Liquid Chromatography–Hybrid Linear Ion Trap–High-Resolution Mass Spectrometry (LTQ-Orbitrap) Method for the Determination of Glycoalkaloids and Their Aglycons in Potato Samples

Potatoes produce biologically active secondary metabolites like glycoalkaloids and their aglycons, which may have both adverse and beneficial effects in the diet. A new analytical method that uses liquid chromatography–mass spectrometry (LTQ-Orbitrap) has been developed for the analysis of glycoalkaloids and their aglycons in potato samples. Two glycoalkaloids, α-solanine and α-chaconine, and two aglycons, demissidine and solasodine, were quantified in potato samples. Samples were extracted using methanol, purified on an SPE Strata C₁₈ cartridge, and then analyzed in HPLC–mass spectrometry (LTQ-Orbitrap) with the FTMS operating in full scan at a resolving power of 30,000 (FWHM), enabling the detection and accurate mass measurement and with the ITMS mode operating in MRM (multiple reaction monitoring) for glycoalkaloids and their aglycons using the [M + H]⁺ ions and their optimized collision energies. After validation, the method was applied to screen different type of potatoes, and some cooking experiment were conducted.     

The influence of thermal process of coloured potatoes on the content of glycoalkaloids in the potato products

Potato products made from potato varieties with coloured flesh (red and blue-fleshed potatoes) may be an interesting alternative to traditional products. The purpose of this study was to determine the influence of peeling, cooking and frying of red and blue-fleshed potato tubers on the content of glycoalkaloids (α-solanine and α-chaconine) in processed potato products. The material taken for the study consisted of seven coloured potato varieties. French fries and crisps were prepared from two potato variety: Rosalinde and Blue Congo. The content of total glycoalkaloids (TGA) in raw material before and after peeling, in cooked unpeeled and peeled potatoes and also in fried potato products have been determined by HPLC method.     

A simplified method for the determination of total glycoalkaloids in potato tubers

A simplified method for the determination of total glycoalkaloids (TGA) in potato tubers has been developed in which potato tissue is extracted with dilute sulphuric acid and the extract is hydrolysed directly. Analysis is completed in less than 4 h using very simple apparatus and reagents. A colorimetric procedure employing bromothymol blue is used for quantitation. A study of the hydrolysis of α-solanine and α-chaconine and the stability of solanidine and solanthrene under hydrolysis conditions, which was made in order to define optimum conditions for the method, showed that hydrolysis time and temperature are quite critical if reproducible aglycone recovery is to be obtained. The results obtained using the method for tubers of fourteen experimental samples with a wide range of TGA contents compare well with corresponding results obtained using a lengthier and more tedious literature method. Its simplicity makes it a suitable method for plant breeders to use to measure the TGA content of new cultivars of potatoes.     

Potato Glycoalkaloids: occurrence,biological activities and extraction for biovalorisation – a review

Potato tuber (Solanum tuberosum L.) is the fourth most important agricultural product after wheat, rice and maize. With a total production of 388 million in 2017, c.a. 70% of this total production is processed in developed countries, producing a large amount of potato peel waste (PPW) as by-product. Although PPW is considered as a zero-value by-product by the feed industry because it is too fibrous, for other recycling industries it is an inexpensive by-product due to its significant contents of some interesting nutrients particularly polyphenols and glycoalkaloids. In potato, and Solanum species in general, many glycoalkaloids, predominantly α-chaconine and α-solanine, have been chemically and structurally identified. However, further research is needed to expand the knowledge of the biological values of potato glycoalkaloids in order to develop a recycling process to extract these technologically and nutritionally interesting bioactive ingredients for different sectors, in particular, the agricultural, food and pharmaceutical ones, which are demanding natural, safe and eco-friendly ingredients.     

