Comparative Metabolomics Profiling of Polyphenols, Nutrients and Antioxidant Activities of Two Red Onion (Allium cepa L.) Cultivars

Onion is among the most widely cultivated and consumed economic crops. Onions are an excellent dietary source of polyphenols and nutrients. However, onions phytonutrient compositions vary with cultivars and growing locations. Therefore, the present study involved the evaluation of polyphenol, nutritional composition (proteins, nitrogen, and minerals), sugars, pyruvate, antioxidant, and α-amylase inhibition activities of red onion cultivars, sweet Italian, and honeysuckle grown in California and Texas, respectively. The total flavonoid for honeysuckle and sweet Italian was 449 and 345 μg/g FW, respectively. The total anthocyanin for honeysuckle onion was 103 μg/g FW, while for sweet Italian onion was 86 μg/g FW. Cyanidin-3-(6”-malonoylglucoside) and cyanidin-3-(6”-malonoyl-laminaribioside) were the major components in both the cultivars. The pungency of red onions in honeysuckle ranged between 4.9 and 7.9 μmoL/mL, whereas in sweet Italian onion ranged from 8.3 to 10 μmoL/mL. The principal component analysis was applied to determine the most important variables that separate the cultivars of red onion. Overall results indicated that total flavonoids, total phenolic content, total anthocyanins, protein, and calories for honeysuckle onions were higher than the sweet Italian onions. These results could provide information about high quality and adding value to functional food due to the phytochemicals and nutritional composition of red onions.


Introduction
Onions are among the most widely grown, consumed, and important economic crops [1]. They are consumed alone or in prepared foods for their unique pungent flavor and sugar content [2]. According to the U.S Statista, the consumption of fresh onions accounted for 20.4 pounds per capita in 2019 [3]. Onions are excellent sources of polyphenols, contribute significantly to the human diet, and have been used in the prevention of infections, cancer, cardiovascular disease, and hyperlipidemia [4,5].
Polyphenols are receiving increasing interest from consumers and food manufacturers due to antioxidant and anti-inflammatory benefits that help prevent illnesses and diseases. Polyphenols are natural substances in plants and include compounds such as phenolic acids and flavonoids [6]. Flavonoids are further categorized into six different subclasses: flavonols, flavones, isoflavones, flavanones, anthocyanins, and flavanols, forming the largest group with antioxidant effects [7]. Health benefits of phenolics attract the researcher and breeders to identify and develop new cultivars The glucose, fructose, and sucrose were detected in all the onion samples ( Figure 2B). The glucose (19.8 mg/mL) and fructose (25.2 mg/mL) were high in sweet Italian, whereas the sucrose (11.29 mg/mL) was high in the honeysuckle variety. The total sugar ranged between 42.13 (honeysuckle) and 53.68 (sweet Italian) mg/mL.

Evaluation of Protein and Minerals
Onion serves as a good supplement of magnesium, calcium, iron, sodium, phosphorous, boron, and potassium. Although onions constitute a small portion of the whole diet, they play an important role in metabolic processes and normal functioning of the human body. The results obtained for the mineral and protein content analyzed in all the samples and their differentiation, according to the cultivars are shown in Table 1. Phosphorous helps to keep bones strong and repair damaged tissues of pungency is as follows: low, 0-3 μmoL/mL; moderate, 3-7 μmoL/mL; high, >7 μmoL/mL [31]. The Brix of two cultivars was 10.9 (honeysuckle) and 11 (sweet Italian) and did not show any significant difference. The red onions are generally regarded as high in pungency and Brix. The glucose, fructose, and sucrose were detected in all the onion samples ( Figure 2B). The glucose (19.8 mg/mL) and fructose (25.2 mg/mL) were high in sweet Italian, whereas the sucrose (11.29 mg/mL) was high in the honeysuckle variety. The total sugar ranged between 42.13 (honeysuckle) and 53.68 (sweet Italian) mg/mL.

Evaluation of Protein and Minerals
Onion serves as a good supplement of magnesium, calcium, iron, sodium, phosphorous, boron, and potassium. Although onions constitute a small portion of the whole diet, they play an important role in metabolic processes and normal functioning of the human body. The results obtained for the mineral and protein content analyzed in all the samples and their differentiation, according to the cultivars are shown in Table 1. Phosphorous helps to keep bones strong and repair damaged tissues The glucose, fructose, and sucrose were detected in all the onion samples ( Figure 2B). The glucose (19.8 mg/mL) and fructose (25.2 mg/mL) were high in sweet Italian, whereas the sucrose (11.29 mg/mL) was high in the honeysuckle variety. The total sugar ranged between 42.13 (honeysuckle) and 53.68 (sweet Italian) mg/mL.

