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Chilean journal of agricultural research

versão On-line ISSN 0718-5839

Chilean J. Agric. Res. vol.77 no.2 Chillán jun. 2017

http://dx.doi.org/10.4067/S0718-58392017000200134 

RESEARCH

Content of biogenic elements and fatty acid composition of fenugreek seeds cultivated under different conditions

Tomasz Bienkowski1  , Krystyna Zuk-Golaszewska1  , Joanna Kaliniewicz2  , Janusz Golaszewski3  * 

1University of Warmia and Mazury in Olsztyn, Department of Agrotechnology, Crop Management and Agribusiness, Oczapowskiego 8, 10-719 Olsztyn, Poland.

2University of Warmia and Mazury in Olsztyn, Department Animal Nutrition and Feed Management, Oczapowskiego 5, 10-719 Olsztyn, Poland.

3University of Warmia and Mazury in Olsztyn, Department of Plant Breeding and Seed Production, Plac Łódzki 3, 10-727 Olsztyn, Poland.

ABSTRACT

Fenugreek (Trigonella foenum-graecum L.) is a medicinal plant that has been recognized for its numerous health benefits throughout the centuries. The species is a rich source of biogenic elements, and it has a favorable composition of fatty acids. This study evaluated the effect of agrotechnological factors on the chemical composition of fenugreek seeds. The experiments conducted in north-eastern Poland had a fractional factorial design with 54 plots. A total of five agrotechnological factors were tested: seed inoculation with Rhizobium meliloti, sowing date, row spacing, weed control, and protection against fungal pathogens. The chemical composition of fenugreek seeds was influenced mainly by sowing date, row spacing and plant protection. Fenugreek seeds grown in north-eastern Poland contained 26.0% protein and 4.8% oil. Delayed sowing increased N content (9.2%) and decreased the content of P (8.8%), K (5.1%) and Mg (2.8%). An increase in row spacing from 15 cm to 45 cm promoted the accumulation of Fe (31%). Agrotechnological factors induced the greatest variations in the composition of saturated fatty acids (mean difference of up to 14.5%), followed by monounsaturated (up to 9.5%) and polyunsaturated fatty acids (up to 4.5%). Total unsaturated fatty acids accounted for 80% of the fatty acid profile, with a predominance of essential fatty acids in oil: linoleic acid (37.9%) and α-linolenic (28.2%) acid. Sowing date and weed control were responsible for up to 3.1%-4.5% of differences in concentrations of essential fatty acids between treatments.

Key words: Agrotechnological factors; biogenic elements; fatty acids; medicinal crop; Trigonella foenum-graecum.

INTRODUCTION

Fenugreek (Trigonella foenum-graecum L.) belongs to the botanical family Papilionaceae. Its native geographic range is the area extending from Iran to northern India, but it is presently cultivated also in other regions of the world (Zakia et al., 2014; Bieńkowski et al., 2016). Fenugreek is grown mostly for its seeds, seldom for straw as cattle forage, and fresh fenugreek leaves are consumed in some cuisines, including Indian. This species has been mainly used in medicine for centuries. Fenugreek seeds contain chemical compounds with medicinal properties, and in the past, they were consumed by pregnant women (Taloubi et al., 2013). Fenugreek seeds, leaf extractions, roots and stems have scientifically proven antidiabetic, anticarcinogenic, antimicrobial, and other health-promoting properties (Chauhan et al., 2011; Khorshidian et al., 2016). It is worth noting that fenugreek seed fibers, which are composed mostly of non-starch polysaccharides (saponins, tannin, pectin, and others), lower the rate of glucose absorption in the intestines and regulate blood sugar levels. On account of those properties, fenugreek seeds are recommended for diabetes diets (Srinivasan, 2006). Fenugreek seeds contain chemical compounds which are highly valued in the cosmetics industry. Akhtar et al. (2010) reported that cream bases and cream formulations containing fenugreek seed extract substantially improved skin elasticity, hydration and skin’s ability to resist photo-aging.

Fenugreek seeds are a natural source of vitamins such as thiamine, biogenic elements such as Fe, Si and Na, and a rich source of P and S (El Nasri and El Tinay, 2007). In the research conducted by Kochhar et al. (2006), fenugreek seeds contained 25.8% crude protein and 6.53% oil. Seed DM had the following chemical composition: 3% ash, 6.28% crude fiber and 58.13% total carbohydrates. El Nasri and El Tinay (2007) estimated the protein content of fenugreek seeds at 28.4%, crude fiber at 9.3% and crude fat at 7.1%. The fatty acid profile was dominated by unsaturated acids: oleic, linoleic, and alpha-linolenic acids which accounted for 16.3%, 50.0% and 24.4% of total fatty acids, respectively. The unique mineral and organic properties of fenugreek are exploited in the production of functional and nutritional foods as well as nutraceuticals and cosmetics (Hooda and Jood, 2005; Lubbe and Verpoorte, 2011).

