Nutrients, bioactive non-nutrients and anti-nutrients in potatoes

Globally, potatoes account for only about 2% of the food energy supply, yet they are the predominant staple for many countries. In developed countries, potatoes account for 540 kJ (130 kcal) per person per day, while in developing countries, it is only 170 kJ (42 kcal) per person per day. In addition to energy, which is derived almost entirely from their carbohydrate content, many varieties of potatoes contribute nutritionally important amounts of dietary fibre (up to 3.3%), ascorbic acid (up to 42 mg/100 g), potassium (up to 693.8 mg/100 g), total carotenoids (up to 2700 mcg/100 g), and antioxidant phenols such as chlorogenic acid (up to 1570 mcg/100 g) and its polymers, and anti-nutrients such as α-solanine (0.001–47.2 mg/100 g); and lesser amounts of protein (0.85–4.2%), amino acids, other minerals and vitamins, and other beneficial and harmful bioactive components. Nutrient content depends on a number of factors, with variety being among the most important. Potato biodiversity is vast, with more than 4000 known varieties. Most belong to the species Solanum tuberosum, but another 10 species are cultivated and 200 wild species have been identified. Modern agricultural practices and climate change are contributing to the loss of potato biodiversity, and thus the loss of the genes coding for nutrient biosynthetic pathways. Knowledge of differences in nutrient composition of potatoes related to their genetic diversity will help guide strategies that may contribute to reducing biodiversity loss and improving food and nutrition security.     

Concentration of glycoalkaloids in the tuber of potatoes found in retail trade

Levels of glycoalkaloids were determined in potatoes sold in grocery shops in summer 1987 and during the period of potato storage (October 1987-April 1983). The average concentration of glycoalkaloids in 66 samples of unpeeled potatoes was 7.5 mg/100 g. In only two samples purchased on July 13th this level was slightly above 20 mg/100 g. Peeled potatoes contained glycoalkaloids in amounts several times lower than whole potatoes. The average concentration of glycoalkaloids was in peeled potatoes only 2.2 mg/100 g.     

Phenotypic, agronomic and nutritional characteristics of seven varieties of Andean potatoes

Potatoes are part of the staple food of Andean populations. Although there are more than 200 Andean potato varieties, only a few are cultivated at present, which endangers the biodiversity of the region. The objective of this paper was to characterize seven varieties of Andean potatoes (Collareja, Runa, Churqueña, Señorita, Imilla Colorada, Imilla Negra and Revolución) and to determine their phenotypic, functional and nutritional properties. The different varieties of Andean potatoes show differences in their agronomic properties, such as area of production and altitude yield per hectare, pest resistance and sowing and harvesting seasons. They are adapted to different altitudes, which influence their agronomic characteristics. Yield varies between 8000 and 18,000 kg/ha according to the variety. They present a diversity of forms, sizes and colors. The energy content ranges from 315 to 424 kJ/100 g, with these values being higher than those of the reference variety (239 kJ/100 g). Vitamin C content ranges from 10.5 mg/100 g found in Revolución varieties to 15.6 mg/100 g in Collareja potatoes; the vitamin C content in Spunta lies within this range (13.3 mg/100 g of potato). Increased knowledge of the nutritional, agronomic and functional properties of Andean potato varieties will contribute to the preservation of a biodiversity that is part of Argentina's regional heritage.     

The influence of genotype on the effects of impact damage and light exposure on the accumulation of glycoalkaloids in potato tubers

The experiment was carried out in 1999 with 24 Polish and 23 West European cultivars of potato tubers. The tubers were analysed for TGA content after 3 months of dark storage conditions in store-house (8 degrees C). 20 tubers of every cultivar were damaged and placed for a week to dark and under 15 W fluorescent lamps--13 mumol m-2 sec(-1)--equivalent to light in supermarkets. Glycoalkaloids content was determined with Bergers (1980) method. Tubers which had been damaged and exposed for a week to fluorescent light had two fold higher levels of TGA, than undamaged tubers stored at dark. It was found that content of glycoalkaloids in potato tubers and the increase of TGA content due to damage and light exposure depended on genotype. It was higher in varieties with higher level of these compounds, for example: Peppo, Albatros, Columbus and Santana (above 200 mg/kg fresh weight)--tab. I. The smaller increase occurred in tubers of varieties with low content of TGA: Polish--Irga, Grot, Baszta, Tokaj and West European--Satina, Ditta Gloria, Victoria--tab. I, II. Therefore it is important to breed new cultivars with low content of TGA.     