Evaluation of Protein and Minerals
Onion serves as a good supplement of magnesium, calcium, iron, sodium, phosphorous, boron, and potassium. Although onions constitute a small portion of the whole diet, they play an important role in metabolic processes and normal functioning of the human body. The results obtained for the mineral and protein content analyzed in all the samples and their differentiation, according to  Table 1. Phosphorous helps to keep bones strong and repair damaged tissues [32]. The highest level of phosphorous was seen in sweet Italian cultivar (2677.64 µg/g) and the lowest in honeysuckle (2525.63 µg/g). Potassium plays an important role in maintaining water balance, regulation of heartbeat, and neurotransmission [33]. The highest level of potassium (13,550.1 µg/g) was observed in sweet Italian and lowest (12,720.37 µg/g) in honeysuckle. Magnesium helps in the carbohydrate metabolism, a cofactor in more than 300 enzymatic reactions, stabilizes protein, and calcium absorption for bones [34]. The average consumption of magnesium for men is 420 mg and women is 320 mg. The values for magnesium in sweet Italian and honeysuckle were 1100.62 and 980.43 µg/g, respectively. Calcium, sodium, zinc, copper, sulfur, and boron were high in honeysuckle with the values 3183. 52, 1001.34, 14.43, 7.38, 3421.58, and 18.34 µg/g, respectively. Sodium regulates the body's water content and helps in the absorption of certain nutrients, while iron is essential for the formation of hemoglobin in red blood cells [35]. Zinc acts as a cofactor for enzymes and helps in reproductive development [36], whereas copper is important for infant growth and producing red and white blood cells. Manganese is a constituent of antioxidant enzyme which helps to prevent free radical-mediated damage to cells. Boron helps the body to metabolize vitamins and minerals [37], whereas sulfur helps to build and repair DNA and protect cells against damage [38]. The protein percentage in honeysuckle (9.21) was higher than the sweet Italian (8.2). Minerals play an essential role from building strong bones to transmitting nerve impulses. There were differences between the concentrations of all the mineral elements studied in the two red onion cultivars. It can, therefore, be assumed that the environment, agronomic practices, and genetic information of the seeds determine the changes in the protein and mineral element composition.

Antioxidant Activity, Total Phenolic Content, and α-Amylase Inhibitory Activity
The DPPH assay is applicable to hydrophobic compounds, whereas ABTS is applicable to both hydrophilic and hydrophobic compounds which provide a flexibility to be used for samples extracted at different pH levels. DPPH and ABTS free radicals react with chemicals compounds by single electron and hydrogen atom transfer mechanisms, respectively [39,40]. The antioxidant activity was measured using DPPH and ABTS assays ( Figure 3A,B). There was no significant difference in DPPH activity in sweet Italian onion and honeysuckle with the value of 262.93 and 259.75, respectively. ABTS radical scavenging activity was high in sweet Italian onions (193.82 µg/g) compared to honeysuckle onions (173.27 µg/g). Sagar et al. [41], Wu et al. [42], and Lu et al. [43] reported 66.79-94.17 µg GA/g, 103.91 µg AA/g, and 1301.508 µg Trolox/g FW DPPH radical scavenging activity in red onions. Antioxidants can inhibit oxidative reactions and help in the functional performance of enzymes for self-defense mechanisms within the cell [43]. The consumption of onions has been reported to lower the risk of neurodegenerative disease, cancers, cataract formation, and ulcer development due to antioxidant effects [44].
The α-amylase activity of red onions was determined and compared with a positive control, acarbose. The inhibition of α-amylase showed a significant difference between both the varieties: sweet Italian was high (46.1%) compared to honeysuckle ( Figure 3C). The total phenolic contents of the two varieties are shown in Figure 3D. The content value in honeysuckle was 1.57 mg GAE/g, while sweet Italian was 1.40 mg GAE/g fresh weight. Prakash et al. [45] reported the total phenolic content in the outer, middle, and inner layers of red onion to be 74.1, 15.9, and 5.6 mg GAE/g dry weight basis. In another study, Yang et al. reported that the total phenolic content in Northern red onions was 0.815 mg GAE/g fresh weight [46].

