Valuable phytochemicals with antioxidant, antimicrobial and other health benefits are synthesized by plants in the process of secondary metabolism. Therefore, medicinal and aromatic plants have been used in health care, food, and cosmetics since ancient times. The importance of herbal medicines in the ХХI century increases significantly due to the rapid development of functional foods and nutraceuticals, which became the main trend in food science and technology, as well as in nutrition and disease prevention (Nitrayová et al., 2014; Kraujaliene, Pukalskas and Venskutonis, 2017). Many plant species have not been sufficiently studied from the phytochemical point of view. This suggestion applies specially to alien plant species, the phytochemistry of which in the secondary distribution range may differ significantly, due to a change in the soil and climatic conditions during the expansion the secondary distribution range. Evaluation of widespread invasive species will, perhaps, reveal new sources of functional ingredients for food, nutraceuticals, cosmeceuticals, medicines, and other applications. Invasive species can be a valid resource and instead of eliminating them, there could be a great benefit obtained.

Canadian goldenrod (Solidago canadensis L.) is a highly aggressive alien plant native to North America. Once established, it can reduce biodiversity or locally outcompete all native plants. It is considered as the worst invasive alien weed in Europe (Lambdon, 2008; Vinogradova et al., 2010). Nowadays it is widely spread in China, Russia (from Kaliningrad to the Far East), Japan, Taiwan, Europe and Australia (Walck et al., 1999; Weber, 2000; Vinogradova, Mayorov and Choroon, 2010). Сomplex Solidago canadensis is a highly variable and its taxonomic status is not clear and difficult to assess (Semple and Cook, 2006; Melville and Morton, 2011; Vinogradova, Ryabchenko and Mayorov, 2013; Semple et al., 2013; Semple et al., 2015; Vinogradova et al., 2017). Invasive S. canadensis may acquire spreading advantage in non-native habitat by using “novel weapons” to inhibit not only local plants but also soilborne pathogens (Zhang et al., 2009). Thus, invasion success of Solidago canadensis is depended on allelopathic compounds which plant can release (Abilasha et al., 2008). It has been found that acetone extracts of S. canadensis showed allelopathic effects on the growth of other weeds (Solymosi, 1994).

Numerous organic compounds were reported for the genus Solidago, for example, flavonoids, phenolic acids and glucosides, polysaccharides, diterpenes, triterpenoid saponosides, tannins, and essential oils. These results highlighted the potential of using S. canadensis extracts as a natural antimicrobial and antioxidant substances for food applications (Deng et al., 2015). The flowers were used in traditional medicine as an analgesic, burns and ulcers treatment, febrifuge, gastrointestinal and liver aids (Vinogradova and Kuklina, 2012; Zihare and Blumberga, 2017). This species has been used in traditional medicine as a urological and antiphlogistic medicament (Apati et al., 2003). Many herbal preparations exploited in traditional medicine contain a significant number of polysaccharides or their glycoconjugates. It has been found that polyphenolic–polysaccharide–protein complexes isolated from medicinal plants of Asteraceae and Rosaceae families showed anticoagulant activity (Pawlaczyk et al., 2009). Special medicals "Goldenrod" with antispasmodic, diuretic and anti-inflammatory effects is produced in Ukraine and Russia. Available for sale “Prostanorm” – for the treatment of prostate diseases, "Marelin" and "Fitolizin" – from urolithiasis (Vinogradova and Kuklina, 2018).

In terms of bioeconomics, large populations of S. canadensis are important for honey production (Botta-Dukat and Dancza, 2008). Our earlier data confirm the availability of Solidago canadensis: its aerial part containe from 0.1 to 0.7% of essential oil in the leaves and from 0.1 to 0.4% of essential oil in the inflorescens. Α-pinene (1.3 – 61.2%), limonene (0.5 – 22.5%), bornyl acetat (3.4 – 29.8%) and germacrene D (1.8 – 39.2%) were the major compounds detected in oil samples of S. canadensis. Samples from inflorescences contained the maximal percentage of monoterpene hydrocarbons, while the leaves' samples showed the maximal cumulative percentage of sesquiterpene and monoterpene hydrocarbons (Shelepova et al., 2018). The threats and benefits to food production from S. canadensis in the Nitra river basin are described in detail (Fehér et al., 2016).

