A capillary electrophoresis laser-induced fluorescence method for analysis of potato glycoalkaloids based on a solution-phase immunoassay. 1. Separation and quantification of immunoassay products

Solution-phase immunoassays are typically faster and more precise than ELISAs. This research developed a solution-phase for the immunoassay of potato glycoalkaloids (GAs) based on quantification by capillary electrophoresis (CE) with laser-induced fluorescence (LIF) detection. Solanidine coupled to 4'-(aminomethyl)fluorescein and a polyclonal antibody solution were used as the immunoreagents. Unbound fluorescent solanidine was detected by CE-LIF (excitation 488 nm, emission 520 nm). Optimum resolution of immunoassay products was achieved with a buffer consisting of 50 mM phosphate, 10% (v/v) methanol, and 1.5 mM SDS, pH 7.5. A plot of signal vs log [GA] produced a sigmoidal curve typical of immunoassays. Analysis of extracts of sprouted Yukon Gold potato tubers and nonsprouted Yukon Gold tubers resulted in total [GA] of 98 microg/g (RSD 9%) and 55 microg/g (RSD 9%), respectively. The findings indicated that CE-LIF coupled with a solution-phase immunoassay can be used to quantify total GA in potatoes.     

Determination of potato glycoalkaloids using a liposome immunomigration, liquid-phase competition immunoassay

Polyclonal anti-solanine antibodies were raised and used in the assembly of a liposome immunomigration, liquid-phase competition strip immunoassay. In this format, a similar cross-reactivity was observed between the glycoalkaloids alpha-solanine and alpha-chaconine. The strip assay was implemented to quantitate total glycoalkaloids (TGA) from potatoes. Recoveries in spiked potato samples using the strip assay and water:acetic acid:sodium bisulfite extracting solvent were in the range of 84-111%. The values of the TGA quantitations by the strip assay as compared with those obtained by HPLC, in nonspiked tubers coming from cloned potato samples donated by potato breeders, were equivalent and highly correlated (r(2) = 0.91). The strip assay proved advantageous over HPLC for extra-laboratory measurements such as the rapid identification of samples that should be rejected due to an elevated TGA content.     

Glycoalkaloids and metabolites inhibit the growth of human colon (HT29) and liver (HepG2) cancer cells

As part of an effort to improve plant-derived foods such as potatoes, eggplants, and tomatoes, the antiproliferative activities against human colon (HT29) and liver (HepG2) cancer cells of a series of structurally related individual compounds were examined using a microculture tetrazolium (MTT) assay. The objective was to assess the roles of the carbohydrate side chain and aglycon part of Solanum glycosides in influencing inhibitory activities of these compounds. Evaluations were carried out with four concentrations each (0.1, 1, 10, and 100 microg/mL) of the the potato trisaccharide glycoalkaloids alpha-chaconine and alpha-solanine; the disaccharides beta(1)-chaconine, beta(2)-chaconine, and beta(2)-solanine; the monosaccharide gamma-chaconine and their common aglycon solanidine; the tetrasaccharide potato glycoalkaloid dehydrocommersonine; the potato aglycon demissidine; the tetrasaccharide tomato glycoalkaloid alpha-tomatine, the trisaccharide beta(1)-tomatine, the disaccharide gamma-tomatine, the monosaccharide delta-tomatine, and their common aglycon tomatidine; the eggplant glycoalkaloids solamargine and solasonine and their common aglycon solasodine; and the nonsteroidal alkaloid jervine. All compounds were active in the assay, with the glycoalkaloids being the most active and the hydrolysis products less so. The effectiveness against the liver cells was greater than against the colon cells. Potencies of alpha-tomatine and alpha-chaconine at a concentration of 1 microg/mL against the liver carcinoma cells were higher than those observed with the anticancer drugs doxorubicin and camptothecin. Because alpha-chaconine, alpha-solanine, and alpha-tomatine also inhibited normal human liver HeLa (Chang) cells, safety considerations should guide the use of these compounds as preventative or therapeutic treatments against carcinomas.     