Quantification of Red Onion Flavonoids
The HPLC-PDA chromatographic separation and elution pattern of different flavonoids are shown in Figure 4A. The identification of onion flavonoids was performed by using LC-HR-ESI-QTOF-MS in positive ionization mode. A total of eight flavonoids was identified, and their tandem mass spectra with +bbCID spectra and the structures of the identified flavonoids are presented in Figures 5 and 6, respectively. The accurate mass and mass error of the identified onion flavonoids are presented in Table 2  Antioxidants can inhibit oxidative reactions and help in the functional performance of enzymes for self-defense mechanisms within the cell [43]. The consumption of onions has been reported to lower the risk of neurodegenerative disease, cancers, cataract formation, and ulcer development due to antioxidant effects [44].
The α-amylase activity of red onions was determined and compared with a positive control, acarbose. The inhibition of α-amylase showed a significant difference between both the varieties: sweet Italian was high (46.1%) compared to honeysuckle ( Figure 3C). The total phenolic contents of the two varieties are shown in Figure 3D. The content value in honeysuckle was 1.57 mg GAE/g, while sweet Italian was 1.40 mg GAE/g fresh weight. Prakash et al. [45] reported the total phenolic content in the outer, middle, and inner layers of red onion to be 74.1, 15.9, and 5.6 mg GAE/g dry weight basis. In another study, Yang et al. reported that the total phenolic content in Northern red onions was 0.815 mg GAE/g fresh weight [46].
It further lost one glucose molecule to give a prominent base peak at m/z 303.0481 [M+H-465-162] + (Y 0 ) + with a mass error of 6.03 ppm. Thus, the present peak was identified as quercetin-3,7,4 -triglucoside based on the mass spectra and published literature [11]. Another peak eluted at (t R ) 16.5 min representing the molecular ion peak at m/z 627.1507 [M+H] + (mass error 7.74 ppm), and aglycone product ion at m/z 303.0476 (mass error 7.68 ppm) was recognized as quercetin-7,4 -diglucoside. Similarly, a prominent peak (t R 17.  Table 3 shows the comparative levels of flavonoids, respectively, in the onion cultivars. There was no significant difference between cultivars in these individual flavonoids measured except isorhamnetin-4՛-glucoside and quercetin-4′-glucoside. Table 3 shows that honeysuckle cultivar had the highest amount of isorhamnetin-4′-glucoside and quercetin-4′-glucoside with values of 25.5 and 184.6 μg/g of fresh onions, respectively, as compared to sweet Italian onions with values 13.52 and 115.3 μg/g of fresh onions, respectively. In our study, we found that quercetin-3,4′-diglucoside and quercetin-4՛-glucoside were the most abundant flavonoids, and these results are in agreement with the previous studies [11,19,47]. Overall, the total flavonoids were higher in honeysuckle cultivar (440.93 μg/g) than sweet Italian (338.39 μg/g). Serban et al. [48] reported the quercetin effect on blood pressure in 7 trials comprising 9 treatment arms (587 patients). The authors reported that supplementation with quercetin >500 mg/day causes significant reductions in both systolic and diastolic blood pressure. Quercetin glucosides possess antioxidant, anti-inflammatory, cardioprotective, and anti-allergic properties. Quercetin also reduces the risk of clot formation near the damaged endothelium [49].   Figure 6. Structure of identified flavonoids from red onion.   Table 3 shows the comparative levels of flavonoids, respectively, in the onion cultivars. There was no significant difference between cultivars in these individual flavonoids measured except isorhamnetin-4 -glucoside and quercetin-4 -glucoside. Table 3 shows that honeysuckle cultivar had the highest amount of isorhamnetin-4 -glucoside and quercetin-4 -glucoside with values of 25.5 and 184.6 µg/g of fresh onions, respectively, as compared to sweet Italian onions with values 13.52 and 115.3 µg/g of fresh onions, respectively. Values are mean ± standard deviation of three samples; * indicate significant difference between two cultivars as determined by students t-test at p < 0.05.
In our study, we found that quercetin-3,4 -diglucoside and quercetin-4 -glucoside were the most abundant flavonoids, and these results are in agreement with the previous studies [11,19,47]. Overall, the total flavonoids were higher in honeysuckle cultivar (440.93 µg/g) than sweet Italian (338.39 µg/g). Serban et al. [48] reported the quercetin effect on blood pressure in 7 trials comprising 9 treatment arms (587 patients). The authors reported that supplementation with quercetin >500 mg/day causes Plants 2020, 9, 1077 9 of 18 significant reductions in both systolic and diastolic blood pressure. Quercetin glucosides possess antioxidant, anti-inflammatory, cardioprotective, and anti-allergic properties. Quercetin also reduces the risk of clot formation near the damaged endothelium [49].