The profile and content of chemical compounds in fenugreek seeds may be differentiated by production technology and growing conditions. The most important agrotechnological factors and postharvest processes determine the chemical composition of seeds and the shelf life of the resulting products by preserving vitamins, enzymes, flavonoids and the structure of components responsible for essentiality, aroma, color and moisture content. Those quality properties of fenugreek seeds and products are largely determined by soil moisture content (Hussein and El-Dewiny, 2011) and agronomic factors such as sowing date, sowing density, fertilization and plant protection during the growing season (Wierzbowska and Zuk-Golaszewska, 2014; Zuk-Golaszewska et al., 2015; Zapotoczny et al., 2015).

The objective of this study was to determine the impact of agrotechnological factors on the chemical composition of fenugreek seeds.

MATERIALS AND METHODS

Origin of seeds

Fenugreek seeds were obtained in a field experiment conducted in 2009 in northeastern Poland (53°43’ N, 20°24’ E). The experiment had a fractional factorial design, and treatments were randomly assigned to 54 plots. Five agrotechnological factors were tested: (A) seed inoculation with Rhizobium meliloti bacteria (0: no, 1: yes); (B) sowing date (0: earliest possible date, 1: delayed by 10 d, 2: delayed by 20 d); (C) row spacing (0: 15 cm, 1: 30 cm, 2: 45 cm); (D) weed control (0: mechanical, 1: chemical); (E) protection against fungal pathogens (0: seeds not dressed, chemical plant protection, 1: seeds dressed, no chemical plant protection, 2: seeds dressed, chemical plant protection). The experiment was set up on Haplic Cambisol (Eutric) soil of quality class IVa with a light loam overlay (IUSS Working Group WRB, 2015). The soil was characterized by slightly acidic pH, moderate content of P and K, and low content of Mg (Bieńkowski et al., 2016).

Laboratory analyses

Harvested seeds were cleaned, dried to 12 ± 0.5% moisture content. Seed samples (0.5 g) were mineralized in concentrated sulfuric acid (VI) with the use of hydrogen dioxide as oxidant. Total N content was determined calorimetrically with hypochlorite (Baethen and Alley, 1989). Phosphorus content was determined by the vanadium-molybdenum method; K, Ca and Na concentrations were analyzed by atomic emission spectroscopy (AES), and Mg content was measured by atomic absorption spectroscopy (AAS) (Zuk-Golaszewska et al., 2015). The content of micronutrients was determined in seed samples (0.5 g) mineralized in a mixture of perchloric and nitric acid with the addition of hydrochloric acid. Mineralized seeds were transferred to 50 cm3 flasks and supplemented with water. Micronutrient concentrations were measured by AAS in a Shimadzu spectrophotometer. The composition of the identified fatty acids (Table 1) was determined by the chromatographic separation method modified by Zegarska et al. (1991).

Table 1: Composition of fatty acids identified in fenugreek seeds. 

Fat was extracted by the Soxhlet method (AOAC, 2005). Fatty acids were separated and determined by gas chromatography in a gas chromatograph (CP-3800, Varian, Walnut Creek, California, USA). Fatty acid methyl esters (FAME) were prepared according to the modified Peisker method (methanol:chloroform:concentrated sulfuric acid, 100:100:1, v/v) (Zegarska et al., 1991). The resulting FAMEs were stored in sealed tubes and were analyzed by gas chromatography-flame ionization detection (GC-FID; column: 50 m ( 0.25 mm ( 0.25 µm). The temperature of the GC injection port was set to 225 °C in split mode (split ratio 50:1) with helium as the carrier gas at a constant flow rate of 1.2 mL min-1. Detector temperature was 250 °C and column temperature was 200 °C. Fatty acids were identified by comparing their retention times with those of pure FAME standards (Sigma-Aldrich, St. Louis, Missouri, USA) and peaks in the analyzed samples. The relative content of fatty acids was expressed as the percentage of the total surface area of all fatty acids detected in each sample.

Statistical analyses

The parameters describing the chemical properties of fenugreek seeds were analyzed by factorial and multivariate ANOVA. Nonsignificant higher-order interactions constituted the experimental error. Data were arranged in two groups of variables to estimate the impact of agrotechnological factors and interactions on the chemical properties of seeds: the “biogenic elements” group describing the content of micronutrients and macronutrients, and the “fatty acids” group describing the fatty acid composition of seeds. In MANOVA, the effect size of agrotechnological factors and interactions was measured with the use of partial eta-squared: η 2 p = SSeffect /( SSeffect+SSerror ), where SSeffect is the sum of squares for the effect of interest and SSerror is the error term associated with this effect. In factorial ANOVA, the effect size η2 was measured as the ratio between the variance of a factor or interaction ( SSeffect ) and the total variance of a given chemical property ( SStotal ). All analyses were performed at a significance level p < 0.05 in the Statistica package (Dell Inc, Round Rock, Texas, USA).