Potato glycoalkaloids and metabolites: roles in the plant and in the diet

Potatoes, members of the Solanaceae plant family, serve as major, inexpensive low-fat food sources providing energy (starch), high-quality protein, fiber, and vitamins. Potatoes also produce biologically active secondary metabolites, which may have both adverse and beneficial effects in the diet. These include glycoalkaloids, calystegine alkaloids, protease inhibitors, lectins, phenolic compounds, and chlorophyll. Because glycoalkaloids are reported to be involved in host-plant resistance and to have a variety of adverse as well as beneficial effects in cells, animals, and humans, a need exists to develop a clearer understanding of their roles both in the plant and in the diet. To contribute to this effort, this integrated review presents data on the (a) history of glycoalkaloids; (b) glycoalkaloid content in different parts of the potato plant, in processed potato products, and in wild, transgenic, and organic potatoes; (c) biosynthesis, inheritance, plant molecular biology, and glycoalkaloid-plant phytopathogen relationships; (d) dietary significance with special focus on the chemistry, analysis, and nutritional quality of low-glycoalkaloid potato protein; (e) pharmacology and toxicology of the potato glycoalkaloids comprising alpha-chaconine and alpha-solanine and their hydrolysis products (metabolites); (f) anticarcinogenic and other beneficial effects; and (g) possible dietary consequences of concurrent consumption of glycoalkaloids and other biologically active compounds present in fresh and processed potatoes. An enhanced understanding of the multiple and overlapping aspects of glycoalkaloids in the plant and in the diet will benefit producers and consumers of potatoes.     

High-performance liquid chromatographic determination of the glycoalkaloids alpha-solanine and alpha-chaconine in 12 commercial varieties of Mexican potato

The glycoalkaloid content in 12 commercial varieties of Mexican potatoes was measured by HPLC in both the peel and the flesh of the potato. The principal glycoalkaloids alpha-solanine and alpha-chaconine were present in higher concentration in the peel than in the flesh of all varieties. The main alkaloid in the peel of the potatoes was alpha-chaconine and comprised about 65-71% of the total glycoalkaloids. The high concentration of alpha-chaconine in peel, which is more toxic than alpha-solanine, gives more protection to the tuber against predators. The total alkaloids in the peel of Alpha, Juanita, Michoacan, Norte?a, Rosita, and Tollocan varieties were higher than the limit recommended for food safety. However, the peel represents less than 10% of the total tuber in most of the varieties. The total alkaloids contained in the peel of Atzimba, Lopez, Marciana, Montsama, Murca, and Puebla was lower than the limits recommended for food safety. The glycoalkaloid content in the boiled peeled potatoes was less than 9 mg/100 g but in Alpha, Montsama, and Puebla varieties, both glycoalkaloids were absent. According to the results, the consumption of the 12 commercial varieties of Mexican potatoes does not represent any danger to human health.     

Inheritance of morphological characters and glycoalkaloids in potatoes of somatic hybrids between dihaploid Solanum acauleand tetraploid Solanum tuberosum.

Steroidal glycoalkaloids occur in potatoes and are reported to impart resistance to phytopathogens including bacteria, fungi, and insects. Because glycoalkaloids can be passed to progenies during breeding programs designed to develop improved potatoes, it is of importance to determine the quality of desired characteristics and the composition of glycoalkaloids of new somatic hybrids. The objective of this study was to determine the appearance, size, and shape (morphological characters) as well as the glycoalkaloid content of potato tubers of somatic hybrids between tetraploid Solanum tuberosum cv. Dejima (2n = 4x = 48 chromosomes) and the dihaploid clone ATDH-1 (2n = 2x = 24 chromosomes) induced by anther culture from Solanum acuale-T (acl-T, 2n = 4x = 48 chromosomes). Tuber size and shape in somatic hybrids were in accord with those of cv. Dejima, whereas the tuber skin color resembled that of ATDH-1. Thin-layer chromatography, high-performance liquid chromatography, and gas-liquid chromatography/mass spectrometry studies showed that the two steroidal glycoalkaloids (alpha-chaconine and alpha-solanine) were present in the tubers of S. tuberosum, whereas acl-T and ATDH-1 tubers were found to contain alpha-tomatine and demissine. The concentrations of total glycoalkaloids in both acl-T and ATDH-1 was >100 mg/100 g of fresh weight tuber cortex, much higher than in S. tuberosum. All somatic hybrids, except one clone, contained four glycoalkaloids (alpha-chaconine, alpha-solanine, alpha-tomatine, and demissine) derived from the fusion parents. The lack of alpha-tomatine in the remaining clone may be due to somaclonal variation. The results show that character expression is influenced by ploidy level and that total glycoalkaloid levels in most somatic hybrids were intermediate between those of the fusion parents. The possible significance of these findings for plant breeding and food safety is discussed.     

