Glycoalkaloid Concentrations in Aerial Tubers of Potato ( Solanum tuberosumL)

The total glycoalkaloid concentrations in aerial and subterranean tubers of 14 potato genotypes were measured using high-performance liquid chromatography immediately after harvest. Post-harvest, aerial tubers from all genotypes were exposed to 144 h continuous fluorescent light; additionally three genotypes (cvs Home Guard, Kerrs Pink and Desiree) were subjected to mechanical wounding prior to glycoalkaloid analysis. Variations in glycoalkaloid concentrations between aerial tubers taken from a single genotype (cv Kerrs Pink) were determined by analysis of eight aerial tubers formed in the second leaf axil, selected from separate individual plants. Irrespective of genotype, total and individual glycoalkaloid concentrations were higher in aerial than in subterranean tubers. The highest glycoalkaloid concentrations were found in aerial tubers of cv Kerrs Pink (1343·0 mg kg⁻¹ FW) and lowest in cv Lindsey (301·0 mg kg⁻¹ FW). Ratios of α-chaconine: α-solanine in aerial tubers differed significantly ( P< 0·05) from those in subterranean tubers of cv Cara, Golden Wonder, Home Guard, Lindsey, Maris Piper, Record and 8859 indicating that exposure to light during aerial tuber growth enhanced the synthesis of one glycoalkaloid to a greater degree than the other. In all cultivars except cv Maris Piper, exposure of aerial tubers to 144 h continuous fluorescent light post-harvest increased total and individual glycoalkaloids compared with dark-treated controls. However, the ratios of α-chaconine: α-solanine in all genotypes except cv Golden Wonder (decreased α-chaconine: α-solanine, P< 0·05) were not significantly altered in comparison with dark controls, indicating that light exposure of aerial tubers post-harvest fails to enhance selectively synthesis of individual glycoalkaloids in the majority of cultivars. Regardless of cultivar, total glycoalkaloid, α-solanine and α-chaconine concentrations were higher in wounded than unwounded aerial tubers. Wounding stimulated synthesis of α-solanine more than α-chaconine ( P< 0·05) in cv Home Guard and Desiree. Glycoalkaloid concentrations in aerial tubers varied widely from a minimum of 1010 mg kg⁻¹ to a maximum of 2520 mg kg⁻¹ FW when harvested from individual plants of cv Kerrs Pink but selected from equivalent positions on the plant. Throughout the experiments large, non-significant increases in total and individual glycoalkaloid concentrations were recorded following light and wounding treatments. The scientific implications of aerial tuber formation are discussed.     

Glycoalkaloid Concentration of Potato Tubers Following Exposure to Daylight

The total glycoalkaloid concentrations in white- (cv Pentland Hawk), pink- (cv Kerrs Pink) and red- (cv Desiree) skinned potato tubers were measured following 21 days exposure to daylight using high-performance liquid chromatography. Average daytime irradiance during this period was 232 μmol m⁻² s⁻¹. Regardless of cultivar, glycoalkaloid concentrations were increased after light exposure compared with initial concentrations. Glycoalkaloid concentrations fluctuated with time and continuous accumulation of glycoalkaloids with time was not demonstrated. Glycoalkaloid synthesis was maximal in the sequence cv Kerrs Pink<cv Pentland Hawk<cv Desiree. Exposure to daylight altered the ratio of α-chaconine: α-solanine in tubers of cv Desiree but not those in cv Pentland Hawk and Kerrs Pink. Glycoalkaloid concentrations in all cultivars were higher than the recommended food safety level, this was reached after 8 days in cv Kerrs Pink and Desiree and at 13 days in Pentland Hawk. The implications of these results in terms of food safety are discussed.     

Glycoalkaloid content of early potato varieties

Samples of Swedish domestic early potatoes were collected from wholesalers and analysed for their content of glycoalkaloids (GA), α-solanine and α- chaconine, using a modified HPLC procedure. The varieties included were, in order of increasing GA content; Maris Bard, Ukama, Pro vita, Evergood Eldorado, Maria, Early Puritan, Silla and Ulster Chieftain. The average total GA content (α-solanine and α-chaconine combined) for the different varieties ranged from 51 to 221 mg kg^?1 fresh weight. α-Solanine constituted on average between 35 and 41% of the GA detected. The GA concentrations in individual samples were in the range 31-344 mg kg^?1. The variety Ulster Chieftain accounted for 88% of the samples above 200 mg kg ^?1. The results obtained with tubers grown experimentally in field trials in two different years were consistent with the findings for commercially grown potatoes in terms of GA content rank among varieties.     

