• Journal of Applied Biological Chemistry
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• v.49 no.3
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• pp.75-81
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• 2006

A full-length cDNA encoding dihydroflavonol 4-reductase (st-dfr) of potato was isolated by rapid amplification of cDNA ends, and their expression was investigated from purple-fleshed potato (Solanum tuberosum L. cv. Jashim). The st-dfr exists as a member of a small gene family and its transcripts was abundant in the order of tuber flesh, stem, leaf, and root. The expressions of st-dfr gene were light inducible and cultivar dependant. Transgenic potato plants harboring antisense st-dfr (AS-DFR) sequences were analyzed. The accumulation of mRNA was nearly completely inhibited as a result of introducing an AS-DFR gene under the control of the 35S CaMV promoter into the red tuber skin Solanum tuberosum L. cv. Desiree. The anthocyanin content of the tuber peels of the transgenic lines was dramatically decreased by up to 70%. The possible production of flavonols in the peels of AS-DFR transgenic potatoes was discussed.

• Korean Journal of Breeding Science
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• v.41 no.4
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• pp.385-390
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• 2009

A resveratrol synthase (RS) gene was isolated from peanut (Arachis hypogaea, L. cv. Jinpoong) plants. This gene was placed under the control of the cauliflower mosaic virus 35S promoter (CaMV35S) and introduced into two Korean varieties of potato (Solanum tuberosum L. cvs. Jasim and Jowon) plants by Agrobacterium-mediated gene transfer. Putative transformants were screened by PCR with primers designed from CaMV 35S promoter, NOS terminator and RS gene. Most of selected transgenic potato plants showed the amplification of expected fragments by PCR of genomic DNA with gene-specific primers, while they were absent in untransformed control plants. Expression of the resveratrol synthase gene was also examined by northern blot analysis. The transformants showed a band which was lacking in the control plant, confirming that the introduced gene is transcribed into mRNA in the transformants. The strength of the band, which reflected the level of mRNA expression, differed among the individual transformants. Among the transformants obtained, the highest trans-resveratrol content in the transgenic young leaves of purple-fleshed "Jashim" was $2.11{\mu}gg^{-1}$ fresh weight and that in the microtubers in vitro of purple fleshed "Jashim" was $8.31{\mu}gg^{-1}$ fresh weight. This amount of resveratrol may have a positive biological effect on human health.

• Food Science and Biotechnology
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• v.14 no.1
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• pp.117-122
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• 2005

Polyphenoloxidase (PPO) was extracted from Solanum tuberosum Jasim by various chromatographic methods and was subsequently purified and characterized. PPO was purified upto 78-fold from the crude extract. SDS-PAGE profile of the enzyme showed a major subunit of PPO with molecular weight of 40 kDa. The optimum pH and temperature for the maximum activity of PPO was 6.5 and $25^{\circ}C$, respectively. The enzyme was found to be quite stable between 10 and $40^{\circ}C$, whereas it was almost inactivated at $70^{\circ}C$ when incubated for 30 min. Substrate specificity study indicated that catechol was the most suitable substrate for PPO isolated from purple-fleshed potato with a $K_m$ value of 21.1 mM. The most effective inhibitor was ascorbic acid, followed by L-cysteine, citric acid, EDTA, and boric acid. Studies on the effect of metal ion on PPO activity showed that magnesium and copper were inhibitory, while iron and zinc ions increased the activity of PPO.

• Journal of Bio-Environment Control
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• v.15 no.2
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• pp.204-210
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• 2006

The purple color in flesh of 'Jasim' potato (Solanum tuberosum L.) tubers is due to an accumulation of anthocyanin. The experiment was conducted to determine what is the key factor among cultural environments that affect the accumulation of anthocyanin in 'Jasim' potato tubers, and the effect of nitrogen fertilization levels on that. Through analysis of anthocyanin content of purple-fleshed tubers produced under the different cultural environments of three localities and two planting dates, we determined that lower temperature during 30days before harvesting resulted in higher anthocyanin accumulation of 'Jasim' potato tubers. In the experiment of different level of nitrogen fertilization, 'Jasim' potato tubers produced in highland (Daegualryeong) showed higher content of anthocyanin in the treatment of recommended level than in treatment of lower or higher level as compared with the recommended level. However, significant difference of anthocyanin content among different nitrogen fertilization levels was not observed in lowland (Gangnung). These results suggest that the selection of locality or cropping system and the optimal fertilization management are very important factors for production of higher pigmented tubers in purple-fleshed potato.