RESULTS AND DISCUSSION

Main and interaction effects of agrotechnological factors - effect size

The analyzed agrotechnological factors had a varied influence on the main effects and interaction effects of the analyzed chemical properties of fenugreek seeds. Multivariate ANOVA (MANOVA) revealed that sowing date (B) contributed to differences in the content of biogenic elements and fatty acids. The second factor which was responsible for significant variations in the fatty acid profile of fenugreek seeds was weed control (D) (Table 2). In the group of main effects and interaction effects of biogenic elements, the main effects of sowing date (B) (70.1%) and row spacing (C) (43.6%) and the Row spacing ( Weed control interaction effect (DE) (39.8%) were chiefly responsible for variations in the analyzed agrotechnological factors (or interactions) and experimental error (η 2 p ). The effect size of fatty acids was significantly greater than the effect size of biogenic elements. Weed control (D) (94.1%), sowing date (B) (86.6%), Sowing date ( Weed control interaction (BD) (85.5%) and Row spacing ( Weed control interaction (CD) (80.2%) were characterized by the greatest effect size.

Table 2: Wilk’s statistic in MANOVA and partial eta-squared (η2 p) for the content of biogenic elements and fatty acids in fenugreek seeds. 

A: Seed inoculation, B: sowing date, C: row spacing, D: weed control, E: antifungal protection.

Factorial ANOVA revealed that sowing date differentiated the content of N, P, K, saturated fatty acids - myristic acid C14:0, palmitic acid C16:0, stearic acid C18:0, arachidic acid C20:0, monounsaturated oleic acid C18:1, and essential fatty acids - linoleic acid C18:2, and alpha-linolenic acid C18:3 (Table 3). Weed control significantly differentiated the concentrations of fatty acids - lauric acid C12.0, stearic acid C18:0, arachidic acid C20:0, heptadecanoic acid C17:1 and linoleic acid C18:2, whereas the date of Sowing ( Weed control interaction (BD) also influenced the content of N and fatty acids - palmitoleic acid C16:1, linoleic acid C18:2, alpha-linolenic acid C18:3 and eicosadienoic acid C20:2. The concentrations of alpha-linolenic acid C18:3, an exogenous essential fatty acid, were determined by seed and plant protection against fungal pathogens.

Table 3: Significant main effects and interaction effects of chemical properties of fenugreek seeds determined by ANOVA. 

A: Seed inoculation, B: sowing date, C: row spacing, D: weed control, E: antifungal protection.

Biogenic elements

In the group of the examined agrotechnological factors, sowing date (B) and row spacing (C) significantly influenced the chemical composition of fenugreek seeds. On average, 1 kg DM contained 41.6 g N, 18.6 g K, 7.17 g P, 3.00 g Ca, 2.12 g Mg, 0.960 g Na and 0.234 g Fe (Table 4). The protein content of seeds from 54 experimental plots, determined by multiplying the N content by an N-to-protein conversion factor, ranged from 22.2% (A1B0C2D1E1) to 29.7% (A1B2C1D0E1), with an average of 26.0%. Our results were approximately 9% higher than the values reported by Rahmani et al. (2014) and Singh et al. (2013), where protein percentages ranged from 21.28% to 22.58% and from 18.1% to 24.63%, respectively. In the other study by Kochhar et al. (2006), protein concentrations were nearly identical to those noted in our study, and 9% higher than those reported by El Nasri and El Tinay (2007).

Table 4: Content of biogenic elements in fenugreek seeds subjected to different treatments of agrotechnological factors. 

A: Seed inoculation with Rhizobium meliloti (A0: no, A1: yes); B: sowing date (B0: earliest date, B1: 10 d delay, B2: 20 d delay); C: row spacing (C0: 15 cm, C1: 30 cm, C2: 45 cm); D: weed control (D0: mechanical, D1: chemical); E: antifungal plant protection (E0: non-dressed seeds, chemical protection, E1: dressed seeds, no chemical protection, E2: dressed seeds, chemical protection).

Values with the same letter do not differ significantly in Tukey’s test.

When sowing was delayed by 20 d (from B0 to B2), the N content of fenugreek seeds increased by 9.2% (from 40.1 to 43.8 g kg-1 DM), whereas P concentrations decreased by 8.8% (from 19.6 to 18.2 g kg-1 DM), K by 5.1% (from 7.30 to 6.93 g kg-1 DM) and Mg by 2.8% (from 2.13 to 2.07 g kg-1 DM). An increase in row spacing from 15 cm (C1) to 45 cm (C3) contributed to the accumulation of Fe whose content increased by 31.1% (from 0.202 to 0.265 g kg-1 DM).