LC-MS analysis of solanidane glycoalkaloid diversity among tubers of four wild potato species and three cultivars (Solanum tuberosum)

Secondary metabolites in potato tubers include both phytonutrients and plant defense compounds. The extent these small molecules vary among different potato genotypes is not well characterized. LC-MS analysis of tuber extracts from seven potato genotypes showed that one large source of small molecule variation is the glycoalkaloids. Glycoalkaloids are involved in the resistance of potatoes to pathogens and pests, but they also have implications for human health and nutrition. This study focused on glycoalkaloids with solanidane or solanidane-like aglycones, of which over 50 were tentatively identified, many of which appeared to be novel glycoalkaloids. Results suggested the variety of glycoalkaloids in potatoes is considerably greater than previously thought. Dissecting the role of these many glycoalkaloids in human health or pest and pathogen resistance will be a formidable undertaking.     

Sulfur compounds reduce potato toxins during extrusion cooking.

Free sulfhydryl groups in sulfur compounds have been reported to act directly on natural toxins to reduce toxicity. The objective of this study was to reduce protease inhibitors and glycoalkaloids in simulated snack foods by the addition of sulfur-containing compounds prior to extrusion. Thiamine, methionine, and benzyl disulfide were added to potato flakes at levels of 0.5% or 1.0% prior to twin-screw extrusion. Total and free thiols and protease inhibitors were monitored before and after extrusion by colorimetric assays. Potato glycoalkaloids were analyzed by HPLC and by immunoassay. Extrusion reduced potato flake disulfide bonds; disulfide bonds were higher in samples containing added sulfur compounds. Trypsin inhibitor activity was reduced by as much as 79% by extrusion plus methionine. Extrusion significantly reduced carboxypeptidase inhibitor, but only when benzyl disulfide and 0.5% methionine were not added. One percent methionine and thiamine resulted in 60% reductions in glycoalkaloids.     

Anticarcinogenic effects of glycoalkaloids from potatoes against human cervical, liver, lymphoma, and stomach cancer cells

Methods were devised for the isolation of large amounts of pure alpha-chaconine and alpha-solanine from Dejima potatoes and for the extraction and analysis of total glycoalkaloids from five fresh potato varieties (Dejima, Jowon, Sumi, Toya, and Vora Valley). These compounds were then evaluated in experiments using a tetrazolium microculture (MTT) assay to assess the anticarcinogenic effects of (a) the isolated pure glycoalkaloids separately, (b) artificial mixtures of the two glycoalkaloids, and (c) the total glycoalkaloids isolated from each of the five potato varieties. All samples tested reduced the numbers of the following human cell lines: cervical (HeLa), liver (HepG2), lymphoma (U937), stomach (AGS and KATO III) cancer cells and normal liver (Chang) cells. The results show that (a) the effects of the glycoalkaloids were concentration dependent in the range of 0.1-10 mug/mL (0.117-11.7 nmol/mL); (b) alpha-chaconine was more active than was alpha-solanine; (c) some mixtures exhibited synergistic effects, whereas other produced additive ones; (d) the different cancer cells varied in their susceptibilities to destruction; and (e) the destruction of normal liver cells was generally lower than that of cancer liver cells. The decreases in cell populations were also observed visually by reversed-phase microscopy. The results complement related observations on the anticarcinogenic potential of food ingredients.     