Light‐induced glycoalkaloid accumulation of potato tubers (Solanum tuberosum L)

The total glycoalkaloid concentration of non‐sprouted potato tubers, cvs Marfona, Fianna, Maris Piper, Kestrel and Golden Wonder, was measured following 15 days of continuous illumination (250 µmol m⁻² s⁻¹ photosynthetically active radiation) using high‐performance liquid chromatography. Comparisons were made of the influence of four sources of illumination: fluorescent tube‐type warm white, high‐pressure sodium, high‐pressure mercury types MB/U and MBFR/U. Irrespective of cultivar, glycoalkaloid concentrations of tubers placed in the dark remained relatively constant from day 0 to day 15 and did not exceed food safety values of 200 mg kg⁻¹ FW. A highly significant cultivar, light and cultivar × light (P < 0.01) interaction was recorded. Cultivar Kestrel was shown to be light‐sensitive with high rates of glycoalkaloid accumulation irrespective of light source, and cv Maris Piper was demonstrated to be light‐insensitive. In the majority of cultivars tested, maximal rates of glycoalkaloid accumulation were recorded following exposure of tubers to sodium or fluorescent light, and minimal rates of accumulation were recorded following exposure of tubers to mercury (MB/U and MBFR/U) illumination. In virtually all cases glycoalkaloid concentrations steadily increased with time during light exposure with no indication of cessation. In some instances the α‐chaconine/α‐solanine ratio decreased over 15 days of illumination (P < 0.05), indicating enhanced α‐solanine synthesis over that of α‐chaconine. The implications of these results in terms of consumer safety are discussed. © 1999 Society of Chemical Industry     

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.     

Effect of bruising on the total glycoalkaloid and chlorogenic acid content of potato (Solanum tuberosum) tubers of five cultivars

Tubers from five potato cultivars were selected on the basis of their low, intermediate or high rates of glycoalkaloid synthesis in response to stresses such as light or cold storage temperatures. The tubers were subjected to a standard degree of damage sufficient to cause bruising but not severe damage such as cracking or splitting. Increases in glycoalkaloid levels in response to damage were observed in all cultivars. Importantly, the rates of glycoalkaloid synthesis in response to damage were in good agreement with cultivar response to light and cold temperature stress. The cultivars, Ailsa and Eden, exhibited a slower response than the higher synthesis rates observed in Pentland Dell or Brodick. The cultivar Torridon exhibited severe internal damage symptoms throughout the tuber as opposed to localised bruising observed in the other cultivars. The extensive cell death observed in the tubers of the cultivar Torridon severely curtailed glycoalkaloid and chlorogenic acid synthesis. The increased levels of glycoalkaloids in response to bruising damage ranged from approximately 27% (Ailsa, Torridon) to 130% for the cultivar Brodick. Chlorogenic acid levels increased in two cultivars (Brodick and Torridon) but not in the others, Ailsa, Eden and Pentland Dell. The α-chaconine/α-solanine ratios observed within the five cultivars were in good agreement with previous research. The consistency across years is notable, indicating a strong relationship in the synthesis of the two glycoalkaloids. The results are discussed in terms of implications for the potato industry, for the retail trade and also for selection within potato breeding programmes. © 1998 SCI.     