马铃薯不同品种各器官糖苷生物碱累积规律研究

为探究马铃薯块茎、茎、叶中糖苷生物碱累积规律,本研究选用云南省2个主栽马铃薯品种丽薯6号、青薯9号以及具有推广潜力的2个新品种滇薯47、滇薯23为试验材料,采用超高效液相色谱-串联三重四级杆质谱仪(UHPLC-MS/MS),测定了不同时期块茎、茎、叶的α-卡茄碱、α-茄碱含量。结果表明:茎、叶中糖苷生物碱含量均随着生长进程的推进逐渐增高,在收获时达到最高,滇薯47收获期茎、叶总糖苷生物碱(Steroidal glycoalkaloids,SGAs)含量达256.84和427.25 mg/100 g·FW,显著高于其他三个品种(P<0.05)。而马铃薯块茎累积规律与茎、叶相反,随着块茎的成熟,块茎表皮、皮层和髓部α-卡茄碱、α-茄碱、总SGAs含量逐渐降低,并且收获时可食用部分(皮层和髓部)含量均低于国际推荐标准20 mg/100 g·FW,在安全食用范围内。综上,四个不同品种马铃薯块茎中糖苷生物碱含量随着马铃薯成熟逐渐降低;茎、叶中糖苷生物碱含量随着马铃薯成熟逐渐升高。滇薯47收获期茎、叶总糖苷生物碱含量显著(P<0.05)高于其他三个品种,可作为提取糖苷生物碱进行综合利用的备选品种。     

Toxic and antifeedant activities of potato glycoalkaloids against Trogoderma granarium (Coleoptera: Dermestidae)

The total glycoalkaloid fraction (TGA) and the two glycoalkaloids, α-chaconine and α-solanine of potato, Solanum tuberosum, were isolated. Their toxic and antifeedant activities against the Khapra beetle, Trogoderma granarium Everts were investigated. Results indicated considerable toxicity, especially when adults were topically treated with the glycoalkaloids. The TGA fraction was the most toxic with LC₅₀’s of 16.7 and 11.9 μg/mg insect, 48 and 96 h post treatment, respectively. LC₅₀’s of α-chaconine and α-solanine 96 h post treatment were 18.1 and 22.5 μg/mg insect, respectively. Moderate toxicities were recorded when insects were confined on dry-film residues of botanicals with LC₅₀’s ranging between 26.1 and 56.6, and 19.4 and 45.7, μg/cm² 48 and 96 h post treatment, respectively. Nutritional studies using the flour disc bioassay revealed significant reduction in the growth rate (RGR), food consumption rate (RCR) and food utilization (ECI) by T. granarium at concentrations ranging between 20 and 30 mg g⁻¹ food with feeding deterrent indices reaching 82.4% with the TGA fraction. When tested as binary or crude alkaloidal mixtures, toxic and antifeedant activities of glycoalkaloids were increased, indicating some additive interaction among these botanicals. There is potential for use of such compounds to protect stored grains from insect infestation.     

Glycoalkaloids (α-chaconine and α-solanine) contents of selected Pakistani potato cultivars and their dietary intake assessment

Glycoalkaloids (α-solanine and α-chaconine) are naturally occurring toxic compounds in potato tuber (Solanum tuberosum L.) that cause acute intoxication in humans after their consumption. Present research was conducted to evaluate α-chaconine, α-solanine, and total glycoalkaloids (TGAs) contents in the peel and flesh portions by high-performance liquid chromatography method in selected Pakistani potato cultivars. The α-solanine content varies 45.98 ± 1.63 to 2742.60 ± 92.97 mg/100 g of dry weight (DW) in peel and from 4.01 ± 0.14 to 2466.56 ± 87.21 mg/100 g of DW in flesh. Similarly, α-chaconine content varied from 4.42 ± 0.16 to 6818.40 ± 211.07 mg/100 g of DW in potato peel and from 3.94 ± 0.14 to 475.33 ± 16.81 mg/100 g DW in flesh portion. The TGA concentration varied from 177.20 ± 6.26 to 5449.90 ± 192.68 mg/100 g of DW in peel and from 3.08 ± 0.11 to 14.69 ± 0.52 mg/100 g of DW in flesh portion of all the potato cultivars tested. All the potato cultivars contained lower concentration of TGA than the limits recommended as safe, except 2 cultivars, that is FD8-3 (2539.18 ± 89.77 mg/100 g of DW) and Cardinal (506.16 ± 17.90 mg/kg). The dietary intake assessment of potato cultivars revealed that Cardinal, FD 35-36, FD 8-3, and FD 3-9 contained higher amount of TGA in whole potato, although FD 8-3 only possessed higher content of TGA (154.93 ± 7.75) in its flesh portion rendering it unfit for human consumption. Practical Application: This paper was based on the research conducted on toxic compounds present in all possible potato cultivars in Pakistan. Actually, we quantify the toxic compounds (glycoalkaloids) of potato cultivars through HPLC and their dietary assessment. This paper revealed safety assessment and their application in food industries especially potato processing.     