Phenolic acids in potatoes,vegetables, and some of their products

The aim of this study was to determine the distribution and contents of soluble and total phenolic acids in a wide range of vegetables consumed in Finland. The determinations were performed from the pooled samples (14 potato and 45 other vegetable samples). Soluble phenolic acids were extracted with methanolic acetic acid and a tentative quantification was performed by HPLC. The contents of total phenolic acids were determined by HPLC after alkaline and acid hydrolyses. Chlorogenic acid derivatives were the most dominant soluble phenolic acids, while caffeic acid was the most dominant phenolic acid aglycone in the samples studied. Highest contents of soluble phenolic acids were found in raw and cooked potato peels: 23–45 mg/100 g fresh weight calculated as aglycones. In addition, pot-grown lettuces, Chinese cabbage, broccoli, carrot, aubergine, Jerusalem artichoke, peanut and most of the boiled and peeled potato tubers contained more than 5 mg/100 g of soluble phenolic acids calculated as aglycones. Among the best vegetable sources of total phenolic acids were potatoes, with contents varying from 7.9 mg/100 g (cooked and peeled Rosamunda variety) to 52 mg/100 g (cooked peel of Van Gogh variety), and red cabbage, carrot, aubergine, Jerusalem artichoke, broccoli, pot-grown lettuce, spinach, radish and red beet, with contents from 11 mg/100 g (spinach) to 52 mg/100 g (pot-grown lettuce Lollo Rosso). Variation in the phenolic acid contents of the vegetables was either moderate or considerable and needs further research.     

The effect of frying on anthocyanin stability and antioxidant activity of crisps from red- and purple-fleshed potatoes (Solanum tuberosum L.)

Red- and purple-fleshed potatoes (Solanum tuberosum L.) are a good source of polyphenols, mainly anthocyanins as one of the most important components. The chemical composition with reducing sugars and the total polyphenol contents were analyzed in four purple potato varieties (Salad Blue, Vitelotte, Valfi, Blue Congo) and three red-fleshed potato varieties (Rosalinde, Herbie 26, Highland Burgundy Red). The anthocyanin composition of raw potato and potato crisps was characterized by high-performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS) method. Moreover, the antioxidant activity was measured with the radical scavenging assays using 2,2′-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical as well as ferric reducing ability of plasma assay (FRAP). In addition, colour parameters in prepared potato crisps were evaluated. Both red and purple-fleshed potato varieties contained high levels of total polyphenols (227–845 mg 100 g⁻¹ dry weight) and anthocyanins (21–109 mg 100 g⁻¹ dry weight). The process of frying caused degradation of anthocyanin compounds (38–70%). The HPLC–MS/MS analysis showed that pelargonidin and malvidin derivates were more stable during frying than petunidin derivatives. Although frying process affected the anthocyanin and polyphenol levels, obtained potato crisps exhibited bright intensive colour and good antioxidant activity.     

Effect of varying amounts of polyunsaturated fat and α-tocopherol on plasma and red cell content of α-tocopherol in the rat

The response of erythrocyte and plasma α-tocopherol levels to changes in dietary linoleate and vitamin E was studied in rats. Sixty wealing rats were fed a diet composed of 15.5% fat made up of a mixture of hydrogenated coconut oil and corn oil to give three levels of linoleic acid (3, 6, 9% by wieght) and three levels of α-tocopherol (30, 50, 100 mg/kg food) in the different experiments. After 8 weeks, blood was drawn by heart puncture, separated and analyzed for α-tocopherol in plasma and erythrocytes. Increased dietary linoleate resulted in a reduced α-tocopherol content of both plasma and red cells. However, only in the red cells were the changes significant when subjected to two way analysis of variance (p<0.05).     