Solanidine hydrolytic extraction and separation from the potato (Solanum tuberosum L.) vines by using solid-liquid-liquid systems

Solanidine is a steroidal aglycon of potato (Solanum tuberosum L.) glycoalkaloids and a very important precursor for the synthesis of hormones and some pharmacologically active compounds. Glycoalkaloids are hydrolyzed by mineral acid, yielding solanidine. This paper deals with the kinetics of solanidine hydrolytic extraction in different solid-liquid-liquid systems. The dried and milled potato (S. tuberosum L.) vines were used as a source of glycoalkaloids and as the solid phase. The solutions of hydrochloric acid in 2 and 10% (w/v) aqueous acetic acid, in 50% (volume) aqueous methanol, and in 50% (volume) aqueous ethanol were first liquid phase, and the medium for glycoalkaloid extraction from potato vines and their hydrolysis to solanidine. The chloroform, trichloroethylene, or carbon tetrachloride were the second, organic, liquid phase and the medium for solanidine extraction. This procedure combines three different processes: extraction of glycoalkaloids from potato vines, their hydrolysis to solanidine, and the extraction of solanidine, in a single step. The term hydrolytic extraction of solanidine was used for these processes. The purpose of the paper was to choose an optimal solid-liquid-liquid system for solanidine extraction and to define the procedure for its isolation from the organic liquid phase. The best degree of solanidine hydrolytic extraction (DHE) of more than 98% was achieved when 10% (w/v) hydrochloric acid in 50% (volume) methanol were the first liquid phase and chloroform was the second liquid phase, after 90 min. The yield of solanidine (q(S)) under these conditions is calculated to be 0.24 g/100 g of potato vines. Approximately 78% of the maximal possible yield of solanidine was isolated from chlorofom liquid phase. The IR and MS spectra of isolated solanidine were recorded.     

Glycoalkaloid and calystegine contents of eight potato cultivars

Diverse procedures have been reported for the separation and analysis by HPLC of the two major glycoalkaloids present in potatoes, alpha-chaconine and alpha-solanine. To further improve the usefulness of the HPLC method, studies were carried out on the influence of several salient parameters on the analysis of the two potato glycoalkaloids. Effects on retention (elution, separation) times of the (a) composition and pH of the mobile phase (acetonitrile and phosphate buffer), (b) concentration of the phosphate buffer, (c) capacity values of column packing of four commercial HPLC amino columns, (d) column temperature were studied. Except for pH, all of the variables significantly influenced the retention times. The results make it possible to select analysis conditions that produce well-separated as well as symmetrical peaks of the two glycoalkaloids. This improved HPLC method (limit of detection of approximately 150 ng) was evaluated with extracts from the cortex of one whole potato variety (May Queen) grown in Japan and the freeze-dried peel and flesh from the following eight cultivars grown in the United States: Atlantic, Dark Red Norland, Ranger Russet, Red Lasoda, Russet Burbank, Russet Norkota, Shepody, and Snowden. In addition, the same samples were analyzed by GC-MS for the presence of two water-soluble nortropane alkaloids, calystegine A(3) and calystegine B(2), reported to be potent glycosidase inhibitors. The following ranges for the eight varieties of total glycoalkaloid and calystegine levels were observed: dry flesh, 5-592 and 6-316 mg/kg; dry peel, 84-2226 and 218-2581 mg/kg; dry whole potatoes, 40-883 and 34-326 mg/kg; wet flesh, 1-148 and 1-68 mg/kg; wet peel, 12-429 and 35-467 mg/kg; wet whole potatoes, 7-187 and 5-68 mg/kg. The possible significance of the results to plant and food sciences is discussed.     

Analysis of phenolic compounds by high-performance liquid chromatography and liquid chromatography/mass spectrometry in potato plant flowers, leaves, stems, and tubers and in home-processed potatoes

Potato plants synthesize phenolic compounds as protection against bruising and injury from bacteria, fungi, viruses, and insects. Because antioxidative phenolic compounds are also reported to participate in enzymatic browning reactions and to exhibit health-promoting effects in humans, a need exists for accurate methods to measure their content in fresh and processed potatoes. To contribute to our knowledge about the levels of phenolic compounds in potatoes, we validated and used high-performance liquid chromatography and liquid chromatography/mass spectrometry to measure levels of chlorogenic acid, a chlorogenic isomer, and caffeic acid in flowers, leaves, stems, and tubers of the potato plant and in home-processed potatoes. The total phenolic acid content of flowers (626 mg/100 g fresh wt) was 21 and 59 times greater than that of leaves and stems, respectively. For all samples, chlorogenic acid and its isomer contributed 96-98% to the total. Total phenolic acid levels (in g/100 g fresh wt) of peels of five potato varieties grown in Korea ranged from 6.5 to 42.1 and of the flesh (pulp) from 0.5 to 16.5, with peel/pulp ratios ranging from 2.6 to 21.1. The total phenolic acid content for 25 American potatoes ranged from 1.0 to 172. The highest amounts were present in red and purple potatoes. Home processing of pulp with various forms of heat induced reductions in the phenolic content. The described methodology should facilitate future studies on the role of potato phenolic compounds in the plant and the diet.     