Glycoalkaloids in potatoes

The glycoalkaloids present in the cultivated potato plant might result in their being unacceptable by present-day food standards, if that vegetable were introduced today. The alkaloids are derived biosynthetically from cholesterol. The range of glycoalkaloids found in nature is given. Two main methods of determining these alkaloids have been developed, enabling a general screening procedure to be employed by growers. The advent of protoplast techniques has opened up the possibility of many new species and they present the chemist with new problems. There can be a conflict between the requirement of pest- and disease-resistant potatoes and those with low levels of glycoalkaloids. Damage and microbial infection to potatoes may cause glycoalkaloids to develop. In the end, the consumer must be the final arbiter.     

Quantitative analysis of phenolic components and glycoalkaloids from 20 potato clones and in vitro evaluation of antioxidant,cholesterol uptake,and neuroprotective activities

Potato (Solanum tuberosum L.) is one of the most important food crops in the world and provides essential nutrients. With an aim to develop potato varieties for functional food or nutraceutial applications, we have conducted metabolomic profiling, total phenolics, chlorogenic acid, anthocyanins, and glycoalkaloids analyses on 20 selected potato clones within the Canadian potato breeding program of Agriculture and Agri-Food Canada. Pigmented potatoes in general contain higher levels of phenolic components, including chlorogenic acid and anthocyanins. Levels of phenolics were retained with granulation processing of pigmented potato tubers, but glycoalkaloids were significantly reduced with granulation. The pigmented potatoes also have higher antioxidant activity reaching up to 35% of that for berries, measured as their potency in scavenging DPPH radicals. Extracts of the 20 potato clones (peel, tuber, and granule) were also evaluated for in vitro effects on liver LDL cholesterol uptake and protection of cortical neurons from cell death caused by oxygen glucose deprivation (OGD). These potato extracts in general showed mild activity in enhancing LDL cholesterol uptake in liver HepG2 cells, and also protected cortical neurons against OGD induced cell death, with extracts from granules of six of the potato clones showing significant neuroprotective effects. The bioactive components are not dependent on pigmentation of potato clones. These novel bioactivities identified in potatoes warrant in-depth investigations in the future. Taken together, our results provide further evidence for the enhanced health beneficial components in potato.     

Genetic and environmental effects on levels of glycoalkaloids in cultivars of potato (Solanum tuberosum L.)

Glycoalkaloids were assayed in fifty-five potato cultivars, fifty-four breeding lines and one other species (S. stolonifer). The total glycoalkaloid content ranged from 16·3 μg/g FW for Alpha to 317·0 μg/g FW for Berita, with most values lying between 35 and 65 μg/g. The α-solanine content, as a percentage of total glycoalkaloids, ranged from 28·3% for Avenir to 57·0% for H42, with the majority of values lying between 38% and 46% α-solanine. There was a highly significant correlation between high total glycoalkaloid content and per cent α-solanine (P < 1%). The presence of β₂-chaconine was also related in a highly significant way to high total glycoalkaloid content. Potatoes grown at Yanco (hot, dry, inland climate) contained more glycoalkaloids (～60%) than when grown at Glen Innes (cooler, high altitude climate). However, there was no significant difference between total and relative glycoalkaloid levels of cultivars grown at Glen Innes and Healesville (coastal, temperate climate). A significantly higher per cent α-solanine content, but not total glycoalkaloid content, was observed for potatoes grown in the second year at Glen Innes.     

Zur Bestimmung der Solanum-Alkaloide Solanin und Chaconin

Zusammenfassung Es wurde eine quantitative Bestimmungsmethode für Solanin und Chaconin in den Knollen, Keimen und Blattern vonsolanum tuberosum entwickelt, die a) einer schonenden Aufarbeitung des Glykosidgemisches aus dem Kartoffelmaterial durch Extraktion mit Pyridin Rechnung trägt und b) eine quantitative Bestimmung des Glykosidgemisches gaschromatographisch durch Derivatisierung mit Trimethylsilyl-Donoren ermöglicht.

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On the determination of the solanum alkaloids solanine and chaconine

Summary A new analytical method for quantitative determination of solanine and chaconine in potato tubers, sprouts and leaves has been developed: a) The extraction with pyridine causes a careful isolation of glycoalkaloids; b) the glycoalkaloids are determined by gaschromatography after silylation.

