• Food Science and Preservation
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• v.17 no.3
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• pp.391-397
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• 2010

Yams (Dioscorea spp.) have been used as medicinal and edible resources worldwide. In the present study, methanol extracts were prepared from various kinds of yam, including D. batatas (Gyeongbuk No. 1 and No. 4), D. alata L. (Gyeongbuk No. 5 and No. 6), and D. bulbifera and D. nipponica, and the antioxidant, antithrombin, and antimicrobial activities of these extracts were evaluated. The water content of the various yams was 54.7~83.2% (D. batatas> D. alata L.>D. nipponica>D. bulbifera) and the methanol extracts contained 0.59-1.59% (w/v) solid matter (D. alata L.>D. batatas >D. nipponica>D. bulbifera). The mean concentrations of total polyphenols, total flavonoids, and total sugars in the different types of yam were 49.82 mg/g, 9.79 mg/g, and 173.81 mg/g, respectively. Analysis of DPPH radical-scavenging activity showed that D. alata L. Gyeongbuk No. 6 had a strong antioxidant capacity (IC50=$142.30{\mu}g/mL$), whereas the other yams showed reduced levels of activity (IC50=371-$486{\mu}g/mL$). D. alata L. Gyeongbuk No. 6 showed a strong antithrombin activity against human thrombin. Upon treatment with a D. alata methanol extract (1.5 mg/mL), thrombin time was increased 7.35-fold compared with that when methanol alone was used. In an antimicrobial activity assay, the D. nipponica extract showed moderate antibacterial activity against Bacillus subtilis, Staphylococcus aureus, Proteus vulgaris, and Salmonella typhimurium. Our results indicate that different varieties of Dioscorea spp., including D. batatas, have useful biochemical attributes, including antioxidant, antithrombin, and antibacterial activities.

• Microbiology and Biotechnology Letters
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• v.38 no.3
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• pp.283-288
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• 2010

Yam (Dioscorea spp.) has been used as important edible and medicinal natural resource in worldwide and D. alata L. is most popular nourishment among the yam. In this study the composition, color, antioxidation and antimicrobial activity of D. alata Gyeongbuk No. 6 (GB-6), which was established in Gyeongbuk Agricultural Research & Extension Services, Andong, Korea, was compared to those of D. batatas Gyeongbuk No. 1 (GB-1), a major domestic cultivation species. Water content of GB-6 was $78.02{\pm}0.16%$, which is slightly lower than that of GB-1 ($82.6{\pm}0.07%$). The contents of crude protein, crude fat, crude fiber and ash of GB-6 were 0.95, 0.26, 0.85 and 0.70%, whereas those of GB-1 were 1.58, 0.15, 1.39 and 0.88%, respectively. Analysis of color using colormeter showed that the GB-6 is slight dark-yellow than GB-1, and total polyphenol content of GB-6 was 2-fold higher compared than that of GB-1. Sequential organic solvent fractions from methanol extract of GB-6 showed that the ethylacetate fraction has highest total polyphenol ($144.1{\pm}3.20\;mg/g$). Determination of antioxidation activity showed that the ethylacete fraction and water fraction has strong DPPH radical scavenging activity ($IC_{50}=78.32\;{\mu}g/mL$) and reducing power, respectively. In antimicrobial activity assay, the n-hexane and ethylacetate fraction showed antibacterial activity against B. subtilis, L.monocytogenes, S. epidermidis, S. aureus, P. vulgaris, and S. typhimurium. These results provide the possibility of domestic cultivated D. alata GB-6 as a healthy food.