Article pubs.acs.org/JAFC
Lipids, Tocopherols, and Carotenoids in Leaves of Amaranth and Quinoa Cultivars and a New Approach to Overall Evaluation of Nutritional Quality Traits Yao Tang,†,‡ Xihong Li,*,† Peter X. Chen,‡,§ Bing Zhang,‡,∥ Marta Hernandez,‡ Hua Zhang,‡ Massimo F. Marcone,∥ Ronghua Liu,‡ and Rong Tsao*,‡ †
Key Laboratory of Food Nutrition and Safety, Ministry of Education of China, Tianjin University of Science and Technology, Tianjin 300457, China ‡ Guelph Food Research Centre, Agriculture and Agri-Food Canada, 93 Stone Road West, Guelph, Ontario, Canada N1G 5C9 § State Key Laboratory of Food Science and Technology, Nanchang University, Nanchang 330047, Jiangxi, China ∥ Department of Food Science, University of Guelph, 50 Stone Road East, Guelph, Ontario, Canada N1G 2W1 ABSTRACT: Composition of lipophilic phytochemicals including fatty acids, tocopherols, and carotenoids in leaves of 6 quinoa and 14 amaranth cultivars was analyzed. The oil yields in quinoa and amaranth leaves were only 2.72−4.18%, which contained mainly essential fatty acids and had a highly favorable ω-3/ω-6 ratio (2.28−3.89). Pro-vitamin A carotenoids, mainly α- and β-carotenes, and xanthophylls, predominantly lutein and violaxanthin, were found in all samples. The primary tocopherol isomers present in both quinoa and amaranth leaves were α- and β-tocopherols. Added to the discussion on the lipophilic nutrients was the normalization of ω-3/ω-6 ratio, α-tocopherol equivalents, and carotenoids, in an attempt to establish a novel system for evaluation of the overall quality attributes of lipophilic nutrients (NQ value). The NQ value, but not the individual components, was highly correlated with all the antioxidant activities, supporting the ranking order of the potential nutritional quality of quinoa and amaranth leaves based on this new method. KEYWORDS: quinoa, amaranth, leaf, fatty acids, tocopherols, carotenoids, nutritional quality, DPPH, FRAP and ORAC
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INTRODUCTION Quinoa (Chenopodium quinoa Willd.) and amaranth (Amaranthus caudatus L.) are two species of the Amaranthaceae family whose leaves or grains have been traditionally consumed as food in different regions of the world, but they have gained popularity in recent years as their new nutritional and health beneficial attributes continue to be found. Previous investigations on quinoa and amaranth have focused on the seeds, as they contain high-quality protein, fatty acids, vitamins, and phenolic compounds.1−3 Quinoa and amaranth seeds are gluten-free and therefore are valuable alternatives to cereals like wheat.3 We have recently examined the hydrophilic and lipophilic bioactive components of quinoa seeds and found at least 23 phenolic compounds in either free or conjugated forms, among them vanillic acid, ferulic acid, and their derivatives as the main phenolic acids and quercetin and kaempferol and their glycosides as the main flavonoids. Black quinoa had the lowest total oil content; however, it contained the highest polyunsaturated fatty acid content (PUFA, 57.34%). Carotenoids, such as lutein and zeaxanthin, were also identified for the first time in quinoa seeds. Carotenoids (mainly lutein) and tocopherols (mainly γ-tocopherol) are considered the major lipophilic contributors to the antioxidant activities in quinoa seeds.4,5 Different from the seeds, only leaves of amaranth have been produced and consumed as a vegetable. Clinical studies have indicated that fruit, vegetable, and grain consumption is associated with lower risk of cancer and cardiovascular and other degenerative diseases.6 Studies on vegetable amaranth suggest the edible leaves of this plant are rich in phytochemical © 2014 American Chemical Society
antioxidants including polyphenols, tocopherols, and betacyanins, the purple pigment in some cultivars.3,7 It is believed that these phytochemicals contribute to the health benefits of vegetable amaranths. As a multipurpose crop supplying high nutritional quality grains and leafy vegetables for both human consumption and animal feed, amaranth leaves are generally considered low in lipids; therefore the lipophilic composition of the leaves has not been well studied.3,7,8 On the other hand, although quinoa seed has been evaluated for its nutritional value and its health benefits such as antioxidant activities are well recognized,4,5 quinoa leaves have not attracted the same attention even though they have been sometimes used in food recipes including salads.2,8 Limited information shows that quinoa and amaranth have been used as Chinese medicines and had a hypocholesterolemic effect and increased postprandial sensitivity and plasma insulin levels.9 In terms of the lipophilic bioactive composition, previous studies only showed α-tocopherol at 31.43 mg/g dry weight (DW) to be in amaranth leaves as a result of simple estimation by a spectrophotometric method, but no information is available on the profile of specific tocopherol isoforms (α-, β-, γ-, and δ-tocopherols) in quinoa and amaranth leaves.3,10 Tocopherols protect lipids in leaves and seeds from oxidation, enabling the Received: Revised: Accepted: Published: 12610
September 24, 2014 November 24, 2014 December 2, 2014 December 2, 2014 dx.doi.org/10.1021/jf5046377 | J. Agric. Food Chem. 2014, 62, 12610−12619
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Article
12-L bulk tray dryer (Labconco, Kansas City, MO) at 0.110 mbar and −40 °C prior to grinding with a commercial coffee blender (particle sizes 400−800 μm). The fine powder was stored in polyethylene tubes at −80 °C until extraction for the various analyses. Lutein, zeaxanthin, β-carotene, and β-cryptoxanthin standards were purchased from Indofine (Hillsborough, NJ). 2,2-Diphenyl-1-picrylhydrazyl (DPPH), Trolox, 1,3,5-tri(2-pyridyl)-2,4,6-triazine (TPTZ), L-ascorbic acid, fluorescein, 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH), randomly methylated-β-cyclodextrin (RMCD), and α-, β-, γ-, and δ-tocopherols were from Sigma−Aldrich (Oakville, ON, Canada). Standards of fatty acid methyl esters (FAMEs) were obtained commercially (mixture 463, Nu-Chek-Prep, Inc., Elysian, MN). All solvents were of HPLC grade and obtained from Caledon Laboratories Ltd. (Georgetown, ON, Canada). Sample Extraction. The powdered samples were accurately weighed then extracted with methyl tert-butyl ether/tetrahydrofuran (MTBE/THF, 1:1 v/v) on a Soxtec extraction system (Soxtec System 2050, Tecator AB, Hdganas, Sweden). In this system, the sample was first immersed in the boiling solvent for 30 min and then continuously rinsed by refluxing solvent from the condenser for 80 min. The solvent recovery lasted 30 min and predrying was for 2 min. During the extraction, solvents were heated to 155 °C. After cooling, ca. 5 mL of hexane each was used to wash the lipid extracts in the container three times. The oil yield was determined by the difference in mass of the container before and after the extraction. The extract was stored at −80 °C until analysis. All extraction tubes were covered with aluminum foil and the experiment was conducted under dim light in order to avoid sample degradation by photooxidation during the extraction period. Analysis of Fatty Acids by Gas Chromatography−Mass Spectrometry. A 1 mL aliquot of the lipophilic extract was dried under a gentle stream of N2 to remove hexane, methylated with anhydrous HCl/methanol (5% w/v), and dried over anhydrous sodium sulfate, and finally the FAMEs were analyzed by gas chromatography (GC; model 6890, Hewlett-Packard, Palo Alto, CA) on a CP-Sil 88 WCOT fused silica column (100 m × 0.25 mm i.d. × 0.2 μm film thickness; Chrompack, Middleburg, The Netherlands). The column was operated at 45 °C for 4 min and then temperatureprogrammed at 13 °C/min to 175 °C, held for 27 min, programmed at 4 °C/min to 215 °C, and finally held for 31 min; total run time was 86 min.15 A flame ionization detector (FID) was used. GC−mass spectrometry (MS) analysis was performed on a Varian Saturn 2000 system running in default electron ionization mode (4 V axial bias and 1400 V multiplier) according to the method described by Karimi et al.17 Samples were injected into the