Total and individual carotenoid profiles in Solanum phureja of cultivated potatoes: I. Concentrations and relationships as determined by spectrophotometry and HPLC

Total and individual carotenoid concentrations were determined by spectrophotometry and HPLC, in raw tubers of a sample of 23 accessions of Solanum phureja potatoes taken at random from the world germplasm collection following its stratification on tuber flesh color. Lutein, zeaxanthin, violaxanthin, antheraxanthin and β-carotene were detected in all accessions and three distinct patterns of carotenoid accumulation were evidenced by cluster analysis. Accessions in group 1 showed the highest concentrations of total carotenoids (1258–1840 μg 100 g⁻¹ FW) comprised largely of zeaxanthin (658–1290 μg 100 g⁻¹ FW) with very low or no presence of β-carotene (below 5.4 μg 100 g⁻¹ FW). Accessions in group 2 presented moderate total carotenoid concentrations with violaxanthin, antheraxanthin, lutein and zeaxanthin as the major carotenoids. Accessions in group 3 showed low concentrations of total carotenoids (97–262 μg 100 g⁻¹ FW) and very low or no zeaxanthin, with lutein and violaxanthin as the predominant carotenoids and relatively high concentrations of β-carotene (up to 27 μg 100 g⁻¹ FW). Five accessions with significant concentrations of zeaxanthin were identified with the accession 703566 showing the highest concentration (1290 μg 100 g⁻¹ FW). This value is to our knowledge higher than any value previously reported for potatoes, including those achieved through genetic modification. For the 23 S. phureja accessions, total carotenoid concentration was positively and significantly correlated with antheraxanthin and zeaxanthin concentrations, and negatively and significantly correlated with β-carotene concentration.     

Interrelationship and competition of α- and λ-tocopherol at the level of intestinal absorption, plasma transport and liver uptake

α- and λ-Tocopherol (T) were measured in the plasma of 3 groups of rats that were fed a normal or modified AIN-76 diet containing normal (NE), high (HE) or low (LE) vitamin E for 3 months. α-T levels (μg/ml±SD; n=10) were 7.6±1.0 (NE), 19.3±5.1 (HE) and 0.48±0.43 (LE). λ-T levels were 0.32±0.16 (NE), 0.02±0.05 (HE) and 0.20±0.30 (LE). 24 hrs after an oral dose of 50 mg λ-T; α-T levels (n=3) were 7.0±1.2 (NE), 10.7±3.7 (HE) and 1.0±0.3 (LE). λ-T levels were 5.7±2.2 (NE), 0.83±0.46 (HE) and 10.8±3.8 (LE). When 3 rats from groups NE and HE were fed low vitamin E for 3 days prior to the administration of 50 mg λ-T; α-T levels were 4.8±1.3 (NE) and 7.1±1.5 (HE); λ-T levels were 5.9±2.0 (NE) and 4.6±2.6 (HE). When rats in group LE received 50 mg α-T, levels increased to 10.0±0.8 μg α-T/ml and were 8 times higher than those of λ-T when a dose of 50 mg of each of α- and λ-T were fed. None or traces of λ-T were found in a liver cytosol protein (32000 MW) that binds α-T specifically (α-TBP) in all three groups. Small amounts of λ-T were detected in α-TBP in LE rats after they were fed 50 mg of λ-T. These data suggest that the mechanisms for intestinal absorption, plasma transport and liver uptake of vitamin E are specific for α-T. Only when the concentration of α-T is low, can λ-T successfully compete for binding sites at these three levels.     

Carotenoid Content in Different Varieties of Pumpkins

Due to the increasing interest in the supply with antioxidants and especially carotenoids in foods, pumpkins were analysed for their content of α -carotene, β -carotene, and lutein. A wide range of varieties of pumpkins that are commercially available in Austria was analysed. For this study the pumpkins were grown in Austria to obtain data that are relevant for local nutrition. The varieties analysed derived from three species i.e. Cucurbita pepo,C. maxima and C. moschata. Additionally, a cross breed of C. maxima and C. moschata was tested. The content of the carotenoids ranged from 0.06 to 7.4 mg/100 g for β -carotene, from 0 to 7.5 mg/100 g forα -carotene and from 0 to 17mg/100g for lutein.     

