We determined the phytochemical diversity, including carotenoids, flavonoids, anthocyanins, and phenolic acids, in sweet potatoes ( L.) with distinctive flesh colors (white, orange, and purple) and identified hydrophilic primary metabolites. Carotenoid content was considerably higher in orange-fleshed sweet potatoes, wherein β-carotene was the most plentiful, and anthocyanins were detected only in purple-fleshed sweet potatoes. The levels of phenolic acids and flavonoids were relatively higher in purple-fleshed sweet potatoes than those in the other two varieties. Forty-one primary and 18 secondary metabolite profiles were subjected to multivariate statistical analyses, which fully distinguished among the varieties and separated orange- and purple-fleshed sweet potatoes from white-fleshed sweet potatoes based on the high levels of sugars, sugar alcohols, and secondary metabolites. This is the first study to determine comprehensive metabolic differences among different color-fleshed sweet potatoes and provides useful information for genetic manipulation of sweet potatoes to influence primary and secondary metabolism.

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In this study, we aimed to characterize fungal samples from necrotic lesions on collar regions observed in different sweetpotato growing regions during 2015 and 2016 in Korea. Sclerotia appeared on the root zone soil surface, and white dense mycelia were observed. At the later stages of infection, mother roots quickly rotted, and large areas of the plants were destroyed. The disease occurrence was monitored at 45 and 84 farms, and 11.8% and 6.8% of the land areas were found to be infected in 2015 and 2016, respectively. Fungi were isolated from disease samples, and 36 strains were preserved. Based on the cultural and morphological characteristics of colonies, the isolates resembled the reference strain of Sclerotium rolfsii. Representative strains were identified as S. rolfsii (teleomorph: Athelia rolfsii) based on phylogenetic analysis of the internal transcribed spacer and large subunit genes along with morphological observations. To test the pathogenicity, sweetpotato storage roots were inoculated with different S. rolfsii strains. ‘Yulmi’ variety displayed the highest disease incidence, whereas ‘Pungwonmi’ resulted in the least. These findings suggested that morphological characteristics and molecular phylogenetic analysis were useful for identification of S. rolfsii.

It is well known that extracts of purple sweet potato (PSP) have potent antioxidant activity. However, it has not been established whether extracts of PSP inhibit oxidation of low-density lipoprotein (LDL) or protein glycation. LDL oxidation and protein glycation are well-known risk factors for chronic metabolic diseases, such as atherosclerosis and diabetes mellitus. Chopped and sliced PSP and yellow sweet potato (YSP) were extracted individually at a concentration of 1 g of PSP tuber/mL using either ethanol or water for 6 hours. The PSP ethanol extract (100-fold diluted) showed stronger radical (2,2-diphenyl-1-picrylhydrazyl radical) scavenging activity than the water extract of PSP and the ethanol extract of YSP (up to a sixfold higher activity). The ethanol extract of PSP also exhibited the highest increase in ferric reducing ability among all extracts. Cupric ion-mediated LDL oxidation was strongly inhibited by the ethanol extract of PSP, with similar potency to vitamin C treatment (final concentration, 10 mM). The PSP extract strongly inhibited fructose-mediated protein glycation as determined by fluorescence spectroscopy. The PSP extract-treated apolipoprotein (apo) A-I showed a decreased multimerization pattern on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, whereas glycated apoA-I showed the strongest multimeric band. PSP extract treatment also inhibited the uptake of oxidized LDL into human macrophage cells with suppression of malondialdehyde production in the cell culture medium. In conclusion, these results suggest that the extract of PSP can be used as a putative anti-atherosclerotic and antidiabetic agent with strong antioxidant functions. This is the first report to show the biological functions of PSP extract to treat hyperlipidemic and hyperglycemic disorders.