GC−MS system via split injection at 1:10. The injection volume was 1 μL. The mass spectrometer (5975C MSD) was equipped with an electron impact ion source (EI). All experiments were carried out in positive-ion mode. The source temperature was set at 230 °C, and the energy was 70 eV. The multiplier voltage was set to 900 V without solvent delay. Analysis of Tocopherols, Tocotrienols, and Carotenoids by HPLC. Tocopherols from the extracts were separated and analyzed following a published procedure with slight modification on an Agilent Technology 1100 series HPLC system equipped with a Phenomenex silica column (250 × 4.6 mm, 5 μm, Torrance, CA), a diode array detector (DAD), and a fluorescence detector. α-Tocopherol equivalents (α-TE) was an expression based on the activity relative to the most active form of vitamin E. α-TE is calculated from the formula α-TE = (α-T) + 0.5(β-T) + 0.1(γ-T) + 0.03(δ-T) + 0.3(α-T3) + 0.05(β-T3) + 0.01(γ-T3), where T = tocopherol and T3 = tocotrienol.18 Carotenoids in the extracts were identified and quantified by the same Agilent Technology 1100 series HPLC system as mentioned above, following the same method used by Zhang et al.15 Separation was on a YMC C30 carotenoid column (250 × 4.6 mm, 5 μm) (Waters, Mississauga, ON) at 35 °C, and peaks were detected by DAD at 452 nm. The carotenoids were tentatively identified on the basis of matching retention time, similarity in elution order, and UV/vis spectra with those of the standards and data reported in the literature. All carotenoids were quantified on the basis of corresponding curves of lutein, zeaxanthin, β-carotene, and β-cryptoxanthin standards.
lipids to perform their roles in assuring plant quality and safety.11,12 Although α-tocopherol has been considered to be the main contributing isoform to vitamin E activity, γ-tocopherol exhibits the greatest antioxidant activity.12−14 Thus, it is necessary to assess the composition of all vitamin E isoforms in quinoa and amaranth leaves. Carotenoids, as pro-vitamin A and/or antioxidants, have not been carefully examined in the leaves of either quinoa or amaranth. Our recent study, however, has revealed that lipophilic phytochemicals including carotenoids in quinoa and amaranth leaves can be present at even higher concentrations than some commonly consumed cereal grains and pulses. Detailed results are reported in the present paper. Evaluation and comparison of the nutritional quality of a large number of foods or feeds are often difficult. Major nutritional components, such as the lipophilic nutrients carotenoids, tocopherols, and fatty acids, in a food or feed have been assessed separately.15,16 However, there is a lack of an evaluation system for the overall lipophilic quality attributes in samples of this nature. The objectives of this study were to carry out a comprehensive examination on the lipophilic bioactive components in leaves of quinoa and amaranth, including the fatty acids, tocopherols, and carotenoids, and to evaluate the possible roles of these compounds in antioxidant and potentially other health promoting activities. This study is part of our current effort in assessing the economic and nutritional values of whole plants of both quinoa and amaranth in Ontario, Canada. A total of 14 amaranth and 6 quinoa cultivars were included in this study to help garner accurate information on the profile of lipophilic bioactives in the leaves and to explore the possibility of using quinoa leaves as healthy vegetables or even functional food ingredients.
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MATERIALS AND METHODS
Leaf Materials. Leaves of 14 amaranth and 6 quinoa cultivars were sampled from a farm near Campbellville, Ontario, Canada, in July 2013 (Table 1). Heads (with at least 4−5 fully opened leaves) of at least 5 plants per cultivar were handpicked, pooled and lyophilized in a
Table 1. Quinoa and Amaranth Cultivars Studied sample
commercial or cultivar name
scientific name
AL1 AL2 AL3 AL4 AL5 AL6 AL7 AL8 AL9 AL10 AL11 AL12 AL13 AL14 QL1 QL2 QL3 QL4 QL5 QL6
Katan-AC12 Katan-ASV Hopi Red Amaranth Katan-ACV Katan-AH12 Red Garnet Amaranth Red Star Amaranth Katan-ATM Amaranth Katan-ATT Red Leaf Amaranth Katan-VA Amaranth Katan-VAT Midnight Red Amaranth Red Leaf Amaranth Russian Red Merlot Amaranth Katan-Maple Leaf Quinoa Temuko Quinoa Faro Quinoa Katan-CVQ Katan-BBRQ Red quinoa
Amaranth cruentus A. cruentus A. cruentus Amaranthus hypochondriacus A. hypochondriacus A. hypochondriacus A. hypochondriacus Amaranthus tricolor A. tricolor A. tricolor A. tricolor A. tricolor A. tricolor A. tricolor Chenopodium formasanum Chenopodium quinoa Willdenow C. quinoa Willdenow C. quinoa Willdenow C. quinoa Willdenow C. quinoa Willdenow 12611
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Structural Identification and Confirmation by Liquid Chromatography−Mass Spectrometry. Carotenoids tentatively identified as described above were confirmed by liquid chromatography (LC)−MS on a Dionex UHPLC UltiMate 3000 liquid chromatograph interfaced to an amaZon SL ion trap mass spectrometer (Bruker Daltonics, Billerica, MA).19 UV/vis data were collected at 190−800 nm and the electrospray positive ionization (ESI + ve) mass spectrometric data were scanned from m/z 50 to 1200. The capillary temperature was 220 °C and the source voltage was 4.50 kV. The chromatographic separation conditions for LC−MS were the same as those described for the HPLC-DAD analyses. The MS conditions for vitamin E were the same as described for carotenoids. Selected ion monitoring (SIM) acquisition mode was used to help in the quantification of tocopherols, and the ions monitored were as follows: m/z 429 for α-tocopherol, m/z 415 for β- and γ-tocopherol, and m/z 401 for δ-tocopherol.20 Antioxidant Activity Assays. The lipophilic extracts were dried under a nitrogen stream and then dissolved in 7% (% w) RMCD in acetone/water (1:1 v/v). The DPPH assay was carried out according to the procedures used by Zhang et al.15 with minor modification: appropriately diluted samples or Trolox solutions were placed in wells of a 96-well plate (flat bottom, Nalge Nunc International, Denmark) and read at 517 nm by use of a Multiskan Spectrum microplate reader (EL 340, Bio-Tek Instruments Inc., Winooski, VT). The DPPH radical scavenging activity of extracts was calculated from the standard curve of Trolox (r2 = 0.999) and expressed as micromoles of Trolox equivalents (TE) per gram dry weight of sample. The ferric reducing antioxidant power (FRAP) assay followed procedures reported by Li et al.21 Briefly, a total of 10 μL of properly diluted samples or L-ascorbic acid solutions (62.5, 125, 250, 500, 750, and 1000 μM) and 300 μL of freshly prepared FRAP reagent were added in a 96-well plate and incubated at room temperature throughout the reaction period. After 120 min, the absorbance was read at 593 nm against a reagent blank. The antioxidant activities were expressed as micromoles of ascorbic acid equivalent (AAE) per gram dry weight of sample (r2 = 1.000). Lipophilic oxygen radical absorbance capacity (ORAC) assay was conducted according to Zhang and others15,22 with slight modifications. The lipophilic extracts and Trolox solutions were dissolved in RMCD solution as discussed before. The fluorescence (excitation/ emission wavelength = 485/528 nm) was read every minute for 120 min or until it reached zero in a fluorescence plate reader equipped with an automatic thermostatic holder (PLX 800, Bio-Tek Instruments, Inc., Winooski, VT). A calibration curve was constructed by plotting the calculated differences of area under the fluorescein decay curve between blank and sample. The results were expressed as micromoles of Trolox equivalent per gram dry weight of quinoa sample (r2 = 0.998). Statistical Analysis. Results were expressed as mean value ± standard deviation of three independent extractions. One-way analysis of variance (ANOVA) was used to compare the means by use of Duncan’s posthoc test. Comparison of assays was made by correlation and linear regression analysis. Differences were considered as significant at p ≤ 0.05. All statistical analyses were performed with Statistics from SPSS (version 18.0, Chicago, IL).