Cooking dependent loss of metabolites in potato breeding lines and their wild and landrace relatives

Elucidating and improving the nutritional value of staple crops is an important focus in breeding programs. Hence, wild and cultivated potatoes have been metabolite profiled to assess metabolic plasticity present in potato tubers and changes that occur in these after cooking. The present data highlighted metabolic similarities of certain wild species to breeding lines, indicating preference during domestication. In the case of potato, the cooking process has to be taken into consideration for the assessment of nutritional quality. The degree of nutritional change during cooking depends on several factors including cooking method, stability of metabolites with nutritional properties and chemotype of the varietal matrix. The differences between raw and boiled tubers were similar within each germplasm group. No notable distinctions of total phenolic levels could be observed within germplasm groups, whereas total carotenoids and glycoalkaloids were significantly decreased. Genotypes/cultivars with notable changes upon cooking distinguished them within their genotype group.     

Ascorbic acid concentration of native Andean potato varieties as affected by environment, cooking and storage

The ascorbic acid (AA) concentration of tubers was determined in 25 Andean potato varieties (Solanum tuberosum L.) grown in three environments, and the effect of cooking and storage time in subsets of samples was evaluated. Significant variation due to genotype, environment and genotype × environment (G × E) interaction was found. AA concentration in freshly harvested raw, peeled tubers ranged from 22.2 to 121.4 mg/100 g on a dry weight basis (DW) and from 6.5 to 36.9 mg/100 g on a fresh weight basis (FW) with the accession 704393 showing the highest levels of AA in all three locations. Differences in AA concentration were found among cooking methods and storage times; and significant non-crossover interactions with genotype were observed for both of these parameters. It was found that AA concentration of boiled tubers of the six varieties evaluated was higher than in oven and microwaved tubers and that AA concentration of tubers of the 23 varieties evaluated decreased with storage time. The variety 704393 retained 54 and 34% of its original AA concentration after boiling and storage during 26 weeks under farmer conditions. One hundred grams of fresh harvested boiled potatoes of this variety (704393) could provide adults with 17–20% of the recommended daily allowance (RDA) of AA.     

Investigation into the role of the cholinergic system in radiation-induced damage in the rat liver and ileum

It has been previously shown that acetylcholine (ACh) may affect pro-inflammatory and anti-inflammatory cytokines. The role of the cholinergic system in radiation-induced inflammatory responses and tissue damage remains unclear. Therefore, the present study was designed to determine the radio-protective properties of the cholinergic system in the ileum and the liver of rats. Rats were exposed to 8-Gy single-fraction whole-abdominal irradiation and were then decapitated at either 36 h or 10 d post-irradiation. The rats were treated either with intraperitoneal physiological saline (1 ml/kg), physostigmine (80 µg/kg) or atropine (50 μg/kg) twice daily for 36 h or 10 d. Cardiac blood samples and liver and ileal tissues were obtained in which TNF-α, IL-1β and IL-10 levels were assayed using ELISA. In the liver and ileal homogenates, caspase-3 immunoblots were performed and myeloperoxidase (MPO) activity was analyzed. Plasma levels of IL-1β and TNF-α increased significantly following radiation (P < 0.01 and P < 0.001, respectively) as compared with non-irradiated controls, and physostigmine treatment prevented the increase in the pro-inflammatory cytokines (P < 0.01 and P < 0.001, respectively). Plasma IL-10 levels were not found to be significantly changed following radiation, whereas physostigmine augmented IL-10 levels during the late phase (P < 0.01). In the liver and ileum homogenates, IL-1β and TNF-α levels were also elevated following radiation, and this effect was inhibited by physostigmine treatment but not by atropine. Similarly, physostigmine also reversed the changes in MPO activity and in the caspase-3 levels in the liver and ileum. Histological examination revealed related changes. Physostigmine experiments suggested that ACh has a radio-protective effect not involving the muscarinic receptors.     