马铃薯糖苷生物碱的水解及其工业应用

马铃薯糖苷生物碱是马铃薯中重要的植物次级代谢产物,在马铃薯的自身防御过程中起到了重要的作用,但同时也给马铃薯产品的品质带来很大的负面影响。本文主要从马铃薯块茎中两种主要的糖苷生物碱α-卡茄碱和α-茄碱的毒性、对马铃薯产品的影响,去除糖苷生物碱的方法以及马铃薯糖苷生物碱水解的研究进展及意义等方面进行综述。本文着重阐述了马铃薯糖苷生物碱在高/低酸浓度下的水解机理、影响水解的因素以及糖苷生物碱对马铃薯浓缩蛋白所带来的影响。期望通过对马铃薯糖苷生物碱水解的综述引起人们对其应用更为广泛的关注,并对马铃薯废弃物的再利用起到指导作用。      

Variation in glycoalkaloid concentration of potato tubers harvested from mature plants

Individual tubers from mature plants of cultivars Pentland Dell and Estima were harvested from experimental plots in two successive years and analysed for α‐solanine, α‐chaconine and total glycoalkaloid concentration (α‐solanine and α‐chaconine combined) using high‐performance liquid chromatography. Mean tuber glycoalkaloid concentration per plant was strongly affected by genotype and was much higher in plants of Pentland Dell (10.0 and 16.3 mg per 100 g fresh weight in 1994 and 1995, respectively) than Estima (4.0 and 4.3 mg per 100 g fresh weight in 1994 and 1995, respectively). The variation between plants in mean tuber glycoalkaloid concentration, expressed as coefficient of variation, was similar for the two cultivars in both years. Variation within plants was higher for cultivar Pentland Dell than Estima for both years but it was statistically significant only in 1995. Tuber position within a plant had no effect on glycoalkaloid concentrations in tubers of similar size. An inverse relationship between total glycoalkaloid concentration and tuber fresh weight of individual tubers was found for both cultivars and small tubers of Pentland Dell (20–40 g fresh weight) exceeded the safety limit of 20 mg per 100 g fresh weight. The pattern of glycoalkaloid accumulation differed between genotypes and appeared related to tuber growth. The implications of these results in terms of food safety are discussed. © 1999 Society of Chemical Industry     

The effect of gamma irradiation on glycoalkaloid and chlorophyll synthesis in seven potato cultivars

The use of gamma irradiation to control sprouting and increase the length of storage time of potatoes has been proposed as an alternative to cold storage or the use of chemical sprout suppressants. Indeed, it is applied on a commercial-scale to potatoes in Japan. This research reports on the effects of different levels of gamma irradiation on seven potato cultivars in relation to chlorophyll and glycoalkaloid synthesis on subsequent exposure to light after a period of storage. There were significant genotype differences between cultivars in their response to gamma irradiation, with some cultivars exhibiting dramatically reduced levels of glycoalkaloid synthesis compared with others. Also, cultivars responded differently to variable irradiation levels. The implications of the results are discussed in relation to public health concerns and selection within potato breeding programmes. © 1997 SCI.     

A simplified procedure for quantification of potato glycoalkaloids in tuber extracts by H.p.l.c.; comparison with ELISA and a colorimetric method

An improved high-performance liquid chromatography (h.p.l.c.) procedure for determination of glycoalkaloid levels in potato tubers has been developed in which Sep-Pak cartridges replace the commonly used alkaline precipitation for clean-up of tuber extracts. Glycoalkaloids are extracted from fresh tuber tissue into an aqueous medium, the extract is submitted to clean-up and α-solanine and α-chaconine are quantitatively separated on a reversed phase column with ethanolamine modifier added to the mobile phase. Potato tubers were comparatively analysed for their glycoalkaloid content by this and two other methods: a recently developed immunoassay (ELISA) and a colorimetric procedure representing the traditional chemical approach. Agreement between the h.p.l.c. and the other methods was good.     

Is there a link between greening and light-enhanced glycoalkaloid accumulation in potato (Solanum tuberosumL) tubers?

Potato (Solanum tuberosum L) tubers (cvs Pentland Dell and Record) were treated with the chlorophyll biosynthesis inhibitors 4-amino-5-fluoropentanoic acid (AFPA) and 3-amino-2,3-dihydrobenzoic acid (gabaculine), and subsequently exposed to daylight for up to 10 days prior to pigment and glyco-alkaloid analysis. AFPA inhibited the accumulation of total chlorophyll (Chl) by between 50 and 70% in both cultivars throughout the duration of light exposure. The synthesis of Chl b was inhibited by over 80% in both cultivars. Neither inhibitor had a significant effect on light-enhanced glycoalkaloid accumulation. It is concluded that there is no direct metabolic link between Chl and glycoalkaloid biosynthesis. © 1998 SCI.     