• Journal of Physiology & Pathology in Korean Medicine
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• v.21 no.3
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• pp.605-610
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• 2007

This experimental study was performed to evaluate the effects of ehtanol extract of Purple Solanum tuberosum L(EPSTL) on obesity and hyperlipidemia in rats induced by high fat diet. Sprague-Dawley rats were divided into normal group, control group, EPSTL (100 mg/kg and 200 mg/kg) treated group. EPSTL was orally administered to the obese rats by high fat diet for 6 weeks. The effect of EPSTL on obesity and hyperlipidemia were examined in vitro and in vivo as follows : EPSTL effectively inhibited the differentiation of 3T3-L1 adipocytes in a concentration dependent manner. EPSTL significantly lowered body weight of rats fe high fat diet for 6 weeks from 4 weeks treatment compared with untreated control. EPSTL significantly reduced the weight of retroperitoneal fat only at 100 mg/kg and epididymal fat pad in rats fed high fat diet for 4 weeks at 100 and 200 mg/kg. EPSTL significantly reduced the level of triglyceride at 200 mg/kg, while EPSTL tended to lower the levels of total lipid and phospholipid in rats fed high fat diet for 4 weeks with no significance. EPSTL significantly attenuated the level of total cholesterol, LDL and atherosclerosis index (Al) as well as increased the level of HDL at 200 mg/kg. EPSTL significantly reduced the levels of total lipid and triglyceride of hepatic tissues in rats fed high fat diet for 4 weeks at 200 mg/kg. EPSTL significantly lowered the level of insulin, while it did not affect leptin compared with untreated control. Taken together, these results suggest that EPSTL can be used for the treatment or prevention of hyperlipidemia and obesity.

• Natural Product Sciences
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• v.15 no.3
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• pp.134-138
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• 2009

In an attempt to establish anti-ulcerogenic activity of potato tubers, inhibitory activity against ethanol- and indomethacin-induced gastric ulcer models in rats was evaluated for the first time. From several varieties of potato tubers including Solanum tuberosum L. cv. Superior (white skin and fresh potato) and two new varieties of (Bora valley and Gogu valley), raw potato juice was prepared and the starch was obtained from each juice by filtration and drying. Upon oral administration to rats, raw potato juice showed more or less inhibitory activity. The starch showed higher and dose-dependent inhibitory activity, suggesting that the active ingredient in raw potato juice may be the starch. Particularly, the starch obtained from the tubers of new potato variety, "Bora valley," with purple color, showed the highest inhibitory activity (62.4% and 37.1% inhibition of ulcer index at 500 mg/kg), while omeprazole (proton pump inhibitor) used as a reference drug showed 74.4% and 75.7% inhibition at 20 mg/kg against ethanol- and indomethacin-induced ulcer formation, respectively. The present study provides a first evidence of anti-ulcerogenicity of raw potato juice and the starch. Especially, the starch from "Bora valley" strongly inhibited ulcer formation in rats. Considering that these are food components, they may be safely used for anti-ulcerogenic nutraceuticals.

• Proceedings of the Korean Society of Crop Science Conference
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• 2018.10a
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• pp.42-42
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• 2018

Anthocyanins has a strong antioxidant capacity but exhibit poor stability in water. Therefore, stability of anthocyanin from purple potato (Solanum tuberosum L.) was encapsulated by the application of food polymers. Solid formulation of purple potato was prepared using whey protein, tapioca and lecithin by capillary rheometer at $80^{\circ}C$. The ratio of the polymer and potato powder was 2:8. Total phenolic compound, total flavonoid, total anthocyanin and antioxidant activity was investigated by the spectrophotometer. Result revealed that total phenolic compound (TP) ($5321{\mu}g/100g$), total flavonoid (TF) ($1352{\mu}g/100g$) total anthocyanin (TA) ($764{\mu}g/100g$) and free radical antioxidant activity (DPPH) (86%) was higher in 0.01 M acetic acid mediated lecithin based formulation compared to control (Potato powder) (TP: $1357{\mu}g/100g$; TF) ($634{\mu}g/100g$, TA) ($264{\mu}g/100g\;DPPH$) (64%). Lecithin is a strong emulsifier having capacity to extract bioactive compound and encapsulate extracted compound by nonpolar tail and negatively charged head. Therefore, it would be concluded that lecithin might be used as an encapsulating agent for the bioactive compound from purple potato.