The presence of a relationship between the mineral status of seeds and agronomic and environmental factors was reported by other authors (Hassanein et al., 2012; Abou-Shleel, 2014; Zuk-Golaszewska et al., 2015). In the work of Al-Jasass and Al-Jasser (2012), production and environmental factors differentiated the percentage of protein (12.91 ± 0.4%) and content of K (603 ± 15.0 mg 100 g-1), Mg (42 ± 5.0 mg 100 g-1), Ca (75 ± 9.0 mg 100 g-1) and Fe (25.8 ± 1.2 mg 100 g-1) in fenugreek seeds. In a study by Ahmed et al. (2012), different fertilizers (organic and bio-fertilizers) significantly increased protein content from 19.9% to 23.8% and oil content from 10.22% to 12.85%. Abou-Shleel (2014) found that sowing dates exerted a significant influence on the chemical composition and active ingredients of fenugreek seeds. In this study, seeds sown on the first (earliest) date were characterized by the highest content of protein and lipids. The authors have attributed this effect to air temperature during seed maturation which increased the plants’ respiration rates and, consequently, decreased the accumulation of chemical components. Our results are consistent with the findings of Hassanein et al. (2012). In another study by Zuk-Gołaszewska et al. (2015), fenugreek was exposed to water deficit stress, and higher rates of K fertilizer significantly increased the content of crude protein (by 3.2%-5.4%) and K (by 7%-8%). Hussein and El-Dewiny (2011) demonstrated that soil water deficit reduced concentrations of N, P and Cu, increased the content of Fe, and stabilized K content of fenugreek seeds across water deficit variants.

Significant two-factor interactions are presented in Figure 1. Non-inoculated seeds (A0) grown in plots with chemical weed control (D1) contained more N than seeds grown in plots with mechanical weed control, whereas a reverse relation was observed in inoculated seeds (Figure 1a). Delayed sowing led to higher N accumulation in seeds from treatments subjected to mechanical weeding than from plots with chemical weed control (Figure 1b). Regardless of fungicide application, the increase in row spacing from 15 to 30 cm increased the N content of seeds. A further increase in row spacing to 45 cm stabilized or decreased N concentrations (Figure 1c).

Mean values with the same letter do not differ significantly. A: Seed inoculation with Rhizobium meliloti (A0: no, A1: yes); B: sowing date (B0: earliest date, B1: 10 d delay, B2: 20 d delay); C: row spacing (C0: 15 cm, C1: 30 cm, C2: 45 cm); D: weed control (D0: mechanical, D1: chemical); E: antifungal plant protection (E0: non-dressed seeds, chemical protection, E1: dressed seeds, no chemical protection, E2: dressed seeds, chemical protection).

Figure 1: Influence of significant interactions between agrotechnological factors on the accumulation of N (1a: Inoculation ( Weeding, 1b: Sowing date ( Weeding, 1c: Row spacing ( Fungicide treatment), Fe (1d: Row spacing ( Fungicide treatment) and P (1e: Inoculation ( Fungicide treatment). 

A similar trend was noted in the content of Fe in agrotechnological variants with seed dressing (E0) and seed dressing combined with fungicide application (E3). In plots subjected to antifungal plant protection only (E1), Fe accumulation increased significantly with the highest row spacing of 45 cm (Figure 1d). Inoculated seeds from treatments subjected to seed dressing only or chemical protection only were more likely to accumulate P, whereas the P content of seeds grown in plots with seed dressing and antifungal plant protection (E3) was significantly lower than in the variant without inoculation (Figure 1e).

Fatty acids

In our study, the total oil content of fenugreek seeds ranged across agrotechnological variants from 3.37% to 5.82%, with an average of 4.77% (SE = 0.077). In a Canadian experiment investigating different fenugreek cultivars grown on semiarid soil in three experimental fields, the lipid content of seeds fluctuated widely from 5.8% to 15.2% (Ciftci et al., 2011). Abdelgani et al. (1999) attributed the significant increase in the oil content of fenugreek seeds to inoculation with Rhizobium strains. The results of the cited studies support the observation that agrotechnological factors and environmental conditions may strongly differentiate the oil content of fenugreek seeds.