compared to the foregoing fatty acids. This is different from the fatty acids in seeds of quinoa and amaranth, which contained more C18:2n-6 (33.56−52.0%) than C18:3n-3.3,23 Food data generated throughout the 20th century indicates that the ratio of ω-3 to ω-6 fatty acids has decreased from 1:1 to 1:30, much lower than the recommended ratio (1:2.3 to 1:4).24,25 Diets having higher ω-6 fatty acids such as C18:2n-6 have been linked to increased risk of prostate cancer, cardiovascular disease, and other chronic diseases,26 whereas ω-3 fatty acids such as C18:3n-3 have been shown positive effects on various cardiac disorders and many chronic illnesses.27 Consequently, foods rich in ω-3 fatty acids, such as fish oils and certain plant oils, are considered a healthier diet. The ω-3/ ω-6 ratios of quinoa and amaranth leaves averaged 2.28−3.89, which is severalfold higher than the ideal ratio and much better than most vegetable oils.28 Incorporation of these leaves into a diet can therefore compensate the unhealthy ω-3/ω-6 ratio. Carotenoids. Leafy green vegetables and fruits have generated interest worldwide as they exhibit multiple benefits for the health of humans, particularly as a source of dietary vitamin A in developing countries.29 The present study showed that carotenoid compositions in amaranth and quinoa leaves were similar but concentrations varied significantly among different cultivars of the same plant. β-Carotene is an important lipid-soluble antioxidant that functions to protect cellular membranes by scavenging free radicals and as a photosensitizer by quenching triplet oxygen in biosynthesis.30,31 As shown in Table 3, β-carotene was the primary carotenoid in both quinoa (302.97−484.86 μg/g DW) and amaranth leaves (115.19−394.31 μg/g DW). Lutein was the second dominant carotenoid in all of the samples, with amaranth leaves containing an average of 67.03 μg/g DW (33.31−136.78 μg/g DW) and quinoa leaves containing a higher average lutein content (83.65 μg/g DW) in a narrower range (65.93−103.39 μg/g DW). A similar trend was found for violaxanthin: quinoa leaves had a higher level at 67.34−93.20 μg/g DW than the amaranth leaves, which ranged between 21.24 and 80.78 μg/g DW. α-Carotene was also found in both quinoa and amaranth leaves, albeit the average concentrations were 42.29 and 28.82 μg/g DW, respectively, ca. 1/9 of that of β-carotene. Leaves richer in β-carotene were also found to have higher α-carotene. Minor carotenoids including β-cryptoxanthin and zeaxanthin were also found in most quinoa and amaranth cultivars at much lower concentrations (Table 3). Carotenoids play essential roles in human health. Carotenes such as α- and β-carotenes are provitamin A nutrients, and xanthophylls such as lutein, zeaxanthin, and violaxanthin are strong antioxidants and provide significant protection against macular degeneration and other light-induced eye and skin damages.32 The total carotenoid concentration as measured by HPLC and expressed in total carotenoid index (TCI) was 496−738 μg/g DW for quinoa leaves and 189−676 μg/g DW for amaranth leaves (Table 3), which were similar to those estimated by spectrophotometric methods.3,1,33,34 Concentrations of individual carotenoids including β-carotene, lutein, violaxanthin, antheraxanthin, and β-cryptoxanthin in amaranth leaves have been studied; however, there was a lack of similar information for quinoa leaves, and the present study is the first report of compositional information for individual carotenoids.30,35 It is also worth mentioning that the total and individual carotenoid concentrations in quinoa and amaranth leaves of the present study are similar to or even higher than many widely consumed leafy vegetables such as spinach and