Design, synthesis and pharmacological evaluation of new 1-[3-(4-arylpiperazin-1-yl)-2-hydroxy-propyl]-3,3-diphenylpyrrolidin-2-one derivatives with antiarrhythmic, antihypertensive, and α-adrenolytic activity

A series of novel arylpiperazines bearing a 3,3-diphenylpyrrolidin-2-one fragment were synthesized and evaluated for their binding affinity for α₁- and α₂-adrenoceptors (ARs), as well as their antiarrhythmic, and antihypertensive activities. The highest affinity for the α₁-AR was displayed by 1-{3-[4-(2-ethoxy-phenyl)-piperazin-1-yl]-2-hydroxy-propyl}-3,3-diphenylpyrrolidin-2-one (7), which binds with a pK_i = 7.28. The highest affinity for the α₂-AR was shown by 1-{3-[4-(2-methoxy-phenyl)-piperazin-1-yl]-2-hydroxy-propyl}-3,3-diphenylpyrrolidin-2-one (5), which binds with a pK_i = 6.68. Compound 7 was additionally evaluated in in vitro functional tests for its affinity for α_1B- and α_1D-AR, which gave pA₂ α_1B = 6.55 and pA₂ α_1D = 7.26. Among the compounds tested, compound 7 also had the highest prophylactic antiarrhythmic activity in adrenaline-induced arrhythmia in anaesthetized rats. Its ED₅₀ value was 1.1 mg/kg (i.v.). The compounds significantly decreased systolic and diastolic pressure in normotensive anaesthetized rats at doses of 2.5–5.0 mg/kg (i.v.) and their hypotensive effects lasted for longer than 1 h. It was found that the introduction of two phenyl ring substituents into the 3rd position of the pyrrolidin-2-one fragment gave compounds with affinity for both α₁- and α₂-AR. The substitution of the 2nd position in the phenyl piperazinyl fragment of the molecule was crucial for activity. To determine detailed information concerning the structure–activity relationship, a preliminary molecular modeling study was undertaken.     

Glycaemic index values for commercially available potatoes in Great Britain

The glycaemic response to eight potato varieties commercially available in Great Britain was compared against a glucose standard in a non-blind, randomised, repeated measure, crossover design trial. Seventeen healthy subjects (three males, fourteen females), mean age 32 (sd 13) years and mean BMI 22.3 (sd 3.6) kg/m2, were recruited to the study. Subjects were served portions of eight potato varieties and a standard food (glucose), on separate occasions, each containing 50 g carbohydrate. Capillary blood glucose was measured from finger-prick samples in fasted subjects (0 min) and at 15, 30, 45, 60, 90 and 120 min after the consumption of each test food. For each potato variety, the glycaemic index (GI) value was calculated geometrically by expressing the incremental area under the blood glucose curve (IAUC) as a percentage of each subject's average IAUC for the standard food. The eight potato varieties exhibited a wide range in GI values from 56 to 94. A trend was seen whereby potatoes with waxy textures produced medium GI values, whilst floury potatoes had high GI values. Considering the widespread consumption of potatoes in Great Britain (933-1086 g per person per week), this information could be used to help lower the overall GI and glycaemic load of the diets of the British population.     

Variations in the carotenoid and anthocyanin contents of Korean cultural varieties and home-processed sweet potatoes

The sweet potato is an important industrial crop and a source of food that contains useful dietary fiber and vitamins. Recently, orange- and purple-fleshed varieties have come under the spotlight due to their healthful components, carotenoids and anthocyanins, respectively. In this study, an HPLC-DAD method was applied to determine the carotenoid composition and content in nine Korean cultural varieties of sweet potato. Changes in carotenoid contents and composition were also observed during home-processing of an orange-fleshed cultivar with high carotenoid content (530 ± 60 μg/g of dry weight, DW as all-trans-β-carotene). A loss of the carotenoids was observed for all of the home-processing methods examined; the baked or boiled or steamed sweet potatoes had higher amounts of all-trans-β-carotene (246 ± 34, 253 ± 29 and 240 ± 21 μg/g DW, respectively) than pressure-cooked, sautéed and fried ones (194 ± 21, 201 ± 28 and 111 ± 19 μg/g DW, respectively). Interestingly, cis-isomer of the all-trans-β-carotene, 13Z-β-carotene was found in elevated amounts in all of the processed samples, particularly in baked, pressure-cooked and steamed sweet potatoes compared to control. Variations in anthocyanin content in the nine cultural varieties and home-processed sweet potatoes were also determined by an HPLC-DAD method.     