The oil content and fatty acid profile of fenugreek seeds were relatively stable across all agrotechnological variants. The content of the identified fatty acids can be arranged in the following descending order: linoleic acid C18:2 37.9%, α-linolenic acid C18:3 28.2%, oleic acid C18:1 13.3%, palmitic acid C16:0 13.1%, stearic acid C18:0 3.8%, arachidic acid C20:0 1.4%, followed by acids with less than 1% content (C22:0 0.82%, C17:0 0.43%, C20:1 0.27%, C15:0 0.19%, C14:0 0.18%, C17:1 0.15%, C20:2 0.082%, C16:1 0.07%, C12:1 0.04%, C12:0 0.02%) (Table 5). The fenugreek seeds analyzed by Ciftci et al. (2011) were characterized by a similar content of the major fatty acids, but significant differences were reported in the concentrations of: linoleic acid C18:2 45.1%-47.5%, α-linolenic acid C18:3 18.3%-22.8%, oleic acid C18:1 12.4%-17.0%, palmitic acid C16:0 9.8%-11.2% and stearic acid C18:0 3.8%-4.2%. Srinivasan (2006) identified the following fatty acids in fenugreek seeds: oleic acid C18:1 35.1%, linoleic acid C18:2 33.7%, α-linolenic acid C18:3 13.8%, palmitic acid C16:0 9.6%, stearic acid C18:0 4.9% and arachidic acid C20:0 2%.

Table 5: Average fatty acid content of fenugreek seeds across the analyzed agrotechnological variants. 

SFA: Saturated fatty acids, MUFA: monounsaturated fatty acids, PUFA: polyunsaturated fatty acids.

A: Seed inoculation with Rhizobium meliloti (A0: no, A1: yes); B: sowing date (B0: earliest date, B1: 10 d delay, B2: 20 d delay); C: row spacing (C0: 15 cm, C1: 30 cm, C2: 45 cm); D: weed control (D0: mechanical, D1: chemical); E: antifungal plant protection (E0: non-dressed seeds, chemical protection, E1: dressed seeds, no chemical protection, E2: dressed seeds, chemical protection).

Values with the same letters do not differ significantly in Tukey’s test.

In the group of the analyzed agrotechnological factors, sowing date and weed control had the greatest influence on the fatty acid content of fenugreek seeds. Delayed sowing increased the concentrations of myristic acid C14:0, stearic acid C18:0, oleic acid C18:1, α-linolenic acid C18:3, and arachidic acid C20:0, but decreased the content of palmitic acid C16:0 and linoleic acid C18:2. Seeds collected from treatments with mechanical weed control (D0) were characterized by a higher content of saturated fatty acids - lauric acid C12:0, stearic acid C18:0, arachidic acid C20:0 and heptadecanoic acid C17:1, and a lower content of essential fatty acid C18:2. Seeds inoculated with R. meliloti contained similar amounts of fatty acids but less myristic acid C14:0 in comparison with unprotected treatments.

Seeds from treatments with greater row spacing were more abundant in MUFAs - palmitoleic acid C16:1 and gadoleic acid C20:1, whereas seeds from treatments with full antifungal protection (E2) were characterized by higher levels of heptadecenoic acid C17:1, α-linolenic acid C18:3 and behenic acid C22:0.

The variations in the fatty acid profile of fenugreek seeds grown in different treatments were relatively low, but percentage changes in the concentration of individual fatty acids ranged from -14.5% to 10.2% for margaric acid C17:0 (Table 6). Significant variations were observed in the content of lauric acid C12:0 (-8.6% to 6.8%), linderic acid C12:1 (-9.5% to 7.8%), eicosadienoic acid C20:2 (-10.0% to 8.2%) and behenic acid C22:0 (-7.8 to 10.8%). The above results suggest that agrotechnological factors modified the fatty acid profile of fenugreek seeds. The concentrations of margaric acid C17:0 (-6.6%) and linderic acid C12:1 (-4.7%) varied significantly in seeds inoculated with R. meliloti. Delayed sowing reduced the content of margaric acid C17:0 from -2.3% to -14.5% and eicosadienoic acid C20:2 from -2.0% to -5.5%, and increased the content of myristic acid C14:0 to 7.4% and lauric acid C12:0 to 6.8%. Greater spacing between rows increased the concentrations of margaric acid C17:0 from -14.0% to 10.2% and eicosadienoic acid C20:2 from -10.0% to 8.2%, and decreased the content of linderic acid C12:1 from 7.8% to -9.5%.

Table 6: Treatment differences in the fatty acid content of fenugreek seeds. 

A: Seed inoculation with Rhizobium meliloti (A0: no, A1: yes); B: sowing date (B0: earliest date, B1: 10 d delay, B2: 20 d delay); C: row spacing (C0: 15 cm, C1: 30 cm, C2: 45 cm); D: weed control (D0: mechanical, D1: chemical); E: antifungal plant protection (E0: non-dressed seeds, chemical protection, E1: dressed seeds, no chemical protection, E2: dressed seeds, chemical protection).