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RESULTS AND DISCUSSION Fatty Acids. The oil content and composition of the major fatty acids of quinoa and amaranth leaves are shown in Table 2. The oil yields of the quinoa leaves ranged from 3.95% to 4.18%, which was higher than that in amaranth leaves (2.13−3.59%). Fatty acids were over 80% in unsaturated form, mainly the two essential fatty acids C18:3n-3 (α-linolenic acid), ranging between 35.1% in QL1 and 49.43% in AL12, followed by C18:2n-6 (linoleic acid, 11.36−18.38%), C16:0 (palmitic acid, 9.28−16.44%), and C18:1(9c) (oleic acid, 5.11−11.22%) in both quinoa and amaranth leaves. C16:1 (palmitoleic acid) and C18:0 (stearic acid) were present in relatively low levels 12612
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12613
0.54 ± 0.03 de
0.14 ± 0.01 a
0.63 ± 0.04 c
0.90 ± 0.03 j
0.74 ± 0.01 h
1.07 ± 0.01 h
12.64 ± 0.13 h
1.94 ± 0.05 i
1.23 ± 0.06 b
8.12 ± 0.11 g
2.23 ± 0.07 j
1.04 ± 0.01 k
16.14 ± 0.35 hi
40.81 ± 0.47 c
0.39 ± 0.01 c
1.06 ± 0.03 i
0.66 ± 0.02 e
0.09 ± 0.02 a
4.06 ± 0.19 ij
0.53 ± 0.02 de
0.38 ± 0.01 c
0.66 ± 0.03 c
1.05 ± 0.02 k
0.87 ± 0.02 j
1.30 ± 0.01 j
16.44 ± 0.20 l
1.36 ± 0.00 fg
1.24 ± 0.04 b
6.62 ± 0.21 ef
2.02 ± 0.08 i
0.43 ± 0.02 h
15.87 ± 0.51 gh
35.10 ± 0.52 a
1.22 ± 0.03 e
1.77 ± 0.04 m
1.07 ± 0.07 i
0.08 ± 0.01 a
3.99 ± 0.15 ij
2.28 ± 0.04 a
22.00 ± 0.35 j
15.93 ± 0.49 f
50.97 ± 1.03 a
AL5
10:1t
12:0
11:1c
12:1
15:0
14:1c
16:0
16:1
18:0
18:1(9c)
18:1(11c)
18: 1(12c)
18:2n-6
18:3n-3
21:0
22:0
24:1
26:0
oil yield (%)
ω3/ω6 ratio
∑SFA
∑MUFA
∑PUFA
fatty acid
0.82 ± 0.03 d
0.60 ± 0.0 e
0.45 ± 0.07 d
0.66 ± 0.05 c
1.09 ± 0.01 l
0.85 ± 0.04 ij
1.37 ± 0.02 g
2.33 ± 0.07 i
0.85 ± 0.01 f
1.37 ± 0.05 e
0.45 ± 0.01 c
0.19 ± 0.00 a
10:1c
10:1t
12:0
11:1c
12:1
15:0
AL6
56.95 ± 0.82 e
17.89 ± 0.39 g
16.29 ± 0.25 ef
2.58 ± 0.02 b
QL2
0.76 ± 0.02 c
QL1
0.89 ± 0.03 e
fatty acids
10:1c
QL3
QL4
0.32 ± 0.01 d
0.81 ± 0.01 ghi
2.00 ± 0.02 i
1.12 ± 0.03 h
3.21 ± 0.08 n
1.86 ± 0.01 k
AL7
54.26 ± 0.49 bc
19.58 ± 1.24 h
15.89 ± 0.84 def
0.24 ± 0.00 bc
0.70 ± 0.03 f
1.98 ± 0.05 i
1.06 ± 0.03 gh
3.21 ± 0.07 n
1.85 ± 0.01 k
AL8
52.78 ± 1.06 b
19.23 ± 1.06 h
16.68 ± 0.84 f
3.23 ± 0.00 g
4.18 ± 0.16 j
4.02 ± 0.17 ij
0.82 ± 0.03 f
1.27 ± 0.03 l
0.74 ± 0.03 d
QL6
0.67 ± 0.02 ef
0.82 ± 0.01 hi
0.22 ± 0.01 ab
2.23 ± 0.03 j
1.23 ± 0.01 i
3.65 ± 0.12 o
2.09 ± 0.09 l
AL10
55.15 ± 1.18 de
19.36 ± 0.59 h
15.41 ± 0.30 bcde
3.60 ± 0.04 h
3.96 ± 0.15 i
0.14 ± 0.02 b
0.88 ± 0.00 g
1.10 ± 0.03 j
0.81 ± 0.01 d
42.95 ± 0.81 de
12.20 ± 0.37 b
1.21 ± 0.04 l
1.97 ± 0.05 hi
9.70 ± 0.28 i
0.23 ± 0.02 ab
0.19 ± 0.01 a
1.78 ± 0.12 g
0.99 ± 0.04 g
2.12 ± 0.01 h
1.42 ± 0.03 h
AL11
59.14 ± 0.83 fg
14.14 ± 0.33 cd
19.68 ± 0.52 h
3.02 ± 0.00 ef
3.00 ± 0.02 cde
1.33 ± 0.01 i
0.53 ± 0.01 d
0.35 ± 0.01 d
0.10 ± 0.02 ab
44.21 ± 0.56 fg
14.93 ± 0.27 def
0.25 ± 0.05 defg
0.42 ± 0.03 bcd
6.77 ± 0.08 f
2.11 ± 0.04 d
1.17 ± 0.07 b
14.83 ± 0.39 k
0.37 ± 0.03 d
0.31 ± 0.02 d
0.62 ± 0.01 d
0.98 ± 0.02 d
0.65 ± 0.03 e
1.61 ± 0.02 g
1.68 ± 0.07 h
cultivar
0.31 ± 0.04 d
AL1 0.91 ± 0.01 e
1.95 ± 0.08 i
11.01 ± 0.12 ef
1.22 ± 0.06 i
0.81 ± 0.04 i
0.91 ± 0.03 j
0.49 ± 0.02 b
0.37 ± 0.01 bc
0.37 ± 0.01 b
0.66 ± 0.02 b
1.86 ± 0.02 h
1.02 ± 0.03 g
2.96 ± 0.01 l
1.78 ± 0.03 j
AL9
55.23 ± 1.13 bc
19.54 ± 0.64 h
15.71 ± 0.31 bcdef
3.89 ± 0.10 i
3.95 ± 0.15 i
0.08 ± 0.01 a
0.82 ± 0.01 f
1.12 ± 0.02 j
0.79 ± 0.01 d
43.77 ± 0.64 efg
40.11 ± 0.81 c
0.79 ± 0.01 i
1.94 ± 0.08 hi
10.86 ± 0.36 j
0.99 ± 0.05 a
1.67 ± 0.02 h
11.67 ± 0.19 g
0.98 ± 0.07 g
0.69 ± 0.02 g
0.84 ± 0.04 i
0.53 ± 0.02 b
0.37 ± 0.01 bc
0.45 ± 0.02 c
11.46 ± 0.49 a
0.07 ± 0.01 a
3.58 ± 0.08 h
QL5 0.66 ± 0.01 b
12.67 ± 0.25 b
1.17 ± 0.04 l
1.90 ± 0.12 h
9.96 ± 0.42 i
1.09 ± 0.07 ab
1.75 ± 0.32 hi
12.46 ± 0.66 h
0.78 ± 0.02 e
0.58 ± 0.03 e
0.79 ± 0.03 gh
0.68 ± 0.04 c
0.47 ± 0.01 d
0.69 ± 0.02 f
0.69 ± 0.02 b
0.07 ± 0.01 a
0.92 ± 0.02 h
1.20 ± 0.05 k
0.71 ± 0.02 d
42.25 ± 0.16 d
12.01 ± 0.33 ab
0.89 ± 0.02 j
1.89 ± 0.07 h
10.81 ± 0.59 j
1.10 ± 0.06 ab