• Proceedings of the Korean Society of Crop Science Conference
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• 2018.10a
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• pp.274-274
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• 2018

Anthocyanins has a strong antioxidant capacity but exhibit poor stability in water. Therefore, stability of anthocyanin from purple potato (Solanum tuberosum L.) was encapsulated by the application of food polymers. Solid formulation of purple potato was prepared using whey protein, tapioca and lecithin by capillary rheometer at $80^{\circ}C$. The ratio of the polymer and potato powder was 2:8. Total phenolic compound, total flavonoid, total anthocyanin and antioxidant activity was investigated by the spectrophotometer. Result revealed that total phenolic compound (TP) ($5321{\mu}g/100g$), total flavonoid (TF) ($1352{\mu}g/100g$) total anthocyanin (TA) ($764{\mu}g/100g$) and free radical antioxidant activity (DPPH) (86%) was higher in 0.01 M acetic acid mediated lecithin based formulation compared to control (Potato powder) (TP: $1357{\mu}g/100g$; TF) ($634{\mu}g/100g$, TA) ($264{\mu}g/100g\;DPPH$) (64%). Lecithin is a strong emulsifier having capacity to extract bioactive compound and encapsulate extracted compound by nonpolar tail and negatively charged head. Therefore, it would be concluded that lecithin might be used as an encapsulating agent for the bioactive compound from purple potato.

• Food Engineering Progress
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• v.21 no.2
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• pp.167-173
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• 2017

Purple-fleshed potato powder (PFPP) was investigated to determine optimal mixing ratio with milk powder and dextrin to produce a ready-to-eat mashed potato powder. The rheological characteristics, color, and anthocyanin contents were studied at a different concentration of ingredients. The power-law model was applied to explain the mechanical spectra of mashed potatoes which represented the change in structure induced by different mixing ratios. Mixture design was used to obtain the experimental points used to establish the empirical models to describe the effects of each ingredient on the characteristic of the mashed potato. The results of mechanical spectra showed that both storage and loss moduli (G' and G'') were significantly influenced by PFPP and milk powder concentration. The power law parameters n' and n'' showed higher values for the mashed potato with a lower concentration of PFPP and a higher concentration of milk powder, which showed that the gel networks involved in the mashed potato were weaker. The optimum mixing ratio with the highest redness and anthocyanin content, while maintaining the rheological properties similar to the commercial mashed potato, was determined as PFPP:milk powder:dextrin = 90.49:4.86:4.65 (w/w). The proportions of PFPP and milk powder in the formulation significantly changed the characteristics of mashed potato, whereas no significant effect of dextrin was observed in this formulation.

• Korean Journal of Food Science and Technology
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• v.31 no.2
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• pp.348-355
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• 1999

Effects of pH, sugars, organic acids, metal ions, ascorbic acid and light on the stability of anthocyanin pigment extracted from purple-fleshed potato (Solanum tuberosum L.) were studied. The pH had marked influences on the color of the potato anthocyanin pigment: i.e., the lower the pH of the anthocyanin solution was, the more stable and intenser of the pigment was. It showed characteristic bathochromic shift as the pH of the solution increased. Generally, the addition of sugars into the purple-fleshed potato anthocyanin solution caused decrease in color stability of the pigment. Among the sugars tested, maltose was the most deleterious followed by sucrose, galactose, fructose and glucose. The addition of organic acids greatly increased the stability of the pigment. Malic acid was found to be the most effective in stabilizing the pigment followed by tartaric, citric and succinic acids, while malonic acid was found to be deteriorative to the stability of the pigment. Most metal ions except $Cu^{2+}$ increased stability of the pigment-especially, $Cd^{2+}\;and\;Al^{3+}$ were more effective than the others. Ascorbic acid degraded the pigment considerably, but the adverse effect was diminished by adding thiourea. Light gave an adverse effect to the stability of the purple-fleshed potato anthocyanin pigment, which could be minimized by shielding the light from the pigment.