In comparison with mechanical weed control (D0), herbicide use (D1) induced the greatest decrease in the content of unsaturated fatty acids - lauric acid C12:0 (-8.6%), heptadecenoic acid C17:1 (-6.8%), behenic acid C22:0 (-6.3%) and stearic acid C18:0 (-6%). Antifungal protection led to the most significant changes in the concentrations of eicosadienoic acid C20:2 (from -7.8% to 10.8%) and heptadecenoic acid C17:1 (from -7.8% to 5.6%). Agrotechnological factors differentiated the content of saturated fatty acids - lauric acid C12:0 and margaric acid C17:0, and unsaturated fatty acids - linderic acid C12:1, heptadecenoic acid C17:1 and eicosadienoic acid C20:2. Relatively low variations in the concentrations of pentadecanoic acid C15:0, palmitic acid C16:0, palmitoleic acid C16:1, stearic acid C18:0, oleic acid C18:1, linoleic acid C18:2, α-linolenic acid C18:3, arachidic acid C20:0 and gadoleic acid C20:1 were noted between treatments, regardless of the agrotechnological factors. In the study Chatterjee et al. (2010) the fatty acid profile was dominated by unsaturated acids, namely oleic, linoleic and linolenic acids accounting for 16.3%, 50% and 24.4%, respectively of the total fatty acids. The mean values of seed yield, and oil content, and fatty acid content (saturated, monounsaturated and polyunsaturated fatty acids) of fenugreek seeds are presented in Table 7. The profiles of fatty acid groups were relatively stable across treatments. Sowing date and weed control were the only agrotechnological factors that exerted a significant influence on seed properties. In the treatment with chemical weed control, seed yield was higher, the concentrations of saturated fatty acids were somewhat reduced, and the content of polyunsaturated fatty acids was somewhat higher. Delaying sowing date led to a decrease in the oil and SFA content and a minor increase in the MUFA content of fenugreek seeds.

Table 7: Influence of agrotechnological factors on the mean values of seed yield, oil content and percentage content of saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids. 

Values with the same letters do not differ significantly in Tukey’s test.

A: Seed inoculation with Rhizobium meliloti (A0: no, A1: yes); B: sowing date (B0: earliest date, B1: 10 d delay, B2: 20 d delay); C: row spacing (C0: 15 cm, C1: 30 cm, C2: 45 cm); D: weed control (D0: mechanical, D1: chemical); E: antifungal plant protection (E0: non-dressed seeds, chemical protection, E1: dressed seeds, no chemical protection, E2: dressed seeds, chemical protection).

The results reported by Ciftci et al. (2011), Ali et al. (2012), Suliema et al. (2008) and Al-Jasass and Al-Jasser (2012) univocally confirmed that fenugreek seed oil is a rich source of polyunsaturated fatty acids, including essential fatty acids. In a study by Ali et al. (2012), α-linolenic acid was the major PUFA (42.5%), oleic acid was the main MUFA (20%), and palmitic acid was the main SFA (10.5%). In the work of Al-Jasass and Al-Jasser (2012), the total content of unsaturated fatty acids was determined at 92.99%. Fenugreek seeds analyzed by Suliema et al. (2008) contained 82.3% unsaturated fatty acids, and were most abundant in linoleic acid (43.2%), followed by α-linolenic acid (22%) and oleic acid (16.7%). Total saturated fatty acids accounted for 17.7% of total fatty acids, and palmitic acid was the dominant SFA (11.0%).

The effect size (eta-squared) of agrotechnological factors and interactions had a significantly varied effect on the concentrations of saturated and unsaturated fatty acids in fenugreek seeds (Figure 2).

A: Seed inoculation, B: sowing date, C: row spacing, D: weed control, E: antifungal protection.

Figure 2: Effect size (eta-squared) of agrotechnological factors and interactions in ANOVA on the concentrations of saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids relative to seed yield and the crude fat content of fenugreek seeds. 

The main agrotechnological factors which contributed to the overall variation in the concentrations of SFAs were sowing date, weed control and the Row spacing ( Weed control interaction. The observed differences in the content of MUFAs were attributed to sowing date, and the variations in the content of PUFAs - to weed control, Inoculation with R. meliloti ( Sowing date and Sowing date ( Row spacing interactions. In comparison with seed yield and crude fat content, agrotechnological factors had a similar contribution to the overall variations in the concentrations of SFAs and MUFAs at approximately 71%, whereas the effect size of PUFAs was significantly lower at around 63%. Those results indicate that agrotechnological factors are more likely to induce variations in the concentrations of SFAs and MUFAs than PUFAs.

CONCLUSIONS

The results of this study indicate that variations in the concentrations of biogenic elements and fatty acids in fenugreek seeds are caused mainly by a specific combination of agrotechnological factors in a farming system. The most influential agrotechnological factors were sowing date, row spacing and plant protection. The seeds of fenugreek plants grown in the humid continental climate of northeastern Poland contained 26.0% protein and 4.8% oil. They had similar protein content and lower oil content than seeds grown in the Mediterranean region and subtropical climates of Asia Minor.