1.69 ± 0.41 h
11.84 ± 0.63 g
0.88 ± 0.01 f
0.63 ± 0.05 f
0.78 ± 0.03 g
0.56 ± 0.04 b
0.34 ± 0.02 bc
0.50 ± 0.02 cd
0.65 ± 0.03 b
cultivar
Table 2. Fatty Acid Composition in Leaves of Different Quinoa and Amaranth Cultivarsa
AL2
AL3
0.29 ± 0.01 d
0.65 ± 0.01 de
1.41 ± 0.03 e
0.82 ± 0.02 f
2.26 ± 0.02 i
1.29 ± 0.03 f
0.28 ± 0.00 cd
0.70 ± 0.01 f
1.91 ± 0.01 h
1.02 ± 0.02 g
3.05 ± 0.03 m
1.78 ± 0.04 j
AL13
56.83 ± 1.05 de
57.30 ± 0.38 e
AL12
16.23 ± 0.47 f
20.60 ± 0.49 i
2.83 ± 0.00 cd
2.13 ± 0.02 a
3.16 ± 0.08 l
ND
0.48 ± 0.01 h
0.17 ± 0.02 b
38.45 ± 0.77 b
18.38 ± 0.28 j
0.23 ± 0.13 cdef
0.61 ± 0.02 g
11.22 ± 0.21 j
1.74 ± 0.04 c
1.09 ± 0.03 e
14.00 ± 0.31 j
1.09 ± 0.04 h
0.75 ± 0.01 h
14.75 ± 0.44 cde
16.67 ± 0.25 f
3.65 ± 0.04 h
2.85 ± 0.18 bc
0.35 ± 0.01 de
ND
0.30 ± 0.02 bc
0.14 ± 0.01 ab
44.82 ± 0.20 gh
12.48 ± 0.18 b
0.40 ± 0.00 h
0.51 ± 0.01 def
5.75 ± 0.25 bc
3.82 ± 0.04 j
1.44 ± 0.03 g
10.88 ± 0.15 de
0.32 ± 0.03 cd
0.29 ± 0.01 d
0.36 ± 0.01 a 0.78 ± 0.01 g
0.69 ± 0.03 f
0.30 ± 0.02 b
0.27 ± 0.01 a
0.58 ± 0.01 a
1.61 ± 0.04 f
0.89 ± 0.01 f
2.53 ± 0.03 j
1.50 ± 0.02 i
AL4
0.75 ± 0.04 h
0.46 ± 0.02 c
2.84 ± 0.04 l
1.67 ± 0.13 k
3.61 ± 0.01 o
2.25 ± 0.01 m
AL14
57.95 ± 0.98 ef
15.46 ± 0.41 def
16.21 ± 0.58 ef
3.03 ± 0.04 ef
3.09 ± 0.10 def
0.44 ± 0.02 f
0.12 ± 0.00 b
0.45 ± 0.01 gh
0.05 ± 0.01 a
43.73 ± 0.41 ef
14.22 ± 0.57 cde
0.21 ± 0.01 bcde
0.52 ± 0.02 def
6.30 ± 0.21 de
2.84 ± 0.09 i
0.76 ± 0.03 bc
10.81 ± 0.34 cde
0.22 ± 0.03 ab
0.24 ± 0.03 bc
0.24 ± 0.02 b
2.40 ± 0.03 k
1.38 ± 0.08 j
2.84 ± 0.04 k
1.85 ± 0.02 k
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12614
17.76 ± 0.65 g
14.57 ± 0.29 cd
61.99 ± 1.41 ij
∑SFA
∑MUFA
∑PUFA
56.21 ± 0.42 bc
14.87 ± 0.23 cde
20.84 ± 0.64 i 60.67 ± 0.76 ghi
16.32 ± 0.27 f
14.93 ± 0.31 bcd
3.21 ± 0.01 g
3.02 ± 0.02 cde
0.70 ± 0.01 h
0.08 ± 0.02 ab
46.05 ± 0.55 i
14.62 ± 0.21 de
0.26 ± 0.02 efg
0.43 ± 0.03 bcde
6.71 ± 0.02 def
2.63 ± 0.15 h
0.67 ± 0.03 b
AL8
61.41 ± 0.54 huj
15.77 ± 0.44 ef
14.80 ± 0.21 b
2.72 ± 0.14 c
3.39 ± 0.06 g
0.49 ± 0.01 g
ND
0.35 ± 0.01 d
0.03 ± 0.01 a
47.26 ± 0.21 j
14.15 ± 0.33 cd
0.18 ± 0.01 abcd
0.45 ± 0.03 cdef
6.11 ± 0.19 cd
2.43 ± 0.04 fg
1.02 ± 0.03 de
10.20 ± 0.11 bc
0.27 ± 0.02 bc
AL9
59.90 ± 0.62 gh
15.55 ± 0.19 def
15.02 ± 0.40 bcd
3.23 ± 0.04 g
2.91 ± 0.03 bcd
0.49 ± 0.01 g
ND
0.34 ± 0.01 cd
0.05 ± 0.00 a
45.54 ± 0.60 hi
14.36 ± 0.02 cde
0.28 ± 0.00 fg
0.48 ± 0.02 cdef
6.14 ± 0.03 cd
2.91 ± 0.14 i
0.85 ± 0.02 cd
9.90 ± 0.17 ab
0.38 ± 0.05 d
AL10
AL11
ND
62.44 ± 1.69 j
15.46 ± 0.55 def
14.83 ± 0.25 bc
2.73 ± 0.17 c
3.59 ± 0.13 h
0.34 ± 0.01 d
AL12
ND
59.13 ± 1.23 fg
13.28 ± 0.43 ab
17.85 ± 0.47 g
2.58 ± 0.03 b
3.18 ± 0.01 ef
64.85 ± 0.73 k
13.07 ± 0.51 a
13.78 ± 0.82 a
3.09 ± 0.15 f
3.25 ± 0.08 fg
0.48 ± 0.01 g
0.16 ± 0.00 c
0.10 ± 0.01 ab
49.43 ± 0.28 k
15.42 ± 0.45 fg
0.31 ± 0.01 g
0.40 ± 0.02 bc
62.32 ± 0.80 ij
14.66 ± 0.52 cd
15.89 ± 0.71 def
3.26 ± 0.03 g
2.72 ± 0.03 b
0.39 ± 0.01 e
ND
0.31 ± 0.03 cd
ND
47.52 ± 0.49 j
14.80 ± 0.31 def
0.15 ± 0.00 abc
0.53 ± 0.02 def
2.31 ± 0.09 ef 5.82 ± 0.32 bc
0.40 ± 0.02 a
11.58 ± 0.56 fg
5.43 ± 0.33 ab
0.33 ± 0.02 cd
0.49 ± 0.00 g
AL13 0.32 ± 0.07 cd
2.48 ± 0.08 g
0.97 ± 0.04 cde
9.28 ± 0.67 a
0.35 ± 0.02 d
0.40 ± 0.01 ef
0.14 ± 0.01 ab
0.04 ± 0.01 a 0.39 ± 0.02 e
42.55 ± 1.00 d
16.58 ± 0.23 i
0.19 ± 0.05 abcde
0.35 ± 0.01 ab
5.48 ± 0.03 ab
2.25 ± 0.04 de
1.41 ± 0.03 g
13.35 ± 0.35 i
0.18 ± 0.04 a
48.68 ± 0.91 k
13.76 ± 0.78 c
0.19 ± 0.02 abcde
0.43 ± 0.01 bcde
5.11 ± 0.23 a
2.42 ± 0.04 fg
0.86 ± 0.01 bcd
10.19 ± 0.15 bc
0.23 ± 0.02 ab
cultivar AL14
57.54 ± 0.67 ef
17.27 ± 0.22 g
15.82 ± 0.72 cdef
4.11 ± 0.05 j
2.72 ± 0.04 b
0.30 ± 0.01 c
0.08 ± 0.01 a
0.27 ± 0.02 b
0.03 ± 0.01 a
46.18 ± 0.63 i
11.36 ± 0.04 a
0.17 ± 0.02 abc
0.62 ± 0.01 g
5.78 ± 0.05 bc
2.47 ± 0.07 g
1.19 ± 0.04 ef
10.33 ± 0.44 bcd
0.27 ± 0.01 bc
