Yeon-Shin Jeong

Isoflavone Attenuates Vascular Contraction through Inhibition of the RhoA/Rho-Kinase Signaling Pathway

Isoflavones decrease blood pressure, improve lipid profiles, and restore vascular function. We hypothesized that isoflavone attenuates vascular contraction by inhibiting RhoA/Rho-kinase signaling pathway. Rat aortic rings were denuded of endothelium, mounted in organ baths, and contracted with 11,9 epoxymethano-prostaglandin F2α (U46619), a thromboxane A2 analog, or KCl 30 min after the pretreatment with genistein (4′,5,7-trihydroxyisoflavone), daidzein (4′,7-dihydroxyisoflavone), or vehicle. We determined the phosphorylation level of the myosin light chain (MLC20), myosin phosphatase-targeting subunit 1 (MYPT1), and protein kinase C-potentiated inhibitory protein for heterotrimeric myosin light-chain phosphatase of 17 kDa (CPI17) by means of the Western blot. We also measured the amount of GTP RhoA as a marker regarding RhoA activation. The cumulative additions of U46619 or KCl increased vascular tension in a concentration-dependent manner, which were inhibited by pretreatment with genistein or daidzein. Both U46619 (30 nM) and KCl (50 mM) increased MLC20 phosphorylation levels, which were inhibited by genistein and daidzein. Furthermore, both genistein and daidzein decreased the amount of GTP RhoA activated by either U46619 or KCl. U46619 (30 nM) increased phosphorylation of the MYPT1Thr855 and CPI17Thr38, which were also inhibited by genistein or daidzein. However, neither genistein nor daidzein inhibited phorbol 12,13-dibutyrate-induced vascular contraction and CPI17 phosphorylation. In conclusion, isoflavone attenuates vascular contraction, at least in part, through inhibition of the RhoA/Rho-kinase signaling pathway.

Effects of light treatment on isoflavone content of germinated soybean seeds.

Our research objective was to increase isoflavone content in the germinated soybean seeds of four different varieties (Pungsannamulkong, Cheongjakong, Aga4, and Aga3) by optimizing light treatments (dark, greenhouse, fluorescent, incandescent, and ultraviolet lamps). The results demonstrated that the highest isoflavone content was produced from the Aga3 variety, which was developed by an interspecific cross between Eunhakong (Glycine max) and KLG10084 (G. soja) at the Plant Genetic Laboratory, Kyunpook National University. Aga3 is known to have one of the highest isoflavone content in the world at present. Our results recommend exposure of 7-day-old Aga3 sprouts to a combined light treatment of greenhouse lamps (12 h per day) and ultraviolet light (40 min per day) for maximum isoflavone production. Aga3 produced high levels of isoflavone because, in part, it contained very high isoflavone levels within the seed as compared with the other varieties. Under stress conditions, Aga3 could produce over 1.90 times more isoflavone than its seed content and 1.53 times more isoflavone than when grown under dark conditions.

Fatty acid composition in each structural part of soybean seed and sprout

Fatty acid composition and C18:2:C18:3 of soybean seed and sprout is important for soy-industries to manufacture quality products. Six soybean varieties were analyzed by gas chromatography to determine fatty acid composition and linoleic to linolenic acid ratio (C18:2:C18:3) in seed, sprout, and their structural parts. In the case of whole seed and its structural parts, significant variation in fatty acid composition and C18:2:C18:3 were observed between varieties except palmitic acid (C16:0), while all the parameters were significantly different for seed parts. Significant interactions of variety with seed parts were observed for oleic acid (C18:1), C18:2 and C18:2:C18:3. The highest saturated fatty acid, C18:1 and polyunsaturated fatty acid were recorded in seed coat, cotyledon, and seed axis, respectively. The lowest C18:2:C18:3 was found in seed axis. In the case of sprout study, variety had significant effect on all the parameters observed for whole sprout, cotyledon, root, and except C18:3 for hypocotyl. Culture days had significant effect on C16:0, C18:2 and C18:3 in whole sprouts, while only on C18:3 and C18:2:C18:3 in cotyledon. For hypocotyl, culture days had significant effect on C18:1, C18:2 and C18:2:C18:3, however, C16:0, C18:1, C18:3, and C18:2:C18:3 were significantly different in root. In sprout, days and variety interacted significantly for C16:0, C18:3 and C18:2:C18:3, and C18:1, C18:2, C18:3, and C18:2:C18:3, respectively for whole, cotyledon, and root. The significantly lowest C18:2:C18:3 (1.1) was observed in hypocotyl and root of Hwangkeumkong in 5 days. Knowledge of fatty acid composition and C18:2:C18:3 of seed, sprout, and their parts could be applicable for oil and other soy-food industries to make quality products.

Comparative Study of Quality Characteristics of Korean Soy Sauce Made with Soybeans Germinated Under Dark and Light Conditions

This study was conducted to evaluate the effects of germinating soybeans under dark and light conditions on the quality characteristics of Korean soy sauce made with germinated soybeans. The germination rate of soybeans germinated under dark conditions (GSD) was higher than that of soybeans germinated under light conditions (GSL), whereas the lengths of sprouts and relative weights of GSL did not differ from those of GSD. The L, a, b, and ΔT values of GSL were significantly lower than GSD. The color of GSD remained yellow, while GSL changed to a green color due to photosynthesis by chlorophyll. The total amino acid contents in soy sauce fermented with soybeans germinated under dark conditions (SSGD) and soy sauce fermented with soybeans germinated under light conditions (SSGL) were lower than in soy sauce fermented with non-germinated soybeans (SNGS). The levels of isoflavone content in SSGD and SSGL were significantly increased compared to the SNGS. In conclusion, the germination of soybeans under dark and light conditions is not only an increasing organoleptic preference, but also has implications for the health benefits of Korean soy sauce.

Differential abilities of Korean soybean varieties to biosynthesize glyceollins by biotic and abiotic elicitors

Glyceollins synthesized in soybeans that are exposed to biotic or abiotic stress have been reported to have health benefits. Considering that glyceollins are de novo synthesized from daidzein via several enzymatic steps and that isoflavone concentration widely varies among soybean varieties, the abilities of 60 soybean cultivars to synthesize glyceollins were compared under different elicitation conditions. Soybeans accumulated glyceollins differentially depending upon the cultivar when elicited with Aspergillus sojae. Contrary to our hypothesis that high isoflavone varieties may accumulate glyceollins more efficiently upon elicitation, glyceollin accumulation in response to fungal elicitation was not related with the concentration of either total isoflavones or daidzein in soybeans. Rather the glyceollin levels were significantly affected by soybean cultivar and most effectively increased by fungal infection. The data suggest that the selection of a strong fungal elicitor and a soybean cultivar with genotype that highly expresses the genes involved in glyceollin biosynthesis is essential for efficient glyceollin production.