The effect size of agrotechnological factors had a much smaller influence on variations in the concentrations of biogenic elements than fatty acids. The greatest effect sizes for biogenic elements were associated with the variation induced by sowing date (B) (70.1%), followed by row spacing (C) (43.6%) and the Row spacing ( Weed control (DE) interaction (39.8%). The main contributors to variations in the fatty acid content of fenugreek seeds were weed control (D) (94.1%), sowing date (B) (86.6%), Sowing date ( Weed control (BD) interaction (85.5%) and Row spacing ( Weed control (CD) interaction (80.2%). Sowing delayed by 20 days increased N concentrations (by 9.2%) and decreased P (8.8%), K (5.1%) and Mg (2.8%) concentrations in fenugreek seeds. An increase in row spacing from 15 to 45 cm promoted the accumulation of Fe by 31%.

Agrotechnological factors modified the fatty acid profile of fenugreek seeds and induced the greatest variations in the SFA content of seeds. Agrotechnological factors were responsible for significant differences in the average content of margaric acid C17:0 (14.5%), behenic acid C22:0 (10.8%), eicosadienoic acid C20:2 (10.0%) and lauric acid C12:0 (8.6%). The variations in the content of EFAs (linoleic C18:2 and α-linolenic C18:3) across experimental treatments (up to 3.1-4.5%) were attributed mainly to sowing date and plant protection. Agrotechnological factors had a greater impact on the concentrations of SFAs and MUFAs than PUFAs. Fenugreek seeds were particularly abundant in linoleic acid (37.9%) and α-linolenic acid (28.2%). The overall PUFA content of seeds was determined at 80.0%. Sowing date influenced the total content of SFAs and MUFAs, whereas weed control was responsible for variations in the total content of SFAs and PUFAs.

REFERENCES

Abdelgani, M.E., Elsheik, E.A.E., and Mukhtar, N.O. 1999. The effect of Rhizobium inoculation and chemical fertilization on seed quality of fenugreek. Food Chemistry 64:289-293. [ Links ]

Abou-Shleel, S.M. 2014. Effect of air temperature on growth, yield and active ingredients of fenugreek (Trigonella foenum-graecum). Nature Science 12:50-54. [ Links ]

Ahmed, A.G., Ebtsam, A., El-Housini, A., Hassanein, M.S., and Zaki, N.M. 2012. Influence of organic and bio-fertilizer on growth and yield of two fenugreek cultivars grown in sandy soil. Australian Journal of Basic and Applied Science 6(10):469-476. [ Links ]

Akhtar, N., Waqas, M.K., Ahmed, M., Saeed, T., Murtaza, G., Rasool, A., et al. 2010. Effect of cream formulation of fenugreek seed extract on some mechanical parameters of human skin. Tropical Journal of Pharmaceutical Research 9:329-337. [ Links ]

Ali, A.M., Abu Sayeed, M., Alam, M.S., Yeasmin, M.S., Khan, M.A., and Muhamad, I.I. 2012. Characteristics of oils and nutrient contents of Nigella sativa Linn. and Trigonella foenum-graecum seeds. Bulletin of Chemical Society of Ethiopia 26(1):55-64. [ Links ]

Al-Jasass, F.M., and Al-Jasser, M.S. 2012. Chemical composition and fatty acid content of some spices and herbs under Saudi Arabia conditions. The Scientific World Journal 1-5. [ Links ]

AOAC. 2005. Official methods of analysis. 18th ed. Association of Official Analytical Chemists (AOAC), Arlington, Virginia, USA. [ Links ]

Baethen, W.R., and Alley, M.M. 1989. A manual colorimetric procedure for measuring ammonium nitrogen in soil and plant Kjeldahl digests. Communications in Soil Science Plant Analysis 20:961-969. [ Links ]

Bieńkowski, T., Zuk-Gołaszewska, K., Kurowski, T., and Gołaszewski, J. 2016. Agrotechnical indicators for Trigonella foenum-gracum L. production in the environmental conditions of northeastern Europe. Turkish Journal of Field Crops 21:16-28. [ Links ]

Chatterjee, S., Variyar, P.S., and Sharma, A. 2010. Bioactive lipid constituents of fenugreek. Food Chemistry 119:349-353. [ Links ]

Chauhan, G., Sharma, M., Kharkwal, H., and Varma, A. 2011. Pharmacognostic, preliminary phytochemical studies and anticancerous potential of Trigonella foenum-graecum. Pharma Science Monitor 2(2):72-81. [ Links ]

Ciftci, N.O., Przybylski, R., Rudzinska, M., and Acharya, S. 2011. Characterization of fenugreek (Trigonella foenum-graecum) seed lipids. Journal of the American Oil Chemists Society 88:1603-1610. [ Links ]