Coloured potatoes (Solanum Tuberosum L.) – Anthocyanin Content and Tuber Quality

Anthocyanins gain more and more importance as natural colourants. Besides many other plant species, coloured potatoes could serve as a potential source. Therefore, 27 potato cultivars and four breeding clones of different origin were analysed for their anthocyanin contents in fresh weight (fw). On average the highest amounts of anthocyanins were found in the skin (0.65 g kg⁻¹ fw) of potatoes. The corresponding values of samples taken from whole tubers (0.31 kg⁻¹ fw) and flesh (0.22 kg⁻¹ fw) were significantly lower (p<0.03). The analysis revealed considerable differences in the amounts of anthocyanins between the 31 cultivars/breeding clones. Among them ȁ8Peru Purpleȁ9 revealed the highest anthocyanin content in the skin with 2.96 g kg⁻¹ fw. A similar high value was reached by ȁ8Violettfleischigeȁ9 and clone 1.81.202–92 N. Also for the other two types of samples, flesh and whole tubers, these three genotypes exhibited the highest level of anthocyanins. Interestingly, different rates of nitrogen fertilization at 100 and 200 kg ha⁻¹ had no significant effect on the pigment content of potatoes. The same was observed with respect to the year or the location of plant growth. There were also no significant changes in the anthocyanin contents of tubers during storage for 135 days. In dry matter, starch and protein contents the coloured potato cultivars/breeding clones were comparable with traditional cultivars. Further tests have shown that the glycoalkaloids were mainly localized in the skin of coloured potatoes.     

Tracer studies on the incorporation of [2-14C]-DL-mevalonate into chlorophylls a and b, alpha-chaconine, and alpha-solanine of potato sprouts

Chlorophyll and glycoalkaloids are synthesized in different parts of the potato plant including leaves, tubers, and sprouts. Although light stimulates the biosynthesis of both constituents, the question of whether the two biosynthetic pathways are under the same genetic control has not been resolved. This study investigated the dynamics of incorporation of labeled [2-(14)C]-DL-mavalonate into chlorophyll a, chlorophyll b, and the glycoalkaloids alpha-chaconine and alpha-solanine in potato sprouts after 7 and 14 days of storage in the light and in the dark. No chlorophyll synthesis occurred in the dark. Fractionation of the "glycoalkaloid" extract followed by high-performance liquid chromatography produced four peaks. The fractions were collected and analyzed for radioactivity. About 80% of the radioactivity resided in fraction 1, the composition of which is unknown. Two of the fractions, with 1-14% of the original label, were alpha-chaconine and alpha-solanine. The radioactivity derived from mevalonate largely resides in unidentified compound(s) eluting as a single peak on the HPLC column before the peaks associated with the glycoalkaloids. The specific radioactivity of alpha-chaconine and alpha-solanine increased approximately 2-fold in going from 7 to 14 days of exposure in the light and in the dark. These and additional observations point to the near identity of the dynamics of biosynthesis of the two glycoalkaloids. These data also implicate a non-mevalonate pathway for the synthesis of both chlorophylls and the glycoalkaloids and are consistent with independent genetic control of the concurrent formation of the two classes of compounds during greening of potatoes.     

