cinale* were harvested in late April from wild plants growing in uncultivated land in the peri-urban area of Lucca (Tuscany Region, Italy). Prior to use, seeds were surfaced-sterilized in 2.2% hypochlorite for 15 min and then rinsed under tap water for 2 min. Besides this, 1000-seed weight and germination percentage were determined (Table 1). Seeds were sown in polystyrene cell trays (27.0 × 53.5 cm2, 392 cells) filled with vermiculite (Asfaltex S.A., Sant Cugat del Vallés, Barcelona, Spain). Seed amount was calculated based on 1000-seed weight and germination percentage in order to obtain about eight plants per cell. After sowing, trays were

kept in the dark at 20 ◦C for 48 h and then moved in a growth chamber at 25 ± 2 ◦C (day) and 17 ± 2 ◦C (night) with a photoperiod of 16 h under fluorescent lighting units OSRAM L36W/77 (36 WATT, 120 cm in length, 26 mm in diameter, four per tray). Trays were placed in polyethylene tanks containing 5 L of half-strength Hoagland's nutrient solution prepared with distilled water (macroelements expressed in mM and microelements in μM: N 7.5, P 0.5, K 3.0, Ca 2.5, Mg 1.0, Fe 25.0, B 23.1, Mn 4.6, Zn 0.39, Cu 0.16, Mo 0.06; pH: 5.56; CE: 1.12 mS/cm) and arranged in a randomized block design with three replicates (1 replicate = 1 tank). The volume of the nutrient solution consumed by the crops was reintegrated at least once a week.

**Table 1.** One thousand-seed weight and germination rate of *Sanguisorba minor* Scop., *Sinapis arvensis* L., and *Taraxacum o*ffi*cinale* Weber ex F. H. Wigg. seeds.


1 Means of eight samples of 100 seeds each × 10 ± SD. 2 Means ± SD of four samples of 50 seeds each, kept in the dark at 20 ◦C for 21 days.

#### *2.2. Harvesting and Yield Assessment*

At the microgreen stage (first true leaf, green and swollen cotyledons), which was reached 14 days after sowing in *S. arvensis* and 16 days after sowing in both *S. minor* and *T. <sup>o</sup>*ffi*cinale*, half of the plants were harvested by cutting them with scissors just above the surface of the growing medium. The remaining plants were thinned to one plant per cell and leaves were harvested by cutting them with scissors after plants had reached the baby leaf stage (5–6 true leaves), 35 days after sowing in *S. arvensis* and *T. <sup>o</sup>*ffi*cinale*, and 43 days after sowing in *S. minor*. Microgreens and baby greens were weighed to determine yield, which was expressed in kg FW/m2.