El Nasri, A.N., and El Tinay, A.H. 2007. Functional properties of fenugreek (Trigonella foenum graecum) protein concentrate. Food Chemistry 103(2):582-589. [ Links ]

Hassanein, R.A., El-Khawas, S.A., and Mohamed, A.M.K. 2012. Effect of heat shock on some biochemical and molecular criteria of fenugreek. Journal of Medical Plant Research 6:1782-1794. [ Links ]

Hooda, S., and Jood, S. 2005. Organoleptic and nutritional evaluation of wheat biscuits supplemented with untreated and treated fenugreek flour. Food Chemistry 90:427-435. [ Links ]

Hussein, M.M., and El-Dewiny, C.Y. 2011. Mineral constituents of fenugreek varieties grown under water stress condition. Australian Journal of Basic and Applied Science 5:2904-2909. [ Links ]

IUSS Working Group WRB. 2015. World Reference Base for Soil Resources 2014, update 2015. International soil classification system for naming soils and creating legends for soil maps. World Soil Resources Reports No. 106. FAO, Rome, Italy. [ Links ]

Khorshidian, N., Asli, M.Y., Arab, M., Mortazavian, A.M., and Mirzaie, A.A. 2016. Fenugreek: Potential applications as a functional food and nutraceutical. Nutrition and Food Science Research 3(1):5-16. [ Links ]

Kochhar, A., Nagi, M., and Sachdeva, R. 2006. Proximate composition available carbohydrates, dietary fiber and anti-nutritional factors of selected traditional medicinal plants. Journal of Human Ecology 19:195-199. [ Links ]

Lubbe, A., and Verpoorte, R. 2011. Cultivation of medicinal and aromatic plants for specialty industrial materials. Industrial Crops and Products 34(1):785-801. [ Links ]

Rahmani, M., Hamel, L., Toumi-Benali, F., Aouissat, M., Dif, M.M., and Hamou, M. 2014. Proximate composition, crude cellulose and minerals of Trigonella foenum-graecum L. seeds cultured in West Algeria. Global Journal of Medical Plant Research 2(4):1-4. [ Links ]

Singh, K.P., Nair, B., Chand, P., and Naidu, A.K. 2013. Contribution of fenugreek (Trigonella foenum graecum L.) seeds towards the nutritional characterization. Journal of Medical Plant Research 7:3052-3058. [ Links ]

Srinivasan, K. 2006. Fenugreek (Trigonella foenum-graecum): A review of health beneficial antidiabetic food adjuncts. Food Reviews International Journal 22:203-224. [ Links ]

Suliema, A.M.E., Ali, A.O., and Hemavathy, J. 2008. Lipid content fatty acid composition of fenugreek (Trigonella foenum-graecum L.) seeds grown in Sudan. International Journal Food Science and Technology 43:380-382. [ Links ]

Taloubi, L.M., Rhouda, H., Belahcen, A., Smires, N., Thimou, A., and Mdaghri, A.A. 2013. An overview of plants causing teratogenicity: fenugreek (Trigonella foenum graecum). International Journal of Pharmaceutical Science and Research 4:516-519. [ Links ]

Wierzbowska, J., and Zuk-Golaszewska, K. 2014. The impact of nitrogen fertilization and Rhizobium inoculation on the yield and quality of Trigonella foenum-graecum L. Journal of Elementology 19(4):1109-1118. [ Links ]

Zakia, B., Gómez-Cordovés, C., and Es-Safi, N.E. 2014. Characterization of flavonoid glycosides from fenugreek (Trigonella foenum-graecum) crude seeds by HPLC-DAD-ESI/MS analysis. International Journal of Molecular Science 15:20668-20685. [ Links ]

Zapotoczny, P., Zuk-Golaszewska, K., and Ropelewska, E. 2015. Discrimination based on changes in the physical properties of fenugreek (Trigonella foenum-graecum L.) seeds subjected to various cultivation conditions. European Food Research and Technology 242(3):405-414. [ Links ]

Zegarska, Z., Jaworski, J., and Borejszo, Z. 1991. Ocena zmodyfikowanej metody Peiskera otrzymania estrów metylowych kwasów tłuszczowych. Acta Academiae Agriculturae Technicae Olstenensis 24:25-33 (in Polish). [ Links ]

Zuk-Golaszewska, K., Wierzbowska, J., and Bienkowski, T. 2015. The effect of potassium fertilization, Rhizobium inoculation and water deficit on the yield and quality of fenugreek seeds. Journal of Elementology 20(2):513-524. [ Links ]

Received: November 20, 2016; Accepted: April 24, 2017

*Corresponding author (janusz.golaszewski@uwm.edu.pl)

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