Distribution of ascorbic acid in potato tubers and in home-processed and commercial potato foods

HPLC was used to analyze the content of ascorbic acid (AA) in tubers of four Korean potato cultivars (Chaju, Sumi, Deso, and Dejima), in a series of baked, boiled, braised, fried, microwaved, pressure-cooked, and sauteed potato slices from the Dejima cultivar and in 14 commercial Korean and 14 processed potato foods sold in the United States (chips, snacks, mashed potatoes, fries). The AA content for the four cultivars ranged from 16 to 46 mg/100 g of fresh weight. The distribution of AA in each of the eight potato slices (sticks, plugs) cut horizontally from the stem end of the Dejima potato ranged from 6.8 to 19.3% of the total. The corresponding distribution in seven sticks cut vertically was much narrower, ranging from 11.7 to 17.5% of the total. Losses of AA in water (pH 5.2) were significantly greater than in 5% metaphosphoric acid (pH 1.0). Less degradation occurred in water solutions of the vitamin stored at 1 degree C than at 25 degrees C. Losses of AA observed during home-processing of three varieties with low (Dejima, 16 mg/100 g), intermediate (Sumi, 32 mg/100 g), and high (Chaju, 42 mg/100 g) AA contents were as follows: boiling in water, 77-88%; boiling in water containing 1-3% NaCl, 61-79%; frying in oil, 55-79%; sauteing, 61-67%; pressure-cooking in water, 56-60%; braising, 50-63%; baking, 33-51%; and microwaving, 21-33%. The content of the Korean foods ranged from trace amounts to 25 mg/100 g and that of the U.S. foods from 0.4 to 46 mg/100 g. These results permit optimization of the vitamin C content of the diet by (a) using high-vitamin C potato varieties such as Chaju, (b) selecting sticks cut horizontally for frying, (c) baking or microwaving rather than boiling or frying, and (d) selecting commercial potato foods with a high vitamin C content.     

基于流形学习算法的马铃薯机械损伤机器视觉检测方法

针对马铃薯表面芽眼和凹凸不平的影响,使之马铃薯机械损伤难以检测的问题,该文提出了一种基于流形学习算法的马铃薯机械损伤检测方法。首先利用马铃薯图像的显著图分割出马铃薯区域,然后利用主成分分析(principal component analysis,PCA)、等距映射(isometric mapping,Isomap)和局部线性嵌入(locally-linear embedding,LLE)3种流形学习方法提取马铃薯区域图像特征参数,然后分别建立基于3种流形特征的支持向量机(support vector machine,SVM)分类模型PCA-SVM、Isomap-SVM和LLE-SVM,利用网格搜索法(grid search)、遗传算法(genetic algorithm,GA)以及粒子群算法(particle swarm optimization,PSO)3种模型参数优化方法,优化支持向量机模型的惩罚参数c和RBF核参数g,以建立最优分类模型,最后比较3种分类模型的识别效果,确定最优分类模型。研究结果表明,PCA-SVM分类模型对训练集识别率为100%,测试集识别率为100%;Isomap-SVM分类模型对训练集识别率为100%,测试集识别率为91.7%;LLE-SVM分类模型对训练集识别率为100%,测试集识别率为91.7%,表明PCA、Isomap和LLE 3种流形学习方法用于马铃薯机械损伤检测是可行的,其中PCA-SVM分类模型检测效果最优。     

Dehydrotomatine and alpha-tomatine content in tomato fruits and vegetative plant tissues

Tomato plants (Lycopersicon esculentum) synthesize the glycoalkaloids dehydrotomatine and alpha-tomatine, possibly as a defense against bacteria, fungi, viruses, and insects. We used a high-performance liquid chromatography method with UV detection at 208 nm for the analysis of these compounds in various tissues. An Inertsil ODS-2 column with a mobile phase of acetonitrile/20 mM KH2PO4 (24/76, v/v) afforded good separation of the two glycoalkaloids in mini-tomato extracts, fruit harvested at different stages of maturity, and calyxes, flowers, leaves, roots, and stems. The two peaks appeared at approximately 17 and approximately 21 min. Recoveries from tomato fruit extracts spiked with dehydrotomatine and alpha-tomatine were 87.7 +/- 6.8 and 89.8 +/- 3.4% (n = 5), respectively. The detection limit is estimated to be 0.39 microg for dehydrotomatine and 0.94 microg for alpha-tomatine. The dehydrotomatine and alpha-tomatine content of tomatoes varied from 42 to 1498 and 521 to 16 285 microg/g of fresh weight, respectively. The ratio of alpha-tomatine to dehydrotomatine ranged from 10.9 to 12.5 in tomatoes and from 2.3 to 7.8 in the other plant tissues. These results suggest that the biosynthesis of the glycoalkaloids is under separate genetic control in each plant part. Degradation of both glycoalkaloids occurred at approximately the same rate during maturation of the tomatoes on the vine. An Inertsil NH2 column, with acetonitrile/1 mM KH2PO4 (96/4, v/v) as the eluent, enabled the fractionation of commercial tomatidine into tomatidenol and tomatidine, the aglycons of dehydrotomatine and alpha-tomatine, respectively. The information should be useful for evaluating tomatoes and vegetative tissues for dehydrotomatine/alpha-tomatine content during fruit development and their respective roles in host-plant resistance and the diet.     