Values with different letters are significantly different from each other. Values are given as percentages, mean ± SD, n = 3, p ≤ 0.05. ND = not detected. ∑SFA, sum of saturated fatty acids; ∑MUFA, sum of monounsaturated fatty acids; ∑PUFA, sum of polyunsaturated fatty acids
a
2.91 ± 0.06 de
ω3/ω6 ratio
3.00 ± 0.01 ef
2.95 ± 0.00 cd
0.48 ± 0.01 h
0.10 ± 0.00 a
22:0
2.87 ± 0.00 bc
0.18 ± 0.03 b
0.03 ± 0.00 a
21:0
oil yield (%)
ND
41.88 ± 0.30 d
46.04 ± 0.80 i
18:3n-3
ND
14.33 ± 0.12 cde
15.95 ± 0.61 ghi
18:2n-6
3.09 ± 0.04 k
0.12 ± 0.01 a
0.19 ± 0.01 abcde
18:1(12c)
ND
0.43 ± 0.03 bcde
0.31 ± 0.02 a
18:1(11c)
1.42 ± 0.01 j
8.82 ± 0.03 h
6.84 ± 0.08 f
18:1(9c)
24:1
1.77 ± 0.06 c
2.38 ± 0.22 efg
18:0
26:0
0.43 ± 0.01 fg
1.08 ± 0.00 e
1.53 ± 0.01 gh
9.65 ± 0.08 ab
14.02 ± 0.39 j
12.79 ± 0.41 hi
16:1
AL7 0.37 ± 0.05 d
16:0
AL6
1.25 ± 0.06 ij
AL5
0.18 ± 0.02 a
14:1c
fatty acid
Table 2. continued
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AL7
12615
54.54 ± 1.14 c
1.55 ± 0.03 cde
1.02 ± 0.03 bc
4.39 ± 0.28 d
ND
56.51 ± 4.41 c
1.97 ± 0.08 fg
0.92 ± 0.03 b
4.97 ± 0.62 fg
0.70 ± 0.10 a
28.50 ± 1.87 def
269.05 ± 2.78 f
441.72 ± 13.10 fg 384.40 ± 12.40 c
lutein
zeaxanthin
β-cryptoxanthin
15-cis-β-carotene
13-cis-β-carotene
α-carotene
β-carotene
TCI
420.90 ± 11.60 ef
268.16 ± 4.38 e
30.93 ± 0.94 fg
ND
5.21 ± 0.37 g
1.01 ± 0.03 bc
1.71 ± 0.21 ef
56.07 ± 1.43 c
2.73 ± 0.11 cde
4.14 ± 0.87 cd
50.94 ± 3.29 d
309.20 ± 4.88 h
QL4
QL5
AL8
675.53 ± 15.3 j
394.31 ± 6.12 l
41.92 ± 2.37 m
7.70 ± 0.68 g
1.32 ± 0.06 ab
0.92 ± 0.04 b
1.90 ± 0.09 f
136.78 ± 2.79 j
4.81 ± 0.24 i
5.09 ± 0.46 fghi
80.78 ± 2.45 l
QL6
286.10 ± 6.52 g
35.57 ± 0.83 hij
4.39 ± 0.31 c
0.84 ± 0.01 a
0.56 ± 0.02 a
1.62 ± 0.03 de
87.89 ± 5.74 g
3.59 ± 0.04 g
4.37 ± 0.55 def
60.37 ± 2.41 ef
AL10
566.82 ± 13.30 i
353.27 ± 4.66 k
41.07 ± 2.43 lm
5.40 ± 0.73 de
1.11 ± 0.07 a
0.62 ± 0.05 a
1.71 ± 0.04 ef
88.43 ± 2.97 g
2.98 ± 0.03 def
4.89 ± 0.21 efgh
67.34 ± 2.29 hi
321.56 ± 17.90 b 485.30 ± 16.50 h
213.16 ± 9.43 c
24.69 ± 2.67 c
3.36 ± 0.31b
0.88 ± 0.03 a
ND
0.96 ± 0.06 b
41.45 ± 1.72 b
2.03 ± 0.15 ab
3.07 ± 0.25 ab
31.96 ± 3.32 b
AL9
561.90 ± 13.30 i
328.01 ± 7.14 i
340.89 ± 4.01 j 574.27 ± 13.20 i
37.91 ± 1.39 jk
5.93 ± 0.42 e
1.00 ± 0.07 a
0.57 ± 0.04 a
1.92 ± 0.10 f
103.39 ± 2.66 i
3.75 ± 0.23 g
5.00 ± 0.18 fghi
74.37 ± 1.11 k
39.06 ± 1.32 kl
6.13 ± 0.63 ef
1.70 ± 0.06 bc
0.59 ± 0.01 a
1.98 ± 0.05 fg
95.53 ± 3.47 h
3.67 ± 0.71 g
5.46 ± 0.21 hi
79.26 ± 2.77 l
AL1
AL2
AL11
499.20 ± 11.00 h
308.30 ± 3.11 h
33.67 ± 1.83 ghi
ND
5.78 ± 0.77 h
1.10 ± 0.08 c
2.44 ± 0.42 h
69.24 ± 1.08 de
3.45 ± 0.28 fg
5.62 ± 0.31 i
69.57 ± 3.11 ij
AL3
276.26 ± 4.88 f
32.37 ± 2.75 gh
4.64 ± 0.59 c
0.91 ± 0.07 a
AL12
487.00 ± 10.80 h
286.10 ± 2.24 g
35.57 ± 1.65 hij
4.39 ± 0.25 c
0.84 ± 0.08 a
0.56 ± 0.07 a
1.62 ± 0.04 de
87.89 ± 3.95 g
3.00 ± 0.06 def
4.40 ± 0.53 def
62.62 ± 1.92 fg
AL4
115.19 ± 2.83 a
12.72 ± 1.89 a
ND
2.04 ± 0.28 c
ND
0.35 ± 0.02 a
33.31 ± 0.84 a
1.81 ± 0.16 a
2.56 ± 0.09 a
21.24 ± 1.17 a
378.12 ± 16.50 c
246.06 ± 7.83 d
28.95 ± 3.66 ef
ND
4.42 ± 0.29 de
0.92 ± 0.3 b
1.36 ± 0.01 cd
51.63 ± 2.25 c
2.48 ± 0.09 bcd
3.54 ± 0.22 bc
38.76 ± 1.87 d
AL13
324.16 ± 12.20 b
181.07 ± 5.78 b
20.32 ± 1.68 b
ND
ND
3.10 ± 0.12 d
3.16 ± 0.14 i
72.02 ± 1.32 e
2.79 ± 0.29 cde
3.42 ± 0.46 b
38.28 ± 2.36 c
AL14
395.82 ± 14.60 cd 189.22 ± 7.28 a
250.82 ± 6.63 e
26.03 ± 1.44 cde
ND
4.93 ± 0.31 efg
1.11 ± 0.04 c
1.28 ± 0.06 c
0.62 ± 0.06 a
56.27 ± 3.40 c
1.53 ± 0.03 cde
2.14 ± 0.07 ab
4.15 ± 0.32 cde
49.09 ± 2.35 d
69.72 ± 2.08 de
3.04 ± 0.19 ef
5.07 ± 0.41 fghi
64.80 ± 2.75 gh
407.77 ± 12.00 de 458.96 ± 13.80 g
255.61 ± 4.09 e
26.81 ± 1.35 cde
ND
4.46 ± 0.17 def
0.96 ± 0.04 bc
1.47 ± 0.07 cde
55.21 ± 4.13 c
2.32 ± 0.25 bc
4.53 ± 0.18 def
56.40 ± 1.75 e
a
Values with different letters are significantly different from each other. Values are given in micrograms per gram dry weight, as mean ± SD, n = 3, p ≤ 0.05. ND = not detected. TCI, total carotenoids index.