We investigated out the effect of cultivation region on the physicochemical characteristics of starch in six sweetpotato cultivars. The following sweetpotato cultivars were analyzed: Daeyumi, Shingeonmi, Jinhongmi, Shinyulmi, Yulmi, and Yeonhwangmi. Samples were cultivated in Muan, Iksan, Nonsan, Boryeong and Hamyang. The soil texture was found to be sandy loam in Muan, Iksan, and Boryeong, sandy clay loam in Nonsan, and loam in Hamyang. The starch content of the sweetpotato was higher in Muan than in Hamyang. The amylose content was 22.3-30.9%, and the highest amylose content was found in samples from Iksan. Rapid viscosity analysis showed that the samples from Hamyang had the lowest values of pasting temperature, while samples of the Daeyumi cultivar had the highest values. Thermal analysis with a differential scanning calorimeter showed that the Muan samples had the highest values of onset temperature, maximum peak temperature, and completion temperature, and the samples from Hamyang had the lowest values. There was no difference between the cultivation regions or the cultivar in the X-ray pattern of the starch or its appearance in scanning electron micrographs. Therefore, the results of this study confirm that cultivation region and cultivar play an important role in determining the quality of sweetpotato and the physicochemical characteristics of sweetpotato starch. 서 론 고구마((Ipomoea batatas (L.) Lam))는 메꽃과에 속하는 쌍떡잎 식물로 B.C. 3,000년경부터 멕시코 지역에서 처음으로 재배되기 시작하였으며 우리나라에는 조선 영조 39년(1763년) 10월, 일본 에 통신정사로 갔던 조엄 선생이 대마도에서 부산진으로 들여오 면서 재배되기 시작하였다(1-3). 고구마가 구황작물로써 국민들의 사랑을 받아왔던 것은 위도, 온도, 토성 등 다양한 생태환경에 적 응성이 뛰어난 광지역적인 특성을 가지고 있기 때문이다. 그러나 1970년 후반, 녹색혁명을 통한 쌀 자급과 경제 성장의 달성으로 고구마의 소비가 급감하였으나 경제 발전과 서구식 식생활 진전 및 2000년대 웰빙 붐을 타면서 다시 소비가 증가하게 되었다. 고구마의 주요 성분은 수분이 68.5%로 대부분을 차지하고 있 으며, 탄수화물 26.4%, 단백질 1.8%, 지방 0.6% 순으로 구성되어 있다. 탄수화물의 대부분을 차지하고 있는 전분은 접착력이 높아 당면 제조 시 타전분에 비하여 질적으로 유리하여 면류 생산에 주로 이용하고 있다. 그러나 최근 당면 생산에 있어 고구마 전분 의 소비량이 감소하고 값싼 중국산이 수입되어 가격 경쟁력이 약 한 국내 고구마 전분산업은 해마다 위축되고 있다. 최근 소비량 이 감소하는 고구마 전분의 용도를 향상시키기 위하여 고구마 전 분의 물리적 및 이화학적 특성에 중점을 두고 국내외의 다양한 연구들이 진행되고 있다. 고구마 전분의 이화학적 특성에 대한 연구로는 한국산 고구마 품종을 이용하여 전분의 이화학적 성질 의 분석(4-8), 고구마 전분을 이용한 호화 특성의 측정(9-15), 고 구마 부위에 따른 전분의 특성 분석(16), 고구마 생장단계 및 재 배환경에 따른 전분의 물리화학적 특성(17-23) 등의 연구 결과가 보고되고 있다. 또한 쌀보리 전분의 입자 크기별 이화학적 성질 (24), 발아 옥수수 전분의 이화학적 성질(25), 강낭콩 조전분 및 정제 전분의 특성(26), 율무전분의 조리과학적 특성 연구(27), 동 부 전분의 분자구조적 성질(28), 녹두전분의 이화학적 특성(29) 등 작물별로 전분을 이용하기 위한 다양한 연구를 진행하였다. 또한 가열방법에 따른 고구마의 호화도 측정(30), 묵 형성 전분 의 특성에 관한 연구(31) 등 고구마 전분의 특성을 활용하여 그 이용도 및 활용도를 높이기 위한 다양한 연구가 발표되어 고구 마 전분이 새로운 식품소재로서 관심과 주목을 받고 있다. 현재 우리나라 여러 지역에서는 다양한 품종의 고구마들이 재배되고