Improving the screening process for the selection of potato breeding lines with enhanced polyphenolics content

Efficient selection of potato varieties with enhanced nutritional quality requires simple, rapid, accurate, and cost-effective assays to obtain tuber chemical composition information. Our objective was to develop simple protocols to determine phenolics, anthocyanins, and antioxidant capacity in polyphenolic extracts of potatoes using Fourier transform infrared spectroscopy combined with multivariate techniques. Lyophilized potato samples (23) were analyzed. Polyphenolic compounds were extracted from potatoes and applied directly applied onto a three-bounce ZnSe crystal for attenuated total reflectance measurements in the infrared region of 4000 to 700 cm (-1). Robust models were generated (r > or = 0.99) with standard error of cross-validation values of 4.17 mg gallic acid equivalent/100 g (total phenolics), 0.87 mg pelargonidin-3-glucoside/100 g (monomeric anthocyanins), and 130.8 mumol Trolox equivalent/100 g (antioxidant capacity) potato powder. In addition, classification models discriminated potato samples at the species and variety level. Application of a simple infrared spectroscopic protocol allowed simultaneous rapid quantification of specific nutritional components in potatoes and efficient selection of value-added potato varieties.     

Immunoaffinity sample purification and MALDI-TOF MS analysis of alpha-Solanine and alpha-chaconine in serum

A sample purification technique was developed for the detection of potato glycoalkaloids (GAs) in blood serum by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). GAs were extracted from spiked serum (5 mL) using a C(18) solid-phase extraction cartridge. The GAs were then selectively captured on antibody-coated agarose beads. The agarose beads were washed with water and the GAs eluted with 25 microL of methanol. MALDI-TOF MS was used to detect the GAs in the methanol eluent. Immunoaffinity sample purification of the GAs effectively reduced the signal suppression observed during the analysis of unpurified samples. alpha-Chaconine and alpha-solanine were detected in serum spiked with 1 ng/mL of each GA.     

Antioxidant profiling of native Andean potato tubers (Solanum tuberosum L.) reveals cultivars with high levels of beta-carotene, alpha-tocopherol, chlorogenic acid, and petanin

The antioxidant profile of 23 native Andean potato cultivars has been investigated from a human nutrition perspective. The main carotenoid and tocopherol compounds were studied using high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD) and a fluorescence detector, respectively, whereas polyphenols (including anthocyanins in colored tubers) were identified by means of both HPLC-mass spectrometry and HPLC-DAD. Antioxidant profiling revealed significant genotypic variations as well as cultivars of particular interest from a nutritional point of view. Concentrations of the health-promoting carotenoids, lutein and zeaxanthin, ranged from 1.12 to 17.69 microg g(-1) of dry weight (DW) and from 0 to 17.7 microg g(-1) of DW, with cultivars 704353 and 702472 showing the highest levels in lutein and zeaxanthin, respectively. Whereas beta-carotene is rarely reported in potato tubers, remarkable levels of this dietary provitamin A carotenoid were detected in 16 native varieties, ranging from 0.42 to 2.19 microg g(-1) of DW. The amounts of alpha-tocopherol found in Andean potato tubers, extending from 2.73 to 20.80 microg g(-1) of DW, were clearly above the quantities generally reported for commercial varieties. Chlorogenic acid and its isomers dominated the polyphenolic profile of each cultivar. Dark purple-fleshed tubers from the cultivar 704429 contained exceptionally high levels of total anthocyanins (16.33 mg g(-1) of DW). The main anthocyanin was identified as petanin (petunidin-3-p-coumaroyl-rutinoside-5-glucoside). The results suggest that Andean potato cultivars should be exploited in screening and breeding programs for the development of potato varieties with enhanced health and nutritional benefits.