Identification and Quantitation of Anthocyanins
In the present study, seven anthocyanins were identified using LC-HR-ESI-QTOF-MS in positive ionization mode. The protonated accurate mass and mass error of the identified anthocyanins are presented in Table 2. The tandem mass spectra with +bbCID spectra and the structures were identified.
Anthocyanins are presented in Figures 7 and 8, respectively. A peak eluted at retention time (t R ) 13.5 min exhibited a UV spectrum at 520 nm, which corresponded to characteristic flavylium cation. A MS spectrum showed an accurate mass at m/z 449.1022 [M] + (mass error 12.4 ppm). The precursor ion lost a glucose molecule to give a product ion at m/z 287.0516 [M-162] + (mass error 11.8 ppm), which corresponded to the aglycone moiety. Thus, based on the MS and +bbCID mass spectra, UV-Vis-spectra, and published literature [50][51][52], the present peak was identified as cyanidin-3-glucoside. Similarly, another peak eluted at t R

Identification and Quantitation of Anthocyanins
In the present study, seven anthocyanins were identified using LC-HR-ESI-QTOF-MS in positive ionization mode. The protonated accurate mass and mass error of the identified anthocyanins are presented in Table 2. The tandem mass spectra with +bbCID spectra and the structures were identified.

Principal Component Analysis and Pearson's Correlation Coefficients
The principal component analysis (PCA) model was applied to determine the essential variables that separate the cultivars of sweet red onion. The first (PC1) and the second (PC2) components  The mass error 11.1 ppm was yielded with a loss of glucose, malonly, and acetyl molecules. On the basis of the accurate mass, fragmentation pattern, and literature reports, the present peak was identified as cyanidin-3-(malonyl)-(acetyl)-glucoside. Figure 4B and Table 3 show the HPLC chromatograph and comparative levels of anthocyanins, respectively, in the onion cultivars. Cyanidin-3-(6"-malonyl-laminaribioside), cyanidin-3-laminaribioside, and peonidin-3-malonoylglucoside, which were 30.1 ± 2.1 µg/g, 5.3 ± 0.4 µg/g, and 1.0 ± 0.08 µg/g, respectively, were significantly higher in honeysuckle onion. The total anthocyanin content was higher in honeysuckle (103 µg/g FW) than sweet Italian (86 µg/g FW). Other authors, such as Pérez-Gregorio et al. [53], Ferreres et al. [54], and Gennaro et al. [55], reported the total anthocyanins in red onions to be 28.68, 233, and 90 µg/g, respectively. Anthocyanins exert different biological effects, and consumption of food rich in anthocyanins may be useful for antidiabetic, anti-obesity, neuroprotective agents, cardiovascular protection, and inhibiting cancer growth [56].

Principal Component Analysis and Pearson's Correlation Coefficients
The principal component analysis (PCA) model was applied to determine the essential variables that separate the cultivars of sweet red onion. The first (PC1) and the second (PC2) components explained 40% and 23.3% of the total variance, respectively (Figure 9). PCA grouped samples into two cultivars that reflected marked differences in the phytochemical depending on the cultivar. The corresponding biplot emphasized that the separation between the two cultivars was characterized by flavonoids, anthocyanins, sucrose, total phenolic content, DPPH, and minerals (Ca, Na, B, Cu, Zn) which were high in honeysuckle red onions. However, the amount of pyruvic acid contributed to the distinction between the two cultivars. explained 40% and 23.3% of the total variance, respectively ( Figure 9). PCA grouped samples into two cultivars that reflected marked differences in the phytochemical depending on the cultivar. The corresponding biplot emphasized that the separation between the two cultivars was characterized by flavonoids, anthocyanins, sucrose, total phenolic content, DPPH, and minerals (Ca, Na, B, Cu, Zn) which were high in honeysuckle red onions. However, the amount of pyruvic acid contributed to the distinction between the two cultivars.