242.70 ± 6.41 d
25.41 ± 0.46 cd
4.25 ± 0.23 de
2.69 ± 0.18 cde
5.26 ± 0.66 ghi
2.43 ± 0.21 bc
antheraxanthin
cis-lutein
AL6
47.88 ± 3.59 e
AL5
71.41 ± 2.32 ijk
violaxanthin
compd
496.15 ± 10.40 h
484.86 ± 4.23 m
5.50 ± 0.07 e 35.87 ± 1.19 ijk
738.00 ± 8.74 k
61.98 ± 0.39 n
302.97 ± 5.08 h
6.73 ± 0.01 f
0.99 ± 0.37 a
501.45 ± 12.1 h
1.74 ± 0.03 bc
1.12 ± 0.03 a
15-cis-β-carotene
0.52 ± 0.03 a
β-carotene
1.12 ± 0.02 c
0.54 ± 0.03 a
β-cryptoxanthin
1.71 ± 0.08 ef
65.93 ± 1.48 d
TCI
2.22 ± 0.02 gh
1.49 ± 0.36 cde
zeaxanthin
4.72 ± 0.02 cd
77.32 ± 1.21 f
71.31 ± 2.53 e
lutein
3.31 ± 0.16 fg
4.37 ± 0.12 def
37.83 ± 0.72 jkl
4.22 ± 0.13 h
4.86 ± 0.72 i
13-cis-lutein
α-carotene
4.67 ± 0.24 defg
4.51 ± 0.17 def
antheraxanthin
QL3 68.75 ± 2.02 hij
13-cis-β-carotene
QL2
93.20 ± 2.46 m
QL1
72.10 ± 2.42 jk
compd
violaxanthin
Table 3. Concentrations of Carotenoids in Leaves of Different Quinoa and Amaranth Cultivarsa
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Table 4. Concentrations of Tocopherols in Leaves of Different Quinoa and Amaranth Cultivarsa cultivar
α-tocopherol
β-tocopherol
γ-tocopherol
QL1 QL2 QL3 QL4 QL5 QL6 avg
5.79 44.71 66.44 62.63 67.40 57.72 50.78
± ± ± ± ± ± ±
0.42 2.94 3.98 1.34 2.96 0.46 2.02
a ef lm kl m j gh
1.02 10.52 19.86 15.79 22.13 6.12 12.57
± ± ± ± ± ± ±
0.04 0.89 0.76 0.85 1.53 0.58 0.78
a gh l j m c i
1.02 3.02 2.90 2.44 2.52 2.03 2.32
± ± ± ± ± ± ±
AL1 AL2 AL3 AL4 AL5 AL6 AL7 AL8 AL9 AL10 AL11 AL12 AL13 AL14 avg
57.11 45.10 48.53 16.24 57.11 50.06 59.34 32.71 53.38 51.79 23.10 42.73 31.00 62.79 45.07
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
1.05 0.63 3.74 1.78 2.05 1.71 1.30 1.99 2.54 0.87 2.51 2.82 0.78 5.14 2.07
ij ef fg b ij gh jk d hi gh c e d kl ef
7.61 11.54 15.50 6.30 20.40 8.67 3.29 6.38 4.01 15.79 2.65 18.32 11.10 7.41 9.93
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.95 0.60 0.53 0.91 1.37 0.94 0.86 0.71 0.12 0.58 0.14 0.73 0.92 0.20 0.68
de hi j cd l ef b cd b j b k gh cde fg
1.40 12.62 1.53 9.99 1.29 10.85 3.44 17.57 4.80 2.44 4.11 7.24 2.15 5.26 6.05
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
δ-tocopherol
Quinoa 0.11 a 0.14 gh 0.39 fgh 0.71 efg 0.59 efg 0.11 bcde 0.34 defg Amaranth 0.04 abc 0.72 p 0.06 abcd 0.50 n 0.32 ab 0.86 o 0.64 hi 0.35 q 0.16 jk 0.07 efg 0.19 ij 0.76 m 0.03 cdef 0.47 k 0.37 l
α-TE
total tocopherols index
1.53 2.33 0.53 2.01 1.63 2.05 1.68
± ± ± ± ± ± ±
0.07 0.25 0.18 0.59 0.33 0.18 0.27
bcdef hi a fgh defg fghi defg
6.45 50.34 76.68 70.83 78.77 61.04 57.35
± ± ± ± ± ± ±
0.40 2.73 3.79 1.17 2.64 0.41 1.86
a e l k l j huj
9.36 60.58 89.73 82.87 93.68 67.92 67.36
± ± ± ± ± ± ±
0.36 2.55 3.51 1.88 2.74 0.75 1.97
a de l k m ghi fgh
1.04 1.75 1.34 1.50 1.14 2.39 0.55 2.15 1.40 2.01 0.98 2.60 1.23 2.45 1.61
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.05 0.46 0.08 0.03 0.05 0.79 0.03 0.03 0.34 0.19 0.07 0.47 0.29 0.09 0.21
abc efg bcde bcdef bcd hi a hij bcde fgh ab j bcde hi cdefg
61.09 52.18 56.47 20.43 67.47 55.55 61.35 37.72 55.91 59.99 24.87 52.69 36.80 67.09 50.69
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
0.91 0.55 3.61 1.59 1.80 1.51 1.14 1.83 2.50 0.76 2.47 2.62 0.68 5.07 1.93
j ef ghi b k fgh j d fgh ij c efg d k e
67.16 71.01 66.90 34.03 79.94 71.97 66.62 58.81 63.59 72.03 30.84 70.89 45.48 77.91 62.66
± ± ± ± ± ± ± ± ± ± ± ± ± ± ±
1.05 1.56 3.45 1.63 1.91 2.28 1.43 1.72 2.29 0.86 2.34 2.50 1.86 4.81 2.12
fgh fgh b jk i fg d ef i b hi c j de
Values with different letters are significantly different from each other. Values are given in micrograms per gram dry weight, as mean ± SD, n = 3, p ≤ 0.05. α-TE, α-tocopherol equivalent. a
kale.30,36,37 Our results confirm that both quinoa and amaranth leaves are excellent source of carotenoids, richer than in their own seeds.3,38 Tocopherols. All four tocopherol isomers (α, β, γ, and δ) but no tocotrienols were detected in quinoa and amaranth leaves (Table 4). The average total tocopherol content of both quinoa and amaranth was around 65 μg/g DW, similar to what was reported by others.39 However, in addition to α-tocopherol, we also found β-, γ-, and δ-tocopherol in quinoa and amaranth leaves. The tocopherol profiles in amaranth and quinoa leaves were generally similar, with α-tocopherol being the predominant isomer (75.38% and 71.93% of total tocopherols on average in quinoa and amaranth, respectively), followed by β-, γ-, and δ-tocopherol. The concentration of α- and β-tocopherol in quinoa leaves was generally higher than in the leaves of amaranth, while γ-tocopherol was at lower levels in quinoa compared with amaranth. Even within the amaranth leaves, a few cultivars such as AL2, AL8, AL4, and AL6 showed exceptionally high γ-tocopherol content compared with all other plants. Both quinoa and amaranth leaves had low concentration of δ-tocopherol averaging from 1.61 to 1.68 μg/g DW. In terms of the α-TE values, the present results suggested that nearly all vitamin E activity of quinoa and amaranth leaves was from α-tocopherol (Table 4). It is also worth mentioning that quinoa leaves had completely different tocopherol profiles than their respective seeds. Quinoa seeds contained overwhelmingly γ-tocopherol (>85%) and ca. 10% α-tocopherol, whereas the primary tocopherol in quinoa leaves was α-tocopherol followed by β-tocopherol (Table 4).4 Similarly the tocopherol profile of amaranth leaves was different from that of amaranth seeds, which have been found to vary significantly from study to study.3,39 As a source of vitamin E, quinoa and amaranth leaves contained nearly twice as much
total tocopherols as those high-tocopherol grains, although compared to other common vegetable leaves, the concentration is lower.12,20,30,40 Overall Evaluation. Fatty acids, carotenoids, and vitamin E are three important lipophilic parameters to be evaluated for fruits, vegetables, and grains for their overall nutritional quality. However, these parameters have only been discussed separately in previous studies.3,10,12,30 Food lipids are generally reported to include oil yield and major groups of saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA), while carotenoids are mainly discussed under pro-vitamin A (β-carotene) and xanthophylls (lutein).40 In terms of vitamin E, four tocopherols and four tocotrienols have been reported to have vitamin E activity, and α-tocopherol equivalency (α-TE) has been recently used as a measure for evaluation of the overall vitamin E activity of foods containing different vitamin E isoforms.18,41 Evaluation of the overall nutritional quality of the lipophilic components of a particular food or feed has been attempted by assessing the nutrients separately.15,16 Such an attempt, however, lacks the cohesiveness that integrates all three lipophilic parameters; thus it is difficult to assess and compare the overall nutritional quality of different foods. A novel approach was then taken in the present study to establish a unified protocol for evaluation of the nutritional quality (NQ) of all lipophilic contents from the original data. Because the original data of the total carotenoids, α-TE and ω-3/ω-6 ratio were in different units, a linear scale transformation method was used to first transform all data to an arbitrary unit between 0 and 1 by use of the following equation: NQ = 12616
NQ i 3NQ max
× 100
dx.doi.org/10.1021/jf5046377 | J. Agric. Food Chem. 2014, 62, 12610−12619
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Figure 1. Nutritional quality (NQ) value of lipophilic extract from quinoa and amaranth leaves. Values with different letters are significantly different from each other. Values are given as mean ± SD, n = 3, p ≤ 0.05.