     

GLYCOALKALOID CONCENTRATION IN BY-PRODUCTS of POTATO STARCH EXTRACTION AS MEASURED BY MATRIX-ASSISTED LASER DESORPTIONIIONIZATION MASS SPECTROMETRY

Starch, potato protein concentrate, and potato pulp were produced in order to determine the fate of endogenous toxic glycoalkaloids during potato processing. Potato protein concentrate was precipitated from potato fruit water using acid and heat. Glycoalkaloid concentrations were determined using matrix- assisted laser desorption/ionization mass spectrometry. No correlation was observed between tuber protein concentration and yield of potato protein concentrate (r = 0.257). Glycoalkaloids could not be detected in starch extracted from tubers with a glycoalkaloid concentration of 6.6 mg/i 00 g (fwb). Dry potato protein concentrate and dry potato pulp produced from the same tubers contained 60 and 50 mg glycoalkaloid/100 g, respectively. the apparent partitioning of glycoalkaloids into the protein concentrate and pulp indicates toxicity might be a concern for these products, given that a maximum acceptable level of 20 mg glycoalkaloid/100 g is often cited for tubers.     

高效液相色谱串联质谱法检测马铃薯及马铃薯粉中α-茄碱和α-卡茄碱含量

建立了高效液相色谱-串联质谱同时测定马铃薯及马铃薯粉中α-茄碱与α-卡茄碱含量的方法。样品采用10%乙酸水溶液匀浆提取3 min,马铃薯粉提取液经Bond Elut C18 SPE柱净化后,采用C18色谱柱分离,液相色谱串联质谱仪检测。结果表明,α-茄碱和α-卡茄碱在0.01~1.00 μg/mL范围内线性关系良好,相关系数分别为0.9998和0.9997。马铃薯和马铃薯粉在低、中、高三个添加浓度范围内,回收率在90.0%~110%之间,相对标准偏差在1.6%~5.0%之间。马铃薯中α-茄碱和α-卡茄碱的定量限分别为0.80和0.42 μg/kg,马铃薯粉中α-茄碱和α-卡茄碱的定量限分别为25和14 μg/kg(S/N=10)。本方法简单快速,灵敏度高,重复性好,适用于马铃薯及马铃薯粉中的α-茄碱和α-卡茄碱检测。     

基质辅助激光解吸电离飞行时间质谱定性分析啤酒中糖类条件的优化

通过选择不同基质(2,5-二羟基苯甲酸、super DHB、2,4,6-三羟基苯乙酮)和设置不同啤酒样品稀释倍数(从原液到1 000倍稀释),优化了MALDI TOF MS定性分析啤酒中糖类的试验条件。研究结果显示,3种基质中,2,4,6-三羟基苯乙酮应用于MALDI TOF MS对啤酒中糖类表征的能力优于另外两种基质。当以2,4,6-三羟基苯乙酮为基质,啤酒样品稀释10倍时,MALDI TOF MS可达良好的定性分析效果。     

Mass Fragmentation Studies of α-Tomatine and Validation of a Liquid Chromatography LTQ Orbitrap Mass Spectrometry Method for Its Quantification in Tomatoes

Tomatoes, members of the Solanaceae plant family, produce biologically active secondary metabolites, including glycoalkaloids, which may have both adverse and beneficial biological effects. By using the linear ion trap (LIT) mass spectrometry, multistage collision-induced dissociation (CID) experiments (MS ⁿ ) were performed to elucidate characteristic fragmentation pathways of the glycoalkaloid α-tomatine. High-resolution with high-accuracy mass analysis using an Orbitrap Fourier transform MS (FTMS) with higher-energy CID (HCD) was used to produce mass spectra data across a wide spectral range for confirmation of proposed ion structures and formulae. In addition, a new liquid chromatography method that utilized LTQ Orbitrap MS was developed for the analysis of α-tomatine in tomatoes. Recoveries of α-tomatine were >96.0 % with relative standard deviations (RSD) below 7.98 %. The limit of detection (LOD) was 0.002 mg/kg. The limit of quantitation (LOQ) was 0.005 mg/kg. The linear range was between 0.010 and 10 mg/kg with an excellent correlation coefficient (R ²)?≥?0.9991. Various tomato samples were analyzed for method application, and the level of α-tomatine in the 11 samples analyzed ranged from 0.0011to 0.3077 mg/kg.     