Light exposure and wounding: synergistic effects on steroidal glycoalkaloid accumulation in potato tubers during storage

Potato tubers contain undesirable steroidal glycoalkaloids (SGAs), which have evoked global concern in terms of feed and food safety due to their toxic effects in humans. The cultivar Unica was exposed to a combination of light and wounding. SGA content among different tissues was analysed. Our results showed that SGA contents of tubers subjected to light was higher than that of intact tubers stored in darkness, and SGA content in the skin varied with time; however, SGA content in the flesh remained stable at a relatively low level. SGA content in the wound was higher than that of intact tubers. Importantly, light and wounding were shown to have synergistic effects on SGA content in the tuber, which only influenced SGA content within approximately 3 mm of the wound surface. Our study provides a theoretical basis for the reasonable and safe consumption of potatoes.     

Glycoalkaloid Content and Anthocyanin Stability to Alkaline Treatment of Red-Fleshed Potato Extracts

Red-fleshed potato (Solanum tuberosum) breeding clones were screened for steroidal glycoalkaloid (SGA) content. SGAs and anthocyanins (ACN) were characterized by HPLC and Mass Spectroscopy (MS). Total SGA ranged from 2.0 to 36.3 mg/100g tuber. Two cultivars with highest anthocyanin content, showed low levels of SGAs. The effect of alkaline treatments on SGA precipitation, anthocyanin content and profile was studied by adjusting the pH of aqueous extracts from 7.6 to 11. Complete removal of SGAs from colored extracts was achieved at pH > 9.2, however it caused substantial anthocyanin loss. Best results were obtained at pH 8.0 with 30% monomeric anthocyanin degradation and 90% SGA precipitation.     

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。     

The Effect of Low-Temperature Storage on the Glycoalkaloid Content of Potato (Solanum tuberosum) Tubers

Tubers from six cultivars selected on the basis of their rates of glycoalkaloid accumulation in response to light exposure were stored at 10, 7 and 4°C. After 9 weeks at 10°C a subset from each cultivar was removed and subsequently stored at lower temperatures. Samples were removed after 9, 18 and 24 weeks storage and analysed for their glycoalkaloid content. At all temperatures the rate of glycoalkaloid accumulation was independent of the level found at harvest and significant interactions were found between cultivar and temperature. The highest rates of accumulation were seen in tubers from the cultivars Brodick and Pentland Crown stored at 4°C. During the first 9 weeks of storage at this temperature the glycoalkaloid content of these two cultivars increased by 7·4 and 19·1 mg per 100 g fresh weight respectively and thereafter remained constant. At 7°C glycoalkaloid content tended to increase more rapidly than at 10°C with again the greatest increases being found for Brodick and Pentland Crown. In the case of the former glycoalkaloid content increased linearly during the 24 weeks of the experiment but the glycoalkaloid content of Pentland Crown tubers stored at 7°C increased rapidly in the first 9 weeks and thereafter increased more slowly, reaching a final value which exceeded the recommended maximum glycoalkaloid concentration for human consumption by 50%. Cultivars which did not accumulate glycoalkaloids rapidly in response to light exposure were the most stable and least sensitive to storage temperature. Tubers transferred to colder conditions nine weeks after storage at 10°C did not accumulate glycoalkaloids at a similar rate to those placed in similar conditions soon after harvest. © 1997 SCI     

Effect of environmental stress during tuber development on accumulation of glycoalkaloids in potato (Solanum tuberosum L)

The effects of low temperature and of combined stresses, cool temperature and waterlogging and also warm temperature and drought, on potato tuber glycoalkaloid levels were investigated, with emphasis on comparison of tubers of similar size. The early maturing cultivars Home Guard, Rocket and British Queen were grown under favourable controlled environment conditions (18/14 °C day/night temperature, 14 h photoperiod) until the imposition of treatments after the start of tuber initiation. Transfer to low temperature (12/9 °C) did not increase total glycoalkaloid concentration in any of the three cultivars. However, waterlogging at 12/9 °C increased total glycoalkaloid concentration during the later stages of development of British Queen. Drought stress at 24/18 °C also increased total glycoalkaloid concentration in British Queen, although the response varied between individual tubers of similar size. Total glycoalkaloid concentrations in tubers of Rocket were not affected by the combined stress treatments, and any effects on Home Guard were very much less than on British Queen. © 1999 Society of Chemical Industry     