Pyruvic Acid Content
The neck, basal plate, and skin of the onion bulbs were removed and blended to extract onion juice. The pyruvic acid content in the onion juice was recorded by an automated dinitrophenyl hydrazine method previously developed by our group [62,63]. Soluble solid content (SSC) was measured in the juice using a refractometer and expressed as • Brix.

Sugar Analysis
The sucrose, glucose, and fructose were analyzed using HPLC and an RI detector. A total of 20 µL of the sample was injected into the HPLC system which was connected to a binary pump (Perkin Elmer LC-200, Norwalk, CT, USA), an autosampler (Perkin Elmer LC-200), a refractive index-150 detector (SystemSpectra), and a carbohydrate column Rezex™ RCM-Monosaccharide Ca 2+ (8%) of 300 × 7.8 mm (Phenomenex, Torrance, CA, USA) equipped with a guard cartridge. The column temperature was maintained at 80 • C using a column heater (Jones chromatography, Lakewood, CO, USA). The water was used as a solvent at a flow rate of 0.6 mL/min that was degassed using degasser Plants 2020, 9, 1077 13 of 18 . Sugar concentrations were calculated using standard curves for sucrose, glucose, and fructose ranging from 1.25 to 20 mg/mL.

Protein and Mineral Analysis
Approximately 45 g pulp was stored at −80 • C for 24 h and lyophilized (Labconco Freeze-Dryer, Kansas City, MO, USA) for two days to obtain the dried powder. The dried samples were weighed, and the protein and mineral content was measured at the Texas AgriLife Extension Soil, Water, and Forage Testing Laboratory. Inductive coupled plasma-atomic emission spectroscopy (ICP-AES) (Spectro Genesis, Deutschland, Germany) was used to estimate the mineral content of onion.

Analysis of Total Phenolic Content, Antioxidant Capacity, and α-Amylase Assay
Total phenolics, DPPH, and ABTS radical scavenging activity of both onion cultivars were determined using our previously published methods [64,65]. Fresh onion samples (15 g) were extracted twice with 15 mL methanol. The extracts were pooled together and further used for quantification of total phenolics and free radical scavenging activities. All standards and samples were pipetted in triplicate into 96 well plates separately. The absorbance was measured using Synergy™ HT Multi-Mode Microplate Reader (BioTek, Instruments, Winooski, VT, USA) at 760, 515, and 734 nm for total phenolics, DPPH, and ABTS assays, respectively. The results of total phenolics were expressed as mg gallic acid equivalent/gram of fresh weight of samples, and radical scavenging activities were expressed as mg ascorbic acid equivalent/gram of dry weight sample.
The α-amylase inhibitory activity was measured using a published protocol with minor modifications [66]. Dextrose was used to prepare a standard curve at different concentrations. Acarbose was used as a positive control and methanol as a negative control to calculate the percentage inhibition.

Analysis of Flavonoids
Onion pulp (10 mg) was weighed and extracted with 20 mL methanol, vortexed for 15 s, sonicated for 30 min, and then centrifuged at 4480× g for 10 min. After decanting the filtrate, the residue was re-extracted with 20 mL methanol followed by the above procedure. The two extracts were combined, filtered, and transferred to an amber HPLC vial. An Agilent 1200 Series HPLC (Agilent, Foster City, CA, USA) system consisting of a degasser, quaternary pump, autosampler, column oven, and a diode array detector. The separation was carried out using an RP C18 Gemini series column (250 × 4.6 mm; 5 µm) (Phenomenex, Torrence, CA, USA). A 5 µL sample was injected into the column with a flow rate of 0.8 mL/min, the oven temperature was set at 35 • C, and the peaks were monitored at 210 and 280 nm with a run time of 30 min. The elution was carried out using gradient mode elution with acetonitrile (A) and 0.03 M phosphoric acid (B). Initially, elution was carried out at 98-75% B for (0-12 min), followed by 75-45% B (12-22 min), 45-5% B (22-26 min), 5-98% B (26-29 min) and returned to 98% B at 30 min. The column was equilibrated for 2 min before the next injection. Quantification of flavonoids was carried out using standards quercetin-3-glucoside, quercetin-3,4 -diglucoside, and quercetin. Flavonoid results were expressed as µg/g of fresh weight of the sample.