The aim of this article was to investigate the composition and structural features of the complex isolated from leaves and inflorescence of S. canadensis, growing in Slovakia for to assess the possibility of using this species for bioeconomics in the future.

Phytochemicals possess various bioactivities and may serve as potential sources of antioxidants in foods and health promoting ingredients in humans. Chemical analyses of Solidago canadensis leaves and inflorescences revealed the presence of protein (12.2 wt/wt%), carbohydrates (4 wt/wt%)), lipids (5.1 wt/w %) and inorganic material (6.7 wt/wt%)) (Table 1a and 1b). Monosaccharide analysis of neutral carbohydrate part showed the presence of one main sugar – fructose (8.8 g.kg^-1), while other saccharides as maltose, sucrose, and lactose were found in low amounts only (<0.5 g.kg^-1). However, this may not always be the case. So, according to Šutovska et al. (2013), S. canadensis complex (hot alkaline extraction of flowers) revealed the presence of rhamnose (∼23 wt/wt%), arabinose (∼20 wt/wt%), galactose (∼17 wt/wt%) and glucose (∼14 wt/wt%). In our study, we did not detect these monosaccharides.

S. canadensis contains vitamin C (L-ascorbic acid (1.53 μmol.g^-1)) and beta carotene (93.9 mg.kg^-1) (Table 1a and 1b). The vitamin E family includes four tocopherols, α-tocopherol being the most potent member of this family (Shahidi and Ambigaipalan, 2015). The major quantitative tocopherol in S. canadensis leaves and inflorescences was α-tocopherol (48.8 ±3.2 mg.kg^-1 DWP). It is in agreement with Kraujaliene, Pukalskas and Venskutonis (2017). Vitamin E is known as a reducing agent and may contribute to antioxidant activity by reducing the oxidized state of the phenolic antioxidant compounds. Thus, these compounds may be regenerated, allowing their antioxidant capacity to increase. Carotenoids have been reported to show chain-breaking antioxidant activity. These compounds are also effective singlet oxygen quenchers (Demir, 2009).

Lipids are another important group of S. canadensis phytochemicals. The oil contents were 5.1% dry weight plant material (Table 1a and 1b). It is reasonable because the majority of botanical materials (leaves and inflorescences) contain low amounts of lipids. The fatty acids composition was comprised of saturated fatty, monounsaturated and polyunsaturated fatty acids (34.0; 14.3 and 44.8 g.100g^-1 oil, respectively). The lipophilic fraction contains of 20 fatty acids; four acids (linoleic acid, C-18:2; oleic acid, C-18:1; palmitic acid, C-16, linolenic acid, C-18:3) is dominated. Of these acids, the first two, the unsaturated C-18 acids, amounted to 57.2% of the total (Figure 2).

S. canadensis fatty acid profiles showed the presence of high amounts of linoleic acid (35.5%) (Figure 2). From linoleic acid is synthesized γ-linolenic acid and is the first intermediate in the conversion of linoleic acid to arachidonic acid. γ-linolenic acid prevents or alleviates a wide variety of human diseases, and it is important as a dietary and cosmetic component. Palmitic acid is the second quantitatively major compound (21.7 %).

Amino acid analysis has shown that the studied S. canadensis leaves and inflorescences contained 18 amino acids (10 essential and 8 non-essential) (Figure 3). Aspartic acid was found to be the dominant free amino acid (12.2 g.kg^-1) followed by a proline (11.0 g.kg^-1) and glutamic acid (10.9 g/kg), respectively. Proline content of S. canadensis inflorescences could be one of the parameters in the determination of S. canadensis honey authenticity and could be a good indicator of the botanical origin of honey. Amino acids found in high levels were: lysine, leucine, valine, arginine, phenylalanine – average content in from 7.1 to over 5.1 g.kg^-1. Lower but also important amounts of glycine, isoleucine, threonine, serine, alanine, histidine, tyrosine, cystine, methionine, and tryptophan (ranging from 1.5 to 4.9 g.kg^-1) were detected in the study. The total number of amino acids was 97.10 g.kg^-1 DM, including total essential amino acids (45.60 g.kg^-1 DM) and percentage of total essential amino acids (46.96%).