Glycoalkaloids in potato tubers: the effect of variety and drought stress on the α‐solanine and α‐chaconine contents of potatoes

Six varieties of Solanum tuberosum L potato grown in the Bolivian highlands under drought stress, with and without irrigation, were analysed for their content of glycoalkaloids (GAs). The plant material consisted of three drought‐tolerant varieties from a local breeding programme (PROINPA), Potosina, Chapaquita and Pampeña, and three control cultivated varieties, Malcacho, Sani Imilla and Desiree, either susceptible or relatively tolerant to drought. α‐Solanine and α‐chaconine were quantified in both the peel and flesh of the tubers. A significant increase in GA concentration (α‐solanine + α‐chaconine) was observed under drought stress conditions in most varieties; average concentration increases of 43 and 50% were registered in the improved and control cultivars respectively. In all tested cultivars, however, the GA concentration remained lower than the recommended food safety level (200 mg kg⁻¹ fresh tubers). It ranged from 52.4 to 100 mg kg⁻¹ fresh tubers in the improved cultivars and from 55.6 to 122.3 mg kg⁻¹ fresh tubers in the controls. In the improved and control varieties the α‐solanine content averaged 42.6 and 35.4% of the total potato GAs respectively and was not significantly affected by drought stress, except in Desiree. In all conditions the peel contained the greatest proportion of total GAs. The hybrid variety Pampeña (new drought‐tolerant variety) contained the lowest amounts of GAs, which were lower than those of the control varieties, with and without irrigation. © 2000 Society of Chemical Industry     

The effect of prior storage on the potential of potato tubers (Solanum tuberosum L) to accumulate glycoalkaloids and chlorophylls during light exposure,including artificial neural network modelling

Potato tubers of four varieties (Brodick, King Edward, Pentland Dell and Record) were stored under commercial conditions and exposed to light for up to 10 days after 0, 10, 20 and 30 weeks. These were analysed for photosynthetic pigment and glycoalkaloid content. There was no significant alteration in either tuber chlorophyll or glycoalkaloid content during dark storage. All four varieties greened in response to light exposure, but only three exhibited a significant increase in glycoalkaloid concentrations during this exposure. Storage duration did not significantly affect pigment accumulation. However, there was a marked effect of storage on the extent of glycoalkaloid accumulation. Tubers of all four varieties stored for more than 10 weeks did not accumulate glycoalkaloids to the same extent as fresh tubers. Indeed, Brodick and Record did not accumulate any glycoalkaloids in response to light after 30 weeks of storage. A number of artificial neural network models of the results were produced. These accurately modelled cultivars individually, but a model encompassing all the data was not successful at predicting cultivar differences. © 1999 Society of Chemical Industry     

Interaction of aqueous extracts of two varieties of Yam tubers (Dioscorea spp) on some key enzymes linked to type 2 Diabetes in vitro

This study sought to assess the effect of processing of yam flour [from white yam (Dioscorea rotundata) and water yam (Dioscorea alata)] to paste, on the antioxidant properties and inhibition of key enzymes linked to type‐2 diabetes (α‐amylase and α‐glucosidase). The phenolic content (phenol and flavonoid), antioxidant properties, α‐amylase and α‐glucosidase inhibitory properties of the aqueous extracts of the yam products were determined. Processing into paste caused significant (P < 0.05) percentage decrease in their total phenol and flavonoid content of the yam varieties. However, significant increase (P < 0.05) in the antioxidant properties of the yam varieties was observed after processing. Furthermore, the yam extracts inhibited α‐amylase and α‐glucosidase activities in vitro in a dose‐dependent parttern (1–4 mg mL^?1), however, the pasting process caused significant (P < 0.05) decrease in the α‐amylase inhibitory and α‐glucosidase inhibitory activities. Therefore, processing the yam varieties into paste (browned) could potentially increase their antioxidant capacity as well as decreasing their α‐amylase and α‐glucosidase inhibitory properties.