The ingredients in Saengshik,a formulated health food,inhibited the activity of α-amylase and α-glucosidase as anti-diabetic function

BACKGROUND/OBJECTIVES

We investigated total 26 ingredients of Saengshik which will be commercially produced as an anti-diabetic dietary supplement.

SUBJECTS/METHODS

Thirteen vegetables, nine cereals, three legumes and one seed were extracted with aqueous ethanol for 2 h at 60℃, and evaluated for their inhibitory effects against α-amylase and α-glucosidase and for total phenolic and flavonoid contents.

RESULTS

All ingredients inhibited α-amylase activity except cabbage. Strong inhibitory activity of α-amylase was observed in leek, black rice, angelica and barley compared with acarbose as a positive control. Stronger inhibition of α-glucosidase activity was found in small water dropwort, radish leaves, sorghum and cabbage than acarbose. All Saengshik ingredients suppressed α-glucosidase activity in the range of 0.3-60.5%. Most ingredients contained total phenols which were in the range of 1.2-229.4 mg gallic acid equivalent/g dried extract. But, total phenolic contents were not observed in carrot, pumpkin and radish. All ingredients contained flavonoid in the range of 11.6-380.7 mg catechin equivalent/g dried extract.

CONCLUSIONS

Our results demonstrate that Saengshik containing these ingredients would be an effective dietary supplement for diabetes.     

Chk1 suppression leads to a reduction in the enhanced radiation-induced invasive capability on breast cancer cells

Radiation therapy is generally effective for treating breast cancers. However, approximately 30% of patients with breast cancer experience occasional post-treatment local and distant metastasis. Low-dose (0.5 Gy) irradiation is a risk factor that promotes the invasiveness of breast cancers. Although an inhibitor of checkpoint kinase 1 (Chk1) suppresses the growth and motility of breast cancer cell lines, no study has investigated the effects of the combined use of a Chk1 inhibitor and radiation on cancer metastasis. Here, we addressed this question by treating the human breast cancer cell line MDA-MB-231 (in vitro) and mouse mammary tumor cell line 4 T1 (in vitro and in vivo) with γ-irradiation and the Chk1 inhibitor PD407824. Low-dose γ-irradiation promoted invasiveness, which was suppressed by PD407824. Comprehensive gene expression analysis revealed that low-dose γ-irradiation upregulated the mRNA and protein levels of S100A4, the both of which were downregulated by PD407824. We conclude that PD407824 suppresses the expression of S100A4. As the result, γ-irradiation-induced cell invasiveness were inhibited.     

The influence of nitrogen and potassium fertilisation on the content of polyphenolic compounds and antioxidant capacity of coloured potato

The effect of fertilisation rates of nitrogen: 0 (control treatment—no soil fertilisation), 40, 80 and 120 kg/ha and potassium: 0 (control treatment), 120, 150 and 180 kg/ha on the content of anthocyanins, phenolic acids and antioxidant capacity in purple–blue potato cv. ‘Blue Congo’ was examined. Anthocyanins and phenolic acids were identified and quantified by LC–MS and UPLC–PDA. Nitrogen was more effective in increasing the anthocyanin content—their quantity in tubers after nitrogen application was twice as much as that found after potassium application. Among phenolic acids, the dominant one was chlorogenic acid, the content of which significantly increased after nitrogen fertilisation at 120 kg/ha, in line with the increase in total concentration of phenolic acids and antioxidant capacity. The adjustment of nitrogen and potassium fertilisation levels during the growth of purple–blue potatoes seems to be an effective way to increase the expression of polyphenolic compounds in these cultivars. Therefore, fertilisation with N at 120 kg/ha and K at 120 and 150 kg/ha is recommended as a way to improve the content of biologically active compounds and antioxidant properties, and consequently, to enhance the nutritional value and the functionality of purple–blue potatoes.