LC-HR-ESI-QTOF-MS Identification of Flavonoids
Flavonoids were identified in onion extract using Agilent 1290 liquid chromatography (Santa Clara, CA, USA) coupled to a maXis Impact high-resolution mass spectrometer (Bruker Daltonics, Billerica, MA, USA) according to our published paper [67]. Briefly, a chromatographic resolution was achieved by column Zorbax Eclipse plus (1.8 µm; 50 × 2.1 mm) with a gradient solvent system, (A) 0.1% formic acid in water, and (B) 0.1% formic acid in acetonitrile with a flow rate of 0.2 mL/min at 30 • C. Elution of flavonoids was performed by programming as follows: 2-25% B (12 min), 25-55% B (11 min), 55-98% B (4 min), 98-2% B (2 min), and 2 min isocratic at 2% B. The injection volume was 1 µL and postrun equilibrium was 1 min. Mass spectral analysis was performed by electrospray ionization (ESI) in positive ionization mode. Mass spectra (MS) and broadband collision-induced dissociation (bbCID) acquisition were acquired in the m/z 50-2000 scan range. Nitrogen was used as a nebulizer and drying gas. A nebulizer gas pressure and drying temperature was 3.2 bar and 250 • C, respectively, and the capillary voltage was kept at 3500 V. The external calibration of the mass spectrometer was performed by sodium formate solution clusters using the high-precision calibration mode. Software Data Analysis 4.3 was used for the determination of accurate mass for the molecular ions and precursors ions.

Analysis of Anthocyanins
Anthocyanin extraction was performed according to published paper [68]. Freshly cut red onion (10 g) was extracted with acidic methanol (1% formic acid). The sample was homogenized (1 min), sonicated for 30 min, and centrifuged at 7826× g under dark conditions. The supernatant was transferred to the new tubes, and residue was re-extracted twice with acidic methanol. All the supernatants were pooled, volume was measured, and the sample was kept at −80 • C for further analysis.

LC-HR-ESI-QTOF-MS Identification of Onion Anthocyanins
Anthocyanins were analyzed by 1290 Agilent LC system (Agilent, Santa Clara, CA, USA). A C18 column, rapid resolution high definition (RRHD) Zorbax Eclipse plus (1.8 µm; 50 × 2.1 mm) (Agilent, Santa Clara, CA, USA), was used for the chromatographic separation. The gradient mobile phase consisted of A) 0.1% formic acid in water and (B) 0.1% formic acid in acetonitrile. Mass spectral analysis was performed according to the published papers [69]. Briefly, a maXis impact mass spectrometer (Bruker Daltonics, Billerica, MA) was used for obtaining the mass spectra in ESI in positive ionization mode. MS and bbCID data were obtained at m/z 50-2000 scan range. Nitrogen was used as a nebulizer (gas pressure of 2.1 bar) and drying gas (8.0 L/min). The capillary ion voltage was 4500 V, and the drying gas temperature was 250 • C. External mass spectrometer calibration was performed by sodium formate solution. The determination of accurate mass data for the molecular ions was performed using the software Data Analysis 4.3.

Statistical Data
Each onion variety had 15 bulbs of an average weight of 170 g and was divided into five groups. The analysis was carried out on five grouped samples belonging to each onion variety. Each experiment was performed in triplicate, and all data are presented as the mean ± SD. Analysis of variance (ANOVA) was carried out using JMP pro 14 software. Excel software was used to prepare graphs, and multiple mean comparisons (p value < 0.05) were carried out by a Student's t-test. Principal component analysis (PCA) was performed by SIMCA-P+ software (version 16, Umetrics AB, Umea, Sweden) using the Pareto scaling method.

Conclusions
This study provides information describing the nutritional values in honeysuckle and sweet Italian red onions. The pungency of honeysuckle was lower than the artisan onions. The total flavonoid for honeysuckle and artisan onions was 449 and 345 µg/g FW, respectively. The total anthocyanin for honeysuckle onion was 103 µg/g FW, while for artisan onion was 86 µg/g FW. Honeysuckle onions showed relatively high levels of calcium, sodium, zinc, and copper along with nitrogen and protein content. The results indicated that the total flavonoids, total phenolic content, total anthocyanins,