where NQmax is the highest value of total carotenoids, α-TE, or ω-3/ω-6 ratio and NQi is the individual value of total carotenoids, α-TE, or ω-3/ω-6 ratio of a particular sample. Three is the number of lipophilic parameters used for normalizing so that the final value can be presented as a percentage. Figure 1 shows the ranking of overall nutritional quality by use of the above-mentioned method. The ω-3/ω-6 ratio was relatively consistent among all quinoa and amaranth samples, whereas the total carotenoids and α-TE varied significantly. The overall nutritional quality was better in quinoa leaves than in amaranth. QL5 and QL3 ranked as the top two among all quinoa and amaranth leaves samples, while AL10 and AL14 had the highest NQ values among amaranth samples. No individual parameter among the three can represent the overall nutritional quality of a sample, and because of the inconsistency, no single individual nutrient group can therefore be used to evaluate or to rank the overall nutritional quality of the samples. Our approach overcomes this dilemma and provides a standardized method for assessment of the lipophilic merits of food. Antioxidant Activities. The antioxidant activities of the lipophilic compounds in quinoa and amaranth leaves were assessed by DPPH, FRAP, and ORAC methods. In general, quinoa leaves had higher antioxidant activity than amaranth leaves (Figure 2). Due to the different mechanisms of in vitro antioxidant assays and the existence of different groups of lipophilic components of food, correlations between the concentration of individual nutrient groups and the different antioxidant activities have not been consistent.10,15 For example, in a study on the lipophilic antioxidants of lentils, the total carotenoids correlated well with the antioxidant activity in the photochemiluminescence assay (PCL) but not with DPPH activity, whereas total tocopherols had a relatively good correlation with DPPH but no correlation with PCL activity. Studies on quinoa seeds also showed that different lipophilic components showed different degrees of correlation with different antioxidant activities.5,15 In the present study, the correlation coefficients (r2) between the ω-3/ω-6 ratio and DPPH, FRAP, or ORAC values were 0.594, 0.639, and 0.674,
respectively; the r2 values for α-TE were 0.700, 0.741, and 0.786, respectively; and for carotenoids, they were all low at 0.428, 0.391, and 0.418, respectively. The r2 values, however, were significantly improved by use of NQ value as an overall marker for food nutritional quality of lipophilic components. The overall NQ value of quinoa and amaranth leafy samples showed a strong positive correlation with all antioxidant activities, with r2 = 0.848, 0.874, and 0.927, respectively, for DPPH, FRAP and ORAC activities. Quinoa and amaranth seeds are emerging as the latest healthy foods on the market, and the demand for these pseudocereal grains has increased in recent years. As a result of the current effort being made to produce quinoa and amaranth seeds in Canada, additional value from the whole plants of these two crops has become an interesting subject of research. The present study examined the lipophilic bioactives in leaves of quinoa and amaranth plants. Three major lipophilic nutrients were analyzed, essential fatty acids, tocopherols, and carotenoids, and the total and individual compounds were identified and quantified for the first time. While the oil yield was only 3−4% of the leaves, both plants contained high-quality fatty acids with 50.97−62.32% PUFA which consisted of almost entirely 18:3n-3 and 18:2n-6. The ratio of these two essential fatty acids, that is, the ω-3/ω-6 ratio, ranged between 2.13 and 4.11, which was more favorable than other plant oils in terms of potential contribution to health benefits. Pro-vitamin A (mainly β-carotene and α-carotene) and xanthophylls (mainly lutein and violaxanthin) were considered the major contributors to the carotenoids in leafy samples of both quinoa and amaranth. Different from the seeds, the tocopherols in quinoa and amaranth leaves were primarily α- and β-tocopherol. A new approach to establishing a unified standard evaluation method for the overall nutritional quality of the lipophilic bioactives was proposed. This novel method calculates the NQ value of each sample by combining the relative quantities of the three major bioactive groups: carotenoids, α-TE, and ω-3/ω-6 ratio. The NQ value correlated strongly with all antioxidant activities as measured by DPPH, FRAP, and ORAC assays, thus 12617
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potentially applied to all other foods. This new approach and the NQ value can be used for more precise comparison of the nutritive quality of lipophilic bioactives in foods. Information obtained in this study will aid the selection process of quinoa and amaranth cultivars adaptable to Ontario climate, and how the whole plant instead of the seeds can be used for the development of value-added products such as nutraceuticals and functional foods.
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AUTHOR INFORMATION
Corresponding Authors
*Telephone +86-22-60601425; fax +86-22-60601341; e-mail
[email protected]. *Telephone +1-226-217-8108; fax +1-226-217-8180; e-mail
[email protected]. Funding
This project was supported by the A-Base Research (1004) of Agriculture & Agri-Food Canada (AAFC) and partially by the Ontario Soil and Crop Improvement Association and Katan Kitchens through Canadian Agricultural Adaptation Program (CAAP) (AAFC RBPI 2882). Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS
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REFERENCES
We thank Dr. Dyanne Brewer and Dr. Armen Charchoglyan, Advanced Analysis Center, University of Guelph, for providing mass spectra reports.
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Figure 2. Antioxidant activities as measured by DPPH assay [A, top; micromoles of Trolox equivalent (TE) per gram dry weight], FRAP assay [B, middle; micromoles of ascorbic acid equivalent (AAE) per gram dry weight], and ORAC assay [C, bottom; micromoles of Trolox equivalent (TE) per gram dry weight]. Values with different letters are significantly different from each other. Values are given as mean ± SD, n = 3, p ≤ 0.05.
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