Determination of α-amino nitrogen in pea protein hydrolysates: a comparison of three analytical methods

Three spectrophotometric methods, using 2,4,6-trinitrobenzenesulphonic acid (TNBS), o-phthaldialdehyde (OPA) or ninhydrin, for the determination of α-amino nitrogen in pea protein isolates and hydrolysates were compared. The determined amounts of α-amino nitrogen differed greatly, depending on the method used. The TNBS and OPA methods produced comparable results, whereas the data obtained with the ninhydrin method were only half of the TNBS or OPA values. Colour stability, recovery of the standard from the protein matrix and reproducibility of the results were determined. The methods showed good accuracy (SE 1–3%) with recovery values of the standard (l-leucine) from the protein matrix of 91, 111 and 75% for the OPA, ninhydrin and TNBS method, respectively.     

High levels of glycoalkaloids in the established swedish potato variety magnum bonum

In 1986, potentially toxic levels of the glycoalkaloids α-solanine and α-chaconine were unexpectedly found in tubers of the established Swedish consumer potato variety Magnum Bonum, leading to the imposition of a conditional sales ban on such potatoes. The combined amounts of α-solanine and α-chaconine in more than 300 commercial lots of Magnum Bonum potatoes analysed as a consequence of the ban ranged from 61 to 665 mg kg^?1 fresh weight with an average of 254 mg kg^?1. Sixty-six percent of the samples exceeded a temporary maximum residue limit of 200 mg kg^?1, 8% were above 400 mg kg^?1. Peeling did not significantly remove the glycoalkaloids in tubers with a high content. The occasional glycoalkaloid elevation was initially attributed to the unusually cold and rainy conditions during the late part of the season in 1986, but subsequent investigations have failed to confirm this hypothesis. Varietal characteristics are likely to have been involved since most other common Swedish varieties seemed to have had normal glycoalkaloid levels in 1986. There were no indications of serious or widespread adverse health effects in consumers due to the high glycoalkaloid levels, although there was circumstantial evidence that a few cases of temporary gastrointestinal disturbances were caused by consumption of Magnum Bonum potatoes with glycoalkaloid concentrations in the range 310–1000 mg kg^?1.     

On the colour reactions of potato glycoalkaloids in strong acids in the presence of paraformaldehyde

The colour reaction of potato glycoalkaloids, containing solanidine as steroid, with strong acids and paraformaldehyde was examined to elucidate the kinetics and mutual relationship of the ‘Clarke’ and ‘Marquis’ reactions. It was found that the influence of time of addition of paraformaldehyde was the major factor in deciding the type of colour changes encountered. This factor and the specific absorption kinetics have important consequences for the use of these types of colour reactions as a quantitative assay. According to the structural similarity of the steroidal part of potato glycoalkaloids and cholesterol, colour reactions of both have been compared, indicating that both steroids react in strong acids in the presence of an oxidator, provided that the more lipophilic character of cholesterol is taken into account. Therefore a similar mechanism of a serial oxidation of carbonium ions as in the case of cholesterol, is suggested as the basis for these specific colour reactions of potato glycoalkaloids.     

Quality of organically and conventionally grown potatoes: Four-year study of micronutrients, metals, secondary metabolites, enzymic browning and organoleptic properties

The quality of potatoes from organic and conventional farming was investigated in this study. Tubers of eight potato varieties, organically and conventionally produced at one or two geographical sites in controlled field trials, were collected in four consecutive harvests from 1996-1999. The parameters analysed included nitrate, trace elements (As, Cd, Co, Cu, Fe, Hg, Mn, Ni, Pb, Se, Zn), vitamin C, potato glycoalkaloids, as well as chlorogenic acid, polyphenol oxidase and rate of tuber enzymic browning. The results indicated lower nitrate content and higher vitamin C and chlorogenic acid content to be the parameters most consistently differentiating organically from conventionally produced potatoes. Elevated concentrations of glycoalkaloids were also observed throughout the experiments in some potato varieties grown in organic farming systems. Principal component analysis (PCA) of the analytical and other data using three PCs confirmed a good separation between the organically and conventionally produced potatoes when studied in single crop years. However, score-plots (objects) and loading-plots (variables) of pooled results from the consecutive harvests showed that between the years' changes and also variety as well as geographical variations are equally or more important factors determining the quality of potatoes than the farming system. Further studies of various marker compounds of potato quality related to the organic or conventional farming systems should be performed before unbiased information can be given to the consumers.