The results of the elemental analysis of S. canadensis leaves and inflorescences are summarized in Table 2; these values are averages of three independent measurements having ±SD. Concentration of various elements decreases in the order: K>Ca>P>S>Mg>Zn>Mn>Fe>Cu> Na>Al>Ni>As>Cr>Se>Pb>Cd>Hg.

Among the various elements As, Cr, Se, Pb, Cd, Hg are found to be present at the trace level. Zn, Mn, Fe, Cu, Na, Al, and Ni are at the minor level and K, Ca, P, S and Mg are at the major levels. This result is supported by the results of Pytlakowska et al. (2012).

We note here that our focus is not to compare but rather to explore the mineral composition in the selected plants and to discuss their importance in human health. Due to a deficiency of these minerals in the human diet, most of these minerals are often taken as supplements (Agarwal et al., 2011) for their important role in human health.

In fact, the chemical constituents present in plants are responsible for their medicinal as well as toxic properties which include vegetable bases comprising of alkaloids and amines, glycosides, essential oils responsible for their characteristic odour, toxic substances known as toxalbumin, resins, and antibiotics. Whereby the trace elements play a very important role in the formation of these compounds.

One important factor for the formation of active constituents in plants are the trace elements because they are known to play an important role in plant metabolism and active constituents of medicinal plants are metabolic products of plant cells. Among the various elements estimated, the potassium and sodium ions play an important role in the diseases related to renal disorder. Potassium and sodium salts are partially responsible for the diuretic action of some drugs. Potassium is readily excreted by the kidneys both by glomerular filtration and by tubular excretion. Potassium salts act as osmotic diuretics and deficiency of potassium causes diabetic acidosis. Calcium ion concentration also plays an important role in the urinary tract system. Hypercalcemia causes renal failure and calcium stones in the urinary tract. Iron deficiency is common in uremic patients, it causes substantial blood losses. Iron may bind to the dialyzer membrane. Some reports indicate that dysgeusia, poor food intake, and impaired sexual function, which are common problems of uremic patients, may be improved by zinc supplements (Rajurkar and Damame, 1998). Magnesium is reported to have a curative effect in more than 300 health disorders, including headache and fatigue (Daur, 2015). Mn ameliorates some of the symptoms of diabetes and plays a role in the function of connective tissue, bones, and blood clotting factors Similarly Cr, Mn, Fe, Co, Cu, and Zn have been reported as essential or beneficial to human health (Kozlowska et al., 2015).

The total antioxidant activity of extracts from freeze-drying leaves of S. canadensis was not high and amounted to 34.9% (aqueous extracts), 35.7% (ethanol extracts) and 54.7% (methanol extracts) (Table 3). While the total antioxidant activity of extracts from air-dry leaves was significantly higher for methanol and ethanol extracts and amounted to 83.2 and 85.8%, respectively. But it was lower for the water extract – 18.6%. The total antioxidant activity of the herbal tea samples from the 2 types of fermentation was generally similar and significantly higher than the native samples for aqueous extracts (66.9 – 58.2 %). The indices of alcoholic extracts of herbal tea were lower than those for dry leaves but higher than those of native samples (55.6 – 56.8% (ethanol extract) and 74.8 – 76.6% (methanol extract)). Deng et al. (2015) determined antioxidant activity from leaves and bark of S. canadensis using DPPH radical. The capacity ranged from 25.3 – 37.2% (ultrasound-assisted extraction) to 18.8 – 21.1% (ethanol extraction) by DPPH method. Demir et al. (2009) reported results antioxidant capacity of young shoots with leaves for S. virgaurea using DPPH method. The antioxidant capacity ranged from 30.7% (aqueous extracts) to 64.3% (methanol extract) of DPPH inhibition.

The results demonstrated that S. canadensis can be a valuable raw material resource for many sectors of the economy. Many high added value products can be obtained from this species. This proves the value of S. canadensis for the bioeconomy and the possibility of its wider application in the future.